四川省都江堰市龙池地区泥石流危险性评价研究

汶川地震灾区震后泥石流灾害较震前活跃,对灾区泥石流危险性进行评价是灾后重建过程中合理防灾减灾的基础工作。通过研究泥石流灾害事件中的泥石流规模、泥石流沟堆积扇面积及相应的灾害损失等基础资料,提出以泥石流在泥石流沟堆积扇上的平均堆积厚度替代泥石流规模作为主要危险因子的单沟泥石流危险性评价方法。用该方法对汶川震区都江堰市龙池镇龙溪河流域2010年"8.13"泥石流事件中的29条沟谷型泥石流进行危险性评价,评价结果中9条为高度危险,12条为中度危险,8条为低度危险。用以泥石流规模为主要危险因子的单沟泥石流危险性评价方法进行对比评价,2种评价方法中有65.5%的泥石流的危险性评价结果一致。以泥石流沟堆积扇平均堆积厚度为主要危险因子的单沟泥石流危险性评价方法更能突出规模对泥石流综合危险度的贡献,能更好地反映小泥石流流域和小泥石流堆积扇的泥石流在中小规模的泥石流总量下的危险程度。

A Study of Hazard Assessment of Debris Flows in Longchi Area of Dujiangyan City, Sichuan Province

Debris flows of Wenchuan earthquake-stricken area are more active than before earthquake.It is the primary work for the disaster prevention and mitigation of reconstruction process to assess debris flow hazard.Based on the study of scales of debris flows,areas of debris flow alluvial fans and the corresponding disaster loss,we used the average deposition thickness on alluvial fan instead of the debris flow scale,as a major factor for hazard assessment of single debris flow.The method was used to assess the hazards of 29 channelized debris flows of Longxi river basin on August 13,2010.The results indicated that 9 debris flows were high hazard,12 debris flows were moderate hazard and 8 debris flows were low hazard.Another method using debris flow scale as a major hazard factor was applied to assess the debris flow hazards in Longchi area.Some 65.5% of the evaluation results were unanimous in the two assessment methods.The method using average deposition thickness on alluvial fan as major hazard factor can strengthen the contribution of the scale to comprehensive hazard degree,and can more truly reflect the hazard level of debris flow with small drainage area and small alluvial fan at small-middle scale.