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This study presents a method to investigate the influence of active floodplains on flood protection, ecology, and socio-economics. We used and further developed the Floodplain Evaluation Matrix (FEM) to systematically assess the Danube River, known as the most international river worldwide. The study also aims to develop a method applicable to other large rivers, taking into account different data availability and research objectives. Hydrological, hydraulic, ecological, and socio-economic parameters were assessed to address the multiple functions and services of floodplains. The evaluation showed that some active floodplains significantly reduce the impact of a 100-year flood event, with relative flood peak reductions by up to 17% and decelerating the flood wave by up to 41.5 h. While other floodplains may not have a noticeable impact on hydrological or hydraulic parameters, they play a crucial role in preserving biodiversity by providing essential habitats for protected species. We introduced an approach to assess whether a floodplain should be preserved and to categorize the restoration demand as low, medium, or high. Our findings indicate a universal need for preservation and restoration measures across all floodplains, with 81% demonstrating a high or medium demand for restoration. Preservation and restoration of floodplains are integral parts of achieving more sustainable floodplain management for each river. Applying the FEM to other large rivers could create a basis for sustainable decision-making, increase awareness of the multiple benefits of floodplains, and foster the implementation of preservation and restoration measures. [ABSTRACT FROM AUTHOR]

The Northern Adriatic Sea Reanalysis and Forecasting (NARF) system is a high-resolution (1/128°) modelling system designed to perform multi-purpose simulations (e.g. from decadal to operational temporal scales) of the oceanographic properties of the northern Adriatic Sea. Validation and quality assessment of horizontal current fields have been carried out for the 2006-2017 time period by comparing model outputs both with available observations and larger scale Copernicus Marine Service (CMS) reanalyses, showing better agreement with the experimental data, and a reduction of the average bias against observations compared to the lower resolution CMS products. In addition, NARF current speed was encountered to be generally more intense, with an overall increase of up to 50% compared to the lower resolution model. This data set was used to assess the energy potential of marine currents in the northern Adriatic. By analysing the statistics of the velocity fields, five areas, where the currents are more intense, were identified. However, none of the selected sites proved to be suitable for large-scale energy generation. Nevertheless, due to the better description of basin hydrodynamics, a drastic increase in the estimated power flux was observed when switching from lower resolution CMS to NARF reanalyses. This work emphasises the importance of high-resolution models in the field of renewable energy feasibility analysis, planning and design. [ABSTRACT FROM AUTHOR]

An unprecedented precipitation event in the hyper‐arid Atacama Desert of Northern Chile occurred in March 2015. Geomorphic alterations to the river channel and the coastal zone, coupled with the exceptional magnitude of the rainfall, caused catastrophic damage and loss of life. On the coast of the El Salado watershed, legacy mine tailings infilled the watershed‐ocean connection, while the river channel was altered both by tailings and urbanization. The consequences of this event resulted from the coupling of anthropogenic geomorphic changes with an unusual climate event. Lack of field data, complex geomorphology and sediment loads influenced by human activity make analysing floods in these regions especially challenging. The objective of this work is to improve our understanding of the factors that control flood hazards by using numerical simulations to reconstruct the 2015 flood in El Salado. We carry out unsteady two‐dimensional simulations fully coupled with the sediment concentration to identify the influence of tailing deposits, considering high‐resolution data of the pre‐ and post‐2015 flood topography. The results highlight the importance of specific event‐based studies, using models that can help designing better strategies for climate change adaptation and risk mitigation, while providing information for risk reduction and channel restoration. [ABSTRACT FROM AUTHOR]

Owing to the high tidal range, the Severn Estuary and Bristol Channel have the potential to generate huge amounts of renewable electricity for the UK. During the flood tide, the surging water travels upstream to form the Severn Bore. This study explores the dynamics of the Severn Bore through hydrodynamic modelling, analyzing how the tidal amplitude, mean water level, and river discharge affect the bore's intensity, reach, and sustainability. The Delft3D simulations show that the downstream tidal amplitude plays a critical role. Tides with an amplitude of less than 6 m will lead to the disappearance of the Severn Bore. The mean water level also significantly influences the bore's propagation, with a 1.5 m drop resulting in a 15 km retreat of the bore. A high river discharge rate weakens the bore's intensity and reduces its reach. These findings underscore the need for careful planning in tidal energy development within the Severn Estuary. Excessive exploitation of tidal energy can be detrimental to the Severn Bore and the ecological function of the estuary. [ABSTRACT FROM AUTHOR]

Wave Energy Converters (WEC) captured the wave energy while Floating Breakwaters (FB) attenuated the wave energy to make a calm area for harbour activities. This study investigates the combination of a pitching Wave Energy Converter (WEC) and Floating Breakwater (FB) for simultaneous wave energy capture and wave attenuation in harbour areas. Three different configurations were analyzed in nine different hydrodynamic conditions to optimise the performance of both FB and WEC. The results show that the optimised combined device with rectangular draft has the most promising performance, with an average wave transmission operation of 38.8% and a captured power of 533.2 kW across all conditions. Longer arms of the device also lead to better performance. Additionally, wave steepness was found to be a significant factor in the performance of the combined device. [ABSTRACT FROM AUTHOR]

