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1. A pilot randomised controlled trial comparing the effectiveness of the MaTerre180' participatory tool including a serious game versus an intervention including carbon footprint awareness-raising on behaviours among academia members in France.

Author

Claudia Teran-Escobar, Nicolas Becu, Nicolas Champollion, Nicolas Gratiot, Benoît Hingray, Gérémy Panthou, and Isabelle Ruin

Subjects
Medicine, Science
Abstract

BackgroundActivities embedded in academic culture (international conferences, field missions) are an important source of greenhouse gas emissions. For this reason, collective efforts are still needed to lower the carbon footprint of Academia. Serious games are often used to promote ecological transition. Nevertheless, most evaluations of their effects focus on changes in knowledge and not on behaviour. The main objectives of this study are to 1) Evaluate the feasibility of a control and an experimental behaviour change intervention and, 2) Evaluate the fidelity (the extent to which the implementation of the study corresponds to the original design) of both interventions.MethodsPeople employed by a French research organisation (N = 30) will be randomised to one of the two arms. The experimental arm consists in a 1-hour group discussion for raising awareness about climate change, carrying out a carbon footprint assessment and participating to a serious game called "Ma terre en 180 minutes." The control arm consists of the same intervention (1h discussion + carbon footprint assessment) but without participating to the serious game. On two occasions over one month, participants will be asked to fill in online surveys about their behaviours, psychological constructs related to behaviour change, sociodemographic and institutional information. For every session of intervention, the facilitators will assess task completion, perceived complexity of the tasks and the perceived responsiveness of participants. Descriptive statistics will be done to analyse percentages and averages of the different outcomes.DiscussionMa-terre EVAL pilot study is a 1-month and a half pilot randomised controlled trial aiming to evaluate the feasibility and the fidelity of a 24-month randomised controlled trial. This study will provide more information on the levers and obstacles to reducing the carbon footprint among Academia members, so that they can be targeted through behaviour change interventions or institutional policies.

Published
2024
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2. Datasets of high-resolution water level and discharge from the Saigon-Dong Nai estuary system impacted by a developing megacity, Ho Chi Minh City - Vietnam

Author

Francisco Rodrigues do Amaral, Tin Nguyen Trung, Thierry Pellarin, and Nicolas Gratiot

Subjects
Tidal river, Low-cost installation, ADCP, Tidal propagation in rivers, Computer applications to medicine. Medical informatics, R858-859.7, Science (General), Q1-390
Abstract

We present a new hydrological dataset collected during a field campaign in the Saigon-Dong Nai estuary system, Vietnam. These data include water level and water temperature measurements at five locations along the Saigon river and 2 locations along the Dong Nai river as well as discharge measurements from four 24-hour Acoustic Doppler Current Profiler (ADCP) campaigns at 2 locations in the Saigon river and 1 location in the Dong Nai river. Additionally, water level was barometrically compensated using air pressure measurements. Data were sampled between October 21st, 2022 and December 16th, 2022 and are provided in three processing stages namely, direct measurements as provided by the sensors (raw), barometricaly compensated measurements (pre-processed) and corrected measurements (post-processed). Even though of short duration (about 2 months), this dataset provides water level measurements at unprecedented spatial and temporal resolution in a region where data is scarce and not freely available. The synchronous logging of multiple water level sensors along river provides an opportunity to study profiles of water surface slope and upstream tidal propagation. Furthermore, the concurrent discharge measurements can be used to calibrate hydrological and/or hydraulic models of this estuary system. Additionally, the spatial resolution of this dataset is similar to the prospective measurements that the novel Surface Water and Ocean Topography (SWOT) satellite will provide. Thus, it enables the study of synthetic SWOT measurements to evaluate the future potential of the SWOT satellite over this estuary system.

Published
2023
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3. The Multi-Channel System of the Vietnamese Mekong Delta: Impacts on the Flow Dynamics under Relative Sea-Level Rise Scenarios

Author

Hoang-Anh Le, Thong Nguyen, Nicolas Gratiot, Eric Deleersnijder, and Sandra Soares-Frazão

Subjects
Vietnamese Mekong Delta, TELEMAC-2D, hydrodynamics, channel system, sea-level rise, Hydraulic engineering, TC1-978, Water supply for domestic and industrial purposes, TD201-500
Abstract

The Mekong Delta has the world’s third-largest surface area. It plays an indisputable role in the economy and livelihoods of Vietnam and Cambodia, with repercussions at regional and global scales. During recent decades, the Vietnamese part of the Mekong Delta underwent profound human interventions (construction of dykes and multi-channel networks), which modified the hydrodynamic regime, especially cycles of field submersion. In this study, we first applied a full 2D numerical hydraulic model, TELEMAC-2D, to examine the effects of the complex channel and river networks on the spatial and temporal distribution of the flow in the 40,000 km2 of the Vietnamese Mekong Delta. Then, two scenarios of relative sea-level rise in 2050 and 2100 were implemented to simulate the future patterns of water fluxes in the delta. The results show that dykes and multi-channel networks would reduce the inundation area by 36% and lessen the peak water level by 15% and the discharge over the floodplains by 24%. Despite this protection, under a relative sea-level rise of 30 cm and 100 cm, the maximum flooded area could occupy about 69% and 85% of the whole delta in 2050 and 2100, respectively.

Published
2023
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4. Effects of hydrological regime and land use on in-stream Escherichia coli concentration in the Mekong basin, Lao PDR

Author

Paty Nakhle, Olivier Ribolzi, Laurie Boithias, Sayaphet Rattanavong, Yves Auda, Saysongkham Sayavong, Rosalie Zimmermann, Bounsamay Soulileuth, Anne Pando, Chanthamousone Thammahacksa, Emma J. Rochelle-Newall, William Santini, Jean-Michel Martinez, Nicolas Gratiot, and Alain Pierret

Subjects
Medicine, Science
Abstract

Abstract In the basin of Mekong, over 70 million people rely on unimproved surface water for their domestic requirements. Surface water is often contaminated with fecal matter and yet little information exists on the underlying mechanisms of fecal contamination in tropical conditions at large watershed scales. Our objectives were to (1) investigate the seasonality of fecal contamination using Escherichia coli as fecal indicator bacteria (FIB), and (2) establish links between the fecal contamination in stream water and its controlling factors (hydrology and land use). We present the results of (1) a sampling campaign at the outlet of 19 catchments across Lao PDR, in both the dry and the rainy seasons of 2016, and (2) a 10-day interval monitoring conducted in 2017 and 2018 at three point locations of three rivers (Nam Ou, Nam Suang, and Mekong) in northern Lao PDR. Our results show the presence of fecal contamination at most of the sampled sites, with a seasonality characterized by higher and extreme E. coli concentrations occurring during the rainy season. The highest E. coli concentrations, strongly correlated with total suspended sediment concentrations, were measured in catchments dominated by unstocked forest areas, especially in mountainous northern Lao PDR and in Vientiane province.

Published
2021
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5. Sedimentological and geochemical data in bed sediments from a tropical river-estuary system impacted by a developing megacity, Ho Chi Minh City - Vietnam

Author

David Noncent, Emilie Strady, Julien Némery, Nguyen Thanh-Nho, Hervé Denis, Brice Mourier, Marc Babut, Truong An Nguyen, Thi Ngoc Tuyet Nguyen, Cyril Marchand, Marc Desmet, Anh Tu Tran, Joanne Aimé, Nicolas Gratiot, Quoc Tuc Dinh, and Phuoc Dan Nguyen

Subjects
Grain size distribution, Trace metal, Carbon, Nitrogen, Phosphorus, Enrichment factor, Computer applications to medicine. Medical informatics, R858-859.7, Science (General), Q1-390
Abstract

Sedimentological and geochemical data were obtained for bed sediments from a tropical estuary environment in Vietnam in October 2014, January 2016, and November 2016. The data include grain-size distribution, percentage of clay, silt and sand, percentage of organic matter, concentration of total particulate phosphorus (TPP), concentration of particulate inorganic phosphorus (PIP), concentration of particulate organic phosphorus (POP), percentage of total nitrogen (TN), percentage of total carbon (TC), trace metals concentrations (V, Cr, Co, Ni, Cu, Zn, As, Mo, Cd, Pb) and major elements (Al, Fe, Mn). Geochemical indexes (Enrichment factor EF and Geo-accumulation Index I-geo) and sediment quality guideline (mean Effect Range Median quotients) were calculated.

Published
2020
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6. Surface Water Evolution (2001–2017) at the Cambodia/Vietnam Border in the Upper Mekong Delta Using Satellite MODIS Observations

Author

Filipe Aires, Jean-Philippe Venot, Sylvain Massuel, Nicolas Gratiot, Binh Pham-Duc, and Catherine Prigent

Subjects
wetlands/inundation, satellite remote sensing, trend analysis, hydrology, vietnam, cambodia, water control, Science
Abstract

Studying the spatial and temporal distribution of surface water resources is critical, especially in highly populated areas and in regions under climate change pressure. There is an increasing number of satellite Earth observations that can provide information to monitor surface water at global scale. However, mapping surface waters at local and regional scales is still a challenge for numerous reasons (insufficient spatial resolution, vegetation or cloud opacity, limited time-frequency or time-record, information content of the instrument, lack in global retrieval method, interpretability of results, etc.). In this paper, we use 17 years of the MODIS (MODerate-resolution Imaging Spectro-radiometer) observations at a 8-day resolution. This satellite dataset is combined with ground expertise to analyse the evolution of surface waters at the Cambodia/Vietnam border in the Upper Mekong Delta. The trends and evolution of surface waters are very significant and contrasted, illustrating the impact of agriculture practices and dykes construction. In most of the study area in Cambodia. surface water areas show a decreasing trend but with a strong inter-annual variability. In specific areas, an increase of the wet surfaces is even observed. Ground expertise and historical knowledge of the development of the territory enable to link the decrease to ongoing excavation of drainage canals and the increase of deforestation and land reclamation, exposing flooded surfaces previously hidden by vegetation cover. By contrast, in Vietnam, the decreasing trend in wet surfaces is very clear and can be explained by the development of dykes dating back to the 1990s with an acceleration in the late 2000s as part of a national strategy of agriculture intensification. This study shows that coupling satellite data with ground-expertise allows to monitor surface waters at mesoscale (2), demonstrating the potential of interdisciplinary approaches for water ressource management and planning.

Published
2020
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7. Ho Chi Minh Ville, des inondations à la submersion…

Author

Georges Vachaud, Nicolas Gratiot, and Tien Dung Tran Ngoc

Subjects
climate change, urbanisation, flooding, Vietnam, mega city, subsidence, Geography (General), G1-922
Abstract

Most of the mega-cities in South-East Asia located on the coast are subject to both very strong demographic growth and increased flood risks resulting from a combination of poorly controlled urban development, increased monsoon rainfall intensity, rising sea levels and subsidence. Ho Chi Minh City is a typical example of this situation, which could lead in the medium to short term to the submergence of the majority of recent districts built on former marshland or rice fields. It is therefore essential to implement appropriate risk management strategies and to develop the region in a sustainable manner.

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8. Hydraulic response of a tropical urban estuary to a typhoon event: case study of Ho Chi Minh City and typhoon Usagi

Author

Francisco Rodrigues do Amaral, Nicolas Gratiot, and Thierry Pellarin

Abstract

We investigate the most severe rainfall event ever experienced in Ho Chi Minh City (HCMC), Vietnam. It occurred on November 25th, 2018 when typhoon (TY) Usagi directly hit HCMC. During this event, there was more than 300 mm in rainfall over 24 h which led to flooding and considerable material damages. We propose an in-depth study of the hydrological response of this urban estuary region at a short time scale by focusing on the days before and after typhoon Usagi. We use a set of data analysis and signal processing tools to characterize and quantify both coastal and continental effects on the hydrosystem. We found that TY Usagi made landfall without forming a significant storm surge. The extreme rainfall does not translate in immediate river discharge but presents a 10 hour time lag between peak precipitation and peak residual discharge. Nevertheless, increased water levels can be seen at both urban and upstream river stations with a similar time lag. At the upstream station, residual discharge represents 1.5 % of available rain water and evidence of upstream wide spread flooding was found. At the urban station, we assess the potential surface run off during the event to be 8.9 % of the upstream residual discharge. Hence, the Saigon river would be capable of evacuating the urban flood water after the event. However, a time lag in peak water level and peak rainfall was found and attributed to the combination of high tide and impervious streets which prevented the evacuation of rain water and resulted in street flooding of up to 0.8 m. Overall, it was found that despite not having a significant storm surge, the coastal tidal forcing is predominant in the hydrodynamics of the river even during severe heavy rainfall with tidal fluctuations of water level and respective discharge much larger than the residuals.

Published
2023

9. Saigon's river response to Typhoon Usagi

Author

Francisco Rodrigues do Amaral, Nicolas Gratiot, and Thierry Pellarin

Subjects
Harmonic Tidal Analysis, Hydrodynamics, Saigon River, Storm Surge, Typhoon Usagi
Abstract

A good understanding of the hydrological cycle, and discharge in particular, in tidal rivers enables reliable forecasting and decision making by researchers and policy makers. We develop the work of Camenen et al. 2021 where the hydrological dynamics of the tidal Saigon river are studied. The study proposes a low-cost technique to estimate tidallyinfluenced river discharge based on high-frequency in-situ measurements. This technique estimates discharge based on a stage-fall-discharge rating curve (Camenen et al., 2017) which requires the estimation of the river’s slope. The application to the Saigon river as in Camenen et al. 2021 shows that its hydrological dynamics are ruled by a complex combination of factors.

Published
2022
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10. The multi-channel system of the Vietnamese Mekong Delta: impacts on the flow dynamics under relative sea level rise scenarios

Author

Hoang Anh Le, Thong Nguyen, Nicolas Gratiot, Eric Deleersnijder, and Sandra Soares-Frazão

Abstract

The Mekong Delta has the world's third largest surface area. It plays an indisputable role in the economy and livelihoods of Vietnam, Cambodia, with repercussions at regional and global scales. During recent decades, the Vietnamese part of the Mekong Delta underwent profound human interventions (construction of dykes and multi-channel networks), which modified the hydrodynamic regime, especially cycles of field submersion. In this study, we first applied a full 2D numerical hydraulic model, TELEMAC-2D, to examine the effects of the complex channel and river networks on the spatial and temporal distribution of the flow in the 40,000 km2 of the Vietnamese Mekong Delta. Then, two scenarios of relative sea level rise in 2050 and 2100 are implemented to simulate the future patterns of water fluxes in the delta. The results show that the dykes and multi-channel networks would reduce by 36% the inundation area and lessen by 15% the peak water level and 24% discharge over the floodplains. Despite this protection, under relative sea level rise of 30 cm and 100 cm, the maximum flooded area could occupy about 69% and 85% of the whole delta in 2050 and 2100, respectively.

