Design of sediment detention basins: Scaled model experiments and application

Sediment detention basins are implemented on mountain rivers to trap solid material that may aggravate the flooding of downstream settlements. However, retention structures built in the past may unnecessarily retain sediment during non-hazardous flood events, resulting in high maintenance costs and sediment deficit downstream. In addition, the so-called spontaneous self-flushing of previously retained sediment during floods has occasionally been observed. Recent research suggests to design sediment detention basins for controlling sediment passage with a guiding channel across the deposition area upstream of a hybrid barrier. Such barriers consist of a check dam with a slot orifice and an upstream bar screen with a bottom clearance in order to benefit from a combined mechanical-hydraulic retention control. The present paper enhances this pioneering research with the help of new experimental data, including a wide range of sediment mixtures and large wood, as well as variable barrier heights. Improved design criteria are provided regarding the bar screen and the basin storage capacity. The functionality of the enhanced concept for sediment detention is illustrated by a case study on a physical model: the protection of the Villard-Bonnot village (France) against torrential hazards.