The limited availability of in situ data has drawn attention towards using remote sensing techniques to monitor river flow. Radar altimetry data has been used to generate stage–discharge rating curves through power-law relations and empirical methods. However, evaluating hydrodynamic models for rating curve generation using multi-mission altimetry data in data-scarce regions is lacking. We used altimetry data (Jason 2, Jason 3, SARAL/AltiKa, Sentinel 3A, and Sentinel 3B) over the Mahanadi River to evaluate rating curves at virtual stations. The Hydrologic Engineering Center’s River Analysis System (HEC-RAS) hydrodynamic model was set up, identifying seven virtual stations along the Mahanadi River from Boudh to Mundali Barrage. Statistical evaluation of “water level” (Root Mean Square Error [RMSE] 0.27–0.88 m) and “discharge” (Kling-Gupta Efficiency [KGE] 0.52–0.88) components of the generated rating curves showed significant agreement with radar altimetry data. These rating curves at virtual stations offer a cost-effective tool for monitoring river flows at additional locations. [ABSTRACT FROM AUTHOR]

Urban flood risk management has been a hot issue worldwide due to the increased frequency and severity of floods occurring in cities. In this paper, an innovative modelling approach based on the Bayesian convolutional neural network (BCNN) was proposed to simulate the urban flood inundation, and to provide a reliable prediction of specific water depth. To develop the model, a series of historical rainfall data during the last 20 years were collected in Rushan China and the responding flood events were reproduced using physically based hydraulic model. The flood condition factors used in modeling include spacial factors and precipitation factors. The results showed that the BCNN model not only inherits the powerful ability of aggregating spacial information from CNNs to perform high level of accuracy and computational efficiency in predicting 2D urban flood inundation maps, but also offers a measure of uncertainty in the form of predictive variance, providing insights into the confidence and reliability of its predictions. The proposed BCNN method offered a new perspective for the analysis of surrogate model regarding real-time forecasting of flood inundation. [ABSTRACT FROM AUTHOR]

Mountain meadows are ecologically important groundwater dependent ecosystems that retain and store water in upland forested landscapes. They tend to occur in low gradient, broad valleys where water slows and sediment accumulates, making them efficient locations for restoration. Over a century and a half of land use has degraded many meadows in the Sierra Nevada, reducing their hydrological and ecological functionality. Process‐based restoration (PBR) is an ecosystem rehabilitation approach that utilises biogeomorphic processes to facilitate functional ecosystem recovery. Low‐tech applications of PBR leverage fluvial processes, plant growth and the manipulation of onsite materials to increase structural and hydrological complexity. In meadows, typical goals associated with restoration are to increase groundwater elevations, expand wetted area, encourage sediment capture and create diffuse flow paths leading to improved ecological function over time. This study compares surface and groundwater conditions in a degraded riparian meadow in the Sierra Nevada, California, USA for 1 year before and after process‐based restoration to understand initial changes in meadow hydrogeomorphic function. Restoration included the installation of 39 postless beaver dam analog structures in ~1 km of incised meadow channel. Stage‐discharge data at the inlet and outlet of the project area were paired with groundwater data collected from 13 wells distributed across the meadow to estimate increased water storage of 3700 m3 due to restoration. After the wet winter of 2023, we estimated that pools upstream of structures filled to over half their volume with fine sediment. We also applied hydrodynamic modelling to evaluate fluvial changes at high flows and found that restoration increased flow complexity and wetted surface area. These short‐term responses highlight the potential speed and ability of low‐tech, process‐based restoration in achieving restoration outcomes. [ABSTRACT FROM AUTHOR]

The flood-prone city of Zaio in Morocco necessitates a precise, fast, real-time flood depth mapping model due to its recurrent flood history. Whether it's the exclusive prediction of one flood category, relying on hard-to-measure inputs like flood hydrographs, or employing less accurate training methods such as cellular automata models, the existing Convolutional Neural Network (CNN) models face limitations in predicting flood depth in a city whose flood dynamics are influenced by outer watersheds such as Zaio. This study addresses these issues by introducing a CNN tailored for real-time pluvial and fluvial flood depth mapping in Zaio at fine resolution (2 m). Training involved eight rainfall hyetographs, with four used for testing. The model's validation included three "unseen" rainfall distribution patterns. The proposed CNN seamlessly connects rainfall-runoff modeling and hydrodynamic 2D flood depth simulation, with a novelty of predicting both pluvial and fluvial flood depth, and reducing computational time by a significant 99.17%. [ABSTRACT FROM AUTHOR]

ABSTRACT Many sharks, rays and skates are highly threatened and vulnerable to overexploitation, as such reliable monitoring of elasmobranchs is key to effective management and conservation. The mobile and elusive nature of these species makes monitoring challenging, particularly in temperate waters with low visibility. Environmental DNA (eDNA) methods present an opportunity to study these species in the absence of visual identification or invasive techniques. However, eDNA data alone can be difficult to interpret for species monitoring, particularly in a marine setting where its distribution can be influenced by water currents. In this study, we investigated the spatial and temporal distribution of elasmobranch species in two Special Areas for Conservation (SAC) off the coast of Wales. We took monthly eDNA samples for 1 year (starting September 2020 and March 2022 for the northern and southern SACs, respectively), and used metabarcoding to reveal the presence of elasmobranch species. We combined these data with hydrodynamic modelling and particle tracking methods to simulate the potential origins of the detected eDNA. We detected 11 elasmobranch species, including the critically endangered angelshark (Squatina squatina) and tope (Galeorhinus galeus). Most detections were in the spring and the fewest in the autumn. The particle tracking simulations predicted that eDNA was shed, on average, approximately 7 km and 15 km (in the northern and southern SACs, respectively) from the sampling stations at which it was detected. These results show that the two SACs represent important areas for elasmobranchs in the United Kingdom and demonstrate that eDNA methods combined with particle tracking simulations can represent a new frontier for monitoring marine species.

