Check dam impact on sediment loads: example of the Guerbe River in the Swiss Alps – a catchment scale experiment

• Published in: Hydrology and earth system sciences 2024-03, Vol.28 (5), p.1173-1190
• Main Authors: do Prado, Ariel Henrique, Mair, David, Garefalakis, Philippos, Schmidt, Chantal, Whittaker, Alexander, Castelltort, Sebastien, Schlunegger, Fritz
• Format: Article
• Language: English
• Subjects: Bed load; Case studies; Catchment area; Catchment scale; Catchments; Check dams; Climatic conditions; Creeks & streams; Dam construction; Dams; Data acquisition; Datasets; Design and construction; Discharge measurement; Effectiveness; Efficiency; Energy gradient; Flood damage; Fluctuations; Flumes; Friction; Gaging stations; Gradients; Grain size; Infrastructure; Landslides; Landslides & mudslides; Mathematical analysis; Mountain streams; Mountains; Particle size; Probability theory; River beds; River channels; Riverbeds; Rivers; Runoff; Sediment; Sediment load; Sediment transport; Sediments; Slopes; Stabilizing; Stream discharge; Streams
• ISSN: 1607-7938; 1027-5606; 1607-7938
• DOI: 10.5194/hess-28-1173-2024

The construction of check dams is a common practice around the world where the aim is to reduce the damage by flooding events through mountain streams. However, quantifying the effectiveness of such engineering structures has remained very challenging and requires well-selected case studies, since the outcome of such an evaluation depends on site-specific geometric, geologic and climatic conditions. Conventionally, the check dams' effectiveness has been estimated using information about how the bedload sediment flux in the stream changes after the check dams are constructed. A permanent lowering of the bedload flux not only points to a success in reducing the probability of sediment transport occurrence but also implies that the sediment input through the system is likely to decrease. Here, we applied a method for data acquisition and two different equations (Meyer-Peter–Müller and Recking approach) to estimate and compare the sediment transport in a mountain stream in Switzerland under engineered and non-engineered conditions. Whereas the first equation is derived from a classical approach that is based on flume experiment data with a slope of less than 0.02 m m−1, the second equation (Recking) has been derived based on a bedload field dataset comprising active mountain streams under steeper conditions. We selected the Guerbe (Gürbe) River situated in the Swiss Alps as a case study, which has been engineered since the end of the 19th century. This has resulted in more than 110 check dams along a ca. 5 km reach where sediment has continuously been supplied from adjacent hillslopes, primarily by landsliding. We measured the riverbed grain size, topographic gradients and river widths within selected segments along this reach. Additionally, a gauging station downstream of the reach engineered with check dams yielded information to calibrate the hydroclimatic situation for the study reach, thus offering ideal conditions for our catchment-scale experiment. Using the acquired data and the dataset about historical runoff covering the time interval between 2009 and 2021 and considering the current engineered conditions, we estimated a mean annual volume of transported bedload which ranges from 900 to 6000 m3 yr−1. We then envisaged possible channel geometries before the check dams were constructed. We inferred (1) higher energy gradients which we averaged over the length of several check dams and which we considered a proxy for the steeper river slope under natura