Search

Your search keyword '"Lague, Dimitri"' showing total 257 results
Start Over Author "Lague, Dimitri"
257 results on '"Lague, Dimitri"'

1. Estimation of Physical Parameters of Waveforms With Neural Networks

Author

Jamal, Saad Ahmed, Corpetti, Thomas, Tiede, Dirk, Letard, Mathilde, and Lague, Dimitri

Subjects
Electrical Engineering and Systems Science - Signal Processing, Computer Science - Artificial Intelligence, Computer Science - Machine Learning
Abstract

Light Detection and Ranging (LiDAR) are fast emerging sensors in the field of Earth Observation. It is a remote sensing technology that utilizes laser beams to measure distances and create detailed three-dimensional representations of objects and environments. The potential of Full Waveform LiDAR is much greater than just height estimation and 3D reconstruction only. Overall shape of signal provides important information about properties of water body. However, the shape of FWL is unexplored as most LiDAR software work on point cloud by utilizing the maximum value within the waveform. Existing techniques in the field of LiDAR data analysis include depth estimation through inverse modeling and regression of logarithmic intensity and depth for approximating the attenuation coefficient. However, these methods suffer from limitations in accuracy. Depth estimation through inverse modeling provides only approximate values and does not account for variations in surface properties, while the regression approach for the attenuation coefficient is only able to generalize a value through several data points which lacks precision and may lead to significant errors in estimation. Additionally, there is currently no established modeling method available for predicting bottom reflectance. This research proposed a novel solution based on neural networks for parameter estimation in LIDAR data analysis. By leveraging the power of neural networks, the proposed solution successfully learned the inversion model, was able to do prediction of parameters such as depth, attenuation coefficient, and bottom reflectance. Performance of model was validated by testing it on real LiDAR data. In future, more data availability would enable more accuracy and reliability of such models.

Published
2023

4. Benchmark dataset for hydraulic simulations of flash floods in the French Mediterranean region.

Author

Godet, Juliette, Nicolle, Pierre, Hocini, Nabil, Gaume, Eric, Davy, Philippe, Pons, Frederic, Javelle, Pierre, Garambois, Pierre-André, Lague, Dimitri, and Payrastre, Olivier

Subjects
DIGITAL elevation models, WATERMARKS, FLOODS, FLOOD warning systems
Abstract

The absence of validation or comparison data for verifying flood mapping methods poses a significant challenge in developing operational hydraulic approaches. This article aims to address this gap by presenting a benchmark dataset for flash flood mapping in the French Mediterranean region. The dataset described in this paper (Nicolle et al., 2024) includes flood hazard maps and simulation results of three actual flash flood events, all computed in steady regime at a 5-meter resolution using a 2D SWE model (neglecting inertia) named Floodos (Davy et al., 2017). Additionally, it includes the input data necessary (Digital Terrain Models, inflow discharges, hydrographic network) for conducting similar simulations with other hydrodynamic modeling approaches, in both steady and unsteady regimes. A comprehensive validation dataset, comprising observed flood extents, high water marks, and rating curves, is also provided, enabling a detailed evaluation of 2D hydraulic simulation results. The simulation results from Floodos, compared against stage-discharge rating curves available at gauging stations, yielded highly encouraging outcomes. The median error (sim. - obs.) was -0.04 m for the 2-year return period and -0.14 m across all simulated return periods, ranging from 2 to 1000 years. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

5. Accurate 3D comparison of complex topography with terrestrial laser scanner: application to the Rangitikei canyon (N-Z)

