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Off-stream reservoirs are hydraulic structures that might cause severe flood damages in case of failure or improper operation. Their safety regulations usually require hydraulic studies for flood hazard and inundation zone mapping. The selection of the break point is not trivial because the topography in its surroundings is commonly highly anthropic. A wrong selection would not provide the worst scenario in terms of maximum flood hazard extent. This work presents a probabilistic approach based on a stochastic definition of the break point along the dyke. A number of failure scenarios are generated automatically, corresponding to different breach formations. Then, an in-cascade calculation process simulates each scenario, providing a framework to carry out statistical analysis. The simulation of the breach formation and the flood wave propagation is performed through a GPU parallelised two-dimensional hydraulic numerical model, which provides a probabilistic inundation zone and flood hazard mapping of all scenarios simulated in a suitable timeframe.

The Aznalcóllar tailings pond failure (1998) is regarded as one of the severe ecological mine disasters ever reported. The spill of the mine tailings affected more than 60 km of the Agrio and Guadiamar rivers and caused major environmental damage. Despite the event being well-documented with more than 400 scientific publications, including two special issues and two reviews, several hydraulic uncertainties and inconsistencies remain. This paper conducts a state-of-the-art review of the most relevant hydraulic aspects of the mine disaster. It addresses the pond and fluid characteristics, the break type, the breaking time, the flow propagation, the volume potentially stored and subsequently spilled, area dimensions affected by the spill, and the morphological changes generated in the river and riverbanks caused by the spill, and later on by the restoration activities. Several discrepancies and plenty of controversial data have been unearthed that may affect general understanding of the event. In addition, new data is introduced and analysed applying photointerpretation and digital terrain analysis techniques, aiming to derive in essential hydraulic parameters. The most important findings are that the spill could have had a volume about 11.5 hm3, affecting about 86.7 km of river length, twice the most referenced values in the literature, and that applied restoration activities have substantially modified the hydro-sedimentary processes of the affected system. Additionally, a first video observation-based classification reveals that the fluid behaved more like a highly concentrated sediment-laden flow than like a mud flow. The authors thank Mr. Beningno Bayán, retired engineer of Confederación Hidrográfica del Guadalquivir and member of the ‘Plan Doñana 2005’ scientific commission, for his collaboration for understanding the physics of the spill, his generous work of information searching, and especially his interest in this work. Additional thanks to the Confederación Hidrográfica del Guadalquivir, especially Mr. Mariano Palancar, who provided us crucial information on the hydraulics of the event (limnograph data). Finally, thanks to the Canal Sur Radio y Televisión (Radiotelevisión Pública de Andalucía, RTVA) and the Fondo Documental RTVE (Radiotelevisión Española, RTVE) for providing the videos of the newscasts broadcasted after the event, which made it possible to analyse the fluid’s behaviour-type, contradicting the precision of third-party sources.

Eco-hydraulic models are wide extended tools to assess physical habitat suitability on aquatic environments. Currently, the application of these tools is limited to short river stretches and steady flow simulations. However, this limitation can be overcome with the application of a high-performance computing technique: graphics processing unit (GPU) computing. R-Iber is a GPU-based hydrodynamic code parallelised in CUDA Fortran that, with the integration of a physical habitat module, performs as an eco-hydraulic numerical tool. R-Iber was validated and applied to real cases by using an optimised instream flow incremental methodology in long river reaches and long-term simulations. R-Iber reduces the computation time considerably, reaching speed-ups of two orders of magnitude compared to traditional computing. R-Iber allows for overcoming the current limitations of the eco-hydraulic tools with the simulation of high-resolution numerical models calculated in a reasonable computation timeframe, which provides a better representation of the hydrodynamics and the physical habitat. The contract of the D.D.-S. is funded by the International Center for Numerical Methods in Engineering (VAC-2021-1).

