WIDENING OF GRAVEL BED RIVERS - PHYSICAL MODEL TESTS IN LARGE SCALE

摘要

Due to the unceasing degradation of the alpine rivers Iller and Isar in Bavaria, Germany, a concept to dissolve the problem was regarded. By removing bank fixations, the river can adjust as well as it's bed elevation, as it's channel slope and as it's width to the hydraulic boundary conditions. Widening of river will result in decreasing shear stress and consequently, degradation will reduce. To determine this process of gravel river widening and estimate the possible changes in the river morphology, physical model tests were carried out in the past two years. For this purpose, a model flume with a total width of 8 m and a length of 100m were constructed. This mounting allows model tests in a scale of up to 1:15, providing sufficient lateral space for widening. The effect of different parameters on the river morphology, like the initial channel width, the initial channel bed slope and the discharge, among others, have been investigated. The main focus of these experiments was on the intensity of widening, the changes in bed elevation, the transported sediment and the velocity of morphological variation to enable a better prediction of morphological changes in nature.