Morphodynamic 2D Modelling at the Confluence of the Wiese River

Dr. Lukas Vonwiller, January 17, 2020

TK CONSULT AG improved the understanding of morphodynamic processes during flood events at the Wiese River using morphodynamic 2D simulations.

The Wiese River flows into the Rhine River directly upstream of the harbour at the Dreiländereck. Several bed-forming flood events occurred during winter 2017/2018. As a result, depositions were observed at the confluence of the Wiese River and further downstream at the harbour in the Rhine River.

On behalf of the Canton of Basel-Stadt, TK CONSULT AG carried out an event analysis based on available echo sounding measurements and performed morphodynamic 2D simulations. This study showed that more than 7'500 m³ of bedload materials were deposited in the area of the confluence of the Wiese River. It also allowed to gain further insights into the temporal evolution of the bed elevation changes. During the first flood, materials were deposited at the confluence while, in the subsequent flood events this deposition - together with the newly added bed materials - were successively transported further downstream and towards the harbour.

The morphological changes of the 2D simulation fitted well with the bed elevation changes observed with the echo sounding measurements. Last but not least, the understanding of morphodynamic processes at the Wiese River was significantly improved based on the combination of the event analysis with high quality echo sounding data and the morphological 2D simulations.

Based on this, important questions could be answered in future revitalization projects and constructional adaptations at the harbour in the Rhine River.

Bed elevation changes (deltaz) at the confluence of the Wiese River during the flood events in winter 2017/2018 (hydrograph on the upper left)