Quantiative Analysis of Debris Flow Gully Based on Geomorphic Excess Entropy in Catchment
ZOU Qiang1,2, WANG Qing1, LIU Yanguo1
1. School of Environment and Resource, Southwest University of Science and Technology, Mianyang 621010, Sichuan Province, China;2. Key Laboratory of Mountain Hazards and Earth Surface Processes; Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China
Abstract：The activity evaluation of debris flow gully is the first step for forecasting, assessing, preventing, and controlling the debris flow. In order to resolve the problems, such as complexity of determination research, difficult of datum collection in the evaluation of debris brow gully, by virtue of GIS information processing technology, an effective and convenient method for quantitatively analyzing the evolution stage and activity degree of debris flow gully is discussed. In the method, a index of valley longitudinal profile shape is used to link the geomorphic system excess entropy with the evolution stage for debris flow gullies, also four ranks of activity for debris flow gully are divided into, they are: activity (-0.097≤δxP＜0,1.225≤N<2.0), sub-activity (-0.097≤δxP<-0.011, 0.585≤N<1.225), sub-stability (δxP≥0, N≥2.0), and stability (-0.011<δxP<0, 0<N<0.585). Furthermore, the method is applied to the middle reaches of Xianshui River along Sichuan-Tibet Highway and detail works are carried out. First of all, 58 catchments are extracted from 1:50000 local DEM with the support of GIS hydrologic analysis technology, and then the main lengths from 353m to 1712m and the areas from 0.47km2 to 58.09km2 of these gullies are acquired. After determining on the activity of debris flow gullies, some significant results are obtained as follows: 26 gullies accounting for 44.83% of total gullies are in the active period; 30 gullies accounting for 51.72% of total gullies are in the sub-active period and only two gullies are in the sub-stable phase. It is shown that the catchments located in the middle reaches of Xianshui River along Sichuan-Tibet Highway are in the developing and active evolution stage, and the activity degree of debris flow gullies is at a high level that is consistent with the actual situation. Based on the result, the method of geomorphic excess entropy analysis on the activity of debris flow catchments is objective, credible, easy to carry out for data scarce areas, and it is also helpful for evaluating, warning, and reducing debris flows.