Judith Zomer

Wageningen University & Research | WUR

Understanding river morphodynamics and accurate prediction models are essential to address current and future challenges in lowland river management in the face of climate change and sea level rise. A basis for both is information about sediment fluxes, which remains scarce. The aim of this research is to improve the quantification of sediment transport in lowland rivers. The focus is both on the use of acoustics to measure suspended and bedload sediment and on the estimation through transport equations in relation to bedforms. The first objective is to improve the estimation of suspended sediment from ADCP backscatter in rivers with mixtures of sand and mud, where fine sediment attenuates the acoustic signal. A second focus is on superimposed bedforms and low-angled river dunes. Little is known about the occurrence and effect of superimposed bedforms on flow and sediment transport processes. We question whether trains of superimposed bedforms form an additional means of bedload transport, which would have implications for the measurement of bedload transport through dune tracking. This is determined through measurements with a fixed, high-resolution multibeam installed in the Dutch IJssel River. The third objective is to identify which variables and processes determine the morphology and migration of low-angle dunes, including the bed grain size distribution and suspended sediment dynamics based on available MBES and ADCP monitoring data, as well as additional field campaigns in the Dutch IJssel River. Finally, we will evaluate and improve sediment transport equations for the lower Dutch delta based on the obtained field evidence.