This research bears significant implications for river management, flood forecasting, and ecosystem preservation in the Lower Narmada Basin. A more precise estimation of Manning's Roughness Coefficeint (n) will enhance the accuracy of hydraulic models and facilitate informed decision-making regarding flood risk management, water resource allocation, and environmental conservation efforts. Ultimately, this study aspires to contribute to the sustainable management of perennial river systems in India and beyond by offering a robust methodology for optimizing Manning's n tailored to the complex hydrological dynamics of the Lower Narmada Basin. Through a synthesis of empirical evidence and computational modelling, it seeks to empower stakeholders with actionable insights toward preserving and enhancing these invaluable natural resources. Using the new HEC-RAS v 6.0, a one-dimensional hydrodynamic model was developed to predict overbank discharge at different points along the basin. The study analyzes water levels, stream discharges, and river stage, optimizing Manning's n and required flood risk management. The model predicted a strong output agreement with R2, NSE, and RMSE for the 2020 event as 0.83, 0.81, and 0.36, respectively, with an optimum Manning's n of 0.03. The lower Narmada Basin part near the coastal zone (validation point) appears inundated frequently. The paper aims to provide insights into optimizing Manning's coefficient, which can ultimately lead to better water flow predictions and more efficient water management in the region. [ABSTRACT FROM AUTHOR]

The present paper aimed to assess the sediment distribution pattern, mode of transport, and its interaction with hydrodynamic and topographic conditions at different depths and regions along the east coast of India. About 900 surficial sediment samples were collected and analysed on a monthly basis for the Chennai coastal region at 32 stations from 2013 to 2015. The study region is classified into four types, such as beach, inlet, 5 m, and 10 m depth. Sediment textural and grain size trend analyses were conducted to achieve the objectives. Sediment characteristics for the region were recorded as sandy, equally dominated by unimodal and bimodal at the beach, while unimodal at shallow depths (5 and 15 m). The sediments were medium sand to coarse sand at the beach, mostly fine followed by medium at 5 and 15 m depths. The sediment sorting is dominated by moderately well-sorted sediments; the skewness of beach sediments was negative, while nearshore sediments were found positive; average kurtosis values of sediments were noticed to be mesokurtic. The CM plot depicts that the sediments were mostly derived by tractive current, and the modes of transport are "bottom suspension and rolling" and "graded suspension no rolling" at beach locations and shallow water depths, respectively. The GSTA analysis reveals the annual average sediment transport pattern is northerly. The numerical hydrodynamic study confirms the GSTA and CM plot analysis. The study reveals a stable sedimentary environment south of the Chennai port and instability in the northern part. The study includes large spatiotemporal nearshore sediment data with hydrodynamic conditions, immensely helpful to coastal stakeholders and researchers. [ABSTRACT FROM AUTHOR]

This study aims to present and validate a methodological procedure for identifying flooding areas in small-size cities in Brazil. In those cities, there is usually a lack of ground-measured information, making citizen reports about floods valuable data for hydrological and hydrodynamic models. The model uses five variables: IDF Curve, land use and land cover, Digital Elevation Model, Urban Road Network, and existing micro-drainage infrastructure. The methodology has two main stages: (i) determination of the overland flow and (ii) determination of the maximum flow captured by micro drainage devices. The population also reported the magnitude of the flood events and their perception of the disasters through questionnaires and engagement meetings. Then, in a Geographic Information System (GIS) environment, the existing drainage system was mapped for the cities, and results were validated through online meetings with local technicians and city managers. Comparing the results from GIS analysis and the floodings hotspots reported by citizens shows that the model achieved an average accuracy of 73.5%. The presented methodology is a valuable alternative for identifying flooding hotspots due to its easy applicability and low cost compared to other models. [ABSTRACT FROM AUTHOR]

Topo‐bathymetric LiDAR (TBL) can provide a continuous digital elevation model (DEM) for terrestrial and submerged portions of rivers. This very high horizontal spatial resolution and high vertical accuracy data can be promising for flood plain mapping using hydrodynamic models. Despite the increasing number of papers regarding the use of TBL in fluvial environments, its usefulness for flood mapping remains to be demonstrated. This review of real‐world experiments focusses on three research questions related to the relevance of TBL in hydrodynamic modelling for flood mapping at local and regional scales: (i) Is the accuracy of TBL sufficient? (ii) What environmental and technical conditions can optimise the quality of acquisition? (iii) Is it possible to predict which rivers would be good candidates for TBL acquisition? With a root mean square error (RMSE) of 0.16 m, results from real‐world experiments confirm that TBL provides the required vertical accuracy for hydrodynamic modelling. Our review highlighted that environmental conditions, such as turbidity, overhanging vegetation or riverbed morphology, may prove to be limiting factors in the signal's capacity to reach the riverbed. A few avenues have been identified for considering whether TBL acquisition would be appropriate for a specific river. Thresholds should be determined using geometric or morphological criteria, such as rivers with steep slopes, steep riverbanks, and rivers too narrow or with complex morphologies, to avoid compromising the quality or the extent of the coverage. Based on this review, it appears that TBL acquisition conditions for hydrodynamic modelling for flood mapping should optimise the signal's ability to reach the riverbed. However, further research is needed to determine the percentage of coverage required for the use of TBL as a source of bathymetry in a hydrodynamic model, and whether specific river sections must be covered to ensure model performance for flood mapping. [ABSTRACT FROM AUTHOR]