Two-dimensional (2D) hydraulic models solve the Shallow Water Equations (SWE) for the simulation of free surface flows. The necessity of considering in the calculations specific hydraulic structures, such as bridges, gates, weirs, culverts, etc., for representing more realistic flood scenarios, imply the integration in the 2D-SWE of empirical equations that represent the flow through these structures. These empirical equations are usually implemented as internal conditions over a 1D line, modifying the equations with which the flow is calculated in the edges of the mesh elements located at both sides of the line. This approach can be good enough for representing the hydraulic behavior in general. However, this 1D condition over a line, which only affects the element edges, is not a good approximation for simulating the hydrodynamics of pressurized flows, as it is the case of very wide bridges and lids over channelized rivers. New modelling strategies for simulating pressurized flows using the 2D-SWE, the Two-Component Pressure Approach method (TPA) and the Preissmann Slot Method (PSM), have been implemented in Iber. Both approaches were tested in a coverage of a channeled river characterized by several abrupt curvature changes and a contraction/expansion of their wide, and in a bridge located in a river reach that obstructs most of the floodplain. The TPA and PSM methods presented good numerical approaches for simulating pressurized flow for 2D-SWE-based models, fine-tuning the hydraulic behavior, and representing the most critical regions when a pressurized flow is generated in hydraulic structures.

Large wood (LW) accumulations can cause several damages, especially if the recruited wood is transported during floods down to urban areas, like Lourdes (France). One of the most serious problems concerning bridges and weirs all around the world is the formation of LW accumulations, that might be responsible for the structure’s failure. However, the transport and deposition of LW during floods are very complex processes, which make predictions of these accumulations’ locations and potential impacts very challenging. Thus, reducing the LW-related risks is difficult. Thereby, we are conducting a study to assess the LW-related hazards by applying a numerical model of the Gave-de-Pau River. The software called Iber-Wood is a hydrodynamic model based on the 2D Saint Venant equations coupled to a wood dynamics module that simulates wood transport explicitly. It allows analyzing the LW accumulations’ formation, depending on several input parameters. The aim of this study was to simulate wood transport during floods, in order to identify the potential risks created by the formation of LW accumulations in Lourdes’ city center. The paper first proposes a framework to calibrate the parameters of LW-supply (flux and size of logs) based on the typical dataset available in France. It then presents a preliminary study of the 2D hydrodynamic model showing its potential to identify preferential storage areas and bridges prone to the formation of LW accumulations. The calibration phase of the model is not finished yet, but we can highlight some recommendations on LW-transport modelling from these early stage results. The study was performed within the scope of the Research Project 2015/19/N/ST10/01526 financed by the National Science Centre of Poland.

Los estudios de rotura de presas permiten evaluar la peligrosidad y el riesgo por inundación asociado a un posible fallo de estas estructuras. La legislación y documentos técnicos vigentes en España marcan el camino a seguir para la correcta clasificación de la presa en función del riesgo potencial que supone para la sociedad, la economía y el medioambiente. Sin embargo, existe un vacío en las recomendaciones a seguir cuando la presa a clasificar se encuentra parcial o totalmente aterrada de sedimentos. El presente documento tiene por objeto presentar una metodología para afrontar estudios de rotura de presas aterradas mediante simulación numérica conjunta de la formación de la brecha y el transporte de sedimentos (fondo móvil). La aplicación de esta metodología a un caso de estudio real ha permitido observar cómo el hidrograma tras la rotura considerando fondo móvil es sensiblemente diferente al obtenido por la metodología estándar que considera fondo fijo dentro del vaso.

This material may be downloaded for personal use only. Any other use requires prior permission of the American Society of Civil Engineers. This material may be found at https://ascelibrary.org/doi/full/10.1061/%28ASCE%29PS.1949-1204.0000560. The wastewater generated in the potash mines of the Bages region in Catalonia (Spain) was experimentally tested at the Paterson & Cooke slurry test facility in Cape Town, South Africa, to determine the flow behavior and limit deposition velocity of various brine and brine-slurry mixtures containing a low solids concentration of fine insoluble particles. The tests measured the limit deposition velocity, viscosity, and flow resistance of a range of brine mixtures at different concentrations of solid particles in suspension, and they are presented and discussed in this paper. Tests were conducted on the slurries using both water tests (WT) and saturated brine tests (BT) as the medium for the solid sediment. In order to replicate the possible situations that could occur during their transport in the pipeline, the mixtures were generated with relatively low sediment concentrations, always less than 5% by volume. The test data showed that the limit deposition velocity at equivalent solid concentrations is higher for the WT mixtures than for the BT mixtures due to the differences in the kinematic viscosity of the medium. Finally, the kinematic viscosity obtained for both WT and BT mixtures trends moderately upward as their volume concentration increases, although the viscosity in BT mixtures presents some particularities that are subsequently described.

