The effects of bottom settlement, vegetation and macro‐roughness on the erosion stability of the relocated River Inde

Abstract

This paper presents the results of research on a river relocation in the Rhenish lignite mining district of Germany. In the year 2005 the natural river bed will be intersected and relocated as the coal mine moves forward to the east. During flood events exceeding critical shear stresses in the new river bed could cause depth erosion, which would damage or eventually destroy the sealing layer and therefore flood the pit mine as a worst‐case scenario. Hence, the distribution of shear stresses, bed load transport and initial depth erosion are calculated for different flood events by means of a 2D depth‐averaged hydrodynamic model. The effects of ripple‐shaped macro‐roughness, vegetation and continued settlement of the river bottom are investigated. The best protection against depth erosion is dense vegetation. The macro‐roughness reduces mean velocities on the one hand but increases shear stresses on the other while preventing the development of the vegetation. Locally, structural operations are needed to stabilize the river bed.

Keywords:

• River relocation
• vegetation
• roughness
• 2D simulation
• erosion