Sediment Replenishment Along Rivers - Advection and Dispersion of Gravel Inputs

Gravel augmentation is a common approach to counteract possible consequences of disturbed sediment balances along European Rivers like the Rhine or the Danube. Therefore, hundreds of thousands cubic meters of gravel are dumped each year to prevent river-bed degradation, secure water-fairways and protect infrastructure. As transverse structures in many cases can act as sediment barriers, this is likely to happen in the vicinity of run-of-river hydropower plants (RoR-HPP). Also, gravel replenishment is a means for ecological habitat improvement. Within this paper, the 1D-advection-dispersion model (1D-ADM) was tested for its suitability to describe the longitudinal propagation of local-short-term (LST) gravel inputs based on a laboratory experiment. This approach is well-known for the modelling of suspended and solute material transport like suspended sediments, contaminants. Here, the advection term is described by the mean value (mu) of the longitudinal movement, while the dispersion parameter is related to the corresponding standard deviation (sigma). The experiments were conducted in a 0.3-meter-wide and 10-meter-long laboratory flume with mobile bed conditions. The data were collected via bathymetric laser scans of the bed surface as well as load cell measurements. A quality assessment is provided together with four model-efficiency measures. Finally, further applications of the 1D-ADM are discussed within the paper. In conclusion, the 1D-ADM is capable to describe the longitudinal propagation of a LST bed load input on high a level of confidence.