Search

Meandering is one of the most common morphological pattern through which rivers manifest themselves. Here, the attention is devoted to meandering streams carving their path through permafrost floodplains, which typically characterize cold environments such as the Arctic. Despite meandering rivers have been widely studied in the last fifty years, little is known about the dynamics of streams where banks are composed of perennially frozen material. It is inquired whether there is a morphological signature in the planform of permafrost streams potentially deriving from specific thermo-mechanical processes occurring in Arctic landscapes, like the formation of thermo-erosional niches and sediment slumps caused by thaw-weakened soil. To this aim, a bend scale analysis of the planform geometry of several Arctic streams by means of Landsat satellite imagery is employed. Morphodynamic features such as lateral migration rates, channel curvatures, and width variations, are extracted from multispectral remotely sensed data by combining Google Earth Engine (GEE) with an established process-based software (PyRIS). Following a methodology based on continuous wavelet transform, a set of metrics quantitatively defining the meander shape, which include fattening and skewing coefficients, are used to compare permafrost streams with a series of natural meandering rivers from tropical and temperate regions obtained from the literature. The present analysis opens the way to a systematic integration between remote sensing and physically-based morphodynamic models able to incorporate thermo-mechanical processes uniquely related to permafrost environments.

While river channel change is a natural process for an alluvial river, increasing human activities such as sediment mining, construction of reservoirs and land use alterations can accelerate this process. Growing urbanization and socio-economic development in South-Eastern Europe over the last 30 years has shown a major impact on the river channel adjustments. New urbanization in Albania has rapidly developed after the collapse of dictatorial regime in 1990, with most rural population moving to the big cites, mostly the nearby capital Tirana and Durres. As consequence a boom in construction industry has occurred in this part of Albania, including new buildings and infrastructures. Rivers have been the primary source of building material. Here we analyse the channel adjustments that occurred on the Erzen River that passes nearby the two major urban centers of Tirana and Durres. The Erzen River has its origin at the Gropa mountain at 1200m asl, its length is 109 km, and it flows approximately westwards towards its mouth in the Adriatic Sea near the Lalzi Bay. The catchment area is 760 km2 and the mean annual flow is 18.1 m3/s. We analyse the incision and channel narrowing at lower part of the river by using remote sensing, historical image analyses, DEM and survey in the field. Major hydromorphological pressures potentially affecting the flow and sediment supply regime have been also analysed. Specifically, sediment mining has been reconstructed by identifying the mining sites in contact with the active river corridor between 1990-2015 along 30 km river length from aerial rivers, and from technical reports providing estimation of sand and gravel removed from the river.Our findings indicate rapid changes of channel morphology, with 20% up to 75% channel narrowing affecting the transitional and meandering reaches between 1968-2015 and high riverbed incision at the reach scale up to 5-6 m, which is also revealed by visual signs like increasing bed rock and bridge foundations exposure. Two cut-offs have been created at the meandering part of the river. Most of the main bridges in Albanian rivers have shown exposed foundation with 3-4 m on the last 15-20 years, where some of them are replaced by other bridges due to unstable structure condition. Compared with previous studies, narrowing and incision rates are among the highest observed in Europe after the 1950s. While on the upstream segment of the river two dams have been built, sediment mining appears as the main driving factors of the observed channel narrowing and incision. Twenty-two mining sites have been detected between 1995 - 2015 and 457,380 m3/year of sediments have been reported as withdrawn from the riverbed. The rapid channel incision has contributed to the increasing salty water intrusion and subsequent freshwater shortage in lowland part of the river. The observed narrowing and incision have likely played a key role also in the reduction of river sediment supply to the sea, which probably explains most of the very rapid coastal erosion that has been observed in the same period in the Lalzi Bay.