Developments in mountain areas prone to natural hazards produce undesired impacts and damages. Thus, disaster assessment is mandatory to understand the physics of dangerous events and to make decisions to prevent hazardous situations. This work focusses on the practical implementation of methods and tools to assess a snow avalanche that affected a road at the Coll de Pal in 2018 (SE Pyrenees). This is a quite common situation in mountain roads and the assessment has to focus specially in the avalanche–road interaction, on the return periods considered and on the dynamics of the phenomena. This assessment presents the field recognition, snow and weather characterization and numerical modelling of the avalanche. Field campaigns revealed evidences of the avalanche triggering, runout trajectory and general behavior. An unstable situation of the snowpack due to a relatively large snowfall fallen some days before over a previous snowpack with weak layers, caused the avalanche triggering when an additional load was added by a strong wind-drift episode. A medium size (&lt, 2500 m3) soft slab avalanche, corresponding to a return period of 15–20 years, occurred and crossed the road of the Coll de Pal pass. The event was reproduced numerically by means of the 2D-SWE based numerical tool Iber aiming to analyze the avalanche behavior. Results of the simulation corresponded with the observations (runout trajectory and snow deposit), thus, relevant information about the avalanche dynamics could be obtained. Identified differences probably come from the terrain elevation data, which represent “snow free” topography and do not consider the snowpack on the terrain.

[EN] The pond-breack of the mining tails of the Aznalcóllar complex that occurred on April 25, 1998 was an unprecedented catastrophe. Millions of cubic meters of a complex fluid flooded the riverbeds and riverbanks of the Agrio, Guadiamar and, to a lesser extent, Guadalquivir rivers. Despite being one of the most studied events, from the hydraulic point of view there are still uncertainties. Denominated as a “muds” spill by several authors, many others treat it as a fluid composed of “muds” and “acidic waters”, both, according to their name, with different hydraulic behavior. This work analyzes the nature of the fluid spilled from the video-recordings made during the event. This has made it possible to establish a first classification according to the dynamic and static behavior observed. According to this analysis, the spill reveals that the fluid behaved more like a highly concentrated sediment-laden flow than like a mud flow., [ES] La rotura de la balsa de estériles mineros del complejo de Aznalcóllar acaecida el 25 de abril de 1998 fue una catástrofe sin precedentes. Millones de metros cúbicos de un fluido complejo inundaron los cauces y riberas de los ríos Agrio, Guadiamar y, en menor medida, Guadalquivir. A pesar de ser uno de los eventos más estudiados, desde el punto de vista hidráulico todavía existen incertidumbres. Denominado como un vertido de «lodos» por diversos autores, otros tantos lo tratan como un fluido compuesto por «lodos» y por «aguas ácidas», ambos, según su denominación, con un comportamiento hidráulico distinto. En este trabajo se analiza la naturaleza del fluido vertido a partir de las grabaciones de vídeo realizadas durante el evento. Esto ha permitido establecer una primera clasificación según el comportamiento dinámico y estático observado. Según este análisis, el vertido se comportó más como un fluido hiperconcentrado de partículas en suspensión que como un fluido de lodo., Los autores quieren agradecer a Canal Sur Radio y Televisión (Radiotelevisión Pública de Andalucía, RTVA) y al Fondo Documental RTVE (Radiotelevisión Española, RTVE) por facilitar los vídeos de los informativos emitidos tras el evento, gracias a lo cual el análisis del comportamiento del fluido ha sido posible para contrastar la precisión de fuentes de terceros. Asimismo, los autores muestran su agradecimiento al Sr. Benigno Bayán, ingeniero retirado de la Confederación Hidrográfica del Guadalquivir, que ha aportado información muy valiosa para la comprensión de la física del vertido.