Published
2022

11. A transition support system to build decarbonization scenarios in the academic community

Author

Nicolas Gratiot, Jérémie Klein, Marceau Challet, Olivier Dangles, Serge Janicot, Miriam Candelas, Géraldine Sarret, Géremy Panthou, Benoît Hingray, Nicolas Champollion, Julien Montillaud, Pascal Bellemain, Odin Marc, Cédric-Stéphane Bationo, Loïs Monnier, Laure Laffont, Marie-Alice Foujols, Véronique Riffault, Liselotte Tinel, Emmanuel Mignot, Nathalie Philippon, Alain Dezetter, Alexandre Caron, Guillaume Piton, Aurélie Verney-Carron, Anne Delaballe, Nelly Bardet, Florence Nozay-Maurice, Anne-Sophie Loison, Franck Delbart, Sandrine Anquetin, Françoise Immel, Christophe Baehr, Fabien Malbet, Céline Berni, Laurence Delattre, Vincent Echevin, Elodie Petitdidier, Olivier Aumont, Florence Michau, Nicolas Bijon, Jean-Philippe Vidal, Sébastien Pinel, Océane Biabiany, Cathy Grevesse, Louise Mimeau, Anne Biarnès, Charlotte Récapet, Morgane Costes-Thiré, Mariline Poupaud, Maialen Barret, Marie Bonnin, Virginie Mournetas, Bernard Tourancheau, Bertrand Goldman, Marie Paule Bonnet, Isabelle Michaud Soret, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Centre d’Ecologie Fonctionnelle et Evolutive (CEFE), Université Paul-Valéry - Montpellier 3 (UPVM)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro Montpellier, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Université de Montpellier (UM), Océan et variabilité du climat (VARCLIM), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut des Sciences de la Terre (ISTerre), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Gustave Eiffel-Université Grenoble Alpes (UGA), Univers, Transport, Interfaces, Nanostructures, Atmosphère et environnement, Molécules (UMR 6213) (UTINAM), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Hydrosciences Montpellier (HSM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM), Erosion torrentielle neige et avalanches (UR ETGR (ETNA)), Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France -Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France, RiverLy - Fonctionnement des hydrosystèmes (RiverLy), Lille économie management - UMR 9221 (LEM), Université d'Artois (UA)-Université catholique de Lille (UCL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Processus et interactions de fine échelle océanique (PROTEO), Nucleus for European Modeling of the Ocean (NEMO R&D ), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)

Subjects
[SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, [SHS.ENVIR]Humanities and Social Sciences/Environmental studies, [SCCO.PSYC]Cognitive science/Psychology, [SHS.PSY]Humanities and Social Sciences/Psychology, [SDE.ES]Environmental Sciences/Environmental and Society
Abstract

A growing portion of scientists realises the need to not only alert about climate change, but also change their professional practices. A range of tools have emerged to promote more sustainable activities, yet many scientists struggle to go beyond simple awareness-raising to create concrete transition actions. Here we propose a game-based transition support system MaTerre180’, which has been designed to build scenarios of greenhouse gas (GHG) emission reductions in the academic community. After providing a common scientific background about the context (global warming issue, its causes and consequences) and setting up a challenge (50% reduction of carbon budget by 2030), the participants belonging to the academic community and its governance bodies immerse themselves into fictional characters, to simulate the behaviour of real research groups. The game has been deployed during the year 2021, with six hundred participants from nine countries and 50 cities. Results explore clear pathways for GHG reductions between 25 and 60%, and a median reduction of 46%. The alternatives allowing the greatest reduction are video communication tools (36%), followed by mutualization of professional activities and voluntary cancellation or reduction, that represent 22 and 14% of reduction, respectively. The remaining 28% of reduction consists of transport alternative, relocation of professional activities, extended duration of some travels, etc. In addition, the analyses pointed out the importance of the guided negotiation phase to bring out some alternatives such as relocation, local partners and computing optimization. An added value of this transition support system is that the information it collects (anonymously) will be used to answer pressing research questions in climate change science and environmental psychology regarding the use of serious games for promoting changes in attitudes and behaviours towards sustainability, and including broader questions on how network structures influence “climate behaviour”, knowledge and the governance of the commons. Modestly, MaTerre180’ offers an innovative game-based transition support system to build scenarios of greenhouse gas (GHG) emission reductions in the academic community. It is not simply a question of moving tokens on a virtual gameboard and a playful adjustment of practices, but rather a question of brainstorming about possible and desirable ways of remodelling research and teaching communities and embracing a new paradigm. After tens of workshops, our results show clear pathways for reaching up to 50% GHG reductions and stress the importance of guided negotiations to bring out alternatives to carbonized activities. This first attempt reinforces our belief that scientific engagement is at the heart of the international development agenda and a key approach to tear down the institutional barriers that inhibit the transformation needed to achieve a more sustainable society.

Published
2023

12. Effects of hydrological regime and land use on in-stream Escherichia coli concentration in the Mekong basin, Lao PDR

Author

William Santini, Chanthamousone Thammahacksa, Bounsamay Soulileuth, Alain Pierret, Emma Rochelle-Newall, Paty Nakhle, Rosalie E. Zimmermann, Olivier Ribolzi, Anne Pando, Saysongkham Sayavong, Sayaphet Rattanavong, Nicolas Gratiot, Yves Auda, Laurie Boithias, Jean-Michel Martinez, Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Institut d'écologie et des sciences de l'environnement de Paris (iEES Paris ), Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Medical Microbiology and Infection Prevention, Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)

Subjects
Wet season, Watershed, MEKONG BASSIN, [SDV]Life Sciences [q-bio], Science, 0208 environmental biotechnology, Indicator bacteria, 02 engineering and technology, 010501 environmental sciences, 01 natural sciences, Article, Hydrology (agriculture), medicine, LAOS, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, Gastrointestinal diseases, 0105 earth and related environmental sciences, Hydrology, Multidisciplinary, Bacteria, Environmental microbiology, Biogeochemistry, 15. Life on land, Seasonality, Contamination, medicine.disease, [SDV.MP.BAC]Life Sciences [q-bio]/Microbiology and Parasitology/Bacteriology, 6. Clean water, 020801 environmental engineering, Environmental sciences, Fecal coliform, Environmental science, Medicine, Pathogens, Surface water
Abstract

In the basin of Mekong, over 70 million people rely on unimproved surface water for their domestic requirements. Surface water is often contaminated with fecal matter and yet little information exists on the underlying mechanisms of fecal contamination in tropical conditions at large watershed scales. Our objectives were to (1) investigate the seasonality of fecal contamination using Escherichia coli as fecal indicator bacteria (FIB), and (2) establish links between the fecal contamination in stream water and its controlling factors (hydrology and land use). We present the results of (1) a sampling campaign at the outlet of 19 catchments across Lao PDR, in both the dry and the rainy seasons of 2016, and (2) a 10-day interval monitoring conducted in 2017 and 2018 at three point locations of three rivers (Nam Ou, Nam Suang, and Mekong) in northern Lao PDR. Our results show the presence of fecal contamination at most of the sampled sites, with a seasonality characterized by higher and extreme E. coli concentrations occurring during the rainy season. The highest E. coli concentrations, strongly correlated with total suspended sediment concentrations, were measured in catchments dominated by unstocked forest areas, especially in mountainous northern Lao PDR and in Vientiane province.

Published
2021

13. Ho Chi Minh Ville, des inondations à la submersion…

Author

Nicolas Gratiot, Georges Vachaud, and Tien Dung Tran Ngoc

Subjects
méga cité, changement climatique, urbanisation, Vietnam, lcsh:G1-922, General Medicine, inondation, lcsh:Geography (General), subsidence
Abstract

La plus grande partie des mega cites du Sud Est Asiatique situees en bordure littorale sont sujettes d’une part a une tres forte croissance demographique, d’autre part a un accroissement des risques d’inondations resultant d’une conjonction entre developpement urbain mal maitrise, augmentation de l’intensite des pluies de mousson, elevation du niveau oceanique et affaissement du niveau du sol (subsidence). Ho Chi Minh Ville est un exemple typique de cette situation qui peut conduire a moyen-court terme a la submersion de la majorite des quartiers recents construits sur d’anciennes zones de marais ou de riziere. Il est donc essentiel de mettre en œuvre des strategies de gestion des risques adaptees et de developper le territoire de maniere durable

Published
2021

14. Biogeochemical functioning of an urbanized tropical estuary: Implementing the generic C-GEM (reactive transport) model

Author

Thanh-Son Dao, Julien Némery, Josette Garnier, Nicolas Gratiot, Vincent Thieu, Goulven Gildas Laruelle, and An Truong Nguyen

Subjects
Biogeochemical cycle, Environmental Engineering, 010504 meteorology & atmospheric sciences, 010501 environmental sciences, 01 natural sciences, Environnement et pollution, Dry season, Phytoplankton, Saigon River Estuary, Environmental Chemistry, Ecosystem, Waste Management and Disposal, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Ho Chi Minh megacity, Self-purification, Sediment, Hypoxia (environmental), Estuary, Pollution, Technologie de l'environnement, contrôle de la pollution, Oceanography, Vietnam, Environmental science, Traitement des déchets, Water quality, Biogeochemical modelling
Abstract

Estuaries are amongst the most productive ecosystems of the land ocean continuum, but they are also under high anthropic pressures due to coastal urbanization. Too sparse observations have hindered the understanding of complex interactions between water quality and estuarine hydrodynamics and biogeochemical transformations. Until now, estuarine modelling studies have mainly focused on temperate estuarine systems in industrialized countries. This study investigates the responses of a tropical estuary to pollution load from a megacity (Ho Chi Minh City, Southern Vietnam) by applying a one-dimensional, biogeochemical estuarine model (C-GEM). The Saigon River Estuary flows through the megacity of Ho Chi Minh (HCMC) and is subject to episodic hypoxia events due to wastewater inputs from urban discharges. Good agreements are found between simulation outputs and observations for tidal propagation, salinity, total suspended sediment, and water quality variables in dry season in Saigon River Estuary. C-GEM reproduces the increases in ammonium, total organic carbon, phytoplankton and dissolved oxygen depletion in the urban section of the Saigon River as an impact of untreated wastewaters from HCMC. The steady-state version of C-GEM also reveals the formation of a pollutant cloud (30-km stretch) resulting from the combined effects of tidal fluctuation and low flushing capacity during the dry season. Furthermore, the quantification of the reaction fluxes simulated by the model demonstrates that nitrification is the main process removing NH4+ from the Saigon River. For the first time in such a type of environment, our study demonstrates the effectiveness of C-GEM at unraveling the complex interplay between biogeochemical reactions and transport in a tropical estuary with a minimized data requirement. This is significant for tropical estuaries in developing countries, where intensive monitoring programs are rare and have thus been rarely the object of modelling investigations., SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2021

15. Flood-related risks in Ho Chi Minh City and ways of mitigation

Author

Fanny Quertamp, Anh Le Tuan Nguyen, Nicolas Gratiot, Tien Dung Tran Ngoc, Thong Nguyen, Thi San Ha Phan, Georges Vachaud, Xuan Loc Luu, Institut des Géosciences de l’Environnement (IGE), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut de Recherche pour le Développement (IRD)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Ho Chi Minh City University of Technology (HCMUT), and Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])

Subjects
Upstream (petroleum industry), education.field_of_study, 010504 meteorology & atmospheric sciences, Flood myth, Flooding (psychology), Population, 0207 environmental engineering, 02 engineering and technology, 01 natural sciences, 6. Clean water, Dam failure, Geography, Megacity, [SDU]Sciences of the Universe [physics], 13. Climate action, Urban planning, Redevelopment, 11. Sustainability, 020701 environmental engineering, education, Environmental planning, 0105 earth and related environmental sciences, Water Science and Technology
Abstract

International audience; With an ever-growing population of around 10 million inhabitants (officially 7.9 in 2013), Ho Chi Minh City (HCMC) is set to become one of the largest cities in South East Asia and already occupies a major economic role in the area. To accommodate the increasing population, the megacity now stretches out in an urban continuum covering more than 800 square kilometers and is currently growing at a rate of 3.2% per year. If the neighboring provinces around HCMC are included, the total population reaches nearly 18 million people.This paper attempts to describe the interplay between HCMC and flood-related risks and offer some guidelines to deal with inundations. The potential risks of flooding by rain, tsunami and/or dam failure upstream of the city are evaluated and contextualized within the perspective of climate and human-induced environmental changes. The region is highly vulnerable to the combined effects of subsidence and rising sea levels and has already led to serious flooding that may extend spatially before the end of the century. We propose possible preventative solutions to urban flooding using a multi-pronged approach to issues regarding urban development and suggest a redevelopment strategy for major infrastructure projects.

Published
2019

16. Does eutrophication enhance greenhouse gas emissions in urbanized tropical estuaries?

Author

An Truong Nguyen, Julien Némery, Nicolas Gratiot, Thanh-Son Dao, Tam Thi Minh Le, Christine Baduel, and Josette Garnier

Subjects
Greenhouse Gases, Health, Toxicology and Mutagenesis, Nitrous Oxide, General Medicine, Carbon Dioxide, Eutrophication, Estuaries, Toxicology, Methane, Pollution, Environmental Monitoring
Abstract

Estuaries are considered as important sources of the global emission of greenhouse gases (GHGs). Urbanized estuaries often experience eutrophication under strong anthropogenic activities. Eutrophication can enhance phytoplankton abundance, leading to carbon dioxide (CO

Published
2022

17. Phytoplankton characterization in a tropical tidal river impacted by a megacity: the case of the Saigon River (Southern Vietnam)

Author

Emilie Strady, Joanne Aimé, Tuyet Thi Nguyen, An Truong Nguyen, Nicolas Gratiot, Thanh-Son Dao, Julien Némery, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Ho Chi Minh City University of Technology (HCMUT), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), and Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Toulon (UTLN)

Subjects
0106 biological sciences, Wet season, 010504 meteorology & atmospheric sciences, Dominant species, Health, Toxicology and Mutagenesis, Context (language use), 010501 environmental sciences, Cyanobacteria, 01 natural sciences, Trace metals, Rivers, Phytoplankton, Dry season, Microalgae, Environmental Chemistry, Dominance (ecology), Tidal river, Cities, 0105 earth and related environmental sciences, Hydrology, geography, Brackish water, 010604 marine biology & hydrobiology, Urbanization, General Medicine, 15. Life on land, Eutrophication, Pollution, 6. Clean water, geography.body_of_water, Vietnam, 13. Climate action, Environmental science, Seasons, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Environmental Monitoring
Abstract

The spatiotemporal variation of phytoplankton and their relationship with environmental variables were analysed in the Saigon River – a tropical river in Southern Vietnam. Two longitudinal profiles were conducted during dry and rainy season at 18 sampling sites covering more than 60 km long in the river. Besides, a bi-weekly monitoring conducted upstream, urban area (Ho Chi Minh City - HCMC) and downstream of Saigon River was organized from December 2016 to November 2017. The major phytoplankton were diatoms (e.g. Cyclotella cf. meneghiniana, Leptocylindrus danicus, Aulacoseira granulata), cyanobacteria (Microcystis spp., Raphidiopsis raciborskii, Pseudanabaena sp) and euglenoids (Trachelomonas volvocina). Commonly freshwater phytoplankton species and sometimes brackish water species were dominant during the monitoring. Phytoplankton abundances in dry season were much higher than in rainy season (> 100 times) which was explained by a shorter riverine water residence time and higher flushing capacity during the dry season. There was a clear separation of phytoplankton abundance between the urban area and the remaining area of Saigon River because of polluted urban emissions of HCMC. Redundancy analysis shows that the environmental variables (TOC, Nitrogen, pH, salinity, Mo, Mn) were the driving factors related to the dominance of L. danicus and Cyclotella cf. meneghiniana in the upstream river and urban section of Saigon River. The dominance of cyanobacterium Microcystis spp in the downstream of Saigon River was related to higher salinity, Mg, Cu concentrations and lower concentrations of nutrients, Mn, Co, Mo. The dominance of potentially toxic cyanobacteria in Saigon River possess health risk to local residents especially upon the increasing temperature context and nutrient loading into the river in the next decades.