The construction of artificial reservoirs for hydropower production strongly alters sediment connectivity, which often produces significant impacts on the river reaches downstream morphology. Assessing sediment connectivity and transport variations is therefore crucial for predicting possible fluvial morphological trajectories and to define scientifically-based management practices in terms of water and sediment releases from Alpine reservoirs. For this reason APRIE, the agency responsible for hydropower regulation in the Trento Province (Italy), is carrying out a project to assess impacts caused by existing hydropower plants, in collaboration with the University of Trento.We focused on the study case of the Travignolo River, a tributary of the Avisio River in the Dolomites. The valley longitudinal connectivity has been completely interrupted by the Forte Buso dam construction in 1953 and by a series of smaller derivations from the main tributaries. We aim at understanding to what extent the presence of the dam affects the overall sediment connectivity, by assessing the relative contribution of sediment sources that currently drain into the lake with respect to the sources that are still connected to the Travignolo River, and by evaluating to what extent the disconnectivity has compromised the morphological equilibrium of the river.To this aim, structural and functional sediment connectivity are analysed through a three step integrated approach, considering connectivity at different spatial scales. First, fluvial morphological trajectories have been studied by investigating a dataset of historical images, which allowed us to identify both morphological changes and vegetation growth. Second, sediment connectivity has been modelled at the hillslope scale through the hydrological index of connectivity calculated by applying the SedInConnect model (Crema, S. & Cavalli, M., 2018, Computational Geosciences) on the basis of terrain elevation data and information on Quaternary deposits. The model allowed us to determine the potential sediment yield contribution from the different subbasins, as well as the position of sediment sources depending on their characteristic grain size. Finally, a quantitative analysis of sediment longitudinal connectivity has been carried on by applying the CASCADE Toolbox model (Tangi, M. et al., 2019, Environmental Modelling & Software) to the main river network of the Travignolo basin. Information on surface and subsurface grain size distribution have been obtained by collecting several samples along the main course of the Travignolo River and along their main tributaries, while channel width was estimated by analysing the high-resolution digital elevation model. To calibrate CASCADE model we have compared the predicted grain size distribution cascades with the measured subsurface composition. Furthermore, we have performed several simulations considering different methods of data spatialization and different choices of the main parameters, to obtain a general assessment of the model uncertainties.Results highlight the potential sediment contributions of different subbasins to the fluvial system, depending on their geological characteristics, slope and distance from the permanent drainage network. Moreover, the analysis of multiple scenarios reveals how sediment transport processes are strongly affected by the dam presence and how they may change depending on water delivery strategies.

We investigated the ecohydraulic effects of a recently implemented hydropeaking mitigation measure in the Upper Noce Stream (NE Italy, Italian Alps), which also allows for additional hydropower production. The Upper Noce, a 3rd order gravel-bed stream, was affected since the mid-1920s by storage hydropower production and associated hydropeaking. The mitigation measure consisted in the diversion of most of the released hydropeaks into a sequence of three newly-installed, cascading run-of-the-river power plants, fed by a penstock running almost parallel to the former hydropeaking reach. The hydropeaking-diversion mitigation measure markedly reduced hydropeaking on a 10-km stream reach, and hydropeaking is now released immediately upstream the confluence with a major free-flowing tributary, which increases the hydropeaking baseflow. The flow regime in the mitigated reach shifted from hydropeaking-dominated to baseflow-dominated regime in winter, with flow variability represented only by snowmelt and rainfall in late spring and summer. We applied two sets of indicators (the Hydropeaking Indicators HP1, HP2 and the COSH method) and conducted a simplified hydraulic analysis of the hydropeaking wave propagation. We assessed the ecological effects of the mitigation measure using three complementary data sources: the analysis of (a) the benthic and (b) hyporheic invertebrate communities, based on datasets collected before and after the implementation of the diversion measure, and (c) ancillary data monitored by the diversion plant manager for required environmental monitoring, which included the suspended sediment regime and the Extended Biotic Index, measured yearly from the year before to the four subsequent years after the implementation of the mitigation measure.Three main changes in eco-hydraulic processes associated with hydropeaking mitigation were detected. i) The flow regime in the mitigated reach changed to a residual flow type, with much less frequent residual hydropeaks, with an average two-fold increase in downramping rates that were recorded downstream the junction with a major tributary. ii) The functional composition of the macrobenthic communities shifted slightly in response to flow mitigation, but the taxonomic composition did not recover to conditions typical of more natural flow regimes. This was likely due to the reduced dilution of pollutants and resulting slight worsening in water quality. iii) The hyporheic communities conversely showed an increase in diversity and abundance of interstitial taxa, especially in the sites most affected by hydropeaking, and this effect was likely due to changes in the interstitial space availability, brought by an alteration of the previous time-space pattern of fine sediment transport, which eventually resulted in reduction of fine sediments clogging of the gravel bed interstices.Besides illustrating a feasible hydropeaking mitigation option for Alpine streams, this work suggests the importance of monitoring both benthic and hyporheic communities, together with the flow and sediment supply regimes, and physico-chemical water quality parameters, for carefully detecting changes in eco-hydraulic processes associated with hydropeaking mitigation that may not be fully expected in the design phase.

Climate change is already altering the hydrological regime of Arctic rivers. However, still little is known about fluvial morphological processes and trajectories in permafrost environments. In such iced floodplains, both hydrological and thermal regimes affect sediment transport and riverine morphological processes. Remote sensing represents a powerful approach to investigate fluvial systems in those isolated areas. Nevertheless, its application presents challenges linked to ice seasonality and the limited time window of the morphological activity, alongside the complex permafrost/river spatial patterns and related spectral signatures, which imply significant computational efforts. Addressing this, we propose an improved integration of existing tools for the spatio-temporal extraction of fluvial morphological indicators, combining in a unique working environment the cloud computing capability of Google Earth Engine (GEE) and a process-based tool for riverine multitemporal planform analysis (PyRIS). Fluvial morphological metrics have been extracted from a set of meandering rivers in the Arctic region, outlining the potential of anisotropic image filtering and image segmentation to enhance active channel detection in complex spatial-pattern areas. A 20-40% refinement in small object removal in river mask detection emerges. The synergy among existing instruments enhances the observation of natural river systems in permafrost environments, setting the basis for further studies on morphological processes and the evolution of such pristine and climatically-sensitive river systems.

