| Geological disasters, usually occur under the action of natural or man-made factors, bringing about the loss of human life and properties and environmental damage. This kind of geo-disasters (such as collapse, landslide and debris flow) is widely dispersed in our country, and one of the most serious regions is located in Longnan city of Gansu province. In recent years, with the development of economy and intense of human activities, the ecological environment is worsening gradually, and the probability of geo-disaster happening is increasing. Moreover, geo-disasters have caused great influence on the sustainable socioeconomic development of Wudu District. Therefore, it is very important to carry out the spatiotemporal dynamic research on the geo-disaster vulnerability, which could provide scientific basis for prevention and mitigation plan in disaster risk management in Wudu District. And it also has an important scientific significance for exploring the method of the specific regional geo-disaster vulnerability.This article selected typical small watershed-Qingshui debris flow disaster and the whole Wudu District as the study areas, and constructed different regional geological disaster vulnerability scale indicator system. Using appropriate indicators, the results calculated by two methods Analytic Hierarchy Process and Information Entropy showed that the weights calculated by Analytic Hierarchy Process was more in line with the actual situation. Then, using high-resolution remote sensing data, GIS technology and the Fuzzy Comprehensive Evaluation method (based on Information Entropy), we carried out comprehensive analysis of vulnerability and component vulnerability of disaster bearers (including population vulnerability-. social economic vulnerability、 ecological environment vulnerability and social cultural vulnerability) on the town scale and the hazard-bearing body scale, especially the spatiotemporal dynamics of the Geological disasters Vulnerability the main results are as follows:1. High population vulnerability area, based on township units, is gradually increasing from seven in2002to ten in2011. The area of high vulnerability area has reached1455km, up to2011, accounting for31%of Wudu District, while low vulnearability coverd an area of2796km2, occupying60%of the region. To spatial distribution, compared to the south of Wudu District, the north had the relatively higher vulnerability, and the highest values located in these regions, such as Chengjiao town, Majie town, Anhua town and et al.2. With the passage of time, the high socioeconomic vulnerability was gradually increasing, especially reached to the maximum in2008. then decreased by2011. From the perspective of spatial distribution, those located near the district are in relatively lower level of vulnerability such as Chengguan town, Dongjiang town, Chengjiao town et al, while other remote villages were in higher level, which showed that the economic development level took an important effect on socioeconomic vulnerability.3. As the result showed the number of higher ecological environment vulnerability regions decreased at the beginning, and increased subsequently, representing relatively great fluctuation, but with the maximum in2002. From the distribution, the north of Wudu District has higher vulnerability than the southern, however, the whole region tends to ease, particularly in northern regions, and the pattern changed from north-centraled to wholly divergence.4. The social culture vulnerability was gradually augmented, and the proportion of high vulnerability area enlarged form39%in2002to67%in2011. The spatial pattern of social culture vulnerability is fully complex, only two villages (Chengguan town and Anhua town) being lower vulnerability area. The number of library and cultural station has significant difference among villages, leading to big difference of vulnerability.5. Based on the above item evaluation, we furtherly conducted sythetical analysis on hazard-affected bodies using Hierarchical Analysis method. According to the results, the comprehensive vulnerability tended to increase gradually during the four periods, with the high vulnerability changing from eight in2002to eighteen in2011. Overall, the higher value regions were concentrated in northern part in2002, whereas, spreaded to the whole district in2005, showing a quite different distribution pattern.6. Based on high resolution remote sensing data, the paper evulated each hazard-affected body in Qingshui ditch, and obtained the spatial distribution situation. From the results, we found that the higher probability of suffering geo-disasters tended to take place in these places where population is high concentrated and the economic density is large. For different types of hazard-affected bodies, the high values often occurred in those regions with great economical fortune. The order of vulnerability degree among different types of artificial building was:reinforced concrete bridge> house> asphalt, and various land use types:building land> farmland> channels> forest land> grassland.In conclusion, we revealed the dynamics and spatial distribution of geo-disaster vulnerability through the spatiotemporal pattern research. We also conducted the vulnerability assessment of each hazard-bearing body in Qingshuigou on large scale, and finally obtain the spatial distribution state about vulnerability, which could provide a scientific and empirical basis for disaster prevention and mitigation work in Wudu District. |
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