基于流域系统超熵的泥石流沟活跃度定量分析

 泥石流沟谷活跃程度评价是泥石流灾害预测、评价和防治的前提。结合GIS信息处理技术,以沟谷纵剖面形态指数为媒介,将泥石流流域系统的超熵与泥石流沟谷演化过程联系起来,探讨了泥石流流域系统活跃度的定量分析方法,并依据超熵值将流域沟谷活跃度分为4个等级：活跃(-0.097≤δ_xP＜0,1.225≤N＜2.0)、较活跃(-0.097≤δ_xP＜-0.011,0.585≤N＜1.225)、较稳定(δ_xP≥0,N≥2.0)和稳定(-0.011＜δ_xP＜0,0＜N＜0.585)。本文利用此方法对川藏公路鲜水河段58条沟谷进行判定,其中,处于活跃期的沟谷26条,占总数的44.83%,处于较活跃期的沟谷30条,占总数的51.72%,处于较稳定—稳定的沟谷仅2条。川藏公路鲜水河段流域沟谷演化处于发展—旺盛阶段,活跃度较高。通过对比验证,评价结果与实际情况具有一致性。评价结果表明,利用流域系统超熵值判断泥石流沟活跃程度,具有较好的客观性、可操作性和可靠性。

Quantiative Analysis of Debris Flow Gully Based on Geomorphic Excess Entropy in Catchment

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≤δ_xP＜0,1.225≤N<2.0), sub-activity (-0.097≤δ_xP<-0.011, 0.585≤N<1.225), sub-stability (δ_xP≥0, N≥2.0), and stability (-0.011<δ_xP<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.