Urban population has been increasing worldwide in recent decades and it is expected to continue growing in the coming years. Cities are facing the effects of the climate crisis, which primarily impact the most vulnerable contexts, first and foremost informal settlements. In this context, the growth of informal neighborhoods, home to one billion people1, poses complex challenges for the cities of today and tomorrow. In these urban areas traditional, informal and formal social dynamics coexist, strengthened by strong community identities and bonds. Major problems are due to the lack of basic services and infrastructure, making these areas more vulnerable to the increasingly frequent and intense extreme rainfall events. In this work, we present the recently launched Europeaid-funded project MUDAR (Mozambique integrated Urban Development by Actions and Relationships), and specifically focus on its component that addresses the dynamics and effects of flooding in an informal urban area: the Macuti neighborhood in the city of Beira, Mozambique. Macuti is situated on the coast, making it particularly vulnerable to frequent cyclones, one of all Idai, which damaged 49% of its buildings in March 20192. Moreover, it is located on a marshy, purely flat area at the end of an inadequate open drainage network serving the entire city, which is unable to drain the flow at high tide. Macuti, with its almost 17 thousand people (2017), since the early 2000s has been experiencing a rapid growth in spontaneous settlements, which has resulted in a higher population density, with the unbuilt area decreasing by 40% from 2004 to 2022, and soil permeability further reducing in a context where the clayey soil composition already strongly limits rainfall infiltration. These changes, in addition to the inadequate water infrastructure, have exacerbated flooding problems associated with heavy rainfall events (the maximum daily precipitation of the 1990-2020 period was 288.5 mm/day). Investigating the socio-hydrology of flooding in these informal settlements is particularly complex because its requirements for high-resolution topographic, soil, land use and meteorological data, which are very limited in these informal settlements. More specifically, we present preliminary outcomes and the proposed project strategy to cope with the intrinsic data scarcity of such context, which is based on carefully designed participatory surveys with local actors. To fill this data gap, a multi-disciplinary approach has been adopted by combining elaborations from satellite image processing (SAR) with in-situ measurements and interviews to inhabitants and professionals. In addition to being involved in providing information about the area, the inhabitants are a crucial actor in the decision-making process for choosing the technical solutions to be implemented. Preliminary results on flooding dynamics in Macuti neighborhood, as well as on three Nature-Based-Solutions scenarios emerging from the participatory process highlight promising factors that can allow adapting the participatory procedure in similar contexts. 1French, M., Trundle, A., Korte, I., Koto, C. (2020). Climate Resilience in Urban Informal Settlements: Towards a Transformative Upgrading Agenda. Climate Resilient Urban Areas, 129-1532UNOSAT-REACH (2019). Mozambique- Beira City -Macuti - Neighbourhood Damage Assessment- As of 26 March 2019. URL: https://m.reliefweb.int/report/3056948

Rivers are increasingly recognised as active players in the global carbon cycle. They are able to transport, transform, and exchange organic matter, and can emit considerable fluxes of greenhouse gases (e.g., CO2) into the atmosphere, with a magnitude comparable to the global carbon input to the oceans. However, the quantification of these processes is still affected by considerable uncertainties, driven by an incomplete understanding of the interplay between physical, geochemical, and biological parameters, and by a lack of spatially and temporally resolved high-quality data. For instance, and despite a potentially strong impact on kilometres of rivers worldwide, the effects of hydropeaking on riverine CO2 emissions have been almost completely neglected until recently (Calamita et al., Unaccounted CO2 leaks downstream of a large tropical hydroelectric reservoir, PNAS 2020). As a contribution to filling this knowledge gap, we present the results of a field-measurement campaign performed in a single-thread Alpine river (River Noce, Italy) during multiple hydropeaking events. Data of water-dissolved CO2, water temperature, and flow discharge, were collected sub-hourly both downstream and upstream of the outlets of a hydropower plant, revealing a complex pattern of variation in time at both locations. Water released from the hydropower plant during hydropeaking had oversaturated CO2 concentrations relative to the atmosphere, in close agreement with water samples collected in the hypolimnion of the upstream reservoir. Higher flow rates during hydropeaking events were associated with higher rates of gas exchange through the water-air interface. Higher exchange rates and higher CO2 concentrations in water during hydropeaking events enhanced CO2 fluxes, as confirmed by measurements with a floating CO2 flux chamber. Meanwhile, the CO2 concentration upstream of the outlets displayed strong diel fluctuations around the atmospheric equilibrium concentration, which were likely driven by primary production within the residual flow during the day. It is shown that the residual flow can have a previously unacknowledged added value as a CO2 sink during the day, fueled by its biological activity. Hydropower releases bypassed the residual flow and discharged hypolimnetic water oversaturated with CO2 at high flow rates during hydropeaking, offsetting CO2 concentration and fluxes downstream of the outlets and increasing emissions on average. These results highlight the ubiquity of hydropeaking impacts also with respect to greenhouse gas emissions. They illustrate the complexity of the riverine carbon cycle and demonstrate the importance of temporally and spatially-resolved data for the accurate assessment of the riverine carbon balance.