International audience; Large wood (LW) accumulations can cause several damages, especially if the recruited wood is transported during floods down to urban areas, like Lourdes (France). One of the most serious problems concerning bridges and weirs all around the world, is the formation of LW accumulations, that might be responsible for the structure’s failure. However, the transport and deposition of LW during floods are very complex processes, which make predictions of these accumulations’ locations and potential impacts very challenging. Thus, reducing the LW-related risks is difficult. Thereby, we are conducting a study to assess the LW-related hazards by applying a numerical model of the Gave-de-Pau River. The software called Iber-Wood is a hydrodynamic model based on the 2D Saint Venant equations coupled to a wood dynamics module that simulates wood transport explicitly. It allows analyzing LW accumulations’ formation, depending on several input parameters. The aim of this study was to simulate wood transport during floods, in order to identify the potential risks created by the formation of LW accumulations in Lourdes’ city center. The paper first proposes a framework to calibrate the parameters of LW-supply (flux and size of logs) based on the typical dataset available in France. It then presents a preliminary study of the 2D hydrodynamic model showing its potential to identify preferential storage areas and bridges prone to the formation of LW accumulations. The calibration phase of the model is not finished but we can yet highlight some recommendations on LW-transport modelling from this early stage results.

The potash mines located in the central region of Catalonia generate waste brines that are transported and discharged beneath the sea on the Catalan central coast through a pipeline facility more than 100 km long. The pipeline has variable diameters; a major part has an internal diameter of 334 mm and is mainly made up of fiberglass-reinforced polyester (GRP). A 4-km-long section was monitored for 3 months. The wastewater level in the head tank, temperature, pressure evolution, and flow rate were recorded during this period. This information enabled the achievement of the major aim of this paper, that is, the discussion of the evolution of the roughness of the pipeline and the prediction of the limit deposition velocity of the suspended solid particles transported by the flow. The values obtained for absolute roughness showed wide variability in the varied between 0.57 and 16.7 mm. The values obtained for the limit deposition velocity indicated that particles of a size greater than 150 µm would settle down inside the pipe. In addition, the effect of the removal of a waste salt stockpile hill located in the vicinity of the monitored pipeline stretch was analyzed. The authors wish to thank the Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR) of the Catalan government for Grant No. 2014 DI 0070 of the Industrial Doctorate Programme. The authors would also like to thank the Aigües de Barcelona for their technical and economic support during the project’s execution.

This material may be downloaded for personal use only. Any other use requires prior permission of the American Society of Civil Engineers. This material may be found at https://ascelibrary.org/doi/abs/10.1061/%28ASCE%29HE.1943-5584.0001979. Onsite and Earth observation (EO) data are used for the calibration of the Natural Resources Conservation Service curve number (NRCS-CN) value in a hydrological simulation model. The model was developed for La Muga catchment (eastern Pyrenees) highly vulnerable to flood and drought episodes. It is an integral part of a regional reservoir management tool, which aims at minimizing the flood risk while maximizing the preservation of water storage. The CN values were optimized for five recorded events for the model to match the observed hydrographs at the reservoir when supported with the measured rainfall intensities. This study also investigates the possibilities of using antecedent moisture conditions (AMC) retrieved from satellite data to inform the selection of the NRCS-CN losses parameter. A good correlation was found between the calibrated CN values and the AMC obtained from satellite data. This correlation highlights the interest in using EO data to update NRCS-CN estimates. This advances in hydrologic-hydraulic coupled modeling combined with new remote sensing datasets present valuable opportunities and potential benefits for flood risk management and water resources preservation. This work was carried out in the framework of the PGRI-EPM project (Prévision et gestion du risque d’inondation en Eurorégion Pyrénées Méditerranée) funded by the call for projects “Water Resources–Risk Management (Floods, Droughts, Submersion)” of the Pyrenees-Mediterranean Euroregion. The authors also thank to the Agència Catalana de l’Aigua and Servei Meteorològic de Catalunya, who provided the rainfall and water-level data, as well as its advisement during the project.