Author

Lague, Dimitri, Brodu, Nicolas, and Leroux, Jérôme

Subjects
Physics - Geophysics
Abstract

Surveying techniques such as Terrestrial Laser Scanner have recently been used to measure surface changes via 3D point cloud (PC) comparison. Two types of approaches have been pursued: 3D tracking of homologous parts of the surface to compute a displacement field, and distance calculation between two point clouds when homologous parts cannot be defined. This study deals with the second approach, typical of natural surfaces altered by erosion, sedimentation or vegetation between surveys. Current comparison methods are based on a closest point distance or require at least one of the PC to be meshed with severe limitations when surfaces present roughness elements at all scales. We introduce a new algorithm performing a direct comparison of point clouds in 3D. Surface normals are first estimated in 3D at a scale consistent with the local surface roughness. The measurement of the mean change along the normal direction is then performed with an explicit calculation of a confidence interval. Comparison with existing methods demonstrates the higher accuracy of our approach, as well as an easier workflow due to the absence of surface meshing or DEM generation. Application of the method in a rapidly eroding meandering bedrock river (Rangitikei river canyon) illustrates its ability to handle 3D differences in complex situations (flat and vertical surfaces on the same scene), to reduce uncertainty related to point cloud roughness by local averaging and to generate 3D maps of uncertainty levels. Combined with mm-range local georeferencing of the point clouds, levels of detection down to 6 mm can be routinely attained in situ over ranges of 50 m. We provide evidence for the self-affine behavior of different surfaces. We show how this impacts the calculation of normal vectors and demonstrate the scaling behavior of the level of change detection.

Published
2013

7. 3D Terrestrial lidar data classification of complex natural scenes using a multi-scale dimensionality criterion: applications in geomorphology

Author

Brodu, Nicolas and Lague, Dimitri

Subjects
Computer Science - Computer Vision and Pattern Recognition, Physics - Geophysics
Abstract

3D point clouds of natural environments relevant to problems in geomorphology often require classification of the data into elementary relevant classes. A typical example is the separation of riparian vegetation from ground in fluvial environments, the distinction between fresh surfaces and rockfall in cliff environments, or more generally the classification of surfaces according to their morphology. Natural surfaces are heterogeneous and their distinctive properties are seldom defined at a unique scale, prompting the use of multi-scale criteria to achieve a high degree of classification success. We have thus defined a multi-scale measure of the point cloud dimensionality around each point, which characterizes the local 3D organization. We can thus monitor how the local cloud geometry behaves across scales. We present the technique and illustrate its efficiency in separating riparian vegetation from ground and classifying a mountain stream as vegetation, rock, gravel or water surface. In these two cases, separating the vegetation from ground or other classes achieve accuracy larger than 98 %. Comparison with a single scale approach shows the superiority of the multi-scale analysis in enhancing class separability and spatial resolution. The technique is robust to missing data, shadow zones and changes in point density within the scene. The classification is fast and accurate and can account for some degree of intra-class morphological variability such as different vegetation types. A probabilistic confidence in the classification result is given at each point, allowing the user to remove the points for which the classification is uncertain. The process can be both fully automated, but also fully customized by the user including a graphical definition of the classifiers. Although developed for fully 3D data, the method can be readily applied to 2.5D airborne lidar data., Comment: Free/Libre software implementation is available at http://nicolas.brodu.numerimoire.net, as well as data sets

Published
2011

8. A multi-sensor approach to monitor the ongoing restoration of edaphic conditions for salt marsh species facing sea level rise: An adaptive management case study in Camargue, France

Author

Davranche, Aurélie, primary, Arzel, Céline, additional, Pouzet, Pierre, additional, Carrasco, A. Rita, additional, Lefebvre, Gaëtan, additional, Lague, Dimitri, additional, Thibault, Marc, additional, Newton, Alice, additional, Fleurant, Cyril, additional, Maanan, Mohamed, additional, and Poulin, Brigitte, additional

Published
2024
Full Text
View/download PDF

18. A Multi-Sensor Approach to Monitor the Ongoing Restoration of Edaphic Conditions for Salt Marsh Species Facing Sea Level Rise: An Adaptive Management Case Study in Camargue, France

Author

Davranche, Aurélie, primary, Arzel, Céline, additional, pouzet, Pierre, additional, Carrasco, Ana Zarcos, additional, Lefebvre, Gaëtan, additional, Lague, Dimitri, additional, Thibault, Marc, additional, Newton, Alice, additional, Fleurant, Cyril, additional, Maanan, Mohamed, additional, and Poulin, Brigitte, additional