We discuss the prioritization of river reaches to be selected for restoration measures under the constraints of financial resource limitation. We propose and apply a simple approach based on the quantification of major hydro‐morphological alterations and the critical comparison with locally proposed restoration actions. The available hydro‐morphological and ecological data for the approach do not go beyond the requirements posed by the implementation of the EU Water Framework and Floods Directives. We describe an example that refers to a heavily regulated Alpine river (Sarca River, NE Italy). The results indicate hydropower facilities as a key source of hydrological alteration, with sediment retention and grade control structures on lateral tributaries playing an additional relevant role in reducing sediment supply. The frequency and duration of sediment‐transporting floods have dramatically decreased, and the bed sediment composition has been markedly altered and become highly compacted. Habitat improvement has been achieved after the implementation of minimum environmental flows. The comparison between the results of the hydro‐morphological indicators and the locally proposed restoration actions highlights that reaches with lower degree of hydro‐morphological alterations do not coincide with the areas chosen for the locally planned actions, which often miss considerations of the relevant spatial scales. In a context of limited available financial resources and data compared to other flagship river restoration projects in the European Alps, the present work suggests viable options for the choice of target restoration reaches., Consorzio dei Comuni BIM Sarca, Italian Ministry of Education, University and Research (MIUR), Rete di Riserve della Sarca

Besides their environmental values, near-natural rivers offer the opportunity to observe and investigate riverine processes as they would occur under limited anthropic pressures, representing fundamental references for river management and restoration. Even so, few large near-natural rivers can still be found in Europe and worldwide, and their knowledge is often scarce due to a lack of hydromorphological monitoring and baseline studies. Among them, the Vjosa/Aoos River (GR, AL) has been recently recognized as a key large fluvial corridor and a significant model ecosystem. We investigate the catchment-scale recent morphological trajectories of the Vjosa river and its tributaries, coupling the reconstruction of channel adjustments over the past 50 years from remote sensing images with the analysis of possible drivers of change at the catchment and reach scale. We considered eight reaches in the main course of the Vjosa river as well as in some major tributaries (Sarandaporo, Drinos, Shushica) with different morphologies and confinement degrees. Our results underline the sensitivity of the Vjosa system to both hydrological alterations and human pressures. Specifically, it is possible to observe a response of the system passing from an intense period of high magnitude, frequency, and duration of flood events in the 1960s to a drier period in the following decades. To study the morphological response, three time periods are considered: 1968-1985, 1985-2000 and 2005-2020. In the first examined decades, river trajectories highlight the narrowing of the active channel as a primary response to the hydrological change in the majority of selected reaches, with a 20-50% active width reduction with respect to 1968. In the following time periods, the narrowing rate decreases at the catchment scale, while in the last phase the effect of human pressures in some reaches can be observed. Indeed, from the late 1980s, human pressures at different spatial and temporal scales can be identified, locally altering the natural trajectory of the affected reaches. Such pressures include sediment mining and extensive bank protection of the lowland reaches, together with flow regime alteration occurring in one headwater sub-catchment. However, our analysis reveals primarily a high sensitivity of the Vjosa system to recent climatic variations, suggesting the importance of accounting for future projected changes in rainfall regime in shaping morphological trajectories. The baseline knowledge on the morphological sensitivity and recovery time developed in this work provides an important reference for the management of highly dynamic river corridors in temperate and Mediterranean climates.

An increase in the demand for renewable energy is driving hydropower development and its integration with variable renewable energy sources. When hydropower is produced flexibly from hydropower plants, it causes rapid and frequent artificial flow fluctuations in rivers, a phenomenon known as hydropeaking. Hydropeaking and associated hydrological alterations cause multiple impacts on riverine habitats with cascading effects on ecosystem functioning and structure. Given the significance of its ecological and socio-economic implications, mitigation of hydropeaking requires an inter- and transdisciplinary approach. An interdisciplinary network called HyPeak has been conceived to enrich international research initiatives and support hydropower planning and policy. HyPeak has been founded based on exchange and networking activities linking scientists from several countries where hydropeaking has been widespread for decades and numerous studies dedicated to the topic have been carried out. HyPeak aims to integrate members from other countries and continents in which hydropower production plays a relevant role, and grow to be a reference group that provides expert advice on the topic to policy-makers, as well as researchers, stakeholders, and practitioners in the field of hydropeaking.