[ES] La legislación española actual exige que en los estudios de inundabilidad se delimite la Zona de Flujo Preferente (ZFP), compuesta por envolvente de la Zona de Inundación Peligrosa (ZIP) y la Vía de Intenso Desagüe (VID). La delimitación de la VID es compleja, subjetiva, y no tiene solución única. Habitualmente se determina mediante la restricción de la zona disponible para el flujo, estrechando la zona que ocupa la avenida de 100 años de periodo de retorno, es decir, no permitiendo el flujo en las zonas más alejadas del eje del río. En el presente trabajo se analiza el concepto de VID, y se muestra cómo, en algunos casos, el método anterior no es el mejor, en especial en presencia de zonas de flujo desconectadas o en casos en los que el flujo puede tener una componente transversal importante. Finalmente, se presenta una metodología para la definición de una VID con el mayor sentido físico posible, mediante modelización numérica bidimensional., [EN] The current Spanish legislation requires flood risk assessment studies to determine the Preferential Flow Zone (ZFP), which consists of the union of the Hazardous Flood Area (ZIP) and the Intense Flow Path (VID). The definition of the VID is complex, subjective, and has no unique solution. It is usually determined by subsequently restricting the area available for flow, narrowing the area that initially occupies the flood of a 100-year return period, and controlling the increase in water depth this floodplain restriction causes. In this work the concept of VID is analysed, and it is shown how, in some cases, the common previous method is not the best, especially in the presence of disconnected flow zones or in cases where the flow may have an important transverse component. Finally, a methodological proposal is presented for the definition of a VID with physical sense, using two-dimensional numerical modelling.

The interest of a consulting company in designing stepped spillways in roller compacted concrete (RCC) dams led us to propose the possibility of building this type of spillway without sidewalls. Previous research on stepped spillways has focused on characterizing the complex hydraulic behavior of flow on these structures, as well as design criteria. Such studies have usually been conducted on stepped spillways with a constant width along the spillway, that is, with sidewalls. In the present work, we report the results of the physical modeling of a generic stepped spillway without sidewalls (slope 1v:0.8h). In general terms, the lack of sidewalls produces a lateral expansion of water and therefore a non-uniform longitudinal and transversal discharge distribution. Consequently, the flow type, characteristic water depth, velocity, air concentration, and pressure fields change along and across the spillway. The resulting data demonstrate that the distribution of the different variables studied depend on the specific discharge at the entrance and the spillway height

Donana National Park wetlands are located in southwest Spain, on the right bank of the Guadalquivir River, near the Atlantic Ocean coast. The wetlands dry out completely every summer and progressively flood again throughout the fall and winter seasons. Given the flatness of Donana's topography, the wind drag action can induce the flooding or emergence of extensive areas, detectable in remote sensing images. Envisat/ASAR scenes acquired before and during strong and persistent wind episodes enabled the spatial delineation of the wind-induced water displacement. A two-dimensional hydrodynamic model of Donana wetlands was built in 2006 with the aim to predict the effect of proposed hydrologic restoration actions within Donana's basin. In this work, on-site wind records and concurrent ASAR scenes are used for the calibration of the wind-drag modeling by assessing different formulations. Results show a good adjustment between the modeled and observed wind drag effect. Displacements of up to 2 km in the wind direction are satisfactorily reproduced by the hydrodynamic model, while including an atmospheric stability parameter led to no significant improvement of the results. Such evidence will contribute to a more accurate simulation of hypothetic or design scenarios, when no information is available for the atmospheric stability assessment. Doñana National Park wetlands are located in southwest Spain, on the right bank of the Guadalquivir River, near the Atlantic Ocean coast. The wetlands dry out completely every summer and progressively flood again throughout the fall and winter seasons. Given the flatness of Doñana’s topography, the wind drag action can induce the flooding or emergence of extensive areas, detectable in remote sensing images. Envisat/ASAR scenes acquired before and during strong and persistent wind episodes enabled the spatial delineation of the wind-induced water displacement. A two-dimensional hydrodynamic model of Doñana wetlands was built in 2006 with the aim to predict the effect of proposed hydrologic restoration actions within Doñana’s basin. In this work, on-site wind records and concurrent ASAR scenes are used for the calibration of the wind-drag modeling by assessing different formulations. Results show a good adjustment between the modeled and observed wind drag effect. Displacements of up to 2 km in the wind direction are satisfactorily reproduced by the hydrodynamic model, while including an atmospheric stability parameter led to no significant improvement of the results. Such evidence will contribute to a more accurate simulation of hypothetic or design scenarios, when no information is available for the atmospheric stability assessment

