地貌信息熵在地震后泥石流危险性评价中的应用

Applicability of Geomorphic Information Entropy in the Post-earthquake Debris Flow Risk Assessment

地貌信息熵可以表示流域地貌面受侵蚀的程度,是判断地貌发育演化阶段的量化指标之一。基于流域系统地貌信息熵的原理和方法,采用GIS技术和Matlab、SPSS软件,对"5·12"汶川地震后都江堰市深溪沟流域内41个子流域的面积-高程积分值和地貌信息熵进行计算,研究了各个子流域的地貌发育演化基本特征和泥石流发育情况,并将分析结果和地震后野外实际调查的成果进行了对比研究,结果表明:在烈度为Ⅺ的都江堰深溪沟地震重灾区,地震引发的大量崩塌、滑坡导致松散固体物质广泛堆积于沟道内,不仅为泥石流提供丰富的物源,而且使沟道局部的地貌发生了突变,但通过"地貌信息熵"这种方法无法表达丰富物源的变化和沟道地貌的突变,因此,根据地貌信息熵判断地震后泥石流的危险性具有一定的局限性。为了使地震区泥石流危险性评价的结果更加真实、可靠与可信,必须结合流域的实际情况,对地貌信息熵判定的危险性结果进行综合分析与修正,或者通过多种评价方法进行对比论证和分析。

Geomorphic information entropy can be used to express the erosive degree of the watershed geomorphic surfaces, which is one of the quantitative indicators to judge the evolution stage of landform development. Based on principles and calculation methods of geomorphic information entropy, this article used GIS technology, Matlab and SPSS soflwares to calculate hypsometric integral value and geomorphic information entropy of the 41 sub-basins in the DuJiangyan Shenxi gully watershed, studied landform development characteristics of overall basin and each sub- basin, explored debris flow development situation of each sub-basin channel, and compared with the field survey after the earthquake. The results showed that in the DuJiangyan of Sichuan earthquake-hit areas, large numbers of loose solid materials induced by Earthquake accumulated in the channel, not only supplied materials for debris flows, but also made the channel local topography change sudden. Using the method of geomorphic information en- tropy could not express these sudden changes, so debris flow risk assessment in the earthquake-hit areas based on geomorphic information entropy had certain limitations. In order to make the debris flow risk assessment result in earthquake-hit areas results more real, reliable and credible, it must be combined with the actual situation of the basin to analyze and correct comprehensive, or demonstrate and analyze through the several methods of risk assess- ment.