THE VALIDATION OF FINE-SEDIMENT DEPOSITION MODEL IN INTER-FLOODPLAIN OF LOWLAND RIVERS

Abstract

 Sediment deposition in the inter-floodplain of a river channel in lowland rivers contain a large amount of fine-grained sediments called “wash load”. The main objective of this study is to validate a prediction model for wash-road deposition that can take into account different sediment concentrations and flow regimes in different rivers, and to understand the effects of ground surface conditions on wash-road deposition at excavated sites along the Ibi and Nagara Rivers in the Kiso River system through field experiments and field surveys. We conducted fixed-point surveys over four outflow periods in the Ibi River, field experiments with four panels of different ground cover conditions, and a total of 67 sites in three excavation sites in the Ibi and Nagara Rivers to determine the amount of sediment deposition and the percentage of wash roads during each study period. The model reproduction and validation results showed that the model performed well under the forested condition. On the other hand, the validation of the model under conditions where only herbaceous vegetation covered the ground surface remained an issue. The model performs well enough to predict the amount of sediment deposited after excavation.