Confined meandering rivers are bounded between valleys and they are limited in their lateral migration compared to free meandering ones. In this study, we designed a model-based analysis to investi...

We study the morphodynamics of channel width oscillations associated with the planform development of river meander bends. With this aim we develop a novel planform evolution model, based on the framework of the classical bend theory of river meanders by Ikedaet al. (J. Fluid Mech., vol. 112, 1981), that accounts for local width changes over space and time, tied to the local hydro-morphodynamics through a two-way feedback process. We focus our attention on ‘autogenic’ width variations, which are forced by flow nonlinearities driven by channel curvature dynamics. Under the assumption of regular, sinusoidal width and curvature oscillations, we obtain a set of ordinary differential equations, formally identical to those presented by Seminaraet al. (J. Fluid Mech., vol. 438, 2001, pp. 213–230), with an additional equation for the longitudinal oscillation of the channel width. The proposed approach gives insight into the interaction between autogenic width variations and curvature in meander development and between forcing and damping effects in the formation of width variations. Model outcomes suggest that autogenic width oscillations mainly determine wider-at-inflection meandering river patterns, and affect their planform development particularly at super-resonant aspect ratios, where the width oscillation reaches its maximum and reduces meander sinuosity and lateral floodplain size. The coevolution of autogenic width oscillation and curvature occurs through temporal hysteresis cycles, whereby the peak in channel curvature lags behind that of width oscillation. Width oscillation amplitudes predicted by the model are consistent with those extracted from remotely sensed data.

This study investigates the dependency of meander lateral migration rates on the spatial distribution of channel centerline curvature in both synthetic and real meandering rivers. It employs Machine Learning techniques (hereafter ML) to relate observed local lateral meander migration rates with the local and the upstream/downstream values of the centerline curvature. To achieve this goal, it was primarily essential to identify the feasibility of using ML in the meandering river's morphodynamics. We then determined the ability of ML to predict the excess near bank velocity based a set of input data using different regression techniques (linear and polynomial, Stochastic Gradient Descent, Multi-Layer Perceptron, and Support Vector Machine). We then moved forward to study the upstream-downstream influence on local migration rate. Synthetic meandering river planforms, as obtained through the planform evolution model of Bogoni et al. (2017), which is based on Zolezzi and Seminara (2001) meander flow model, were used as test cases for the calibration and check of the different adopted ML algorithms. The calibrated algorithms were then applied to multi-temporal information on meander planform dynamics obtained through the PyRiS software (Monegaglia et al., 2018), to quantify to which extent the upstream and downstream distribution of meander centerline curvature affects the local meander migration rate in real rivers.References 1- Zolezzi, G., & Seminara, G. (2001b). Downstream and upstream influence in river meandering. Part 1. General theory and application overdeepening. Journal of Fluid Mechanics, 438(September 2015), 183–211. https://doi.org/10.1017/S002211200100427X2- Monegaglia, F., Zolezzi, G., Güneralp, I., Henshaw, A. J., & Tubino, M. (2018). Automated extraction of meandering river morphodynamics from multitemporal remotely sensed data. In Environmental Modelling & Software (Vol. 105, pp. 171–186). https://doi.org/10.1016/j.envsoft.2018.03.0283- Bogoni, M., Putti, M., & Lanzoni, S. (2017). Modeling meander morphodynamics over self-formed heterogeneous floodplains. In Water Resources Research (Vol. 53, Issue 6, pp. 5137–5157). https://doi.org/10.1002/2017wr0207264- Benozzo, D., Olivetti, E., Avesani, P. (2017). Supervised Estimation of Granger-Based Causality between Time series. In Frontiers in Neuroinformatics. https://doi.org/10.3389/fninf.2017.00068 5- Sharma A., Kiciman, E. (2020). DoWhy: An End-to-End library for Causal Inference. arXiv preprint arXiv:2011.04216. https://arxiv.org/abs/2011.04216

Flow regimes profoundly influence river organisms and ecosystem functions, but regulatory approaches often lack the scientific basis to support sustainable water allocation. In part, this reflects ...

