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泥石流分布密度是区域泥石流危险度评价的主要指标。泥石流分布密度分为点密度和面密度,前者是指每103km内泥石流沟的数量;后者是指每103km内泥石流沟的流域面积。以川西山区60个县市区为研究样本,分别以泥石流点密度和面密度作为区域泥石流危险度的主要评价指标,结合7个相同的区域泥石流危险度的次要评价指标,对研究区以县市区为基本单元的区域泥石流危险度进行了定量评价。结果表明,各县市区面积加权平均后的泥石流危险度分别为0.51(面密度)和0.52(点密度),差别甚微,整体上均属于泥石流中度危险区。两者的平均绝对差值0.04,远小于0.2这一危险度等级差值,平均相对差值为6.49%,小于10%这一允许的均方差范围。由此可知,用泥石流面密度来评价区域泥石流危险度,并非优于点密度;相反地,由于泥石流点密度具有获取资料相对容易、计算比较简便、工作量较小等优点,因而具有更为便利的推广应用价值。
Debris flow distribution density is the main index of regional debris flow risk assessment. Debris flow distribution density is divided into point density and surface density, the former refers to the number of debris flow groove per 103km; the latter refers to the debris flow ditch within every 103km drainage area. Taking 60 counties and cities in western Sichuan as study samples, the debris flow point density and areal density were respectively used as the main evaluation indexes of the regional debris flow hazard degree. Combined with the secondary evaluation index of the same regional debris flow hazard degree, Urban area as the basic unit of the regional debris flow risk were quantitatively evaluated. The results show that the hazard ratios of debris flows after the weighted average of the urban areas are 0.51 (surface density) and 0.52 (point density), respectively, with little difference, and they all belong to the moderate danger zone of debris flow. The average absolute difference between the two 0.04, far less than 0.2 the level of risk difference, the average relative difference of 6.49%, less than 10% of the allowable mean square error range. Therefore, it is more convenient to evaluate the risk of debris flow in the area by the density of debris flow surface. On the contrary, it is more convenient because the density of debris flow is relatively easy to obtain data, easy to calculate and work less. The promotion of application value.