• surface water hydrology;
  • runoff;
  • flow analysis;
  • landslide dammed lake watershed;
  • ungauged watershed;
  • topography-based runoff model;
  • disaster control;
  • satellite image classification

Abstract: The Chi-Chi earthquake, which occurred on September 21, 1999, and had a magnitude of 7.3 on the Richter scale, resulted in an extensive landslide that blocked the Ching-Shui Creek in Taiwan, forming a large lake with a storage volume of 40 million m3. This paper describes an analytical procedure used to perform flow analysis of the Tsao-Ling watershed, which includes the new landslide dammed lake. In this study, a digital elevation model was applied to obtain the watershed geomorphic factors and stage-area storage function of the landslide dammed lake. Satellite images were used to identify the landslide area and the land cover change that occurred as a result of the earthquake. Two topography-based runoff models were applied for long term and short term streamflow analyses of the watershed because the watershed upstream of the landslide dam was ungauged. The simulated daily flow and storm runoff were verified using limited available measured data in the watershed, and good agreement was obtained. The proposed analytical procedure for flow analysis is considered promising for application to other landslide dammed lake watersheds.