Restoration of spawning and juvenile habitats is often used to restore fish abundances in rivers, although often with unclear results. To study the effects of habitat limitations on the common barbel (Barbus barbus), a riverine litophilic cyprinid fish, an age-structured population model was developed. Using a Bayesian modeling approach, spawning and fry (0+ juvenile) habitat availability was integrated in the model in a spatially explicit way. Using Beverton-Holt and Ricker recruitment models, density dependence was incorporated in the spawning process and the recruitment of 0+ juveniles. Model parameters and their uncertainty ranges were obtained from reviewing the existing literature. The uncertainty of the processes was intrinsically accounted for by the inherently probabilistic nature of the Bayesian model. By testing various scenarios of habitat availabilities for the barbel, we hypothesize that improvement of the fish stock will be reached only at a well specified ratio of spawning to fry habitat. Model simulations revealed substantial abundance improvements at rather equal amounts of about 10% cover of both habitats, while even substantial improvements of either spawning or fry habitats only will result in little or no increase of abundance. Higher ratios of spawning to fry habitat were found to lower population recovery times. This work provides a tool that serves the assessment and comparison of river restoration scenarios as well as benchmarking rehabilitation targets in the planning phase. When targeting restoration of fish stocks, focusing only on one key life stage or process (such as spawning), without considering potential bottlenecks in other stages, can result in little to no improvement.

Coastal vulnerability is evaluated against inundation risk triggered by waves run-up, through the employment of coastal vulnerability indexes (referred to as “CVI”) introduced by Bosom García and Jiménez Quintana (2011). CVI are assessed through different wave climate characterizations, referring to regional (offshore wave climate) or local (near-shore wave climate) scale. The study is set along the Lalzit bay, a coastal area nearby Durres (Albania). The analysis reveals that the results vary due to uncertainties inherent in the run-up estimation, showing that the computational procedure should be developed by taking into account detailed information about local wave climate, especially concerning seasonal behaviour and fluctuations. Different approaches in choosing wave characteristics for run-up estimation affect significantly the estimate of shoreline vulnerability. The analysis also shows the feasibility and challenges of applying CVI estimates in contexts characterized by limited data availability, through targeted field measurements of the coast geomorphology and an overall understanding of the recent coastal dynamics and related controlling factors.

We analyse recent morphological evolution of braiding rivers of disparate regions of the Earth to develop and address the hypothesis that braiding of rivers tends to be reduced by human presence and related activities. Firstly, through a large-scale literature survey we observe generalised paths of bed degradation, channel narrowing and shift towards single-thread configuration in braided reaches due to multiple anthropogenic stressors. Secondly, we select three rivers from different geographic contexts characterised by complementary anthropic stressors for a detailed analysis (the lower Waitaki River in New Zealand, the middle Piave River in Italy and the lower Dunajec River in Poland) which shows that these rivers have undergone very similar trajectories of morphological change. In previous works, these morphodynamic changes have been related to the alteration of the fundamental physical processes of braided rivers, due to anthropogenic changes in constraints and controls. Here, a closer analysis of these alterations shows that analogous morphological evolutionary trajectories can result from very different paths of causation, i.e., from different management causes and different alteration of physical processes. Through the use of pattern predictors we analyse observed morphological trajectories and potential for recovery. We highlight the role of different geographic contexts as sources of constraints and drivers to the river evolution, with reference both to the physical and human environment, showing that the observed similar trajectories are the product of different local conditions and characteristics. These observations have implications for river management and restorations.

The presence of lateral planimetric constraints preventing free migration and avulsion has a significant influence on the planform dynamics of river meanders. This particular confined kind of meandering rivers is definitely understudied, especially in comparison to freely migrating ones. Through a semi-analytical meander model, here we attempt to investigate the effect of the confined floodplain width through a morphodynamic modeling approach. The confined floodplain width is defined as the width between symmetric lateral confinement where the river is free to migrate, on the planform pattern and dynamics. Model results illustrate that weak confinement (i.e. loose floodplain boundaries) increases planform irregularity, with the river centerline preferentially lying close to floodplain boundaries, while strong confinement (tight floodplain boundaries) leads to a remarkable planform regularity, constituted by periodic sequences of sawtooth-shaped meanders. Bend orientation is reminiscent of the sub/super-resonant regime regardless of the confinement width. Model results are supported by good agreement with available field and remote sensing observation on selected case studies of confined meandering rivers in Canada previously studied by Nicoll and Hickin (2014).

