灾变山地环境影响下小流域脆弱性评价研究

RESEARCH ON WATERSHED VULNERABILITY ASSESSMENT RESPONDED TO CATASTROPHIC MOUNTAIN ENVIRONMENT

流域脆弱性评价中,如何有效结合自然及社会等多方面因素开展较大区域尺度评价是目前研究的难点之一,特别是结合灾变山地环境影响,开展小流域脆弱性评价,对于山区流域防灾减灾及可持续发展具有积极的指导意义。采用栅格单元与小流域单元相结合的评价方法,综合自然与社会因素,并引入活跃灾害事件对小流域脆弱性的影响,从灾害危险度与社会易损性角度构建评价体系,应用3S技术,选取彭州龙门山区开展典型案例研究,开展灾变山地环境影响下的小流域脆弱性评价。最终将研究区小流域脆弱性划分为轻度、中度、高度及重度4个等级,各级含小流域个数分别为12、21、27及17个,相应面积占整个研究区面积的比例分别为11.53%,38.63%,40.46%及9.38%。针对区域内重大灾害事件,对评价结果进行验证表明,综合自然和社会因素,并引入灾害事件构建评价体系,并以栅格与小流域单元相结合的评价方法,对灾变山地环境下较大区域尺度流域脆弱性评价具有可行性,可为区域尺度小流域脆弱性评价研究提供一定参考。

Small watershed is a regional unit which has relatively intact natural ecological processes. Watershed vulnerability assessment has an extremely significant impact on the reasonable utilization of regional resource and sustainable development. Large-scale evaluation considering natural, social and even other factors is one of the difficulties encountered in current watershed vulnerability assessment study. The 8.0 Ms Wenchuan Earthquake has caused severe damage to the mountains of southwest China. Because of the earthquake, the mountain areas have been facing with debris-flow hazard and landslides more frequently and the mountain environment has been increasingly vulnerable. Secondary mountain disasters have seriously affected regional economic and social development and would constant influence on the production and daily life of local people in a long time. Therefore, it is of great essentiality to enrich small watershed vulnerability assessment, especially to coordinate the relationship among natural and social factors and the effects mountainous watershed of catastrophic mountain environment. And it is also highly important for disaster prevention, mitigation and regional sustainable development. Longmen Mountain of Pengzhou city, the case area in this study, is situated in the core impacted region and the characteristics of post-earthquake secondary mountain disaster are more obvious. The study area was divided into 77 small watersheds by GIS technology and remote sensing image with high resolution. With the comprehensive consideration of natural, social factors and disaster events, the evaluation index system of small watershed vulnerability was constructed with Analytic Hierarchy Process （AHP）. And the evaluation of small watershed vulnerability was conducted from the aspects of disaster degree and social vulnerability in the combination of small watershed and grid as unit by the overlay tools of GIS. In the end, the degree of small watersheds vulnerability is classified into slight, moderate, high and extreme fragility, with the number of small watersheds being 12, 21, 27 and 17, respectively. And the corresponding area accounted for the entire study area is 11.53%, 38.63%, 40.46% and 9.38%, respectively. Taking the regional major disaster events from 2009 to 2013 to test and verify, the evaluation results are consistent with the actual situation. However, the influencing factors of watershed vulnerability are numerous and it is of certain difficulty to evaluate the watershed vulnerability quantitatively and exhaustively. There are also some deficiencies in social vulnerability analysis and socio-eeonomic data digitization. Last but not the least, the methods applied in this paper are feasible for larger-scale watershed vulnerability assessment under catastrophic mountain environment, which can also provide a reference for regional vulnerability assessment.