12 December 2020
The Dutch Rhine River branches (Rijntakken) provide, among other things, for drinking water to millions of citizens and with a means of transportation. At the same time, the rivers pose a continuous threat to life in the Netherlands. Rijkswaterstaat is responsible for managing the river system and facilitating all of its functions. This is a difficult task that Rijkswaterstaat has done for centuries.
Until recently, river maintenance was mainly concerned with single-function interventions to, for instance, improve the river's navigability or reduce flood risk. This type of interventions framework has the negative consequence that an improvement in one function may not be beneficial for another function or service. For this reason and having in mind the long-term impact of interventions, Rijkswaterstaat has devised an Integral River Management (IRM) programme. This programme develops the necessary policy for providing both short-term and long-term solution to river problems from a multidimensional and multidisciplinary point of view, contrary to past single-function interventions.
The IRM programme requires a tool to evaluate the long-term and large-scale morphological effects of river interventions as well as the impact of different future scenarios related, for instance, to climate change. To help Rijkswaterstaat in gaining insight into the morphological impact of river interventions, a numerical model of the Rijntakken is built.
The model is one-dimensional and uses the D-HYDRO Suite. It comprises the Dutch Rhine River branches and downstream part of the German Rhine. The upstream end of the domain is found at the confluence of the Lippe with the Rhine at Wesel (Germany, Rhine kilometre 815). The downstream ends of the domain are found at Hardinxveld, Krimpen aan de Lek, and the Ketelmeer. The model stems from combining the official SOBEK 3 schematizations of the Rijntakken and an existing model, also in SOBEK 3, of the German Rhine. These models have been built for hydrodynamic studies and need to be adjusted for being suitable to predict morphodynamic changes.
In a first step, the hydrodynamic parameters of the models are calibrated. This is done by comparing water level, velocity at the main channel, and discharge partitioning at the bifurcations with WAQUA two-dimensional results on steady-state hydrodynamic simulations. The calibrated model is extended with morphodynamic parameters based on the \sre schematization by Sloff (2006). The morphodynamic parameters are then calibrated by comparing bed-level changes in the period 1995-2011. Afterwards, the model is validated against morphodynamic development between 2011 and 2019.
The model is available here. Check how to access it in the download page.
dr. ir. V. (Victor) Chavarrias
Researcher and Advisor, River Dynamics and Inland Waterways