Abstract
This research targets the debris flow caused by heavy rain by the Minddule, Aere Typhoons in July and August, 2004 in the Xiao Xue River Watershed (22.0km2) in middle portion of the Da-Chia River, Taiwan. The sediment movement area were extracted and divided into slope failure and river using the 5m mesh DEM made from high-resolution stereo satellite images and 2-dimentional satellite image analysis. The historical variation, sediment movement volume and topographical characteristics in the slope failure and river were analyzed. As a result, it was found that the collapsed sediment caused by the slope failures at the Chi-Chi Earthquake had accumulated in the bottom of slope or river and the accumulated sediment have flown down the slope and river and become debris flow by heavy rain caused by Minddule, Aere Typhoons and had led to big scale sediment disasters. The volume of sediment yield and the accumulated sediment in slope failures was 9, 814 thousand m3, 2, 898 thousand m3 respectively. The volume of scoured sediment and accumulated sediment in river was 1, 353 thousand m3, 2, 387 thousand m3 respectively. The volume of sediment discharge from the Xiao Xue River Watershed to the Da-Chia River was 5, 882 thousand m3. It is inferred that the analysis method proposed in this research will be a new effective method for sabo plans in a wide area.
