Design improvements for combined sediment-wood detention at mountain streams

Bedload transport and driftwood in steep mountain streams can cause serious damage to local communities in the vicinity of watercourses. To prevent such damage, check dams are typically built to hold back sediment and driftwood. However, by completely interrupting sediment transport, check dams are also detrimental to the ecology of mountain streams. A new type of partially permeable structure has emerged, which allows the sediment to pass during non-hazardous flows. This paper investigates the concept of partially permeable sediment and driftwood detention with the help of a physical model, based on a case study in Switzerland. This study shows that detention basins design can be improved by a combination of methods used to manage sediment in steep mountain streams and driftwood in lowland rivers. This offers an advanced way to improve flood resilience while maintaining sediment transport and ecomorphological continuity.