Modelling sediment accumulation and dispersion of contaminants in Lake Ijsselmeer (The Netherlands)

In this study two models are integrated for the simulation of sediment distribution and quality in the Lake IJsselmeer area. STRESS-2d, a two dimensional dynamic model for simulation of sediment transport due to resuspension, erosion, sedimentation and horizontal advection and dispersion is used to simulate the sediment transport dynamics for a period of one year. The model is calibrated on water level, suspended solids concentration and sedimentation flux measurements. The model has a high spatial and temporal resolution. The model DIASPORA, which is based on STRESS-2d results, simulates the effects of sediment transport on morphology and contaminant concentrations in the sediment for a period of decades. DIASPORA also simulates dilution by internally produced CaCO3 and consolidation of sediment layers. The models produce a reasonable reconstruction of suspended solids concentrations and long term accumulation of sediments in deep areas within the lake. Also the temporal and spatial variability in the contaminant concentration in sediments in Lake IJsselmeer is reconstructed with sufficient quality. Model simulations show that internal redistribution of old deposits in the IJsselmeer area and internal production of CaCO3 are diluting the contaminated solids supplied by the river IJssel.