Sediment nourishments to mitigate bed degradation in the River Waal in the Netherlands

Over the past century, the bed level of the River Waal, a Dutch distributary of the River Rhine, has degraded by 1 to 2 metres. The high rate of degradation and its spatial non-uniformity places the various functions of the river under stress. Solutions are therefore sought to mitigate bed degradation. In this research, the effects of sediment nourishments of various sedi-ment compositions, distributions and volumes are investigated. It is shown that nourishments can mitigate bed degradation by orders of centimetres. By choosing the nourishment characteristics, the nourishment behaviour can be influenced. The findings of this study can be used as a basis for the design of sediment nourishments to mitigate bed degradation in the River Waal and similar rivers.