This research work proposes a combined method for mapping flood loss in catchment scale in which direct rainfall modelling and fuzzy approach are linked. The direct rainfall modelling was carried out using HEC-RAS 2D in which rainfall event hyetograph was defined as the boundary condition, and infiltration layer and roughness layer were other main inputs of the model. The fuzzy loss model was developed to assess direct-tangible damages of the flood in which expert opinions were applied to generate verbal fuzzy rules of flood loss. In this model, depth and velocity are inputs and normalized flood loss (between 0 and 1) is output. The results of the direct rainfall model and the fuzzy loss model were combined to generate loss map using python scripting in geographical information system. The output of direct rainfall model was verified based on recorded depths at downstream hydrometric station in which the Nash–Sutcliffe efficiency (NSE) and root mean square error (RMSE) were applied as the evaluation indices. Due to acceptability of indices (NSE = 0.75, RMSE = 0.83 m), the direct rainfall model was reliable. Maximum flood loss was 0.91 in the case study. Using the proposed approach is recommendable for to improve flood damage assessment in the catchments. [ABSTRACT FROM AUTHOR]

The Indonesian government has set goals for increasing the use of renewable energy in the coming years. Currently, Indonesia relies heavily on non-renewable energy sources, which poses a threat to the environment due to the country's growing energy needs. This study aims to assess the potential for developing a tidal power plant in Capalulu Strait, North Maluku. Using hydrodynamic modelling, the study identified two potential locations at coordinates 1.877°S – 125.328°E (Capa-2) and 1.863°S – 125.323°E (Capa-4) which were selected for having median current speeds exceeding 1.8 m/s and maximum current speeds exceeding 3.5 m/s. The study tested a hypothetical implementation of KHPS Gen5 instrument(s) by Verdant Power, a 5 m diameter turbine with a rated nominal power of 37 kW and a maximum rated power of 56 kW. A power plant layout was designed to be placed at Capa-2 and Capa-4, each location accommodating 45 turbines. The development of this power plant is estimated to produce up to 22 GWh per year. Financial analysis resulted in a LCOE of IDR 5,930/kWh. However, this price is still high compared to the national electricity tariff of IDR 1,027.70/kWh. Variations in the number of turbines also may not result in a lower LCOE than the national tariff. Nevertheless, the estimated cost of generating electricity is still competitive compared to diesel, which is around IDR 5,804/kWh.

Owing to the high tidal range, the Severn Estuary and Bristol Channel have the potential to generate huge amounts of renewable electricity for the UK. During the flood tide, the surging water travels upstream to form the Severn Bore. This study explores the dynamics of the Severn Bore through hydrodynamic modelling, analyzing how the tidal amplitude, mean water level, and river discharge affect the bore’s intensity, reach, and sustainability. The Delft3D simulations show that the downstream tidal amplitude plays a critical role. Tides with an amplitude of less than 6 m will lead to the disappearance of the Severn Bore. The mean water level also significantly influences the bore’s propagation, with a 1.5 m drop resulting in a 15 km retreat of the bore. A high river discharge rate weakens the bore’s intensity and reduces its reach. These findings underscore the need for careful planning in tidal energy development within the Severn Estuary. Excessive exploitation of tidal energy can be detrimental to the Severn Bore and the ecological function of the estuary.

There is an opportunity for efficient implementation of floating photovoltaics (FPV) by coupling with other renewable energies, such as hydropower. The resulting synergies benefit both technologies. Particularly in arid regions, hydropower reservoirs face considerable evaporation. As a benefit, FPV minimizes evaporation while simultaneously generating renewable energy. In this study, we simulate the evaporation reduction due to FPV by applying the hydrodynamic General Lake Model together with the yield simulation model Zenit to the Aswan High Dam Reservoir. We estimate a 49.7% evaporation reduction at 90% FPV occupancy and water savings of up to 5.9 billion m3 per year (BCM a−1). The mean specific water saving of the FPV system is 7.67 m3 a−1 kWp−1. We analyse possible ways to use the saved water, such as additional hydropower, filling up the Toshka Lakes, or agricultural irrigation. The use of FPV water savings for irrigation appeared to be most efficient. [ABSTRACT FROM AUTHOR]