Published
2021

18. Monitoring discharge in a tidal river using water level observations: Application to the Saigon River, Vietnam

Author

An Truong Nguyen, F. Gard, J.-A. Cohard, Guillaume Dramais, Viet Quoc Tran, Julien Némery, Benoît Camenen, Nicolas Gratiot, T H M van Emmerik, Riverly (Riverly), Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Vietnam National University - Ho Chi Minh City (VNU-HCM), Institut de Recherche pour le Développement (IRD), Wageningen University and Research [Wageningen] (WUR), Rhone-Alpes region through the CMIRA Coopera, and RiverLy - Fonctionnement des hydrosystèmes (RiverLy)

Subjects
Environmental Engineering, 010504 meteorology & atmospheric sciences, tidal river, Rating curve, 010501 environmental sciences, Hydrology and Quantitative Water Management, 01 natural sciences, Flood, Water discharge, Complex response, Environmental Chemistry, Tidal river, Precipitation, Saigon River, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Waste Management and Disposal, water discharge, 0105 earth and related environmental sciences, Hydrology, Stage-fall-discharge rating curve, geography, geography.geographical_feature_category, WIMEK, Discharge, water level, Estuary, flood, Water level, Pollution, 6. Clean water, geography.body_of_water, Environmental science, stage-fall-discharge rating curve, Groundwater, Hydrologie en Kwantitatief Waterbeheer
Abstract

International audience; The hydrological dynamics of the Saigon River is ruled by a complex combination of factors, which need to be disentangled to prevent and limit risks of flooding and salt intrusion. In particular, the Saigon water discharge is highly influenced by tidal cycles with a relatively low net discharge. This study proposes a low-cost technique to estimate river discharge at high frequency (every 10 min in this study). It is based on a stage-fall-discharge (SFD) rating curve adapted from the general Manning Strickler law, and calibrated thanks to two ADCP campaigns. Two pressure sensors were placed at different locations of the river in September 2016: one at the centre of Ho Chi Minh City and one in Phu Cuong, 40 km upstream approximately. The instantaneous water discharge data were used to evaluate the net residual discharge and to highlight seasonal and inter-annual trends. Both water level and water discharge show a seasonal behaviour. Rainfall, including during the Usagi typhoon that hit the megalopolis in November 2018, has no clear and direct impact on water level and water discharge due to the delta flat morphology and complex response between main channel and side channel network and ground water in this estuarine system under tidal influence. However, we found some evidences of interactions between precipitation, groundwater, the river network and possibly coastal waters. This paper can be seen as a proof of concept to (1) present a low-cost discharge method that can be applied to other tidal rivers, and (2) demonstrate how the high-frequency discharge data obtained with this method can be used to evaluate discharge dynamics in tidal river systems.

Published
2021

19. What Is the Future of the Lower Mekong Basin Struggling against Human Activities? A Review

Author

Vo Le Phu, Mathieu Le Meur, and Nicolas Gratiot

Subjects
010504 meteorology & atmospheric sciences, 0208 environmental biotechnology, InformationSystems_INFORMATIONSTORAGEANDRETRIEVAL, Mekong river, Environmental science, 02 engineering and technology, Water resource management, 01 natural sciences, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), 020801 environmental engineering, 0105 earth and related environmental sciences
Abstract

The Mekong River (MR) is recognized the 12th biggest rivers in the world. The Mekong watershed is the biggest one in Southeast Asia (795,000 km2), is densely populated (70 million people), is considered as the most productive one in Southeast Asia and is economically essential to the region. However, nowadays, the Lower Mekong River (LMR) and its delta are facing several emerging and critical anthropogenic stressors (dams construction, climate change, water poor quality, delta sinking). This review attempts to: (i) present the Mekong regional characteristics (geography, topological settings, climatic conditions, hydrology, demographic features and the anthropogenic activities), (ii) present the different factors that endanger the LMR, including the dam’s impacts, the climate change, the delta subsidence, and the degradation of the water quality, (iii) make comparison with different big rivers around the world and (iv) promote future decisions in order to minimize the negative impacts and seek for a trajectory that assures well-being and sustainability. International consultation and cooperation leading to sustainable management is now of a pivotal importance to try to avoid the deterioration of the LMR and its delta.

Published
2021

20. Sedimentological and geochemical data in bed sediments from a tropical river-estuary system impacted by a developing megacity, Ho Chi Minh City - Vietnam

Author

Phuoc Dan Nguyen, David Noncent, Marc Desmet, Marc Babut, Thi Ngoc Tuyet Nguyen, Anh Tu Tran, Nguyen Thanh-Nho, Julien Némery, Hervé Denis, Truong An Nguyen, Quoc Tuc Dinh, Cyril Marchand, Nicolas Gratiot, Brice Mourier, Emilie Strady, Joanne Aimé, Université Quisqueya, Ho Chi Minh City University of Technology (HCMUT), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Toulon (UTLN), Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Nguyen Tat Thanh University [Vietnam] (NTTU), Laboratoire de Gestion du Risque En Sciences de l'Environnement (GRESE), Ecole Nationale du Génie Rural, des Eaux et des Forêts (ENGREF), Riverly (Riverly), Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC), Muséum national d'Histoire naturelle (MNHN)-Institut de recherche pour le développement [IRD] : UR206-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), GéoHydrosystèmes COntinentaux (GéHCO EA6293), Université de Tours, Faculty of Geology and Petroleum Engineering [Ho Chi Minh City] (GEOPET), VNU: B2016-20-05, Auvergne-Rhone-Alpes Region, through the CMIRA-Coopera program, French Research Institute for Sustainable Development IRD, Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), RiverLy - Fonctionnement des hydrosystèmes (RiverLy), Université de Tours (UT), Institut de sciences exactes et appliquées (ISEA), and Université de la Nouvelle-Calédonie (UNC)

Subjects
Nitrogen, [SDV]Life Sciences [q-bio], [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, chemistry.chemical_element, Silt, Grain size distribution, lcsh:Computer applications to medicine. Medical informatics, 03 medical and health sciences, 0302 clinical medicine, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Organic matter, Trace metal, lcsh:Science (General), ComputingMilieux_MISCELLANEOUS, 030304 developmental biology, chemistry.chemical_classification, 0303 health sciences, geography, Multidisciplinary, geography.geographical_feature_category, Phosphorus, Sediment, Estuary, Particulates, I-geo, Enrichment factor, 6. Clean water, Carbon, chemistry, 13. Climate action, Environmental chemistry, Environmental Science, [SDE]Environmental Sciences, Environmental science, lcsh:R858-859.7, 030217 neurology & neurosurgery, lcsh:Q1-390
Abstract

International audience; Sedimentological and geochemical data were obtained for bed sediments from a tropical estuary environment in Vietnam in October 2014, January 2016, and November 2016. The data include grain-size distribution, percentage of clay, silt and sand, percentage of organic matter, concentration of total particulate phosphorus (TPP), concentration of particulate inorganic phosphorus (PIP), concentration of particulate organic phosphorus (POP), percentage of total nitrogen (TN), percentage of total carbon (TC), trace metals concentrations (V, Cr, Co, Ni, Cu, Zn, As, Mo, Cd, Pb) and major elements (Al, Fe, Mn). Geochemical indexes (Enrichment factor EF and Geo-accumulation Index I-geo) and sediment quality guideline (mean Effect Range Median quotients) were calculated.

Published
2020

21. An implicit wetting–drying algorithm for the discontinuous Galerkin method: application to the Tonle Sap, Mekong River Basin

Author

Hoang Anh Le, Sandra Soares-Frazão, Jonathan Lambrechts, Nicolas Gratiot, Eric Deleersnijder, Sigrun Ortleb, UCL - SST/IMMC/GCE - Civil and environmental engineering, and UCL - SST/IMMC/MEMA - Applied mechanics and mathematics

Subjects
Mekong, Hydrogeology, 0208 environmental biotechnology, Wetting-drying, Front (oceanography), 02 engineering and technology, Structural basin, 01 natural sciences, Finite element method, 010305 fluids & plasmas, 020801 environmental engineering, Water level, Numerical model, DG-FEM, Discontinuous Galerkin method, 0103 physical sciences, Tonle Sap lake, Environmental Chemistry, Wetting–drying, Algorithm, Conservation of mass, Shallow water equations, Geology, SLIM, Water Science and Technology
Abstract

The accurate simulation of wetting–drying processes in floodplains and coastal zones is a challenge for hydrodynamic modelling, especially for long time simulations. Indeed, dedicated numerical procedures are generally time-consuming, instabilities can occur at the wet/dry front, rapid transition of wet/dry interface and mass conservation are not always ensured.We present the extension of an existing wetting–drying algorithm in two space dimensions and its application to a real case. The wetting–drying algorithm is implemented in Second-generation Louvain-la-Neuve Ice-ocean Model (www.slim-ocean.be), a discontinuous Galerkin finite element model solving the shallow water equations in a fully implicit way. This algorithm consists in applying a threshold value of fluid depth for a thin layer and a blending parameter in order to guarantee positive values of the water depth, while preserving local mass conservation and the well balanced property at wet/dry interfaces.The technique is first validated against standard analytical test cases (Balzano 1, Balzano 3 and Thacker test cases) and is subsquently applied in a realistic domain, the Tonle Sap Lake in the Mekong River Basin, where the water level can vary by about 10 m between the dry and the wet season.

Published
2020

22. Suspended sediment properties in the Lower Mekong River, from fluvial to estuarine environments

Author

Xavier Mériaux, Olivier Ribolzi, Hoang Anh Le, Eric Deleersnijder, Sandra Soares-Frazão, Nicolas Gratiot, William Santini, Duc Tran, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Nord]), Université du Littoral Côte d'Opale (ULCO), UCL - SST/IMMC/GCE - Civil and environmental engineering, UCL - SST/IMMC/MEMA - Applied mechanics and mathematics, Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), and Centre National de la Recherche Scientifique (CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Institut national des sciences de l'Univers (INSU - CNRS)

Subjects
0106 biological sciences, 010504 meteorology & atmospheric sciences, SCAF, Fluvial, Aquatic Science, Oceanography, 01 natural sciences, LISST, Settling, 0105 earth and related environmental sciences, Settling velocity, Hydrology, Sand mining, Mekong, geography, geography.geographical_feature_category, 010604 marine biology & hydrobiology, Sediment, Flocculation, Estuary, 15. Life on land, Sedimentation, 6. Clean water, Siltation, 13. Climate action, [SDE]Environmental Sciences, Erosion, Fluid mud layer, Environmental science
Abstract

The Mekong river is one of the largest rivers in the world, which flows through six countries of Southeast Asia (China, Myanmar, Laos, Thailand, Cambodia and Vietnam). Its hydro-sedimentary regime is changing rapidly, as a consequence of a regional shift of land use (agriculture, road, etc.), damming, sand mining and climate changes, among others. This study assesses the behavior of particles transported in suspension in the Lower Mekong River (LMR), along approximately 1700 km from fluvial to estuarine environments. Suspended sediment properties were estimated, simultaneously with hydrodynamic conditions, during three field campaigns. In addition, further investigations were performed in the laboratory to assess the structures of particles (flocculated or not), their capacity to flocculate (and the impacts on siltation), under a wide range of sediment concentration (20–30,000 mg.L−1). This study confirms that suspended sediment transported in the LMR are predominantly (75% by volume) flocculi (or freshly eroded soils aggregates), with median aggregated particle size in the range 10–20 μm and median settling velocity of the order of 0.01–0.1 mm s−1. These flocculi are robust under the hydrodynamic conditions (turbulence and suspended sediment concentration – SSC) existing in the LMR. Laboratory investigations reveal the existence of a threshold sediment concentration (400 mg.L−1), beyond which flocculation and sedimentation increase of orders of magnitudes. Thus, concentration that exceeds this threshold might promote the formation of so-called fluid mud layers. Because of the nonlinear response of flocculation and sedimentation with SSC and considering the ongoing changes at a regional scale in the LMR, higher occurrence of fluid mud layers in the fluvial upstream waterbodies might be anticipated, and a lower occurrence in estuaries and alongshore where the concentration decrease. The geomorphology could be impacted, with an over-siltation in dams and an exacerbated erosion of the muddy-mangrove coast.

Published
2020

23. Nutrient budgets in the Saigon-Dongnai River basin: Past to future inputs from the developing Ho Chi Minh megacity (Vietnam)

Author

Son Tung Cao, Trang P.T. Huynh, Nicolas Gratiot, Emilie Strady, Tuyet Thi Nguyen, Josette Garnier, Viet Quoc Tran, Julien Némery, An Truong Nguyen, Dan P. Nguyen, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Centre Asiatique de Recherche sur l'Eau CARE-HCMUT, Vietnam, HCMUT, Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols (METIS), Université Pierre et Marie Curie - Paris 6 (UPMC)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Toulon (UTLN), Ho Chi Minh City University of Technology (HCMUT), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), and Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE)

Subjects
0106 biological sciences, Dissolved silica, 0208 environmental biotechnology, Drainage basin, Context (language use), 02 engineering and technology, 01 natural sciences, 12. Responsible consumption, Nutrient, 11. Sustainability, Environmental Chemistry, ComputingMilieux_MISCELLANEOUS, General Environmental Science, Water Science and Technology, Hydrology, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, geography, geography.geographical_feature_category, 010604 marine biology & hydrobiology, Aquatic ecosystem, Sediment, Estuary, 6. Clean water, 020801 environmental engineering, 13. Climate action, [SDE]Environmental Sciences, Environmental science, Eutrophication
Abstract

International audience; Ho Chi Minh City (HCMC, Vietnam) is one of the fastest growing megacities in the world. In this paper, we attempt to analyse the dynamics of nutrients, suspended sediments , and water discharges in its aquatic systems today and in the future. The work is based on nine sampling sites along the Saigon River and one on the Dongnai River to identify the reference water status upstream from the urban area and the increase in fluxes that occur within the city and its surroundings. For the first time, the calculated fluxes allow drawing up sediment and nutrient budgets at the basin scale and the quantification of total nutrient loading to the estuarine and coastal zones (2012-2016 period). Based on both national Vietnamese and supplementary monitoring programs, we estimated the water, total suspended sediment, and nutrients (Total N, Total P, and dissolved silica: DSi) fluxes at 137 m 3 year −1 , tonSS year −1 , 5,323 tonN year −1 , 450 tonP year −1 , and m 3 year −1 for the Saigon River and 1,693 year −1 , 3,292 2,734 1,175 × 10 3 tonSi × 10 3 tonSS year −1 , 31,030 tonN year −1 , 1,653 tonP year −1 , and 31,138 tonSi year −1 for the Dongnai River, respectively. Nutrient fluxes provide an indicator of coastal eutrophication potential (indicator of coastal eutrophication potential), using nutrient stoichiometry ratios. Despite an excess of nitrogen and phosphorus over silica, estuarine waters downstream of the megacity are not heavily impacted by HCMC. Finally, we analysed scenarios of future trends (2025-2050) for the nutrient inputs on the basis of expected population growth in H C M C and improvement of wastewater treatment capacity. We observed that without the construction of a large number of additional wastewater treatment plants, the eutrophication problem is likely to worsen. The results are discussed in the context of the wastewater management policy.

Published
2020

24. Sediment flocculation in the Mekong River estuary, Vietnam, an important driver of geomorphological changes

Author

Tran Tuan Anh, Heiko Thoss, Audrey Bildstein, Heiko Apel, Nicolas Gratiot, Hervé Michallet, Hervé Denis, Centre Asiatique de Recherche sur l'Eau CARE-HCMUT, Vietnam, Université Paris Diderot - Paris 7 (UPD7), Laboratoire des Écoulements Géophysiques et Industriels [Grenoble] (LEGI ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Manighetti, I (ed.), De Witt, R. (ed.), Duvail, Stéphanie (ed.), and Seyler, Patrick (ed.)

