Targets for ecological rehabilitation of the lower Rhine and Meuse based on a historic-geomorphologic reference.

Abstract

Ecological restoration of the lower Rhine and Meuse floodplains aims at improvement of biodiversity and enhancement of natural hydro-morphodynamics, this within the constraints of safety and navigability. Restoration plans, the choice of landscaping measures, and the eco-morphological targets should account for the natural differences in morphodynamics and ecological patterns along the rivers. To achieve this, the hydro- and morphodynamics as well as the landscape pattern that existed in historic times - before the main regulation works in 1850 - served as a reference. Bio-geomorphological characteristics were determined of 20 to 30-km river reaches along the lower Rhine and Meuse, including the estuary. Using old river maps and historic water level data the 19 th century pattern of geomorphology, natural vegetation, and land use was reconstructed. Quantitative hydro-morphological parameters (width-depth ratio, specific stream power, Shields parameter, water level fluctuations) were determined for 12 river reaches. From these, the downstream charges along the river reaches were assessed, landscape types were related to hydro-morph/)dynamic processes, and characteristic processes and landscape patterns for different reaches were identified. Using these results, guidelines for floodplain restoration targets and landscaping measures were given at the scale of the river reaches.