Algal bloom has been a persistent problem for both fresh and marine water, with no exception for a coastal reservoir (CR). Among the algal bloom mitigations for a CR, shape optimisation to reduce algal bloom occurrence has been frequently mentioned. However, there was no literature found on the actual shape optimisation study or process for CR. Thus, this research was done to bridge this gap, particularly for the second-generation CR. Hydrodynamic model of MIKE 21 has been used, with secondary data obtained from published papers and Google Earth. The secondary data of critical velocity corresponding to algal growth were only available for cyanobacteria, chlorella, filamentous algae and phytoplankton. Hence, only these algae species were considered in the algal mapping. All models were simulated for eight idealised cases of second-generation CR at the Yangtze Estuary. These different geometric shapes were analysed and compared, considering several factors including the average velocity in the reservoir, presence of stagnant water, percentage of occurrence for each algae species and so on. From the results, the reservoir model with the shape of "shorter piano key" ranked the highest among all the shapes in terms of proneness to algal bloom, based on the flow velocity within the reservoir. From the findings, further shape optimisation was done on second-generation CRs. From shape optimisation process, the optimised shape of the "little dinosaur" and "little pencil" showed excellent reduction in algal blooming. However, "little dinosaur" was preferred as its location for algal bloom is small and controllable due to the presence of "piano key" structure. Lastly, all the findings were applied to an existing CR at Qingcaosha to see if shape optimisation based on the analysis can reduce areas prone to algal blooming. The optimised model of Qingcaosha showed great reduction on area prone to algal blooming compared to its original shape but the addition of "piano key" structure did not have significant impact on the reduction of algal bloom occurrence since the shape of Qingcaosha is highly dependent on its natural topography. From the study, it was concluded that shape optimisation for topographic-dependent CR should be done on case-by-case basis, following the flow direction in the reservoir. As for second-generation CR without topographical constraints, the shape optimisation can be done by placing inlet perpendicular to the flow direction, minimising corners, implementing piano-key-like structure, optimising shape based on flow direction and refer "little dinosaur" or "little pencil" for the overall shape optimisation design. [ABSTRACT FROM AUTHOR]

Hypersaline Hamelin Pool, with mean salinity >65, is located in Shark Bay, Western Australia. The high salinity has reduced its biodiversity, but it is home to a diverse assemblage of modern marine stromatolites. The limited exchange of water between Hamelin Pool and the rest of Shark Bay, due to the presence of the shallow Faure Sill together with high evaporation and low rainfall-runoff have resulted in a hypersaline environment. With climate-change-induced mean sea level rise (MSLR), hydrodynamic processes that maintain the hypersaline environment may be affected and are the focus of this paper. Oceanographic observations, together with hydrodynamic model results, were used to examine the hydrodynamic processes under present and future MSLR scenarios. A large attenuation in the tidal range, changes in the tidal characteristics, and current speeds together with a strong salinity gradient were observed across the Faure Sill under present-day conditions. Under an MSLR scenario of 1 m, the tidal amplitude decreased by up to 10% to the north, whilst to the south, the tidal range increased by up to 15%. Regions of strong vertical stratification were present on both sides of the Faure Sill. The simulations indicated that, under MSLR scenarios, these regions expanded in area and exhibited higher levels of vertical stratification. The salt flux across the Faure Sill was maintained as a diffusive process under MSLR scenarios. [ABSTRACT FROM AUTHOR]

During flood events, river topography and fluvial habitats can change drastically, potentially affecting the ecological status. In case of multiple floods, whether each single event modifies the habitat characteristics in the same direction or not, is still an open question. We gathered high quality topographical data of one braided Alpine reach before, between and after multiple floods. Considering the full dynamics of the hydrological regime affected by hydropower production, we calculated water depth and flow velocities distributions for relevant discharge conditions using hydrodynamic modelling. We then calculated four ecological indicators related to habitat diversity, habitat quantity, habitat connectivity and stranding risk. Despite the consistent depositional morphological trend, the habitat diversity and stranding metrics returned to pre-floods values after an initial deviation. The habitat quantity and connectivity metrics did not show a clear trend towards an alternative state. Habitat prevalence varied seasonally and with hydropower water release, and also changed markedly between floods, possibly affecting species composition. We show the possible intrinsic variability in several ecological indicators which can aid in the management and restoration of river floodplains. [ABSTRACT FROM AUTHOR]

Image‐based methods have compelling, demonstrated potential for characterizing flow fields in rivers, but algorithms like particle image velocimetry (PIV) must be further tested and improved to enable more effective use of these techniques. This paper presents a framework designed for this exact purpose: Simulating Hydraulics and Images for Velocimetry Evaluation and Refinement (SHIVER). The approach involves coupling a hydrodynamic model with a synthetic particle generator to advect particles between frames, as dictated by local velocity vectors and thus construct a plausible image sequence specific to the reach of interest. The resulting time series can then be used as input to a velocimetry algorithm to compare image‐derived estimates with known (modelled) velocities to perform an exhaustive, spatially distributed accuracy assessment. As an example application of SHIVER, we examined the effects of interrogation area (IA) size, frame rate, flow velocity, and image sequence duration on the performance of a standard PIV algorithm. This analysis indicated that image‐derived velocities were generally in close agreement with those from the flow model (root mean square error <10% and mean bias <3%), except when small IAs were coupled with low frame rates. Velocity estimates were most accurate for the lowest modelled discharge (R2=0.97 at baseflow) and became less reliable as the mean flow velocity increased (R2=0.92 for an intermediate discharge and R2=0.86 at bankfull). Accuracy was essentially independent of image sequence duration, implying that long occupations might not be necessary. Errors were concentrated along channel margins, where PIV‐based velocities tended to be greater than those from the flow model. Small IAs led to underpredictions of velocity, while larger IAs led to overpredictions. SHIVER is highly modular and could be updated to make use of different hydrodynamic models or image simulators. The framework could also facilitate more thorough sensitivity analyses and comparison of various velocimetry algorithms. [ABSTRACT FROM AUTHOR]