Subjects
0106 biological sciences, Flocculation, 010504 meteorology & atmospheric sciences, Particle (ecology), Coastal erosion, 01 natural sciences, Settling, [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], 14. Life underwater, Mekong estuary, ComputingMilieux_MISCELLANEOUS, Settling velocity, 0105 earth and related environmental sciences, Hydrology, Global and Planetary Change, geography, geography.geographical_feature_category, 010604 marine biology & hydrobiology, Sediment, Estuary, Particle size, Siltation, Floc, 13. Climate action, General Earth and Planetary Sciences, Environmental science, Mangrove
Abstract

Over the past several decades, major hydro-sedimentary changes have occurred in both continental and coastal regions of the Mekong Delta, and this has severely impacted coastal erosion. A good characterization of floc properties and of their changes over time is necessary to gain comprehensive understanding and modelling of hydrodynamics and of the associated geomorphological changes. This paper quantifies the influence of sediment concentration, turbulence and differential particle settling on flocculation through field and laboratory investigations of the Mekong estuary. For concentrations lower than 200 mg·L −1 , the particles do not exhibit a dynamic response to their environment, while for higher concentrations (up to 3–4 g·L −1 ), particle size and settling velocity increased by more than one order of magnitude. Flocculation by differential settling has not been sufficiently investigated yet, but this study reveals it as a predominant factor for siltation in quiescent environments such as the ones existing in the inner mangrove fringe. Such results are important to provide realistic simulations of the coastal evolution.

Published
2017

25. Développement d’un système de caractérisation des agrégats et flocs (SCAF)

Author

Valentin Wendling, Cédric Legout, Nicolas Gratiot, Catherine Coulaud, and Bernard Mercier

Subjects
Engineering (miscellaneous), Instrumentation
Abstract

L'etude du transport des matieres en suspension dans les cours d'eau pour en determiner les impacts revet un interet grandissant. Il n'existe cependant pas d'instrument capable d'effectuer des mesures de vitesse de sedimentation en temps reel et pour des regimes tres concentres, a fortiori en situation de crue. Pour repondre a ce besoin, un Systeme de Caracterisation des Agregats et Flocs (SCAF) a ete developpe. L'appareil a ete concu pour s'integrer dans un preleveur automatique, d'usage courant en hydrologie. L'une des difficultes principales a consiste a integrer l'electronique de mesure aux flacons des preleveurs automatiques. Lors de ses evaluations, le SCAF a permis des mesures dans des gammes de concentrations allant jusqu'a plusieurs dizaines de g/l, valeurs courantes pour des cours d'eau de montagne. Outre la determination des vitesses de depot, la methode de traitement des donnees permet de calculer un "indice de floculation" caracterisant l'aptitude des particules a s'agglomerer.

Published
2016

26. Mangroves and shoreline erosion in the Mekong River delta, Viet Nam

Author

Frédéric Bouchette, Patrick Marchesiello, Edward J. Anthony, Nicolas Gratiot, Marc Goichot, Manon Besset, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA), Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Université des Antilles (UA)-Centre National de la Recherche Scientifique (CNRS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), Echanges Côte-Large (ECOLA), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)

Subjects
0106 biological sciences, Delta, 010504 meteorology & atmospheric sciences, [SDE.MCG]Environmental Sciences/Global Changes, Aquatic Science, Oceanography, 01 natural sciences, Mekong river, Mangroves, 14. Life underwater, Transect, 0105 earth and related environmental sciences, Shore, geography, geography.geographical_feature_category, Sediment supply, 010604 marine biology & hydrobiology, Viet nam, Coastal squeeze, 15. Life on land, Coastal erosion, Shoreline erosion, 13. Climate action, Mangrove, Mekong river delta, Geology, Accretion (coastal management)
Abstract

International audience; The question of the rampant erosion of the shorelines rimming the Mekong River delta has assumed increasing importance over the last few years. Among issues pertinent to this question is how it is related to mangroves. Using high-resolution satellite images, we compared the width of the mangrove belt fringing the shoreline in 2012 to shoreline change (advance, retreat) between 2003 and 2012 for 3687 cross-shore transects, spaced 100 m apart, and thus covering nearly 370 km of delta shoreline bearing mangroves. The results show no significant relationships. We infer from this that, once erosion sets in following sustained deficient mud supply to the coast, the rate of shoreline change is independent of the width of the mangrove belt. Numerous studies have shown that: (1) mangroves promote coastal accretion where fine-grained sediment supply is adequate, (2) a large and healthy belt of fringing mangroves can efficiently protect a shoreline by inducing more efficient dissipation of wave energy than a narrower fringe, and (3) mangrove removal contributes to the aggravation of ongoing shoreline erosion. We fully concur, but draw attention to the fact that mangroves cannot accomplish their land-building and coastal protection roles under conditions of a failing sediment supply and prevailing erosion. Ignoring these overarching conditions implies that high expectations from mangroves in protecting and/or stabilizing the Mekong delta shoreline, and eroding shorelines elsewhere, will meet with disappointment. Among these false expectations are: (1) a large and healthy mangrove fringe is sufficient to stabilize the (eroding) shoreline, (2) a reduction in the width of a large mangrove fringe to the benefit of other activities, such as shrimp-farming, is not deleterious to the shoreline position, and (3) the effects of human-induced reductions in sediment supply to the coast can be offset by a large belt of fringing mangroves.

Published
2019

27. Seasonality of riverine macroplastic transport

Author

Emilie Strady, Thuy Chung Kieu-Le, Luan Nguyen, Nicolas Gratiot, Tim van Emmerik, Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Ho Chi Minh City University of Technology (HCMUT), Centre Asiatique de Recherche sur l'Eau CARE-HCMUT, Vietnam, HCMUT, Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Toulon (UTLN), and Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut de Recherche pour le Développement (IRD)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])

Subjects
010504 meteorology & atmospheric sciences, lcsh:Medicine, 010501 environmental sciences, Hydrology and Quantitative Water Management, 01 natural sciences, Article, Environmental impact, medicine, Life Science, Ecosystem, 14. Life underwater, lcsh:Science, 0105 earth and related environmental sciences, Hydrology, Multidisciplinary, WIMEK, Discharge, lcsh:R, Seasonality, medicine.disease, Debris, Environmental sciences, 13. Climate action, [SDE]Environmental Sciences, Environmental science, lcsh:Q, Plastic pollution, Hydrologie en Kwantitatief Waterbeheer
Abstract

Marine plastic pollution is an increasing environmental threat. Although it is assumed that most marine plastics are transported from land to the ocean through rivers, only limited data on riverine plastic transport exists. Recently, new methods have been introduced to characterize riverine plastics consistently through time and space. For example, combining visual counting observations and plastic debris sampling can provide order of magnitude estimations of plastic transport through a river. In this paper, we present findings from multi-season measurement campaign in the Saigon River, Vietnam. For the first time, we demonstrate that macroplastic transport exhibits strong temporal variation. The monthly averaged plastic transport changes up to a factor five within the measurement period. As it is unclear what drives the variation in plastic transport, relations between rainfall, river discharge, presence of organic material and plastic transport have been explored. Furthermore, we present new findings on the cross-sectional and vertical distribution of riverine plastic transport. With this paper we present new insights in the origin and fate of riverine plastic transport, emphasizing the severity of the emerging thread of plastic pollution on riverine ecosystems.

Published
2019

28. Exceptional rates and mechanisms of muddy shoreline retreat following mangrove removal

Author

Antoine Gardel, Edward J. Anthony, Guillaume Brunier, Nicolas Gratiot, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratoire Ecologie, Evolution, Interactions des Systèmes amazoniens (LEEISA), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Guyane (UG)-Centre National de la Recherche Scientifique (CNRS), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), and Université Grenoble Alpes (UGA)

Subjects
010504 meteorology & atmospheric sciences, Geography, Planning and Development, Wetland, 010502 geochemistry & geophysics, 01 natural sciences, Mangrove protection, cheniers, Earth and Planetary Sciences (miscellaneous), 14. Life underwater, Amazon-influenced muddy coast, 0105 earth and related environmental sciences, Earth-Surface Processes, coastal erosion, Shore, geography, geography.geographical_feature_category, 15. Life on land, Coastal erosion, Chenier, Oceanography, 13. Climate action, [SDE]Environmental Sciences, mud banks, Progradation, Mangrove, Beach morphodynamics, Geology, Accretion (coastal management), mangrove removal
Abstract

Probably the largest regular shoreline fluctuations on Earth occur along the 1500 km-long wave-exposed Guianas coast of South America between the mouths of the Amazon and Orinoco Rivers, the world's longest muddy coast. The Guianas coast is influenced by a succession of mud banks migrating northwestward from the Amazon. Migrating mud banks dissipate waves, partially weld onshore, and lead to coastal progradation, aided by large-scale colonization by mangroves, whereas mangrove-colonized areas between banks (inter-bank areas) are exposed to strong wave action and undergo erosion. On large tracts of this coast, urbanization and farming have led to fragmentation and removal of mangroves, resulting in aggravated shoreline retreat. To highlight this situation, we determined, in a setting where mangroves and backshore freshwater marshes have been converted into rice polders in French Guiana, shoreline change over 38 years (1976-2014) from satellite images and aerial orthophotographs. We also conducted four field experiments between October 2013 and October 2014, comprising topographic and hydrodynamic measurements, to determine mechanisms of retreat. The polder showed persistent retreat, at peak rates of up to -200 m/yr, and no recovery over the 38-year period of monitored change. Notwithstanding high erosion rates, mangrove shorelines show strong resilience, with recovery characterized by massive accretion. Retreat of the polder results in a steep wave-reworked shoreface with a lowered capacity for bank welding onshore and mangrove establishment. Persistent polder erosion is accompanied by the formation of a sandy chenier that retreats landwards at rates largely exceeding those in inter-bank situations. These results show that anthropogenic mangrove removal can durably modify the morphodynamics of muddy shorefaces. This limits the capacity for shoreline recovery and mangrove re-establishment even when there is no sustained long-term deficit in mud supply, as in the case of the Amazon-influenced Guianas coast. (c) 2019 John Wiley & Sons, Ltd.

Published
2019

29. Nutrient dynamics and eutrophication assessment in the tropical river system of Saigon – Dongnai (southern Vietnam)

Author

Viet Quoc Tran, An Truong Nguyen, Tuyet Thi Nguyen, Joanne Aimé, Julien Némery, Alice Peyne, Nicolas Gratiot, Emilie Strady, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), Centre Asiatique de Recherche sur l'Eau CARE-HCMUT, Vietnam, HCMUT, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut de Recherche pour le Développement (IRD)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), and Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Toulon (UTLN)

Subjects
Silicon, Environmental Engineering, 010504 meteorology & atmospheric sciences, Nitrogen, 010501 environmental sciences, 01 natural sciences, Megacity, Nutrient, Rivers, Water Quality, 11. Sustainability, Dry season, Tributary, Environmental Chemistry, Tidal river, 14. Life underwater, Cities, Waste Management and Disposal, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Total organic carbon, Hydrology, Tropical Climate, geography, geography.geographical_feature_category, Phosphorus, Estuary, Nutrients, Eutrophication, 15. Life on land, Pollution, 6. Clean water, Water quality, geography.body_of_water, Vietnam, 13. Climate action, [SDE]Environmental Sciences, Environmental science, Seasons, Water Pollutants, Chemical, Environmental Monitoring
Abstract

Saigon-Dongnai Rivers in Southern Vietnam is a complex lowland hydrological network of tributaries that is strongly influenced by the tidal cycles. The increasing economic, industrial and domestic developments in and around Ho ChiMinh City (HCMC) have led to serious impacts on water quality due to lack of appropriate wastewaters treatment. Drinkingwater production is impacted and the large aquaculture production areas may also be affected. We analyzed spatial and seasonal variability of nutrient concentrations (Phosphorus, Nitrogen and Silica) and eutrophication indicators (Organic Carbon, Chlorophyll-a and Dissolved Oxygen) based on bi-monthly monitoring during two hydrological cycles (July 2015-December 2017). Four monitoring sites were selected to assess the impact of HCMC: two upstream stations on the Saigon River and Dongnai River branches to provide the reference water quality status before reaching the urbanized area of HCMC; one monitoring station in the city center to highlight Saigon River water quality within the heart of the megacity; the fourth station downstream of the confluence to evaluate the impact of HCMC on the estuarine waters. This study points to excess nutrients in HCMC's water body with concentrations of NH4+ and PO43- averaging to 0.7 +/- 0.6 mgN L-1 and 0.07 +/- 0.06 mgP L-1, respectively in mean over the monitored period and rising up to 3 mgN L-1 and 0.2 mgP L-1, in extreme conditions. During the dry season, we evidenced that untreated domestic discharges leads to degradation of the Saigon River's water quality with extreme values of algal biomass (up 150 mu Chl-a L-1) and hypoxic conditions occurring episodically (DO < 2 mg L`(-1)) in the heart of the megacity. Until now, eutrophication in the urban center has had no clear effect downstream because eutrophicwater mass from the Saigon River is efficiently mixed with the Dongnai River and sea water masses during the successive semi-diurnal tidal cycles.

Published
2019

30. Where has the pollution gone? A survey of organic contaminants in Ho Chi Minh city / Saigon River (Vietnam) bed sediments

Author

Pierre Labadie, Tran Anh Tu, Caroline Simonnet-Laprade, Marc Babut, Brice Mourier, Nicolas Gratiot, Marc Desmet, Hélène Budzinski, Emilie Strady, Luiz Felippe De Alencastro, RiverLy (UR Riverly), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés (LEHNA), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État (ENTPE)-Centre National de la Recherche Scientifique (CNRS), GéoHydrosystèmes COntinentaux (GéHCO EA6293), Université de Tours, Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Ecole Polytechnique Fédérale de Lausanne (EPFL), Ho Chi Minh City University of Science (HCMUS), Centre Asiatique de Recherche sur l'Eau CARE-HCMUT, Vietnam, Université Paris Diderot - Paris 7 (UPD7), Institut des Géosciences de l’Environnement (IGE), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut de Recherche pour le Développement (IRD)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université de Tours (UT), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État (ENTPE), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE)-Centre National de la Recherche Scientifique (CNRS), and Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)

Subjects
Pollution, Wet season, Geologic Sediments, Insecticides, Environmental Engineering, Hydrocarbons, Fluorinated, Health, Toxicology and Mutagenesis, media_common.quotation_subject, 0208 environmental biotechnology, 02 engineering and technology, 010501 environmental sciences, Monsoon, 01 natural sciences, Sedimentary depositional environment, Polybrominated diphenyl ethers, Rivers, Surveys and Questionnaires, 11. Sustainability, Halogenated Diphenyl Ethers, Environmental Chemistry, Saigon River, Cities, Organic Chemicals, Polycyclic Aromatic Hydrocarbons, Insecticide, 0105 earth and related environmental sciences, media_common, Public Health, Environmental and Occupational Health, Sediment, General Medicine, General Chemistry, PAH, Polychlorinated Biphenyls, 6. Clean water, 020801 environmental engineering, Vietnam, 13. Climate action, Environmental chemistry, Environmental science, Polybrominated Biphenyls, Perfluoroalkyl substance, Mangrove, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Environmental Pollution, Water Pollutants, Chemical, Environmental Monitoring
Abstract

[Departement_IRSTEA]Eaux [TR1_IRSTEA]BELCA [ADD1_IRSTEA]Systèmes aquatiques soumis à des pressions multiples; International audience; A wide range of persistent organic chemicals, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), some insecticides, as well as polybrominated diphenyl ethers (PBDEs) and some perfluoroalkyl substances (PFASs) were analyzed in 17 bed sediments collected along the Saigon River and at adjacent canal mouths from upstream to downstream in Ho Chi Minh City (Vietnam). Concentrations were rather low for PAHs, as well as for legacy PCBs and dichloro-diphenyl-trichlorethane and metabolites (DDTs), or below detection limits for several PFASs and all PBDEs measured. Several insecticides (chlorpyrifos-ethyl, and the pyrethroids cypermethrin and λ-cyhalothrin) displayed rather high concentrations at a few sites within the city. There was no distinct upstream – downstream trend for PAHs, (DDTs) or PCBs. Although adjacent canal sediments tended to be more contaminated than Saigon River sediments, the differences were not significant. Emissions are almost certainly substantial for PAHs, and probably also for other contaminants such as PBDEs and some PFASs. During the dry season, contaminants are presumably stored in the city, either in canals or on urban surfaces. Heavy rainfall during the monsoon period carries away contaminated particle flows into the canals and then the Saigon River. The strong tidal influence in the river channel hinders the accumulation of contaminated particles. Contaminated deposits should accordingly be investigated further downstream in depositional environments, such as the mangrove.