Amongst different climatic and anthropogenic drivers, water resources management can cause massive changes to the natural regime of a lake after its regulation, thereby affecting the quantity and quality of water intended for satisfying the multiple basin water requirements. Here, we investigate the multi-decadal variation of the water levels and outflows of Lake Garda, the largest in Italy, where the dam operational rules and the related basin water needs heavily altered the annual and seasonal trend of the lake regime since its regulation in 1951. Daily lake levels and outflows were first collected and digitized for the period 1888–2020, thus providing a unique database of 133 years that allowed a consistent comparison between natural and regulated periods. Statistical analyses highlighted a significant change of the inter-annual trend of the lake outflows, which passed from upward to downward after regulation, against a constant increasing trend of the water levels. Conversely, water levels showed a more remarkable shifts on a seasonal scale if compared to the outflows, revealing the influence of summer and winter basin water needs. Additional analyses on the inter-annual variation of the main downstream water demands regulated by the dam, i.e. the irrigation, hydropower and fluvial ecosystem requirements, outlined their relevance in changing the lake regime, influencing dam operational policies, which progressively limited the share of water released for ecosystem integrity. A comparison between the lake levels and outflows recorded for the pre-regulation and post-regulation periods of some selected European perialpine lakes finally highlighted different effects on the lake regime, drawing attention to the importance of defining the role of the dam operational policies within the current scenario of climate change and changing water demands.

Within the past 30 years there have been two major heatwave events (in 2003 and 2006) that broke 500-year-old temperature records in Europe. Owing to the growing concern of rising temperatures, we analyzed the potential response in a number of river sections that are subject to hydropeaking and thermopeaking through the intermittent release of water from hydropower stations. Thermopeaking in alpine streams is known to intermittently cool down the river water in summer and to warm it up in winter. We analyzed the response of river water temperature to air temperature during heatwaves at 19 gauging stations across Switzerland, using a 30-yr dataset at a 10-min resolution. Stations were either classified into “unpeaked” or “peaked” groups according to four statistical indicators related to hydropeaking and thermopeaking pressure. Peaked stations were exposed to reduced temporal variability in river water temperature, and it was determined that correlations between river water and air temperature were weaker for peaked stations compared with unpeaked stations. Similarly, peaked stations showed a much weaker response to heatwaves compared with unpeaked stations. It is important to note that this “cooling effect” created by hydro-thermopeaking was most pronounced during the two major heatwave events that took place in 2003 and 2006. Furthermore, results from thermal stress events on the growth of a typical cold eurythermic fish species (brown trout) increased continuously in rivers subject to peaked station water release during heatwaves. While hydropower operations that take place high up on mountains releasing hypolimnetic water may mitigate the adverse effects of heatwaves on downstream alpine river ecosystems locally, our results show the complexity of an artificial physical template associated with flow regime regulation in alpine streams.

et al., Higher Education Institutions play a critical role in societies transition towards sustainable development, educating future professionals and decision makers. In the last few decades, a number of technical universities have devoted major efforts to integrating sustainable development into engineering curricula. There is still, however, an increasing need to further transform learning and training environments and build capacity of educators and trainers on sustainable development issues. Against this background, this paper assesses the role of online training courses, within continuing professional development strategies, in promoting sustainable human development in engineering degrees. It was built upon the implementation of a European initiative, the Global Dimension in Engineering Education, promoted by a transdisciplinary consortium of technical universities and non-governmental organisations. In terms of method, this study analyses two sets of quantitative and qualitative indicators to assess i) the perceived quality/relevance of the training proposals, and ii) the learning acquisition of participants. Quantitative indicators were complemented by a descriptive analysis of findings from a semi-structured survey. The results provide evidence that online learning can be an effective approach for continuing professional development of academics. The findings also suggest that participants perceived online courses’ contents and curricula, developed jointly by academics and practitioners of non-governmental organisations, as relevant and useful for integrating sustainability principles in teaching activities. To conclude, authors recommend the leaders of higher educational institutions to explore the integration of online courses addressed to faculty into university policy and strategies, as a way to promote professional development and the engagement of academics on sustainable development., The research was conducted in the framework of the European initiative Global Dimension in Engineering Education financed by: - European Commission, Non-State Actors and Local Authorities in Development, Raising public awareness of development issues and promoting development education in the European Union Reference: EuropeAid/131141/C/ACT/MULTI, Number of proposal: DCI-NSAED/2012/280-929. - Barcelona City Council, Program: Barcelona Solidaria 2013. Grant number: 13ED0046.

To date, the role of riparian trees in the formation of scroll bars, ridges and swales during the evolution of meandering channels has been inferred largely from field observations with support from air photographs. In situ field observations are usually limited to relatively short periods of time, whereas the evolution of these morphological features may take decades. By combining field observations of inner bank morphology and overlying riparian woodland structure with a detailed historical analysis of airborne LiDAR data, panchromatic and color images, we reconstruct the spatial and temporal evolution of the morphology and vegetation across four meander bends of the Tagliamento River, Italy. Specifically we reveal (i) the appearance of deposited trees and elongated vegetated patches on the inner bank of meander bends following flood events; (ii) temporal progression from deposited trees, through small to larger elongated vegetated patches (pioneer islands), to their coalescence into long, linear vegetated features that eventually become absorbed into the continuous vegetation cover of the riparian forest; and (iii) a spatial correspondence between the resulting scrolls and ridge and swale topography, and tree cover development and persistence. We provide a conceptual model of the mechanisms by which vegetation can contribute to the formation of sequence of ridges and swales on the convex bank of meander bends. We discuss how these insights into the biomorphological processes that control meander bends advance can inform modelling activities that aim to describe the lateral and vertical accretion of the floodplain during the evolution of vegetated river meanders.