Published
2023
Full Text
View/download PDF

22. Using bispectral full waveform LiDAR to map seamless coastal habitats in 3D

Author

Letard, Mathilde, Collin, Antoine, Lague, Dimitri, Corpetti, Thomas, Pastol, Yves, Ekelund, A., École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL), Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN), Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Littoral, Environnement, Télédétection, Géomatique (LETG - Rennes), Université de Nantes (UN)-Université de Nantes (UN)-Université de Caen Normandie (UNICAEN), LTER Zone Atelier Armorique, Rennes, Service Hydrographique et Océanographique de la Marine (SHOM), Ministère de la Défense, and Airborne Hydrography AB - Jönköping

Subjects
[SDE]Environmental Sciences
Abstract

International audience

Published
2022

32. Towards a Universal Theory of Multi-Grain Size Sediment Transport Using the Transport Length and Erosion-Deposition Model Framework

Author

Le Minor, Marine, Davy, Philippe, Howarth, Jamie, Lague, Dimitri, Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Victoria University of Wellington, and Dubigeon, Isabelle

Subjects
[SDU.STU.CL] Sciences of the Universe [physics]/Earth Sciences/Climatology, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy, [SDU.STU.ST] Sciences of the Universe [physics]/Earth Sciences/Stratigraphy
Abstract

International audience; Due to flow variability and sediment heterogeneity, different modes of transport are observed, either successively or simultaneously, in natural rivers. All these modes contribute to the total sediment transport and thus should be considered in the context of fluvial sediment transport and morphodynamic modeling. However, a universal sediment transport law from bed load to suspended load applicable to the full range of hydraulic conditions and to sediment mixtures is lacking despite numerous published transport capacity laws. Similarly, morphodynamic fluvial models typically assume transport-limited conditions that can not capture under-capacity conditions occurring potentially for a certain range of grain sizes and flow conditions. Thus, we aim at building a self-consistent theory by gathering widely accepted concepts of sediment transport in the framework of erosion-deposition models using a disequilibrium transport length. First, we develop a new transport length model that takes into account the different transport modes as a physical continuum. Second, we combine this continuous model of transport length with the erosion-deposition model that we adapt to account for multi-grain sizes. All these steps use existing, tested elementary ingredients that do not require further calibration parameters. Predicted transport lengths range over several orders of magnitude and, for the same hydraulic conditions, the transport length increases with finer grain sizes. Modeled stream capacities obtained at saturation are in agreement with flume observations for both single-grain and multi-grain approaches with at least 70% of the experimental data predicted within a factor 10. The main result is, to our knowledge, the first Multi-Grain Size Sediment Transport model encompassing the diversity of transport modes in non-stationary regimes and predicting how stream capacities scale with bed shear stress. We illustrate how this universal theory of sediment transport can be used to better understand the relationship between grain sizes and transport distances. And we develop long-term transport laws that include the effects of water discharge variability and sediment heterogeneity on fluvial morphodynamic instabilities and deposit stratigraphy, e.g., armor layer and downstream fining.

Published
2021

33. Investigating Stochastic-threshold Incision Models accros a Climatic Gradient : example from the South-eastern Margin of the Massif Central, France

Author

Desormeaux, Clément, Godard, Vincent, Lague, Dimitri, Duclaux, Guillaume, Fleury, Jules, Benedetti, Lucilla, Bellier, Olivier, American Geophysical Union [Washington], Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), 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), Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Géoazur (GEOAZUR 7329), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])

