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River reaches downstream of dams with constant residual discharge often lack sediment supply and periodic high flows due to dam sediment retention and flow regulation, respectively. To test a novel multi‐deposit methodology for defining environmental flows for activating the dynamics of the river morphology downstream of dams, a flood was released from Rossens Dam in Switzerland. This event was combined for the first time with a multi‐deposit configuration of sediment replenishment consisting of four artificial deposits allocated as alternate bars along the riverbanks as a restoration measure. To validate the sediment transport behaviour observed in laboratory tests, stones were equipped with radiofrequency identification (RFID) passive integrated transponder (PIT) tags, a fixed antenna was installed at the river bed and a mobile antenna was used to enable the investigation of the erosion, transport and deposition of replenished sediments. The duration of the erosion period was determined for the tracked stones, and average transport velocities were found to be on the order of 10–3 m/s. To estimate the erosion efficiency of the flood, defined as the eroded tagged stones compared with the released water volume, the hydrograph was divided into different periods: rising limb, constant peak discharge, decreasing limb. During the rising limb of the flood, which lasted for 20% of the total flood duration, more than 40% of the PIT tags were transported. The defined erosion efficiency is a measure to support the hydrographic design of artificial flood releases from dams. The deposition of tagged stones resulted in a repeating cluster formation, as expected from previous laboratory experiments, creating an increase in hydraulic habitat diversity. Comparison of the results obtained in the field and from laboratory experiments confirmed the robustness of the multi‐deposit sediment replenishment method. Combined with the knowledge gained on the erosion efficiency, these results could motivate further applications and research into multi‐deposit sediment replenishment techniques as a habitat‐oriented river restoration measure. © 2020 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Extreme flood estimates for dam safety are routinely obtained from hydrologic simulations driven by selected design storms. The temporal structure of such design storms can be obtained from Rainfall Mass Curves (RMCs), which are adimensionalized curves of the cumulative precipitation depth as a function of event duration. This paper assesses for the first time the spatialand temporal variability of observed RMCs for Switzerland, an Alpine region with complex topography. The relevance of the detected RMC variability for extreme flood estimation is illustrated based on an application to a high elevation catchment, the Mattmark dam catchment in the Swiss Alps. The obtained results underline that quantile RCMs represent a simple yet powerful tool to construct design storms for dam safety verification and that regional, seasonal and event-duration effects on RMCs are small enough to justify the use of a unique set of Swiss-wide quantile RMCs. The presented analysis could be refined in the future by explicitly accounting for orographic, convective or frontal precipitation events. [ABSTRACT FROM AUTHOR]

We present a new hydro-morphological index of diversity (HMID), a tool aimed for use in river engineering projects and firstly developed at gravel-bed streams in Switzerland, but intended for a broader use. We carried out field work with extensive hydraulic and geomorphic data collection, conducted correlation analysis with hydro-morphological variables, formulated the HMID, and analyzed the correlation between HMID and a visual habitat assessment method. The HMID is calculated by means of the coefficient of variation of the hydraulic variables flow velocity and water depth, which have been demonstrated to sufficiently represent the hydro-morphological heterogeneity of alpine gravel-bed stream reaches. Based on numerical modeling, the HMID can be calculated easily for a comparison of different alternatives in river engineering projects and thus achieves predictive power for design decisions. HMID can be applied at a reach-related scale in engineering programs involving geomorphic measures that aim at the enhancement of habitat heterogeneity of a stream. However, the application of HMID has to be integrated with evaluations of the long-term streambed evolvements that are considered at a catchment scale and strongly related to the sediment regime of the stream under study. [ABSTRACT FROM AUTHOR]

Reservoir sedimentation hinders the operation of the Lavey run-of-river hydropower plant (HPP) on the Rhone River in Switzerland. Deposits upstream of the gated weir and the lateral water intake reduce the flood release capacity and entrain sediments into the power tunnel. Past flushing operations of the relatively wide and curved reservoir have been inefficient. To improve sediment management, the enhanced scheme Lavey+ with an additional water intake and a training wall for improving flushing was set up. The performance of the enhancement project was tested on a physical model. For its calibration, sediment transport, deposition, and flushing of the present scheme were investigated and compared with prototype measurements. The enhanced scheme was then analyzed in detail to define the flushing discharge and duration, and define the gate operation to ensure maximal erosion of deposits with minimal water loss. [ABSTRACT FROM AUTHOR]

Abstract: Shore protection in lakes is an issue of major importance in Switzerland where several big lakes in plains suffer from a pronounced bank erosion. For the moment, in shallow lakes, soft and biotechnical protection measures proved their reliability. Unfortunately, the scientific basis for the design of such techniques does not exist in some cases or not appropriate enough in order to have an optimized effect. Therefore, the aim of an on-going research project is to study, on the basis of physical and numerical modeling, the impact of such measures on the shores regarding bank erosion, and to establish the main basis for their dimensioning. A 2-D numerical model was used to simulate the eroded beach of Préverenges on the North coast of Lake Geneva. Hence, this case study allowed a better understanding of the numerical capacities of the program by modelling wave effect on bedload sediment transport and shore erosion as well as wind role in the generation of littoral currents. [Copyright &y& Elsevier]