Published
2019

31. Science et développement durable : 75 ans de recherche au Sud

Author

Marie-Lise Sabrié, Thomas Mourier, Corinne Lavagne, Thivent, V., Isabelle Guérin, François Roubaud, Christophe Guilmoto, Mireille Razafindrakoto, Marc Pilon, Isabelle LEGLISE, Pierre-Yves Le Meur, Fatoumata Ouattara, Christian Seignobos, Jean-Pierre Chauveau, Eric Léonard, Dominique Guillaud, Alain Froment, Nelly Robin, Michel Agier, Sophie Bava, Annabel Desgrées Du Loû, Flore Gubert, Eric Delaporte, Gonzague Jourdain, Alexandre Dumont, Serge Trèche, Jacques Berger, Pierre Traissac, Valérie Delaunay, Vincent Robert, Frédéric Darriet, Cheikh Sokhna, Michel Cot, Martine Peeters, Eric Leroy, Alice Desclaux, Jean-Marc Hougard, Didier Paugy, Michel Boussinesq, Philippe Solano, Dorothée Missé, Louis-Clément Gouagna, Jean-Loup Lemesre, Anne-Laure Bañuls, Menkès, Christophe E., Morgan Mangeas, Benjamin Sultan, Thomas Condom, Marielle Gosset, Serge Janicot, Jean Nocquet, Jean-Luc Le Pennec, Sébastien Hardy, Philippe Charvis, Yann Hello, Emmanuel Bonnet, Emilie Strady, David Point, Bernard Ollivier, Biegala, Isabelle C., Christian Feller, Christian Valentin, Eric Giraud, Eric Blanchart, Jean-Pierre Montoroi, Philippe Cecchi, Jean Albergel, Jean-Michel Vouillamoz, Vincent Simonneaux, Gilles Boulet, Thierry Ruf, Geneviève Michon, Jean-Baptiste Boutrais, Laure Emperaire, Robin Duponnois, Philippe Boulanger, Eugénie Hébrard, Valerie Verdier, Boris Szurek, Bruno Le Ru, Paul-André Calatayud, Olivier Dangles, Frédérique Aberlenc, Sevastianos Roussos, Gauthier Dobigny, Marc Legendre, Daniel Gaertner, Pierre Chavance, Pascal Bach, Arnaud Bertrand, Jérôme Vialard, Jacques Merle, Bruno Voituriez, Bernard Bourlès, Pierrick Penven, Thierry Lebel, Gil Mahe, Luc Descroix, Pierre Chevallier, Stéphane Calmant, Bruno Turcq, Adrien Favreau, Jean-Louis Rajot, Raphaël Pelissier, Philippe Cury, Riccardo Rodolfo-Metalpa, Hervé De Tricornot, Frédéric Simard, Jean-François Etard, Bernard Taverne, Florence Fournet, Alexis Drogoul, Marc Souris, Monique Simier, Marie Bonnin, Alain Ghesquière, Serge Hamon, Yves Vigouroux, Sophie Gonzalez, Jean-François Molino, Geneviève Bourdy, Christian Moretti, Pierre Ottino Garanger, Francisco Valdez, Benoît Antheaume, Nicolas Gratiot, Institut de Recherche pour le Développement (IRD), Laboratoire d'Economie de Dauphine (LEDa), Institut de Recherche pour le Développement (IRD)-Université Paris Dauphine-PSL, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Centre population et développement (CEPED - UMR_D 196), Institut de Recherche pour le Développement (IRD)-Université de Paris (UP), Structure et Dynamique des Langues (SeDyL), Institut National des Langues et Civilisations Orientales (Inalco)-Institut de recherche pour le développement [IRD] : UR135-Centre National de la Recherche Scientifique (CNRS), Gouvernance, Risque, Environnement, Développement (GRED), Université Paul-Valéry - Montpellier 3 (UPVM)-Institut de Recherche pour le Développement (IRD [France-Sud])-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Laboratoire Population-Environnement-Développement (LPED), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU), Régulations foncières, politiques publiques et logiques d'acteurs (REFO), Patrimoines locaux, Environnement et Globalisation (PALOC), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU), Centre d'études africaines (CEAf), École des hautes études en sciences sociales (EHESS)-Centre National de la Recherche Scientifique (CNRS), Recherches Translationnelles sur le VIH et les maladies infectieuses endémiques er émergentes (TransVIHMI), Institut de Recherche pour le Développement (IRD)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Universtié Yaoundé 1 [Cameroun]-Université Cheikh Anta Diop [Dakar, Sénégal] (UCAD)-Université Montpellier 1 (UM1)-Université de Montpellier (UM), Épidémiologie clinique, santé mère-enfant et VIH en Asie du Sud-Est (IRD_PHPT), Harvard University [Cambridge]-Chiang Mai university (Thaïlande), Mère et enfant face aux infections tropicales (MERIT - UMR_D 216), Nutrition et Alimentation des Populations aux Suds (NutriPass), Université Montpellier 1 (UM1)-Institut de Recherche pour le Développement (IRD)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Diversity, ecology, evolution & Adaptation of arthropod vectors (MIVEGEC-DEEVA), Evolution des Systèmes Vectoriels (ESV), Maladies infectieuses et vecteurs : écologie, génétique, évolution et contrôle (MIVEGEC), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Maladies infectieuses et vecteurs : écologie, génétique, évolution et contrôle (MIVEGEC), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Vector Control Group (MIVEGEC-VCG), Vecteurs - Infections tropicales et méditerranéennes (VITROME), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut de Recherche Biomédicale des Armées (IRBA), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Biologie des Organismes et Ecosystèmes Aquatiques (BOREA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA), Interactions hôtes-vecteurs-parasites-environnement dans les maladies tropicales négligées dues aux trypanosomatides (UMR INTERTRYP), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Université de Bordeaux (UB), Du gène à l'écosystème (MIVEGEC-GeneSys), Pathogènes, Environnement, Santé Humaine (EPATH), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU), UMR 228 Espace-Dev, Espace pour le développement, Université des Antilles (UA)-Université de Guyane (UG)-Université de Montpellier (UM)-Université de La Réunion (UR)-Avignon Université (AU)-Université de Perpignan Via Domitia (UPVD)-Institut de Recherche pour le Développement (IRD), Institut de Modélisation et d'Analyses en géo-environnement et santé - Espace Développement (IMAGES-Espace DEV), Université des Antilles (UA)-Université de Guyane (UG)-Université de Montpellier (UM)-Université de La Réunion (UR)-Avignon Université (AU)-Université de Perpignan Via Domitia (UPVD)-Institut de Recherche pour le Développement (IRD)-Université des Antilles (UA)-Université de Guyane (UG)-Université de Montpellier (UM)-Université de La Réunion (UR)-Avignon Université (AU)-Université de Perpignan Via Domitia (UPVD)-Institut de Recherche pour le Développement (IRD), Institut des Géosciences de l’Environnement (IGE), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Géosciences Environnement Toulouse (GET), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Météo France-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Météo France-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Océan et variabilité du climat (VARCLIM), Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU), UMR 215 Prodig (PRODIG), Université Paris 1 Panthéon-Sorbonne (UP1)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Nord])-AgroParisTech, Géoazur (GEOAZUR 7329), Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA), Identités et Différenciation de l'Environnement des Espaces et des Sociétés (IDEES), Normandie Université (NU)-Normandie Université (NU)-Université Le Havre Normandie (ULH), Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche Interdisciplinaire Homme et Société (IRIHS), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Unité mixte internationale Résiliences (UMI RESILIENCES), Centre ivoirien de recherches économiques et sociales (CIRES)-Université de Cocody, Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes (UMR Eco&Sols), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Institut d'écologie et des sciences de l'environnement de Paris (IEES (UMR_7618 / UMR_D_242 / UMR_A_1392 / UM_113) ), Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Sorbonne Université (SU)-Université de Paris (UP), Laboratoire des symbioses tropicales et méditerranéennes (UMR LSTM), Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université de Montpellier (UM)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD), Gestion de l'Eau, Acteurs, Usages (UMR G-EAU), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-AgroParisTech-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Laboratoire d'étude des Interactions Sol - Agrosystème - Hydrosystème (UMR LISAH), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut de Recherche pour le Développement (IRD)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro), Institut de gestion des entreprises -USJ (IGE), Université Saint-Joseph de Beyrouth (USJ), Centre d'études spatiales de la biosphère (CESBIO), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Météo France-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Météo France, Dynamiques environnementales entre forêt, agriculture et biodiversité : des pratiques locales sur la nature aux politiques de conservation, UMR - Interactions Plantes Microorganismes Environnement (UMR IPME), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Université de Montpellier (UM)-Institut de Recherche pour le Développement (IRD [France-Sud]), Laboratoire Génome et développement des plantes (LGDP), Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS), UMR Evolution, Génomes, Comportement, Ecologie, Évolution, génomes, comportement et écologie (EGCE), Centre National de la Recherche Scientifique (CNRS)-IRD-Université Paris-Sud - Paris 11 (UP11), INRA - Mathématiques et Informatique Appliquées (Unité MIAJ), Institut National de la Recherche Agronomique (INRA), Diversité, adaptation, développement des plantes (UMR DIADE), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Institut méditerranéen de biodiversité et d'écologie marine et continentale (IMBE), Centre National de la Recherche Scientifique (CNRS)-Institut de recherche pour le développement [IRD] : UMR237-Aix Marseille Université (AMU)-Avignon Université (AU), Centre de Biologie pour la Gestion des Populations (UMR CBGP), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université de Montpellier (UM)-Institut de Recherche pour le Développement (IRD [France-Sud])-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Caractérisation et valorisation de la diversité ichtyologique pour une aquaculture raisonnée (CAVIAR), UMR 212 EME 'écosystèmes marins exploités' (EME), Université de Montpellier (UM)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut de Recherche pour le Développement (IRD), Institut Pluridisciplinaire Hubert Curien (IPHC), Université de Strasbourg (UNISTRA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Météo France-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Météo France-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire de physique des océans (LPO), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Hydrosciences Montpellier (HSM), Institut de Recherche pour le Développement (IRD)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Variabilité à long terme du climat de l'océan (VALCO), Institut Français de Pondichéry (IFP), Ministère de l'Europe et des Affaires étrangères (MEAE)-Centre National de la Recherche Scientifique (CNRS), Botanique et Modélisation de l'Architecture des Plantes et des Végétations (UMR AMAP), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), MARine Biodiversity Exploitation and Conservation (UMR MARBEC), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Biocomplexité des écosystèmes coralliens de l'Indo-Pacifique (CoReUS2), Unité de modélisation mathématique et informatique des systèmes complexes [Bondy] (UMMISCO), Sorbonne Université (SU)-Universtié Yaoundé 1 [Cameroun]-Université Cadi Ayyad [Marrakech] (UCA)-Université Gaston Bergé (Saint-Louis, Sénégal)-Université Cheikh Anta Diop [Dakar, Sénégal] (UCAD)-Institut de la francophonie pour l'informatique-Institut de Recherche pour le Développement (IRD [France-Nord]), Conditions et territoires d'émergence des maladies : dynamiques spatio-temporelles de l'émergence, évolution, diffusion/réduction des maladies, résistance et prémunition des hôtes (CTEM), Unité des Virus Emergents (UVE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut National de la Santé et de la Recherche Médicale (INSERM), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Paul-Valéry - Montpellier 3 (UPVM)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut de Recherche pour le Développement (IRD [France-Sud]), Sorbonne Université (SU)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD), Université Montpellier 1 (UM1)-Institut de Recherche pour le Développement (IRD)-Université Cheikh Anta Diop [Dakar, Sénégal] (UCAD)-Universtié Yaoundé 1 [Cameroun]-Institut National de la Santé et de la Recherche Médicale (INSERM)-Université de Montpellier (UM), Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Maladies infectieuses et vecteurs : écologie, génétique, évolution et contrôle (MIVEGEC), Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM), Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM), COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA), Normandie Université (NU)-Normandie Université (NU)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Université Le Havre Normandie (ULH), Normandie Université (NU)-Institut de Recherche Interdisciplinaire Homme et Société (IRIHS), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Toulon (UTLN), Université Paris-Sud - Paris 11 (UP11)-IRD-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM), Institut de Recherche pour le Développement (IRD)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Université Paris Dauphine-PSL-Centre National de la Recherche Scientifique (CNRS), Centre d'Etudes des Mondes Africains (CEMAf), Université Panthéon-Sorbonne (UP1)-Université de Provence - Aix-Marseille 1-École pratique des hautes études (EPHE)-Centre National de la Recherche Scientifique (CNRS), Systèmes RF (XLIM-SRF), XLIM (XLIM), Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS)-Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS), Université Paul-Valéry - Montpellier 3 (UM3)-Institut de Recherche pour le Développement (IRD [France-Sud])-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Patrimoines Locaux et Gouvernance (PALOC), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD), Eco-Anthropologie et Ethnobiologie (EAE), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Université Paris Descartes - Paris 5 (UPD5), Recherches Translationnelles sur le VIH et les maladies infectieuses (TransVIHMI), Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Recherche pour le Développement (IRD)-Université Montpellier 1 (UM1)-Université Cheikh Anta Diop [Dakar, Sénégal] (UCAD)-Universtié Yaoundé 1 [Cameroun]-Université de Montpellier (UM), Prévention des malnutritions er des pathologies associées, Physiologie de la reproduction et des comportements [Nouzilly] (PRC), Centre National de la Recherche Scientifique (CNRS)-Université de Tours-Institut Français du Cheval et de l'Equitation [Saumur]-Institut National de la Recherche Agronomique (INRA), Institut de recherche pour le développement (IRD [Sénégal]), Centre IRD de Montpellier (IRD), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Environnement, Géo-ingénierie et Développement (EGID), Carcinose Angiogenèse et Recherche Translationnelle, Angiogenese et recherche translationnelle (CART U965), Université Paris Diderot - Paris 7 (UPD7)-Institut National de la Santé et de la Recherche Médicale (INSERM), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Environnement urbain (URBI), Géoazur (GEOAZUR 6526), Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Centre Asiatique de Recherche sur l'Eau CARE-HCMUT, Vietnam, Université Paris Diderot - Paris 7 (UPD7), Laboratoire Mixte International – Evolution et Domestication de l'Ichtyofaune Amazonienne (LMI - EDIA), Intitut de Recherche en Amazonie Péruvienne, Centre National de la Recherche Scientifique (CNRS)-Université de Toulon (UTLN)-Aix Marseille Université (AMU)-Institut de Recherche pour le Développement (IRD), Caractérisation et modélisation des échanges dans des lagons soumis aux influences terrigènes et anthropiques (CAMELIA), Institut de Recherche pour le Développement (IRD [Nouvelle-Calédonie])-Institut de Recherche pour le Développement (IRD [Guyanne]), Lyonbiopôle, Centre de recherche rétrospective de Marseille (CRRM), Université Paul Cézanne - Aix-Marseille 3, Institut National de la Recherche Agronomique (INRA)-Institut de Recherche pour le Développement (IRD)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut de Recherche pour le Développement (IRD)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro)-AgroParisTech-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut de Recherche pour le Développement (IRD [ Madagascar])-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Laboratoire d'étude des transferts en hydrologie et environnement (LTHE), Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique de Grenoble (INPG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Université Montpellier 1 (UM1)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut de Recherche pour le Développement (IRD [France-Sud])-Université de Montpellier (UM)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad), Avignon Université (AU)-Aix Marseille Université (AMU)-Institut de recherche pour le développement [IRD] : UMR237-Centre National de la Recherche Scientifique (CNRS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Université Montpellier 2 - Sciences et Techniques (UM2)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM), IRSH, Université Abdou Moumouni [Niamey], Cultures et Sociétés en Europe (CSE), Université Marc Bloch - Strasbourg II-Centre National de la Recherche Scientifique (CNRS), UMI 2019, Université Pierre et Marie Curie (Paris 6), Centre National de la Recherche Scientifique (CNRS)-Institut National des Langues et Civilisations Orientales (Inalco)-Institut de recherche pour le développement [IRD] : UR135, Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Institut de Recherche pour le Développement (IRD [ Madagascar])-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro), Institut de Recherche pour le Développement (IRD)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Ministère de l'Europe et des Affaires étrangères (MEAE)