The Ganga River hosts a metapopulation of endangered aquatic species. This study uses a hydrodynamic model (HEC‐RAS) to assess the habitat suitability of the Ganga River dolphins (GRDs) in a small reach (7.5 km) of the Ganga River at the upstream of Narora barrage in varying flow. We use Lidar points clouds to generate topography, Acoustic Doppler Current Profiler (ADCP), and differential GPS (DGPS) to measure channel bathymetry and streamwise water surface slope. Further, the water level data from satellite altimeter is used to calibrate the model and discharge measured in field to validate the model output. We found that in the high flow period, the required flow depth for dolphin habitat is available throughout in the study reach. However, in the lean flow, the required flow depth and velocity are available only in some patches. The methodology developed here would be very useful in monitoring hydraulic habitat suitability of aquatic species in ungauged rivers. [ABSTRACT FROM AUTHOR]

In recent decades, fluvial geomorphology and ecohydraulic research have extensively used field observations, remote sensing or hydrodynamic modelling to understand river systems. This study presents an innovative approach that combines field surveys, Light Detection and Ranging (LiDAR)‐based topographical and biomass analyses and model‐derived hydro‐morphodynamic geostatistics to examine short‐term biogeomorphological changes in the wandering gravel‐bed Orco River in Italy. Our primary hypothesis is that hydro‐morphological variables can be robust descriptors for riparian vegetation distribution. From a geomorphological perspective, our study confirms the prevalent wandering behaviour of the Orco River. Moreover, we identified a widening trend in braiding and anabranching sections, particularly downstream. This is evident because of hotspots of flood‐induced morphological reactivation and the redistribution of sediments from the riverbed to lateral bars, resulting in a multi‐thread pattern. Our analysis reveals a net increase in biomass during the observation period despite frequent flood disturbances. We attributed it to two opposing biogeomorphological dynamics: the reduced flow disturbance in some regions due to flood‐induced geomorphological changes and the self‐healing of lateral connectivity through river wandering. Such a net increase indicates that transitional rivers store carbon in the form of vegetation biomass due to their short‐term morphological instability and the different timescales between vegetation and morphological adjustments. Finally, we supported our initial hypothesis with three key findings: (i) a signature of vegetation not just on topography but also on hydro‐morphological conditions, summarised by inundation probability; (ii) the lower variance in vertical topographical changes in vegetated areas compared with bare ones; and (iii) the introduction of a new parameter, named inundation viscosity, derived from the product of mean bed shear stress and average inundation duration, as a discriminating factor for colonisation conditions. These results underscore the value of our comprehensive approach. [ABSTRACT FROM AUTHOR]

Increasing extreme weather events pose significant challenges in hydrology, requiring tools for preparedness and prediction of intense rainfall impacts, especially flash floods. Current risk reduction measures for pluvial flood risk management rely on flood hazard maps, but inconsistencies in transregional standards that are used for risk assessment hinder cross-regional comparisons. While there are existing guidelines for the development of pluvial flood hazard maps, there is still a lack of holistic modelling systems that enable harmonised predictions of the impacts of heavy rainfall events. Furthermore, sensitive city data (e.g., critical infrastructure, sewer network) exist in many municipalities, which cannot be readily disclosed for modelling purposes. In this work, we propose an approach using distributed analytics to distribute computation commands to existing hydrodynamic models at different locations. In combination with harmonising model adapters, we enable the generation of harmonised pluvial flood hazard maps of different regions to tackle the inconsistencies and privacy concerns. We apply our approach to four adjacent urban areas in the Rhein-Sieg Kreis of North Rhine-Westphalia. Our results demonstrate the ability of our approach to produce cross-regional pluvial flood hazard maps, supporting disaster preparedness and management in regions prone to extreme weather events and flash floods. HIGHLIGHTS Decentralised flood modelling: Innovative approach using distributed analytics for harmonised pluvial flood hazard maps, addressing inconsistencies.; Improved risk assessment: Enables standardised cross-regional comparisons, enhancing disaster preparedness.; Real-world validation: Practical application in North Rhine-Westphalia validates the approach's feasibility and relevance for complex urban areas prone to flooding.;

This research work proposes a novel method of environmental flow analysis in hypersaline lakes in which the outputs of the hydraulic rating method considering the base flow as a known approach for environmental flow assessment in rivers are analyzed in terms of providing suitable aquatic habitats in the lake by linking a continuous hydrological model and a hydrodynamic model of salinity simulation. Soil and Water Assessment Tool (SWAT) as a hydrological model was applied to simulate the natural inflow of the lake's ecosystem in the simulated period. Moreover, a hydrodynamic model was applied to simulate the salinity distribution of the lake in the same simulated period. Based on the results of the models and monthly analysis of the environmental flows, both models are robust for simulations. The Nash–Sutcliffe Efficiency (NSE) of both hydrological and hydrodynamic models average more than 0.5, which means that they are reliable for simulating the natural inflow and salinity distribution respectively. Furthermore, outputs indicated that using the hydraulic rating method considering the base flow for assessing the environmental flow of rivers is not able to provide environmental requirements in the lake's ecosystem of the case study. HIGHLIGHTS New method for environmental flow analysis.; Linking catchment model and hydrodynamic model.; Assessing environmental flow supply.;