Subjects
[SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology
Abstract

International audience; Investigating landscapes evolution and their responses to tectonic or climatic perturbation requires accurate representations and models of surfaces processes. Rivers are keys agents of the transmission of external forcing through landscape and the main drivers of continental denudation. For these reasons the mechanisms of fluvial incision have been a key focus of geomorphological research over the last decades.Long-term river incision is usually modeled with the Stream Power Model (Howard et al. 1997; Whipple & Tucker 1999) based on the along-stream evolution of drainage area and channel elevation gradient. More complex development of the SPM (Tucker 2004; Lague et al. 2005) combine instantaneous river incision with the probability for discharge occurrence and take into account incision threshold and discharge variability. These models have been confronted with fields data in a limited number of cases (DiBiase et al. 2011, Scherler et al. 2017, Campforts et al. 2020).Our objective is to investigate the behavior of stochastic-threshold incision models across the south-eastern margin of the Massif Central (France) where a strong gradient in discharge variability is reported. We present a new dataset combining measurements of discharge variability from gauging stations, denudation rates on 34 basins from 10Be cosmogenic nuclides and morphometric parameters from river long-profile analysis.Our results show a complex relationship between denudation rates and steepness index which cannot be explain only by the regional discharge variability gradient. When compared with measured erosion rates, we observe that the predictions of a stochastic-threshold incision model are not better than simpler versions of the SPM and require to take into account spatial variations in incision thresholds.

Published
2021

35. Influence de la variabilité des débits sur les taux d'érosions et le relief long-terme : l'exemple de la bordure sud-est du Massif Central, France

Author

Desormeaux, Clément, Godard, Vincent, Lague, Dimitri, Duclaux, Guillaume, FLEURY, Jules, Benedetti, Lucilla, Olivier, Bellier, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), 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), and SGF, CNRS, Laboratoire de Géologie de Lyon ou l’étude de la Terre, des planètes et de l’environnement

Subjects
Massif Central, événements extrêmes, [SDU]Sciences of the Universe [physics], modèles d'incisions, taux de dénudation, morphométrie, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2021

36. Coupling topographic airborne lidar and photo-sieving methods for grain-size mapping

Author

Piasny, Guillaume, Chardon, Valentin, Garambois, Pierre-André, Finaud-Guyot, Pascal, Lague, Dimitri, Schmitt, Laurent, University of Strasbourg, Laboratoire Image, Ville, Environnement (LIVE), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Géosciences Rennes (GR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS), Littoral, Environment: MOdels and Numerics (LEMON), Inria Sophia Antipolis - Méditerranée (CRISAM), Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Institut Montpelliérain Alexander Grothendieck (IMAG), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-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)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), 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), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), and Dubigeon, Isabelle

Subjects
[SDU.STU.GM] Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2021

37. Depicting architecture and sedimentology of a hypertidal point bar through Lidar and sedimentary-core data

Author

Cosma, Marta, LAGUE, Dimitri, D’Alpaos, Andrea, Leroux, Jérôme, Feldmann, Baptiste, Ghinassi, Massimiliano, DEPARTMENT OF GEOSCIENCES UNIVERSITY OF PADOVA ITA, Partenaires IRSTEA, Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), Géosciences Rennes (GR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS), Observatoire des Sciences de l'Univers de Rennes (OSUR), Università degli Studi di Padova = University of Padua (Unipd), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 1 (UR1), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)

Subjects
[SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology
Abstract

International audience; Morphodynamic behaviour of tidal meanders and internal architecture of related sedimentary bodies havereceived scarce attention, although they are ubiquitous features of coastal landscapes. Expansion of tidalmeanders is known to produce a progressive increase of bend sinuosity, along with accretion of point-bardeposits and formation of inclined heterolithic strata. These deposits are considered to be rich in fine-grainedsediments and tend to record tidal rhythmic deposition in the upper part of the bar, being the lower bar depositsdominated by erosional and bypass processes. Although these criteria are widely accepted, faciesmodels for tidal point bars still lack a 3D perspective and overlook the along-bend variability of sedimentaryprocesses. This knowledge gap can have a direct impact on understanding intra-point-bar heterogeneitiesand connectivity, with implications for reservoir production. The present study focuses on a 3 m deep tidalmeandering channel located in the salt marshes of the hypertidal Mont-Saint-Michel Bay (France), and investigatessedimentology of a time-framed bar accretionary package by means of Lidar-topographic data,geomorphological-field surveys and sedimentary cores. The studied accretionary package was accretedalong the bar between 28/03/2012 and 29/11/2012. Integration between Lidar and sedimentary-core datashows that over this time the bar expanded alternating depositional phases along its seaward and landwardside. The maximum thickness of deposits was accumulated in the bar apex zone, and just landwardof it, where the largest amount of mud was also stored. High accretion rate of the bar apex zone endorsedalso a better preservation of rhythmites, which are almost missing from deposits accumulated along thebar sides (i.e. close to riffles). We suggest that alternating depositional loci and high sediment accretion atthe bend apex zone emerge due to a combination of factors, including: i) the spatio-temporal asymmetricnature of tidal currents, which influenced deposition and preservation of flood and ebb deposits along thebend; and ii) the development of low-energy conditions at the apex due to ebb and flood flow configuration,which also promoted mud settling.This study highlights that mud and tidal rhythmites are not uniformly distributed within point-bar deposits,and their occurrence is strongly controlled by the asymmetric and mutually evasive nature of ebb and floodtides.

