Author(s): M. Hengl; U. Stephan
Linked Author(s):
Keywords: River training; Degradation; Bed stabilisation; Ramp; Ecology
Abstract: The present paper deals with a special ramp type – the module ramp – to address the problem of degradation in gravel bed rivers. A module ramp consists of several independent steps. Depending on morphological boundary conditions, e.g. varying amount of bed load transport over time, steps can easily be removed or added. Thus, a module ramp is an efficient solution, which is easy to adapt and maintain. Upstream of the module ramp, the river bed and consequently the water level rise. Special attention is given to the requirements of stabilising the whole river reach. Two main stability considerations must be taken into account: the stability of the ramp itself and the stability of the river bed upstream and downstream of the ramp. First, the ramp must be stable up to the design flood. Also a possible scouring downstream of the ramp must be considered. Secondly, a sustainable solution for the whole river reach can only be achieved if the bed slope of the river upstream and downstream of the ramp is chosen in accordance with the balance slope, i.e. a final slope towards which a river will always tend. An easy method of calculating the balance slope of a river reach is presented. Module ramps are an ecologically sound measure because the risen bed and, consequently, the water level upstream of the ramps lead to a better link between river and wetlands. The ground water level is raised. If the steps of the module ramp are low enough, migration of fishes and other aquatic species is guaranteed. Leisure activities on the river such as canoeing or rafting are also possible over module ramps.
Year: 2003