Ghed region is located in the deep western part of Gujarat state, having the cup shape geometry. The Ozat River begins near the Gir forest's hilly part and moves towards the river mouth near Navi Bandar. The part before the river mouth is called Ghed, near the coastal line. The inundation in this region occurred due to higher coastal line and cup shape geometry with an area of more than 200 km2. This research emphasized early warning of the local community aside from the region during the peak flow condition. The hydrological engineering centre-river analysis system software developed the hydrodynamic model for FEWS (flood early warning system). The model has been validated with observed water depth data at four locations from the river reach area for more precision. In this regard, various statistics have been performed to compare the observed and modelled data. The result depicts the 19 h of leg time available to evacuate the local community. After that, water takes 115 h more time to reach the river mouth due to cup-shaped region filling. This research helps the administration with the decision-making system and establishes new hydraulic structures. HIGHLIGHTS The case study focuses on developing a hydrodynamic model for a unique cup-shaped region.; The 2D flood assessment model was validated using a limited observed dataset of water depth.; Hydrological engineering centre-river analysis system hydrodynamic model used for inundation mapping and early warning systems, mainly relying on open-source data.; Study results aid the emergency evacuation system and the establishment of new hydraulic structures in the Ghed region.;

This study quantified transfer losses over the 2021/2022 water year for irrigation releases from Darlington Dam into the Sundays River, which are diverted at the Korhaans Drift Weir. A one-dimensional (1D) hydrodynamic model was set up and calibrated to simulate the transfer losses which were assumed to consist primarily of evaporation and evapotranspiration (ET). Flow measurements were undertaken with an acoustic doppler current profiler (ADCP) to verify the calibrations of the Parshall flumes at Darlington Dam and at Korhaans Drift Weir. The ADCP results showed that the Department of Water and Sanitation's (DWS's) existing discharge tables underestimated lower flows by 13% and higher flows by 16%. The hydrodynamic model results also estimated transfer losses between Darlington Dam and Korhaans Drift to range between 2.0% and 5.3%. It was determined that the transfer losses were seasonal and were lower than those determined by similar studies for other South African rivers. [ABSTRACT FROM AUTHOR]

Information on genetic divergence and migration patterns of vent‐ and seep‐endemic macrobenthos can help delimit biogeographical provinces and provide scientific guidelines for deep‐sea conservation under the growing threats of anthropogenic disturbances. Nevertheless, related studies are still scarce, impeding the informed conservation of these hotspots of deep‐sea biodiversity. To bridge this knowledge gap, we conducted a population connectivity study on the galatheoid squat lobster Shinkaia crosnieri – a deep‐sea foundation species widely distributed in vent and seep ecosystems in the Northwest Pacific. With the application of an interdisciplinary methodology involving population genomics and oceanographic approaches, we unveiled two semi‐isolated lineages of S. crosnieri with limited and asymmetrical gene flow potentially shaped by the geographic settings, habitat types, and ocean currents – one comprising vent populations in the Okinawa Trough, with those inhabiting the southern trough area likely serving as the source; the other being the Jiaolong (JR) seep population in the South China Sea. The latter might have recently experienced a pronounced demographic contraction and exhibited genetic introgression from the Okinawa Trough lineage, potentially mediated by the intrusion of the North Pacific Intermediate Water. We then compared the biogeographic patterns between S. crosnieri and two other representative and co‐occurring vent‐ and seep‐endemic species using published data. Based on their biogeographical subdivisions and source‐sink dynamics, we highlighted the southern Okinawa Trough vents and the JR seep warrant imperative conservation efforts to sustain the deep‐sea biodiversity in the Northwest Pacific. [ABSTRACT FROM AUTHOR]

Abstract Background Fish migration has severely been impacted by dam construction. Through the disruption of fish migration routes, freshwater fish communities have seen an incredible decline. Fishways, which have been constructed to mitigate the problem, have been shown to underperform. This is in part due to fish navigation still being largely misunderstood. Recent developments in tracking technology and modelling make it possible today to track (aquatic) animals at very fine spatial (down to one meter) and temporal (down to every second) scales. Hidden Markov models are appropriate models to analyse behavioural states at these fine scales. In this study we link fine-scale tracking data of barbel (Barbus barbus) and grayling (Thymallus thymallus) to a fine-scale hydrodynamic model. With a HMM we analyse the fish’s behavioural switches to understand their movement and navigation behaviour near a barrier and fishway outflow in the Iller river in Southern Germany. Methods Fish were tracked with acoustic telemetry as they approached a hydropower facility and were presented with a fishway. Tracking resulted in fish tracks with variable intervals between subsequent fish positions. This variability stems from both a variable interval between tag emissions and missing detections within a track. After track regularisation hidden Markov models were fitted using different parameters. The tested parameters are step length, straightness index calculated over a 3-min moving window, and straightness index calculated over a 10-min window. The best performing model (based on a selection by AIC) was then expanded by allowing flow velocity and spatial velocity gradient to affect the transition matrix between behavioural states. Results In this study it was found that using step length to identify behavioural states with hidden Markov models underperformed when compared to models constructed using straightness index. Of the two different straightness indices assessed, the index calculated over a 10-min moving window performed better. Linking behavioural states to the ecohydraulic environment showed an effect of the spatial velocity gradient on behavioural switches. On the contrary, flow velocity did not show an effect on the behavioural transition matrix. Conclusions We found that behavioural switches were affected by the spatial velocity gradient caused by the attraction flow coming from the fishway. Insight into fish navigation and fish reactions to the ecohydraulic environment can aid in the construction of fishways and improve overall fishway efficiencies, thereby helping to mitigate the effects migration barriers have on the aquatic ecosystem.