Subjects
MONDE, [SDE]Environmental Sciences, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], [SHS]Humanities and Social Sciences
Abstract

International audience; Comment, depuis plusieurs décennies, la recherche scientifique contribue-t-elle au développement des pays du Sud ? À travers plus de 100 succès emblématiques de la recherche en partenariat, cet ouvrage nous plonge au coeur des grandes questions de développement : oeuvrer pour des sociétés plus justes, lutter contre les maladies, faire face aux risques naturels, mettre en place une agriculture durable garantissant la sécurité alimentaire, préserver la biodiversité, partager les savoirs... Il montre ainsi comment la recherche contribue à l'amélioration des conditions de vie et à la préservation de l'environnement dans les pays en développement, en soulignant le rôle de la science pour répondre aux défis du monde actuel et à venir. Composé de textes courts, didactiques et richement illustrés, il s'adresse à tous les publics.

Published
2019

32. Interaction of Mangroves, Coastal Hydrodynamics, and Morphodynamics Along the Coastal Fringes of the Guianas

Author

Antoine Gardel, Jaak Monbaliu, Edward J. Anthony, S. Naipal, Kene Moseley, Nicolas Gratiot, Oudho Homenauth, Nicolas Huybrechts, Pieter G.E.F. Augustinus, Erik Toorman, Makowski, Chris, and Finkl, Charles W

Subjects
Shore, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, 0208 environmental biotechnology, Climate change, 02 engineering and technology, 01 natural sciences, 020801 environmental engineering, Oceanography, Wind wave, Ecosystem, Mangrove, Sediment transport, Geology, Beach morphodynamics, 0105 earth and related environmental sciences, Accretion (coastal management)
Abstract

The mangrove belt along the coast of the three Guianas, South America, forms a unique ecosystem and acts efficiently as a natural soft coastal defence structure. The general mechanisms have been studied for over four decades and the processes governing the coastal morphodynamics are now understood, at least qualitatively. They consist of an interaction between mangroves, hydrodynamics and sediment mechanics. Twenty percent of the mud discharged by the Amazon in the Atlantic Ocean is transported to the west along the coast by waves and currents in discrete mud banks of a few 10 s of km length, which travel at a speed of the order of 2 km/year. During the presence of a mud bank waves are damped, mud is trapped and colonized by mangroves. Once a mud bank has passed, the waves can attack the shore again. This results in a cycle of land accretion and erosion, with an average net gain of 1 m coast per cycle of roughly 30 years. However, in locations where too many mangroves have been removed, the coast has lost its natural resilience and the settlements and fields are prone to flooding, a concern that increases with climate change and predicted sea-level rise (SLR). Hard coastal defence structures, such as those in Guyana, are expensive and not sustainable. Based on many lessons learnt, pilot projects on mangrove rehabilitation have started. At the same time research efforts are undertaken to allow making quantitative estimates of the potential risks for the coastal communities. For this purpose, numerical prediction models are developed which can compute currents, wave action and sediment transport along the coast of the Guianas. Different climate change scenarios can be investigated. These models can serve in the near future as decision support tool for the local authorities for the management of the coastal zone.

Published
2018

33. A new wetting – drying algorithm integrated in SLIM, with an application to the Tonle Sap lake, Mekong

Author

Le, Hoang Anh, Vu Xuan Huyen Dang, Lambrechts, Jonathan, Sigrun Ortleb, Vallaeys, Valentin, Vincent, David, Nicolas Gratiot, Soares Frazao, Sandra, Deleersnijder, Eric, European Geosciences Union General Assembly 2018, UCL - SST/IMMC/MEMA - Applied mechanics and mathematics, and UCL - SST/IMMC/GCE - Civil and environmental engineering

Subjects
Mekong, Finite element method, wetting – drying algorithm, Wetting-drying, Tonle Sap, SLIM, discontinuous Galerkin
Abstract

Numerical simulation of inundation processes and subsequent drying of floodplains is a challenging issue for hydrodynamic models. In particular, classical approaches are designed for explicit schemes, hence they are time- consuming and prevent fully implicit time integration. In this work, a new wetting – drying algorithm with implicit time-stepping is developed based on piecewise linear Runge - Kutta discontinuous Galerkin approximations for the shallow water equations. The principle of this algorithm is to set a limitation for the fluid depth and a blending parameter in order to ensure local mass conservation and rapid transition of a wet - dry interface. This scheme is integrated into the Second-generation Louvain-la-Neuve Ice-ocean Model (SLIM). The method is first validated by means of the analytical Thacker test case, showing its well-balancing property. Then, it is applied to the Tonle Sap Lake in the Cambodia floodplain, an integral component of the Mekong River Basin. This lake plays an important role in livelihoods of the Southeast Asian riparian residents and has a unique flow feature: it constitutes a storage area for flows coming from the Mekong River during the flooding seasons and then, during the dry seasons, it provides water to the Mekong delta. As a consequence, the Tonle Sap Lake experiences significant water level fluctuations during a year, with large variations of the total flooded area. The simulation results are investigated for two distinct flow seasons, pointing to the well-foundedness of the new wetting-drying scheme.

Published
2018

34. Eutrophication of turbid tropical reservoirs: Scenarios of evolution of the reservoir of Cointzio, Mexico

Author

Julien Némery, Phuong Thuy Kim Doan, Nicolas Gratiot, and Martin Schmid

Subjects
Hydrology, Biogeochemical cycle, Ecology, Applied Mathematics, Ecological Modeling, Climate change, Plankton, Algal bloom, Computer Science Applications, Water level, Computational Theory and Mathematics, Modeling and Simulation, Phytoplankton, Environmental science, Turbidity, Eutrophication, Ecology, Evolution, Behavior and Systematics
Abstract

This study provides the first numerical simulation of physical and biogeochemical processes in a very turbid and highly eutrophic tropical reservoir of the Trans-Mexican Volcanic Belt in Mexico. The Cointzio reservoir (capacity 66 Mm 3 ) is characterized by a lack of water treatment plants upstream and a high content of very fine clay particles. It suffers serious episodes of eutrophication associated with high levels of turbidity and benthic anoxia. Different scenarios for future climate inputs, nutrient inputs and water levels were simulated. The results pointed out the potential negative long-term impact of climate change on this reservoir. In this region, an increase of average air temperature as high as 4.4 °C is expected by the end of the century. When coupled with a low water level, this increase could lead to critical conditions with a severe depletion of dissolved oxygen and important algal blooms with chlorophyll a reaching values of up to 94 μg L − 1 . The calculations indicated that a drastic reduction of nutrient inputs (up to 90%) would be required to significantly reduce chlorophyll a concentrations. If such mitigation measures are adopted, the maximum peak of chlorophyll a would be reduced by 55% after a ten-year period of efforts, with corresponding positive effect on dissolved oxygen concentrations. The main limitation of the chosen numerical approach comes from the assumption of a constant water level in the model. This may be particularly critical for shallow type reservoirs. While this region remains poorly studied, this study brings original information that will help stakeholders to adopt appropriate strategies for the management of their waterbodies that experience critical eutrophication.

Published
2015

35. Using an optical settling column to assess suspension characteristics within the free, flocculation, and hindered settling regimes

Author

Ian G. Droppo, Cédric Legout, Catherine Coulaud, Valentin Wendling, Bernard Mercier, Nicolas Gratiot, Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut des Géosciences de l’Environnement (IGE), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut de Recherche pour le Développement (IRD)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut de Recherche pour le Développement (IRD), Environment and Climate Change Canada, and Centre National de la Recherche Scientifique (CNRS)

Subjects
Flocculation, [PHYS.PHYS]Physics [physics]/Physics [physics], Stratigraphy, Sediment, Soil science, Optical measurement, 6. Clean water, Suspension (chemistry), [SPI]Engineering Sciences [physics], Settling, [SDE]Environmental Sciences, Erosion, Range (statistics), Cohesive sediments, Particle, Environmental science, Geotechnical engineering, Suspended sediment transport, Sediment transport, ComputingMilieux_MISCELLANEOUS, Settling regimes, Settling velocity, Earth-Surface Processes
Abstract

Instruments able to measure the settling velocity distribution (SVD) and investigate the flocculation behavior of suspensions for a wide range of concentrations and settling regimes are required to understand and model sediment transport in headwater catchments. Such knowledge will improve our water resource management capabilities. An optical settling column, equipped with a vertical array of optical sensors, was used to provide light transmission through a suspension during quiescent settling. A new method to determine the settling velocity and the propensity of suspensions to flocculate is proposed. Its reliability was evaluated based on settling tests for (1) noncohesive sediments, (2) cohesive sediments at medium (similar to 1 g l(-1)) concentration in a natural and deflocculated state, and (3) a cohesive sediment at a very high concentration (similar to 10 g l(-1)). This choice of sediments and concentrations allowed for the assessment of free, flocculated, and hindered settling regimes. The proposed data processing method provides measurements for a range of test conditions. The result showed that different populations of particles with different settling behaviors can be identified within the suspensions. In the case of noncohesive sediments, the proposed method provided SVD similar to those obtained with reference methods. The propensity to flocculate was zero as expected for inert material. The natural cohesive sediment at medium concentration exhibited a large range of SVD (10(-2)-10(-5) m s(-1)) and high propensity to flocculate. These were both reduced with the addition of a deflocculant. Identified particle behaviors were consistent with independent measurement of size distribution, microscopic, and erosion properties. In the hindered regime, a narrow SVD corresponded to the hindered front settling velocity (similar to 10(-4) m s(-1)). An optical settling column was able to provide reliable SVD and an evaluation of the propensity of particles to flocculate. The settling column was able to detect variations of the settling velocities with settled depth, thus highlighting that settling columns with a single measurement point may provide erroneous results by not accounting for the full spectrum of settling depth.

Published
2015

36. A new wetting – drying algorithm integrated in SLIM, with an application to the Tonle Sap lake, Mekong

Author

UCL - SST/IMMC/MEMA - Applied mechanics and mathematics, UCL - SST/IMMC/GCE - Civil and environmental engineering, Le, Hoang Anh, Vu Xuan Huyen Dang, Lambrechts, Jonathan, Sigrun Ortleb, Vallaeys, Valentin, Vincent, David, Nicolas Gratiot, Soares Frazao, Sandra, Deleersnijder, Eric, European Geosciences Union General Assembly 2018, UCL - SST/IMMC/MEMA - Applied mechanics and mathematics, UCL - SST/IMMC/GCE - Civil and environmental engineering, Le, Hoang Anh, Vu Xuan Huyen Dang, Lambrechts, Jonathan, Sigrun Ortleb, Vallaeys, Valentin, Vincent, David, Nicolas Gratiot, Soares Frazao, Sandra, Deleersnijder, Eric, and European Geosciences Union General Assembly 2018

Abstract

Numerical simulation of inundation processes and subsequent drying of floodplains is a challenging issue for hydrodynamic models. In particular, classical approaches are designed for explicit schemes, hence they are time- consuming and prevent fully implicit time integration. In this work, a new wetting – drying algorithm with implicit time-stepping is developed based on piecewise linear Runge - Kutta discontinuous Galerkin approximations for the shallow water equations. The principle of this algorithm is to set a limitation for the fluid depth and a blending parameter in order to ensure local mass conservation and rapid transition of a wet - dry interface. This scheme is integrated into the Second-generation Louvain-la-Neuve Ice-ocean Model (SLIM). The method is first validated by means of the analytical Thacker test case, showing its well-balancing property. Then, it is applied to the Tonle Sap Lake in the Cambodia floodplain, an integral component of the Mekong River Basin. This lake plays an important role in livelihoods of the Southeast Asian riparian residents and has a unique flow feature: it constitutes a storage area for flows coming from the Mekong River during the flooding seasons and then, during the dry seasons, it provides water to the Mekong delta. As a consequence, the Tonle Sap Lake experiences significant water level fluctuations during a year, with large variations of the total flooded area. The simulation results are investigated for two distinct flow seasons, pointing to the well-foundedness of the new wetting-drying scheme.

Published
2018

37. Estimation d'une courbe de tarage hauteur-dénivelée-débit pour une rivière influencée par la marée

Author

Guillaume Dramais, Stéphane Piney, Jérôme Le Coz, Benoît Camenen, Nicolas Gratiot, Tuan Duc Ho, Hydrologie-Hydraulique (UR HHLY), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), CARE, IRD, SRN/B2HPC, and DREAL NORMANDIE

Subjects
COURS D'EAU, rating curve, Computer Science::Sound, COURBE DE TARAGE, 0208 environmental biotechnology, tides, [SDE]Environmental Sciences, 02 engineering and technology, 6. Clean water, rivers, 020801 environmental engineering, Water Science and Technology, MAREE
Abstract

Un modele de courbe de tarage a deux points de mesure du niveau d'eau est propose pour les rivieres tidales. Il est base sur une simple application de la loi de Manning-Strickler en se donnant la possibilite d'une pente negative pour obtenir un debit remontant la riviere. Deux variables permettent le calage du modele : le coefficient de Strickler et le decalage temporel entre la pente mesuree par les deux niveaux et celle a appliquer a la section de reference. Le modele a ete applique sur la Riviere de Saigon au Vietnam et la Seine en France ou des campagnes de jaugeages ADCP ont ete realisees sur un ou deux cycles de maree. Les resultats sont tres encourageants dans le cas de la Riviere de Saigon ou les variations de hauteur restent moderees. Dans le cas de la Seine, les resultats ne sont pas aussi satisfaisants du fait de la variation brutale du niveau d'eau et du debit lors du flot observee pendant une tres forte maree qui rend le calage difficile. Le modele semble neanmoins valide pour les rivieres tidales tant que le gradient temporel du debit lors du flot de la maree reste modere.