Published
2021

38. Performance of automated methods for flash flood inundation mapping: a comparison of a digital terrain model (DTM) filling and two hydrodynamic methods

Author

Hocini, Nabil, Payrastre, Olivier, Bourgin, François, Gaume, Eric, Davy, Philippe, Lague, Dimitri, Poinsignon, Lea, Pons, Frederic, Eau et Environnement (GERS-LEE ), Université Gustave Eiffel, Hydrosystèmes continentaux anthropisés : ressources, risques, restauration (UR HYCAR), Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Géosciences Rennes (GR), Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), Centre d'Etudes et d'Expertise sur les Risques, l'Environnement, la Mobilité et l'Aménagement - Direction Méditerranée (Cerema Direction Méditerranée), Centre d'Etudes et d'Expertise sur les Risques, l'Environnement, la Mobilité et l'Aménagement (Cerema), ANR-17-CE03-0011,PICS,PICS: vers une Prévision Immédiate intégrée des Impacts des Crues Soudaines(2017), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), and ANR-17-CE03-0011, Agence Nationale de la Recherche

Subjects
[PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology
Abstract

Flash floods observed in headwater catchments often cause catastrophic material and human damage worldwide. Considering the large number of small watercourses possibly affected, the use of automated methods for flood inundation mapping at a regional scale can be of great help for the identification of threatened areas and the prediction of potential impacts of these floods. An application of three mapping methods of increasing level of complexity is presented herein, including a digital terrain model (DTM) filling approach (height above nearest drainage/Manning–Strickler or HAND/MS) and two hydrodynamic methods (caRtino 1D and Floodos 2D). These methods are used to estimate the flooded areas of three major flash floods observed during the last 10 years in southeastern France, i.e., the 15 June 2010 flooding of the Argens river and its tributaries (585 km of river reaches), the 3 October 2015 flooding of small coastal rivers of the French Riviera (131 km of river reaches) and the 15 October 2018 flooding of the Aude river and its tributaries (561 km of river reaches). The common features of the three mapping approaches are their high level of automation, their application based on a high-resolution (5 m) DTM, and their reasonable computation times. Hydraulic simulations are run in steady-state regime, based on peak discharges estimated using a rainfall–runoff model preliminarily adjusted for each event. The simulation results are compared with the reported flood extent maps and the high water level marks. A clear grading of the tested methods is revealed, illustrating some limits of the HAND/MS approach and an overall better performance of hydraulic models which solve the shallow water equations. With these methods, a good retrieval of the inundated areas is illustrated by critical success index (CSI) median values close to 80 %, and the errors on water levels remain mostly below 80 cm for the 2D Floodos approach. The most important remaining errors are related to limits of the DTM, such as the lack of bathymetric information, uncertainties on embankment elevation, and possible bridge blockages not accounted for in the models.

