Development of a methodology to assess functional performance of the Dutch Rhine

Abstract

The summer and autumn of 2018 showed the negative effects of both low-flow conditions and bed degradation over the last century on the river functions of the Dutch Rhine. These resulted in record-breaking water levels, extreme low navigation depth and subsequently nautical problems. As climate change will increase the inter-annual variability of the Rhine’s discharge pattern, low-flow conditions are likely to occur more often, reinforcing the above-mentioned impacts on nature and navigation. Sediment management is considered as a sustainable way to counteract the bed degradation. To justify an investment in a large scale nourishment, the impact of a nourishment on the river functions has to be compared with the result of a reference situation without nourishment. This study aims to develop a methodology that evaluates the future performance of rivers functions accounting for the autonomous trends (bed level and climate changes) and provides insights in the functional performance and cost effectiveness of river interventions. The methodology enables the assessment of the impact of the trends on the river system without intervention. It appears that the navigational efficiency is decreased enormously by climate change en bed erosion, which will increase transportation costs. Based on these indicative analysis a nourishment is predicted to be cost effective by improving both the navigational efficiency and counteracting dehydration of the floodplains.