De manera tradicional, los sistemas de información geográfica disponen de información sobre el territorio en dos formatos: formato ráster y formato vectorial, y cada uno de estos formatos es tratado con sus algoritmos independientes. Por consiguiente, cualquier tipo de estudio hidráulico realizado sobre el territorio es una información susceptible de ser clasificada en estos dos formatos y también dispone de sus propios algoritmos. Por otro lado, LiDAR es la tecnología más precisa para generar Modelos Digitales de Elevaciones (MDE) para grandes áreas, con una resolución espacial de 1 o 2 m, y con una gran precisión en altura. Ello confiere un carácter ráster a la información cartográfica, cuya unidad básica de información es la celda. Por consiguiente, este tipo de material resulta muy adecuado para la generación de mallas de cuadriláteros, estructuradas para los modelos numéricos de flujo en lámina libre 2D. El objetivo principal es presentar una adaptación del esquema clásico explícito de primer orden de volúmenes finitos a una malla de Volúmenes Finitos Cuadrangulares (VFC), que hace equivaler —directamente y sin interpolaciones— cada celda del MDE (o ráster), con el correspondiente VFC. Por consiguiente, las dimensiones del VFC serán las de la Celda del MDE de base. Ello se presenta aquí como el enfoque ráster al problema del problema hidrodinámico del flujo en lámina libre en 2D. En el enfoque ráster, el hecho de que a cada instante de tiempo de integración no sea necesaria la consulta de la base de datos de la topología de la malla hace que el proceso numérico mejore de forma enorme su eficiencia de cálculo. Por consiguiente, se pueden abordar problemas con mayor dimensión. También es objetivo comparar ambos enfoques a través de la resolución de un ejemplo ilustrativo.

This paper presents a new freeware simulation tool (IberWQ) for 2D water quality modelling in rivers and non-stratified estuaries. The model computes the spatial and temporal evolution of several species and variables which are relevant for the evaluation of the environmental status of rivers and estuaries, including: Escherichia coli, dissolved oxygen, carbonaceous biochemical oxygen demand, organic nitrogen, ammoniacal nitrogen, nitrate–nitrite nitrogen, water temperature and salinity. A depth-averaged transport equation is solved for each variable with a mass conservative unstructured finite volume solver. IberWQ is fully coupled to the hydrodynamic module of the software Iber, a freeware simulation tool for solving the 2D shallow water equations. Both models are integrated in the same windows graphical environment, including several tools which allow the user to generate unstructured meshes adapted to the site topography, define spatially variable input parameters and visualize model outputs. We present four application examples to illustrate the possibilities of the software for the dynamic simulation of water quality in rivers and estuaries.

The pressure profiles on the horizontal and vertical step faces of a stepped spillway in the fully developed skimming flow region were measured. These observations allow to provide generalized equations that enable designers to analyze the amount and the location of negative pressures along the steps. The step locations subjected to negative pressure are also discussed including an analysis of the duration of the negative pressures. On the horizontal step faces, negative pressure were only observed on their upstream half for dimensionless discharges larger thandc/h= 1.3. On the vertical step faces, only the region close to the adjacent horizontal face was not subjected to negative pressure

This document presents a dam wall break simulation of the La Parota hydropower project in Guerrero, Mexico, by means of the CARPA system, which is based in a 2D WAF-TVD (Weight Averaged Flux-Total Variation Diminishing) high resolution finite volume numerical scheme. With the results, it is possible to produce maps containing water depth, flow velocity, and affected zones, which are useful in the civil protection field.

This paper presents an analysis of the pressure field on the steps of a stepped spillway on an RCC dam. The fundamental component of this study is a series of pressure measurements obtained in the fully-developed zone of skimming flow regime along a reduced-size stepped spillway model constructed at the Department of Hydraulic, Maritime and Environmental Engineering Laboratory of the Technical University of Catalonia (UPC). A mathematical model was fitted to the pressure profiles on the horizontal and vertical faces of the steps. This equation allows designers to estimate the possible negative values of pressure on the vertical and horizontal faces of the steps in the fully-developed zone of skimming flow regime.

