Application of remote sensing and GIS-based modelling in the analysis of floodplain sedimentation

This paper presents the application of remote sensing and GIS-based techniques in the analysis of floodplain sedimentation, using a case study from the lower river Rhine in the Netherlands. Using a Landsat TM image, the longitudinal decrease in sediment concentrations and spatial patterns of sediment concentrations within the floodplain were analysed. Patterns of sediment deposition after the large magnitude December 1993 flood were determined, using sediment trap measurements that have been interpolated and converted to sedimentation maps in a GIS. These data formed the basis for the development of a GIS-based mathematical model for the simulation of floodplain sedimentation. The model comprises two components: (1) the existing hydrodynamic WAQUA model that calculates two-dimensional water flow patterns, and (2) the SEDIFLUX model that calculates deposition of sediment, using a simple mass-balance concept with a limited number of model parameters. The SEDIFLUX model has been calibrated and validated using interpolated raster maps of sediment deposition. The model appeared to be an adequate tool to predict patterns of sediment deposition, as the product of the complex interaction among river discharge and sediment concentration, floodplain relief, and the resulting water flow patterns. In the investigated areas, the resulting annual average sedimentation rates varied between 0.5 and 4.0 mm per year. The role of floodplain relief controlling water flow patterns and sediment conveyance over the floodplain, and the resulting spatial patterns of overbank sedimentation are discussed.