Published
2017

38. Phosphorus adsorption/desorption processes in the tropical Saigon River estuary (Southern Vietnam) impacted by a megacity

Author

Emilie Strady, Nicolas Gratiot, An Truong Nguyen, Claire Golliet, Tuyet Thi Nguyen, Thi Thanh Nguyen, Joanne Aimé, Josette Garnier, Julien Némery, Viet Quoc Tran, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Structure et fonctionnement des systèmes hydriques continentaux (SISYPHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Centre Asiatique de Recherche sur l'Eau CARE-HCMUT, Vietnam, HCMUT, Université Paris Diderot - Paris 7 (UPD7), Ho Chi Minh City University of Technology (HCMUT), Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Mines Paris - PSL (École nationale supérieure des mines de Paris)

Subjects
0106 biological sciences, 010504 meteorology & atmospheric sciences, Aquatic Science, Tropical region, Oceanography, 01 natural sciences, Nutrient, Dry season, Tidal river, Phosphorus dynamics, 14. Life underwater, 0105 earth and related environmental sciences, Hydrology, geography, geography.geographical_feature_category, 010604 marine biology & hydrobiology, Flocculation, Sediment, Estuary, Eutrophication, 6. Clean water, Salinity, geography.body_of_water, [SDE]Environmental Sciences, Environmental science, Water quality
Abstract

International audience; The Saigon River flows through one of the most rapidly growing megacities of Southeast Asia, Ho Chi Minh City (HCMC, > 8.4 million inhabitants). This tidal river is characterized by a tropical monsoon climate, alternating a wet and a dry season. In the last few decades, increased economic and urban developments of HCMC have led to harmful impacts on the water quality of this tidal river, with severe eutrophication events. This situation results from the conjunction of contrasting hydrological seasons and the lack of upgraded sanitation infrastructures: indeed, less than 10% of the domestic wastewater is collected and treated before being discharged directly into urban canals or rivers. This study focuses on P dynamics because this is considered the key nutrient factor controlling freshwater eutrophication. Based on field measurements and original laboratory experiments, we assessed the P levels in the river water and sediments, and investigated P adsorption/desorption capacity onto suspended sediment (SS) within the salinity gradient observed. Field surveys showed a clear impact of the HCMC megacity on the total P content in SS, which increased threefold at HCMC Center, as compared with the upstream values (0.3-0.8 gP kg −1). Downstream, in the mixed estuarine area, the Total P was lower than 0.5 gP kg −1. Laboratory experiments were carried out to characterize the influence of SS concentrations (SS = [0.25-0.9] g L −1), salinity (S = [2.6-9.3]) and turbulence (G = [22-44] s − 1) on the sorption capacity of P onto sediment. The size of sediment particles and their propensity to flocculate were also originally measured with a recently developed instrument: the System for the Characterization of Aggregates and Flocs (SCAF®). Under the experimental conditions considered, SS concentrations had the greatest effect on the adsorption of P onto sediment, e.g., P adsorption capacity increased when SS concentrations rose. In contrast, salinity and turbulence had a smaller effect on the adsorption properties of sediments. Among these observed variables, the SS concentration was shown to be the main driver for adsorption capacity of P onto SS within the salinity gradient. We discuss the implication of these findings on understanding P dynamics within a highly urbanized, tropical estuary.

Published
2019

39. Développement d'un Système de Caractérisation des Agrégats et Flocs (SCAF)

Author

Bernard Mercier, Valentin Wendling, Catherine Coulaud, Cédric Legout, Nicolas Gratiot, Laboratoire d'étude des transferts en hydrologie et environnement (LTHE), Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique de Grenoble (INPG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), and Sciencesconf.org, CCSD

Subjects
[SPI]Engineering Sciences [physics], [SPI] Engineering Sciences [physics]
Abstract

International audience; L'étude du transport des matières en suspension dans les cours d'eau pour en déterminer les impacts revêt un intérêt grandissant. Il n'existe cependant pas d'instrument capable d'effectuer des mesures de vitesse de sédimentation en temps réel et pour des régimes très concentrés, a fortiori en situation de crue. Pour répondre à ce besoin, un Système de Caractérisation des Agrégats et Flocs (SCAF) a été développé. L'appareil a été conçu pour s'intégrer dans un préleveur automatique, d'usage courant en hydrologie. L'une des difficultés principales a consisté à intégrer l'électronique de mesure aux flacons des préleveurs automatiques. Lors de ses évaluations, le SCAF a permis des mesures dans des gammes de concentrations allant jusqu'à plusieurs dizaines de g/l, valeurs courantes pour des cours d'eau de montagne. Outre la détermination des vitesses de dépôt, la méthode de traitement des données permet de calculer un "indice de floculation" caractérisant l'aptitude des particules à s'agglomérer.

Published
2016

40. Dynamics of soil aggregate size in turbulent flow : respective effect of soil type and suspended concentration

Author

Thomas Grangeon, Cédric Legout, Nicolas Gratiot, Valentin Wendling, Hervé Michallet, Laboratoire d'étude des transferts en hydrologie et environnement (LTHE), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratoire des Écoulements Géophysiques et Industriels [Grenoble] (LEGI ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), GéoHydrosystèmes COntinentaux (GéHCO EA6293), Université de Tours (UT), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Université de Tours, Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique de Grenoble (INPG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Laboratoire des Écoulements Géophysiques et Industriels [Grenoble] (LEGI), and Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)

Subjects
Suspended sediment dynamics, Flocculation, Aggregates, 010504 meteorology & atmospheric sciences, Soil science, 01 natural sciences, complex mixtures, Disaggregation, [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], 0105 earth and related environmental sciences, Earth-Surface Processes, Hydrology, Suspended solids, [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Mechanics of the fluids [physics.class-ph], Soil classification, 04 agricultural and veterinary sciences, 15. Life on land, Sediment transport, Soil type, Particle size distribution, 6. Clean water, Soil water, Particle-size distribution, 040103 agronomy & agriculture, Erosion, Soil erosion, 0401 agriculture, forestry, and fisheries, Environmental science, Particle size
Abstract

International audience; The fate of eroded soil particles impacts soil loss, river engineering and aquatic ecosystems. However, little is known about soil aggregate dynamics within the flow just after their detachment from the soil matrix. The relationship between particle size and turbulence has already been studied but few studies analysed the associated effect of particle concentration. The disaggregation/flocculation of three soils, two badland materials and a well developed calcareous brown soil, was studied by using a grid-stirred tank. An isotropic and homogeneous turbulence was generated to focus on the effects of suspended concentration on particle sizes. Increasing the suspended concentration in the range 1 − 10 g L−1 leads to a decrease of the proportion of the medium size particles and of an increase of the proportion of the smallest particles, as a consequence to enhanced abrasion. The soil aggregates with the largest organic content had the highest strength but were still subject to disaggregation within the turbulentflow, the resulting particle size depending on the suspended concentration. This study demonstrates that soil aggregate characteristics are in fluenced by concentration, this behaviour being dependent upon the soil type.

Published
2016

41. Coastal engineering and large-scale mangrove destruction in Guyana, South America: Averting an environmental catastrophe in the making

Author

Edward J. Anthony and Nicolas Gratiot

Subjects
Environmental Engineering, geography.geographical_feature_category, Mangrove restoration, Amazon rainforest, Coastal plain, Management, Monitoring, Policy and Law, Ecological engineering, Coastal erosion, Geography, Environmental protection, Agricultural land, Coastal engineering, Mangrove, Nature and Landscape Conservation
Abstract

This short communication highlights potential destabilisation of the muddy coast of Guyana, South America, caused by large-scale mangrove destruction. The stability of the coast of Guyana, which is part of one of the world's most extensive mangrove coasts, depends on large mud banks migrating alongshore from the mouth of the Amazon River and on mangrove colonisation of these banks. Under the pressures of economic development, the coastal zone of Guyana is progressively being transformed into agricultural land and aquaculture estates, protected by coastal dikes. These hard coastal defence structures, constructed in recent years, are less effective in dissipating wave energy than mud banks. They also hinder the various processes involved in the consolidation and subsequent mangrove colonisation of these banks, notably by enclosing mature mangrove forests and preventing propagule transport from these forests to mud banks. If unchecked, the progressive breakdown in the mud-bank and associated mangrove system that has led to progradation of the coastal plain of Guyana over the last 5000 years will result in large-scale coastal erosion that can only be countered by further engineering structures at prohibitive costs. The only coastal defence strategy, sound and viable over the long term, with regards to both environmental conservation and cost, consists in restoring a dynamic mud-bank and mangrove system on this wave-exposed coast.

Published
2012

42. Tracing sediment sources in a tropical highland catchment of central Mexico by using conventional and alternative fingerprinting methods

Author

Jérôme Poulenard, Clément Duvert, Christian Prat, Philippe Bonté, Irène Lefèvre, Sophie Ayrault, Julien Némery, Nicolas Gratiot, Olivier Evrard, and Michel Esteves

Subjects
Hydrology, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Erosion control, Drainage basin, 010501 environmental sciences, 15. Life on land, Andisol, 01 natural sciences, 6. Clean water, Siltation, Streamflow, Soil water, Surface runoff, Sediment transport, Geology, 0105 earth and related environmental sciences, Water Science and Technology
Abstract

Land degradation is intense in tropical regions where it causes for instance a decline in soil fertility and reservoir siltation. Two fingerprinting approaches (i.e. the conventional approach based on radionuclide and geochemical concentrations and the alternative diffuse reflectance infrared Fourier transform spectroscopy method) were conducted independently to outline the sources delivering sediment to the river network draining into the Cointzio reservoir, in Mexican tropical highlands. This study was conducted between May and October in 2009 in subcatchments representative of the different environments supplying sediment to the river network. Overall, Cointzio catchment is characterized by very altered soils and the dominance of Andisols and Acrisols. Both fingerprinting methods provided very similar results regarding the origin of sediment in Huertitas subcatchment (dominated by Acrisols) where the bulk of sediment was supplied by gullies. In contrast, in La Cortina subcatchment dominated by Andisols, the bulk of sediment was supplied by cropland. Sediment originating from Potrerillos subcatchment characterized by a mix of Acrisols and Andisols was supplied in variable proportions by both gullies and rangeland/cropland. In this latter subcatchment, results provided by both fingerprinting methods were very variable. Our results outline the need to take the organic carbon content of soils into account and the difficulty to use geochemical properties to fingerprint sediment in very altered volcanic catchments. However, combining our fingerprinting results with sediment export data provided a way of prioritizing the implementation of erosion control measures to mitigate sediment supply to the Cointzio reservoir supplying drinking water to Morelia city. Copyright © 2012 John Wiley & Sons, Ltd.

Published
2012

43. Acoustic turbulence measurements of near-bed suspended sediment dynamics in highly turbid waters of a macrotidal estuary

Author

Aldo Sottolichio, David Hurther, Patrice Bretel, Nicolas Gratiot, Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Écoulements Géophysiques et Industriels [Grenoble] (LEGI), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), RIVER, Laboratoire d'étude des transferts en hydrologie et environnement (LTHE), Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique de Grenoble (INPG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique de Grenoble (INPG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Morphodynamique Continentale et Côtière (M2C), Centre National de la Recherche Scientifique (CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU), Programme REAGIR-INSU-CNRS, Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), and Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)

Subjects
cohesive sediment transport, 010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Turbid water, Suspended sediment concentration, Gironde estuary, Soil science, Aquatic Science, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, ADV, [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph], Settling, Turbulent flux, Mud flows, Estuary hydrodynamics, Lutoclines, Shear stress, [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], 14. Life underwater, Turbidity, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Acoustic inversion, 0105 earth and related environmental sciences, [SPI.ACOU]Engineering Sciences [physics]/Acoustics [physics.class-ph], Hydrology, [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Mechanics of the fluids [physics.class-ph], [SDE.IE]Environmental Sciences/Environmental Engineering, Turbulence, Sediment, ADCP, Geology, [PHYS.MECA.ACOU]Physics [physics]/Mechanics [physics]/Acoustics [physics.class-ph], Current (stream), Turbulence kinetic energy, Environmental science, Sediment transport
Abstract

Sediment-turbulence interactions near the bed are still poorly understood in highly turbid estuaries, especially in the presence of fluid mud layers. This results primarily from the difficulty in measuring co-located velocity and suspended sediment concentration (SSC) at sufficiently high rate to resolve small turbulent flow scales. In this paper, we show how a set of commercial acoustic and optical bacicscattering systems known as ADCPs, ADVs and OBSs, can be deployed and used in a complementary way to perform large-scale profilings of tidal current and SSC combined with high-resolution velocity and SSC measurements in the highly turbid near-bed zone. The experiment was done in the Gironde estuary (France) which is well known for its turbidity maximum zone characterized by high SSC values, above 1 g l(-1) near the surface. A first simple inversion method is proposed to convert the backscattered acoustic intensity measured with ADV into SSC data in the highly turbid near-bed zone. Near-bed SSC data from the OBS are used to compensate for the important acoustic sediment attenuation effect at an acoustic frequency of 6 MHz. No a priori knowledge of acoustic backscattering properties of mud suspensions is required with this calibration procedure. We obtain an attenuation coefficient for mud suspensions of 0.28 m(2)/kg at 6 MHz leading to a good agreement between the SSC timeseries from the three ADV receivers and the OBS over the entire tidal cycle. The obtained SSC data are then analyzed with respect to the near-bed velocity, Reynolds shear stress and turbulent kinetic energy (TKE) timeseries in order to identify the relevant sediment transport processes during the tidal cycle. Significant differences in bed shear stress and TICE levels are found between ebb and flood stages with effects on near-bed sediment dynamics. During the ebb, maximum levels of tidal current, bed shear stress and TKE are associated with a reduction of near-bed sediment concentration (from 400 kg m(-3) down to 100 kg m(-3)). Bed liquefaction process is assumed to occur at this moment with the presence of highly concentrated mud layer and a possible lutocline at a distance of less than 20 cm above the bed. During the first 1.5 h of flood, turbulent activity remains moderate. The near-bed flood current is then inhibited very abruptly while a sudden increase in SSC occurred above the bed. Assuming that the ADV is able to estimate relevant turbulent erosion fluxes, the co-located velocity and SSC are multiplied and compared with settling flux measurements made onboard under quiescent water conditions. The mean sediment settling fluxes (averaged over 3 min) increase with SSC and are in relative good coherence with fluxes in quiescent water below the hindered regime, for SSC below 15 g l(-1). Reducing averaging time from 3 min to 30 s allows to increase the range of turbulent fluxes and SSC values, up to 99 g l(-1). At this scale, fluxes keep increasing quasi-linearly at higher SSC, suggesting the inhibition (delay or reduction) of the hindered settling regime as previously shown by Gratiot et al. (2005) from laboratory experiments. However, the 3-min averaged concentration field remained too low to conclude definitively on the effectiveness of such a process. Further analysis conducted at higher SSC regimes and under fully verified equilibrium are necessary.

Published
2011

44. Sediment properties in the fluvial and estuarine environments of the Mekong River

Author

Eric Deleersnijder, Olivier Ribolzi, Sandra Soares-Frazão, Nicolas Gratiot, William Santini, and Hoang Anh Le

Subjects
lcsh:GE1-350, Delta, Hydrology, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Fluvial, Estuary, Numerical models, 010502 geochemistry & geophysics, 01 natural sciences, Water column, Settling, Mekong river, Environmental science, Sediment transport, lcsh:Environmental sciences, 0105 earth and related environmental sciences
Abstract

The Mekong river, located in Southeast Asia, is one of the largest rivers in the world. It is facing serious problems related to sediment transport, e.g. the reduction of sediment volume supply to the delta and estuary. This study focuses on the physical properties of suspended particles in the upstream fluvial section (Luang Prabang, Laos) and in the region of tidal influence (Song Hau estuary, Vietnam). These sites are respectively the upper and lower limits of the Lower Mekong River (LMR), which are experiencing contrasted transport modes. The main objective of this study is to quantify the proportion of inert sand and of cohesive particles in the water through comprehensive measurements of particle size, settling velocity and flocculation in the water column. Two field campaigns were undertaken in the summer monsoon season. The results point out the predominance of flocculi, with sizes of 18 ± 5 μm in the fluvial environment and 15 ± 5 μm in the estuary and the similarities in patterns, mixture of sand (12 ± 5 %) and mud (88 ± 5 %). They also provide a statistically representative set of suspended particle populations in the upstream and downstream regions that could be used for improving numerical models.

