MECHANISM OF NATURAL DAM COLLAPSE FORMED IN A STEEP SLOPE CHANNEL AND SIMULATION

Abstract

In gorges of Mountain Rivers, banks with weak geological configuration and landslide-prone, formation of natural dams is common and such kinds of dams exist every year in Nepal, chiefly, in rainy season.
The present study discusses on mechanism of natural dam collapse and makes an effort to simulate collapse mechanism of the dams in a steep gradient flume made up with two kinds of mixtures. Firstly, using fine uniform particles; and secondly, a mixture of coarse and fine particles, i.e., non-uniform mixture. Natural dams, trapezoidal in shape, with downstream frontal slope nearly equal to the angle of repose of dam forming materials, were made in the channel for the experiment. One-dimensional momentum and continuity equations for unsteady flow in open channel and Janbu method of slope stability were used to verify the experimental results.