FLOODPLAIN SEDIMENTATION - QUANTITIES, PATTERNS AND PROCESSES

This paper presents the result of measurements of flood plain sedimentation using sediment traps. The study was carried out on two embanked floodplains along the Rivers Rhine and Meuse in The Netherlands during a 3 day flood in January 1993. Raster maps of sediment accumulation were made by interpolating the measurements from the traps using block kriging. The sediment maps show clear patterns in sediment accumulation:, together with the estimated interpolation errors. Average sediment accumulation ranges between 0.57 and 1.0 kg m(-2) High sediment accumulation is found on the levees (4 kg m(-2) or more) and on low lying areas (1.6 kg m(-2)); sediment accumulation decreases with distance from the main channel. The sedimentation patterns are related to floodplain topography and sediment transporting mechanisms. Sediment transport by turbulent diffusion as well as by convection can be recognized. Also, flood duration and the process of sediment settling out in pending water in closed depressions are important. The applied method allows comparison of the results with raster-based sedimentation models.