Published
2018

45. Monitoring of Nesting Leatherback Turtles (Dermochelys coriacea): Contribution of Remote Sensing for Real-Time Assessment of Beach Coverage in French Guiana

Author

Laurent Kelle, Isabelle Nolibos, Jocelyn Thérèse, Nicolas Gratiot, Benoit de Thoisy, Ronald Wongsopawiro, WWF Guianas, WWF, Laboratoire d'étude des transferts en hydrologie et environnement (LTHE), Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Sépanguy Kourou, Kulalasi, Réserve Naturelle de l'Amana, Réserves Naturelles de France-Réserves Naturelles de France, Association Kwata, Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique de Grenoble (INPG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)

Subjects
PLAGE, EROSION, SATELLITE SPOT, IMAGE SATELLITE, Population, Biology, LIGNE DE RIVAGE, law.invention, ESPECE MENACEE, Nest, law, LITTORAL, 14. Life underwater, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, Turtle (robot), education, Ecology, Evolution, Behavior and Systematics, Remote sensing, Shore, education.field_of_study, geography, geography.geographical_feature_category, TELEDETECTION SPATIALE, Fishery, Remote sensing (archaeology), Nesting (computing), Animal Science and Zoology, TORTUE AQUATIQUE, VARIATION PLURIANNUELLE
Abstract

International audience; Over 4 years, 2001–2004, leatherback-turtle monitoring was conducted on all the potential nesting sites in French Guiana. We estimated minimal leatherback turtle nest numbers of 23,107, 12,229, 13,480, 11,012, respectively. The Awala-Yalimapo Beach, sometimes considered a good estimator of the overall nesting activity for the country, has hosted a significant proportion of the leatherback turtle nests (42%±2%), but this percentage is much lower than formerly described. The relative importance of this nesting site is discussed in light of remote sensing data, suggesting that nest numbers recorded in Awala-Yalimapo may have misrepresented leatherback turtle population trends. Indeed, remote sensing data indicate that the total sandy shoreline available in French Guiana has regularly evolved over the last decades, allowing leatherback turtle nesting attempts out of the scope of monitoring. The importance of a monitoring effort integrating the specific coastal dynamic of the Guianas region is highlighted.

Published
2007

46. Trade-wind waves and mud dynamics on the French Guiana coast, South America: Input from ERA-40 wave data and field investigations

Author

Edward J. Anthony, Antoine Gardel, Nicolas Gratiot, Laboratoire d'étude des transferts en hydrologie et environnement (LTHE), Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), PNEC et CNES, soutiens PNEC et CNES, Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique de Grenoble (INPG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD), Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Centre National de la Recherche Scientifique (CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Institut national des sciences de l'Univers (INSU - CNRS), and Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Nord])

Subjects
010504 meteorology & atmospheric sciences, trade wind waves, Intertidal zone, Forcing (mathematics), ERA 40 wave dataset, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Geochemistry and Petrology, ERA-40, Wave height, Wind wave, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, 14. Life underwater, ComputingMilieux_MISCELLANEOUS, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences, [SDV.EE]Life Sciences [q-bio]/Ecology, environment, Shore, geography, geography.geographical_feature_category, wind waves, mangroves, ERA-40 wave dataset, Geology, French Guiana, 13. Climate action, mud banks, Geostrophic wind, Channel (geography)
Abstract

The South American coast between Brazil and Venezuela is affected by longshore migrating mud banks derived from the fine-grained Amazon sediment discharge. Onshore mud migration prevails over shallow 'bank' areas alternating alongshore with deeper 'inter-bank' areas. The transport on the inner shelf, and attachment to the shoreline, of this migrating mud has been attributed mainly to wind waves. However, the lack of in situ data on waves hampers understanding of the relationship between waves and mud dynamics. A 44-yr record (1960-2004) of the ERA-40 wave dataset generated by the European Centre for Medium-Range Weather Forecasts (ECMWF) was used, in conjunction with field investigations in French Guiana, to define both event-scale and longer-term patterns of mud mobilisation induced by waves. The ratio H-0(3)/T-2, combining wave height H and period T, and the angle of wave incidence alpha, were singled out as the most relevant parameters for describing wave forcing. Typical 'bank' and 'inter-bank' profiles and corresponding mud densities, and a 3-month record of changes in the thickness of the fluid mud layer in an estuarine navigation channel were monitored by echo-sounding from October 2002 to January 2003. An 80-day record of bed-level changes in the intertidal zone was obtained from August to November 2004 using a pressure transducer. The results on the wave regime of French Guiana confirm a distinctly seasonal pattern, and highlight an increase in H-0(3)/T-2 over the 44-yr period related to an increase in trade-wind velocities determined from corresponding trends in Atlantic wind pseudo-stress off the South American coast. Wave forcing over bank areas leads to the liquefaction of a 1-3 m-thick layer of mud that is transported onshore (and alongshore by the longshore component of wave energy). The episodic nature of high wave energy events generally results in the formation of mud bar features from the shoreward mobilisation of gel-like fluid mud. The effect of waves on mud is particularly marked following long periods of low energy, and especially at the onset of the high wave energy season (October to May), when even moderate wave energy events can lead to significant mobilisation of mud. Significant phases of increased wave energy are attended by higher long-term (annual) rates of longshore mud bank migration but the correlation is rather poor between the wave forcing parameter H-0(3)/T-2 and migration rates because stronger wave forcing is generally associated with low angles of wave incidence. This suggests a complementary role of other hydrodynamic mechanisms, such as geostrophic and tidal currents, in longshore mud bank migration.

Published
2007

47. Structural effects of tidal exposures on mudflats along the French Guiana coast

Author

Nicolas Gratiot and Jérôme Fiot

Subjects
Hydrology, mangrove, coastal dynamics, biology, Avicennia germinans, Intertidal zone, Sediment, Geology, Context (language use), Oceanography, biology.organism_classification, Siltation, French Guiana, desiccation, Pore water pressure, Geochemistry and Petrology, Erosion, Amazon, mudflat, Erodability
Abstract

Wetting and drying cycles on intertidal mudflats vary considerably with altitude, modifying the physical characteristics of surface sediment in ways favoring (or not) plant colonization. In this context, sediment properties were investigated by means of laboratory experiments and field surveys on a wide range of fluid to desiccated muds from the highly dynamic coastline of French Guiana. Changes in physical parameters, such as sediment erodability (yield stress), water loss and pore water salinity indicated a long term compaction of mudflats as well as fluctuations related to the successive wetting and drying cycles. Muderacks constituted a spectacular feature representative of the contractional stress. They (re)opened after a few days of dewatering and (re)healed during the subsequent wetting. From the analysis of field data, the trapping of Avicennia germinans propagules in ephemeral mudcracks turned out to be responsible of 95% of the sprouting on the coastal fringe. Thus, desiccation process, usually considered as a typical feature of erosion, revealed herein to be a major mechanism of colonization. This mechanism undoubtedly affects the 1600 km long Amazon coastal system and is believed to exist in many other tropical environments submitted to important siltation. (c) 2006 Elsevier B.V. All rights reserved.

Published
2006

48. Estimation of the nesting season of marine turtles from incomplete data: statistical adjustment of a sinusoidal function

Author

Laurent Kelle, Nicolas Gratiot, Julien Gratiot, Benoit de Thoisy, Laboratoire d'étude des transferts en hydrologie et environnement (LTHE), Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Association Kwata, WWF Guianas, WWF, Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique de Grenoble (INPG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)

Subjects
0106 biological sciences, Estimation, Chelonia mydas, Ecology, biology, 010604 marine biology & hydrobiology, Lepidochelys olivacea, nesting counts, Residual, biology.organism_classification, Dermochelys coriacea, 010603 evolutionary biology, 01 natural sciences, Nest, Environmental science, Nesting (computing), 14. Life underwater, Physical geography, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, marine turtle, Nesting season, Nature and Landscape Conservation
Abstract

International audience; Because of logistical and financial constraints, nest counts of marine turtles are often limited in time and space. To overcome this difficulty, we developed a numerical model that fits the seasonal pattern of marine turtles nesting from complete or fragmented datasets. The duration of the main nesting season, the position and amplitude of its maximum as well as the residual number of nests, outside of the main season are obtained numerically by a least square adjustment. For the seven complete time series at our disposal (Dermochelys coriacea and Lepidochelys olivacea turtles, coast of French Guiana), the model reproduces the seasonal pattern with a correlation of r≥0.97. When applied on a fragmented dataset, the model accuracy depends on the duration and on the temporal distribution of the monitoring (effort equally distributed during the entire season or concentrated on a part of it only). As a result of this study, we clearly advocate a strategy of monitoring distributed all over the nesting season. Following this recommendation, the model estimates the annual number of nests with a median error lower than 10% when considering only 50 days of monitoring.

Published
2006

49. A Satellite Image–Based Method for Estimating Rates of Mud Bank Migration, French Guiana, South America

Author

Antoine Gardel and Nicolas Gratiot

Subjects
Shore, geography, Tidal range, geography.geographical_feature_category, Ecology, Bedrock, Intertidal zone, Estuary, Oceanography, Aerial photography, Satellite imagery, Physical geography, Coastal management, Geology, Earth-Surface Processes, Water Science and Technology
Abstract

GARDEL, A. and GRATIOT, N., 2005. A satellite image-based method for estimating rates of mud bank migration, French Guiana, South America. Journal of Coastal Research, 21(4), 720‐728. West Palm Beach (Florida), ISSN 07490208. The muddy Guyanas coastline in South America experiences significant short-term change involving alternations of accretion and erosion as a result of the influence of mud from the Amazon River. In French Guiana, the dynamic changes due to mud banks permanently migrating alongshore have a considerable impact on both coastal ecology and economic activities. As a result, monitoring of these mud banks constitutes an important coastal management issue. In this article, focus is placed on the development of a method for the monitoring mud bank migration rates since 1986 between the coastal cities of Cayenne and Kourou, spaced 60 km apart and using for the first time high temporal resolution satellite images rather than aerial photographs. To achieve this, 16 satellite pour l’observation de la terre (SPOT) images and one Landsat image covering the period 1986‐2002 were acquired and integrated in a geographical information system (GIS). Because of tidal range variation on this mesotidal coast, mud bank characteristics cannot be objectively quantified using classical methods. Mathematical processing of the satellite imagery data, including correction for tides, was performed to obtain a set of coherent data for analysis of parts of the mud bank associated with intertidal mudflat development, from which quantification rates of mud bank migration becomes feasible. Rates of long shore migration of the mud bank recorded up to 2002 are highly variable. The intertidal part of the bank has slowed down in the past years, resulting in a cross-shore extension of the bank. This slowdown occurred following a rate of migration much higher than those reported in the literature. Seasonal events are also recorded between 2001 and 2002. The variability in rates of migration deduced from the method reported in this study corroborates a pattern reported from earlier studies in Guyana, Surinam, and French Guiana based on more traditional methods, notably aerial photographs. This variability is tentatively attributed to changes in wind intensity and to local environmental parameters, such as coastline orientation, and the occurrence river estuary outflow and bedrock headlands.

Published
2005

50. Coastline and mudbank monitoring in French Guiana: contributions of radar and optical satellite imagery

Author

Nicolas Gratiot, Carlos Oliveros, Anne Bourguignon, Jean Pierre Lefebvre, Nicolas Baghdadi, Territoires, Environnement, Télédétection et Information Spatiale (UMR TETIS), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-AgroParisTech-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Laboratoire d'étude des transferts en hydrologie et environnement (LTHE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Mécanique et d'Acoustique [Marseille] (LMA ), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Université Grenoble Alpes (UGA), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées

Subjects
010504 meteorology & atmospheric sciences, IMAGE SATELLITE, 0211 other engineering and technologies, ZONE COTIERE, Submarine, 02 engineering and technology, RADAR, 01 natural sciences, law.invention, Geography, Remote sensing (archaeology), law, [SDE]Environmental Sciences, ETUDE COMPARATIVE, General Earth and Planetary Sciences, Satellite, Satellite imagery, 14. Life underwater, Radar, VASE, CARTOGRAPHIE, IMAGE OPTIQUE, 021101 geological & geomatics engineering, 0105 earth and related environmental sciences, Remote sensing
Abstract

International audience; The constant migration of mudbanks resulting from the sedimentary discharge of the Amazon River has an enormous impact on the French Guianese economy. Consequently, there is great local interest in finding tools that can be used in mapping and monitoring the mudbank migration with an acceptable level of reliability and a high frequency of measurement. This involves the ability to detect submarine mudbanks that interfere with access to port channels and impede navigation. Radar and optical satellite images of French Guiana acquired between 1997 and 2001 have been analysed to assess their utility in detecting mudbanks and monitoring coastline change. In the present study, the information derived from radar and optical satellite imagery was analysed with respect to tidal height. The influence of the radar incidence angle was considered, as well as the advantages of having multidate sequences when mapping coastal zones undergoing significant change. A comparative study between radar (European Remote Sensing Satellite (ERS) and RADARSAT) and optical (advanced spaceborne thermal emission and reflection radiometer (ASTER)) images was also conducted. The results show that low-angle radar is more suitable for detecting mudbanks, whereas high-angle radar is more appropriate for monitoring coastline change. Emerged mudbanks and mudbanks under a shallow layer of water (a few tens of centimetres at the most) are easily detectable in radar images. For high tidal levels, the optical images provide more information on the mudbanks than the radar images. Conversely, for low tidal levels, the information on the mudbanks is more detailed with radar imagery.; Le déplacement continu des bancs de vase en provenance de l'Amazone a un impact très important sur l'économie guyanaise. La recherche d'outils permettant la cartographie des bancs et le suivi de leur migration dans des conditions acceptables de fiabilité et de rapidité présente donc un grand intérêt local. Ceci se traduit par la détection en mer des bancs de vase qui viennent perturber l'accès aux chenaux (ports) ce qui constitue un gêne pour la navigation. Des images satellitaires radar et optique, acquises sur la Guyane française entre 1997 et 2001, ont été analysées pour examiner leurs apports à la détection des bancs de vase, et au suivi de l'évolution du trait de côte. L'information issue de l'imagerie satellitaire radar et optique a été étudiée en fonction de la hauteur d'eau. Nous avons analysé l'influence de l'angle d'incidence radar et l'intérêt des séquences multi-dates pour cartographier les zones côtières soumises à des importantes modifications. Une étude comparative entre imagerie radar (ERS et RADARSAT) et optique (ASTER) a également été effectuée ainsi que la relation entre bathymétrie et information satellitaire. Les résultats montrent qu'une incidence radar faible est plus adaptée à la détection des bancs de vase tandis qu'une incidence radar forte est plus appropriée pour le suivi du trait de côte. Les bancs de vase émergés ou immergés sous une faible couche d'eau (quelques dizaines de centimètres au maximum) sont facilement détectables sur les images radar. Pour des hauteurs d'eau élevées, l'imagerie optique permet une meilleure caractérisation des bancs de vase comparativement à l'imagerie radar. Dans le cas d'une faible hauteur d'eau, les résultats montrent que les informations sur les bancs de vase sont plus détaillées avec l'imagerie radar.

Published
2014

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