RIVER STABILISATION BY BREACH-RAMPS AND WIDENING

摘要

Numerous gravel-bed rivers are affected by unceasing degradation problems, mostly caused or increased by technical measures upstream. In Germany removing the bank fixations is regarded as a concept to dissolve the problem. By allowing lateral erosion and in consequence river widening the bed load transport capacity will be decreased. Additionally the eroded bank material will serve as additional sediment influx. Nevertheless in some cases additional measures are required for a sustainable stabilization of the river bed. Since several years ramps consisting of boulders are used for a reduce of the slope. Despite some ecological and esthetical advantages they cannot accomplish all requirements related to a migration of fishes and organisms. Ramps having a breach in their centre offer better conditions concerning the migration and the sediment transport. Actually they are under theoretical and experimental investigation for a project in Germany. This paper illustrates exemplarily some results of the preliminary investigations about breach ramps as well as results of the large scale tests on river widening.