Suspended sediment concentration assessment as a precursor to river channel shifting in the Bengawan Solo River, Indonesia

This study attempts to recognize the fundamental issues in river morphology by examining suspended sediment concentration (SSC) and flow velocity at the curved channel in an alluvial river. To capture the entire set of the afore mentioned conditions, a field investigation was conducted at the inner and outer banks of the flow path of a curved channel, which is considered as the critical section in river change development. The field observations were conducted over a 1-year period, from January to December 2014, in which both dry and rainy seasons occurred. Because the curved channel is subject to severe erosion, especially around the outer bank, lateral migration of the channel might regularly occur. The field investigation showed that the outer side of the curved section migrated approximately 0.0625 m/month during the study period. The SSC, which peaked at 25% and 43% of the maximal flow velocity in the upstream and downstream sections, respectively, showed the rapid erosion of the curved section leading to lateral channel shifting. A channel resistance evaluation confirmed the potential capability of the riverbed material at the curved section was 20% lower than that in the upstream and downstream sections. According to the SSC and flow features, a new understanding of changing river morphology with respect to a curved channel of the Bengawan Solo River was developed.