The provision of important river ecosystem services (ES) is dependent on the flow regime. This requires methods to assess the impacts on ES caused by interventions on rivers that affect flow regime, such as water abstractions. This study proposes a method to i) quantify the provision of a set of river ES, ii) simulate the effects of water abstraction alternatives that differ in location and abstracted flow, and iii) assess the impact of water abstraction alternatives on the selected ES. The method is based on river modelling science, and integrates spatially distributed hydrological, hydraulic and habitat models at different spatial and temporal scales. The method is applied to the hydropeaked upper Noce River (Northern Italy), which is regulated by hydropower operations. We selected locally relevant river ES: habitat suitability for the adult marble trout, white-water rafting suitability, hydroelectricity production from run-of-river (RoR) plants. Our results quantify the seasonality of river ES response variables and their intrinsic non-linearity, which explains why the same abstracted flow can produce different effects on trout habitat and rafting suitability depending on the morphology of the abstracted reach. An economic valuation of the examined river ES suggests that incomes from RoR hydropower plants are of comparable magnitude to touristic revenue losses related to the decrease in rafting suitability.

We report on a multi-decadal analysis of alternate bar dynamics in a 41.7 km reach of the Alpine Rhine River, which represents an almost unique example of a regulated river with fixed levees, straight reaches and regular bends in which alternate gravel bars spontaneously formed and migrated for more than a century. The analysis is based on freely available Landsat imagery, which provided an accurate and frequent survey of the dynamics of the alternate bar configuration since 1984. Bars were characterized in terms of wavelength, migration, and height. Longitudinal and temporal patterns are investigated as a function of flood occurrence and magnitude and in relation to the presence of local planform discontinuities (bends and ramps) that may affect their dynamics. Bars in the upper part of the reach are mostly steady and relatively long (about 13 channel widths); bars in the lower part of the reach are migrating and shorter (about 9 channel widths). Bar height is rather uniform along the reach, ranging between 3 to 4 m. The temporally long hydrological dataset allowed the investigation of bar migration during flood events, showing that bars migrate faster for intermediate floods. The observed relationship between bar migration and wavelength was consistent with linear theories for free migrating and steady forced bars in straight channels. The comparison of theories with observations highlights the key role of theories to support interpretation of observations, for a better understanding of the morphodynamic processes controlling bar formation and dynamics. This article is protected by copyright. All rights reserved.

We propose a bio-morphodynamic model at bend cross-sectional scale for the lateral migration of river meander bends, where the two banks can migrate separately as a result of the mutual interaction between river flow, sediments and riparian vegetation, particularly at the interface between the permanently wet channel and the advancing floodplain. The model combines a non-linear analytical model for the morphodynamic evolution of the channel bed, a quasi-1D model to account for flow unsteadiness, and an ecological model describing riparian vegetation dynamics. Simplified closures are included to estimate the feedbacks among vegetation, hydrodynamics and sediment transport, which affect the morphology of the river-floodplain system. Model tests reveal the fundamental role of riparian plants in generating bio-morphological patterns at the advancing floodplain margin. Importantly, they provide insight into the biophysical controls of the ‘bar push’ mechanism and into its role in the lateral migration of meander bends and in the temporal variations of the active channel width.

River research often addresses the influence of anthropogenic and natural processes on the ecological, hydrological, and geomorphological dynamics of river systems. However, here we take a river-centered approach and consider how rivers influence their landscapes by developing concepts of river landscape ‘signatures’ and ‘envelopes.’ The influence of a river penetrates well beyond its channel into the atmosphere, across the land surface, and into the subsurface. We define a signature as an emergent property of a set of processes acting on a river landscape, and its envelope as the dynamic penetration of the signature across the landscape. The potential to recognize river signatures and envelopes is driven by unprecedented expansion in data acquisition, processing, and modeling technologies. The spatial envelope of any particular signature will have fuzzy and temporally dynamic edges, may rapidly expand and contract, may differ in its extent from other signatures, and may be highly permeable to many organisms using the river (and broader) landscape. However, an understanding of the approximate dynamic envelope of a signature is crucial to understanding the contribution of rivers at a landscape scale and to informing the sustainable management of these landscapes and their ecosystem services. WIREs Water 2016, 3:313–325. doi: 10.1002/wat2.1143 For further resources related to this article, please visit the WIREs website.