Accurate predictions of water surface elevation (WSE) in rivers at high spatial and temporal resolution are important for flood/drought risk assessment and flood/drought forecasting and management. WSE in a river is controlled by three main factors: discharge, riverbed geometry, and hydraulic roughness. In remote and poorly instrumented rivers, discharge and riverbed geometry are highly uncertain and WSE is therefore hard to predict. ICESat-2 laser altimetry provides accurate elevation transects across the river at very high spatial resolution (70 cm along track). This paper demonstrates how ICESat-2 elevation transects can be used to parameterize a basin-scale hydraulic model of a continental-scale river. The workflow is demonstrated for the transboundary Amur River in North-East Asia. Simulated WSE is subsequently validated against a large dataset of in situ and satellite altimetry observations, and we demonstrate that the model can reproduce available WSE observations throughout the basin with an accuracy of 1–2 m. [ABSTRACT FROM AUTHOR]

Here, we report on numerical modelling of AlGaN/GaN HEMT terahertz detectors using a two-dimensional solver based on three Boltzmann transport equation (BTE) moments and the Poisson equation. We use the Synopsys TCAD Sentaurus program package, which offers a wide material database and the possibility to include traps and polarization charges for the formation of the channel without any doping. The implications of different levels of model simplifications are addressed both analytically and numerically. We calculated the current responsivity ℜI to THz radiation on the drain voltage in the frequency range 0.01-3.0 THz for three AlGaN layer thicknesses d = 15, 20 and 25 nm and different gate lengths. We demonstrate that only a hydrodynamic model can reproduce the change in the sign in current responsivity at the gate voltage UG0 (ℜI = 0 at UG = UG0). The energy flux factor in the energy balance equation determines this effect. For the simulated structures, we find that the noise equivalent power may be as low as 0.1 pW/√Hz at 0.04 THz and 10 pW/√Hz at 3.0 THz. [ABSTRACT FROM AUTHOR]

The B1 dam of Córrego do Feijão Mine, owned by Vale, S.A. mining company and located on the Ferro-Carvão stream, collapsed and injected 2.8 Mm3 of clayey, silty, and sandy iron- and manganese-rich tailings into the Paraopeba River (Minas Gerais state, Brazil). The accident occurred on 25 January 2019 and the tailings have been co-transported with coarser natural sediment since then, being partly trapped in the Igarapé Weir reservoir located on the Paraopeba River nearly 45 km downstream the injection point. The general purpose of the current study was to model suspended sediment transport in the vicinity of the Igarapé Weir aiming to assess the concomitant barrier effect imposed by this structure. Specifically, the spatial distributions of suspended clay, silt, and very fine-grained sand fractions (CSS) of sediment were mapped around the Igarapé Weir under low-flow (16 m3/s) and high-flow (5 to 10,000 years return period stream discharge; 699–2,699 m3/s) regimes, using RiverFlow2D as the modelling tool. The concentrations of the various grain materials in the upstream and downstream sectors were quantified linking the barrier effect to concentration reductions in the direction of stream flow. It was also a study goal to calculate differences of iron and manganese concentrations in the sediment + tailings mixtures along the Paraopeba River. The study results showed reductions in the CSS between 6.6% and 18%, from upstream to downstream of the Igarapé Weir, related with backwater effects, free and submerged hydraulic jumps, bank sedimentation in periods of high flow, and streambed sedimentation controlled by channel sinuosity and tailings density. These reductions were accompanied by drops in the concentrations of iron and manganese present in the clay and silt fractions, which varied between 6% and 42% under low flows and between 16% and 44% under high flows. Bank sedimentation was viewed as a potential threat to the riparian vegetation in the long-term. Dredging is the potentially most effective mitigation measure to help lead the Paraopeba River to a pre-rupture condition. The retention of sediment + tailings transported in suspension is less effective than the trapping of bedload sediment + tailings behind the Igarapé weir. The efficacy of sediment trapping is expected to be larger for natural sediment because it is much coarser than the tailings. In that context, the simulations revealed for the low-flow period that 33.6% of the sediment deposition comprised suspended transport of natural sediment (thus, was comprised 66.4% of bedload transport), this proportion rose to 86.9% for mixtures of natural sediment + tailings, a result that did not differ much for the high-flow periods. [Display omitted] • The Igarapé weir effectively retained B1 dam tailings composed of clay and silt; • The capacity to retain suspended clay+silt+very fine-grained sand was 6 – 18%; • The concomitant retention of Fe and Mn can reach nearly 50%; • The barrier effect relates with backwater effects, hydraulic jumps and bank sediment sedimentation; • Bank sedimentation is a threat to riparian vegetation and dredging a potentially effective mitigation measure; [ABSTRACT FROM AUTHOR]

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Hydraulic structures can be a promising place for tidal energy extraction due to the high flow velocities, easy access to the power grid and easy access for maintenance. However, quantification of the impacts of a tidal power plant in a hydraulic structure is not straight forward. In 2015 a pilot plant consisting of an array of five Tocardo tidal turbines was installed in the Eastern Scheldt Storm Surge Barrier in the Netherlands. This pilot was accompanied by monitoring studies to verify that the operation of the plant had no adverse impact on the barrier and its surroundings. This paper presents the assessment of the hydraulic impact of the tidal power plant in the storm surge barrier based on an analysis of water level and current measurements, combined with numerical modeling and followed by an assessment of the environmental impact with emphasis on the effects on the intertidal areas in the estuary. This validation approach by a pilot plant is imperative to understand the interaction between tidal turbines and the hydraulic structure on the local scale. This understanding gives extra credibility to the predictions of the extrapolated large-scale and large array assessments which will always be fully numerical. [ABSTRACT FROM AUTHOR]