Upstream from a dam reservoir, river hydrodynamics may be directly changed by temporary inundation driven by the reservoir. This triggers morphological river changes which may additionally modify the initial hydrodynamics, even at the time when backwater inundation does not occur (indirect effects of backwater). We verified these hypotheses, applying two-dimensional hydraulic modelling of flood flows to a section of the mountainous Dunajec River upstream from the Czorsztyn Reservoir. The modelling was performed for small, medium and large floods, and hydraulic conditions were compared between the scenarios with lacking and maximum backwater inundation and between the river reaches subjected to backwater inundation and unaffected by backwater fluctuations. Direct effects of reservoir level fluctuations were limited to the reach subjected to backwater inundation during floods and comprised: significantly increased water depth and decreased flow velocity and bed shear stress in the channel and on the floodplain, as well as a re-established hydrological connectivity between the channel and floodplain during small and medium floods. Indirect effects of backwater inundation reflected channel widening and bed aggradation that triggered a positive feedback with changes in hydrodynamics, mostly by reducing the velocity of flood flows in the channel zone. These latter changes occurred on a longer distance upstream from the reservoir than the backwater reach itself, and they modified the river hydrodynamics even when backwater inundation did not occur. We propose a conceptual model which indicates that changes of mountain rivers upstream from dam reservoirs are driven by modified hydrodynamics and lead to different morphological adjustments than those induced by waters underloaded with sediment downstream from dams. Changes in hydrodynamics and the associated morphological and sedimentary adjustments of mountain rivers recorded upstream from dam reservoirs may locally mitigate impacts of channelization and channel incision on riverine and riparian ecosystems of these rivers. The study was performed within the scope of the Research Project 2015/19/N/ST10/01526 financed by the National Science Centre of Poland. The Czorsztyn–Niedzica Hydropower Plant Inc. provided the data on reservoir water stages. We thank two anonymous reviewers for their critical comments on the manuscript.

Voellmy–Salm friction model is one of the most extensively used theories for assessing the frictional terms of the equations that describe the motion of non-Newtonian flows such as snow avalanches. Based on the Coulomb- and turbulent-type friction, this model has been implemented in numerical tools for computation of snow avalanche dynamics based on the Shallow Water Equations (SWE). The range of the Voellmy parameters has been discussed widely, focusing mainly on the required values for achieving good results for the description of the moment and position of the avalanche when it stops. However, effects of parameters on the SWE terms, and their physical interpretation have not been investigated sufficiently. This work focuses on analysing the effects of the Voellmy–Salm parameters and cohesion on the avalanche characteristics and evolution of the new SWE-based numerical model Iber. In the numerical scheme, an upwind discretization was used for the solid friction and cohesion terms, while a centred one was used for the turbulent friction. Results show that the Voellmy–Salm model dominates the avalanche dynamics and the cohesion model allows the representation of long tails, whereas the friction and cohesion parameters may vary within a wide range.

[ES] La creciente preocupación por los riesgos naturales, como las avalanchas de nieve, ha propiciado el desarrollo de modelos numéricos ad hoc como una herramienta de soporte para su análisis y evaluación. Los modelos existentes para simulación de aludes se basan en la conservación de la masa y de la cantidad de movimiento, que son unas ecuaciones similares a las ecuaciones de Saint Venant para agua con diferencias sólo en los términos de fricción (modelo reológico). Este documento muestra las posibilidades de estas ecuaciones para simular avalanchas de placa-densa y el tratamiento numérico realizado en Iber. Se ha empleado una nueva metodología para equilibrar el término fuente y el vector de flujo evitando así oscilaciones espurias y movimientos no reales, y que modifica la pendiente de fondo en base a los parámetros del fluido y así detener su movimiento. La herramienta se ha probado en dos casos de estudio para analizar el comportamiento del fluido en función de los parámetros del mode, [EN] The growing concern about natural hazards, such as snow avalanches, has led to the development of ad hoc numerical models as a support tool for their analysis and evaluation. Existing models for avalanche simulation are based on the conservation of mass and the momentum, which are similar equations to the Saint Venant equations for water with differences only in terms of friction (rheological model). This document shows the possibilities of these equations to simulate dense-slab avalanches and the numerical treatment carried out in Iber. A new methodology has been used to balance the source term and the flow vector to avoid spurious oscillations and unreal movements, modifying the bottom slope based on the fluid parameters and thus stop its movement. The tool has been tested in two case studies to analyse the behaviour of the fluid depending on the parameters of the rheological model.