Eco-morphological assessment of sediment augmentation in gravel-bed rivers

The construction of a dam alters the sediment inflow and outflow balance that can be  observed for natural conditions and the continuity of the sediment flow is interrupted, resulting in sedimentation in the reservoir and a sediment deficit downstream of the dam. In the riverine environment, the riverscape, sediment and flow regime are essential drivers for natural habitat dynamics. Sediment augmentation measures have been performed since several decades, gaining in importance in recent years. They consist of artificial supply of sediment to a watercourse. They are usually used in hydropower mitigation and river rehabilitation projects. The main objectives of theses measures are to balance the bedload budget, promote the channel dynamics, restructure and diversify the riverbed structure and improve the substrate quality. In Switzerland, they are widely applied as constructional measures to re-establish sediment continuity across hydraulic transverse structures. This research project investigates hydromorphological assessment strategies and design optimisation. It focuses on alternating in-channel deposits in low-gradient, sediment-starved, gravel-bed rivers.