The Preliminary Study on the Effect of Debris Flow on the Tianchi Lake

Abstract

In these years the southern part of Tianchi Lake has been occupied by deposited sediments which were carried by debris flows. As a result, the lake is shrunk and the sight of the lake is ruined. In the paper, on the basics of field work, we first combine both of the geographical maps 1971 and 2003 to make sure the landscape difference; secondly we estimate the average thickness of earth eroded by debris flow; thirdly we estimate the volume of the soil on the fan. In the 32 years between 1971 and 2003 the deposit fan has gone forward for 216m, and the deposits reaches at 1.85 million m³, of which 49％ come from upstream and 51％ comes from the old fan. The frequent debris flow occurrence is due to both natural conditions and over grazing.