The analysis of degradation and aggradation of the riverbed: A case study of the Winongo River

Abstract

The Winongo River, with a soil base, makes it possible to experience sedimentation events. In rivers with groundsill for retaining sediment rate, the flow can occur, grinding sediment (degradation) or aggradation on the riverbed. This study was conducted in Winongo River to see the effect of groundsill on riverbed degradation and aggradation levels. This research was carried out using the MPM, Engelund & Hansen, and Laursen-Copeland equations in HEC-RAS 6.3.1 by dividing Winongo River into 71 points with a spacing of ± 500 m, including nine with groundsills. Based on the effect of the groundsill on the riverbed, the cross sections at its upstream and downstream tend to experience quite different riverbed elevation changes. Conditions in the upstream groundsill tend to experience aggradation while the downstream experiences degradation. The three equations modelling results show that MPM and Engelund & Hansen equations are closer to field conditions than the Laursen-Copeland equation. The use of D50 sediment to model changes in riverbed elevation is more likely to experience degradation because the average grain size of D50 in this study sample was 0.82 mm.