Sediment transport in Säveån and its implications for erosion and bank stability

Abstract: This master thesis study is a preliminary investigation of the Säveån River as part of the Swedish Geotechnical Institute’s (SGI) landslide risk assessment project. The main objectives include building a hydrodynamic model for the river, estimating sediment transport along the river, assessing the implications for erosion and bank stability and evaluating climate change effects on sediment transport. The study section is from downstream Jonsered hydropower plant to the outlet at Göta Älv. The model selected for the hydrodynamic study is the one dimensional river analysis model HEC-RAS. ArcGIS was used in combination with Hec-GeoRAS to map out the river and extract cross sections from a Digital Elevation Model (DEM) of the river. Steady flow and sediment transport simulations were then done to obtain the hydrodynamics and sediment transport of the river respectively. Model results revealed schematized cross section 12500 close to the upstream end of the study reach to have the most erosion. This section was then used as an example to find the loss in slope stability due to sediment transport using the model SLOPE/W. Climate change simulations were then done with flow data from a simulated period of 2021-2050 and 2069-2098 and compared to a reference period of 1963-1992. Results show that sediment transport is to increase more than twice moving from the reference period to the period 2021-2050 and increase again more than twice from this period to the period 2069-2098 which signifies the end of the century.