Published
2021
Full Text
View/download PDF

48. Links between erosion, runoff variability and seismicity in the Taiwan orogen

Author

Dadson, Simon J., Hovius, Niels, Chen, Hongey, Dade, W. Brian, Hsieh, Meng-Long, Willett, Sean D., Hu, Jyr-Ching, Horng, Ming-Jame, Chen, Meng-Chiang, Stark, Colin P., Lague, Dimitri, and Lin, Jiun-Chuan

Abstract

Author(s): Simon J. Dadson (corresponding author) [1]; Niels Hovius [1]; Hongey Chen [2]; W. Brian Dade [4]; Meng-Long Hsieh [2]; Sean D. Willett [5]; Jyr-Ching Hu [2]; Ming-Jame Horng [6]; [...]

Published
2003
Full Text
View/download PDF

49. Investigation of stochastic-threshold incision models across a climatic and morphological gradient.

Author

Desormeaux, Clément, Godard, Vincent, Lague, Dimitri, Duclaux, Guillaume, Fleury, Jules, Benedetti, Lucilla, Bellier, Olivier, and the ASTER Team

Subjects
WATERSHEDS, LONG-Term Evolution (Telecommunications), SPATIAL variation, BED load, FLUVIAL geomorphology, GEOMORPHOLOGY, RUNOFF, RIVER sediments
Abstract

Long-term landscape evolution is controlled by tectonic and climatic forcing acting through surface processes. Rivers are the main drivers of continental denudation because they set the base level of most hillslopes. The mechanisms of fluvial incision are thus a key focus in geomorphological research and require accurate representation and models. River incision is often modeled with a stream power model (SPM) based on the along-stream evolution of drainage area and channel elevation gradient but can also incorporate more complex processes such as threshold effects and statistical discharge distributions, which are fundamental features of river dynamics. Despite their importance in quantitative geomorphology, such model formulations have been confronted with field data only in a limited number of cases. Here we investigate the behavior of stochastic-threshold incision models across the southeastern margin of the French Massif Central, which is characterized by significant relief and the regular occurrence of high-discharge events. Our study is based on a new dataset combining measurements of discharge variability from gauging stations, denudation rates from 34 basins from 10Be cosmogenic radionuclide (CRN) concentration measurements in river sediments, morphometric analysis of river long profiles, and field observations. This new dataset is used for a systematic investigation of various formulations of the SPM and to discuss the importance of incision thresholds. Denudation rates across the SE margin of the Massif Central are in the 20–120 mm kyr -1 (equivalent to mm/ka in the figures) range, and they positively correlate with slope and precipitation. However, the relationship with the steepness index is complex and supports the importance of taking into account spatial variations in parameters (D50 , discharge variability k , runoff) controlling the SPM. Overall, the range of denudation rate across the margin can mainly be explained using a simple version of the SPM accounting for spatially heterogeneous runoff. More complex formulations including stochastic discharge and incision thresholds yield poorer performances unless the spatial variations in bedload characteristics controlling incision thresholds are taken into account. Our results highlight the importance of the hypotheses used for such a threshold in SPM application to field studies and notably the impact of actual constraints on bedload size. [ABSTRACT FROM AUTHOR]

Published
2022
Full Text
View/download PDF

50. Flash flood impacts nowcasting within the PICS project (2018-2022): End-users involvement and first results

Author

Javelle, Pierre, primary, Payrastre, Olivier, additional, Boudevillain, Brice, additional, Bourgin, François, additional, Bouttier, François, additional, Caumont, Olivier, additional, Charpentier-Noyer, Maryse, additional, Ducrocq, Veronique, additional, Fleury, Axelle, additional, Garambois, Pierre-André, additional, Gaume, Eric, additional, Hocini, Nabil, additional, Janet, Bruno, additional, Jay-Allemand, Maxime, additional, Lague, Dimitri, additional, Lovat, Alexane, additional, Moncoulon, David, additional, Naulin, Jean-Philippe, additional, Nicolle, Pierre, additional, Peredo, Daniela, additional, Perrin, Charles, additional, Pons, Frédéric, additional, Ramos, Maria-Helena, additional, Ruin, Isabelle, additional, and Terti, Galateia, additional

Published
2021
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results