基于GIS和PSR的江苏省水土流失易发区划分研究

水土流失易发区划分是新一轮水土保持规划的现实需要。基于PSR概念模型,选取12个指标建立评价指标体系,并采用改进的层次分析法求得指标权重,通过多级加权求和,对江苏省平原区进行水土流失易发区划分评价。该方法以250m×250m栅格为单元,借助GIS的空间分析功能制作各层次指标的空间分布图,并分别从压力、状态、响应3个子层次和综合目标层进行评价分析。结果表明:全省平原区水土流失压力分布较为普遍,Ⅲ级及以上压力区域占全省总面积的40.75%;Ⅰ、Ⅱ、Ⅲ、Ⅳ级易发区域面积分别为10.12%、42.90%、25.73%和1.24%,无Ⅴ级易发区域;最终划定江苏省水土流失易发区面积约占全省总面积的26.97%。具有现状数据的评价单元划分结果与实际情况较一致,说明水土流失易发区划分结果能基本反映江苏省水土流失特点和状况,可作为江苏省水土保持规划的重要依据。

STUDY ON DELIMITATION OF SOIL AND WATER LOSS-PRONE AREAS OF JIANGSU PROVINCE BASED ON GIS AND PSR

According to the newly revised “Law of the People’s Republic of China on Soil and Water Conservation”, the delimitation of Soil and Water Loss prone Areas is significant and the new Soil and Water Conservation Program is quite necessary. It’s different between assessment on “Sensitivity to Soil and Water Loss” and “Soil and Water Loss prone Areas”. In rapid urbanization areas, the artificially pressure should be emphasized in the research of Soil and Water Loss prone Areas. The plain area of Jiangsu Province is determined to be the studied area which is around 8.21 km2. Based on the “Pressure State Response” conceptual model, an index system of twelve indices is established to delimiting Soil and Water Loss prone Areas. The pressure index, which describes the pressure that human activities or nature factors exerting on the soil and water environment, consists of land use intensity of human disturbance, population density, fixed asset investment, distance to the city, distance to major transportation routes, average annual precipitation, relief of topography, soil erodibility K factor, vegetation coverage, and river density. The state index, which relates to the situation of the soil and water loss, is composed of the ratio of soil and water loss areas. The response index, which reflects the reaction of human beings to protecting environment, is defined as the areas protected by the Ecological Red Line. The indices weight is obtained with the improved classical analytical hierarchy processes. Through digitizing, the spatial database including the indices’ maps and their attributes data is built in ArcGIS software. Each index map is converted into grid format with size 250 m×250 m. Then each index is classified into several classes with regard to their changing in Jiangsu, and each class is valued with 1/3/5/7/9 according to their impacting degree on soil and water loss. Subsequently, the values of the indices classes are multiplied by derived weights for each index and then are summed together. Furthermore, the evaluation and analysis is made separately from the three sub level indices of pressure, state, response and the general index. The results showed that the distribution of the pressure which would cause soil and water loss is common in the plain area of Jiangsu Province. The area of Ⅲ degree and above pressure accounts for 40.75%, and artificially pressure is greater than the natural pressure both in grade and area. The areas ofⅠ to IV degree Soil and Water Loss prone Areas accounts for 10.12%, 42.90%, 25.73% and 1.24%, respectively. There is no V degree Soil and Water Loss prone Areas. Finally, the regions confirmed as the Soil and Water Loss prone Areas of Jiangsu Province accounts for 26.97% of the total area, mainly distributed in the regions such as the urban district and suburb of the city and the county, urban area of the town, and development zones, as well as the Coastal Plain Sandy Area, the High content Sands in Tongnan Area, and the Disused Sandy Districts of the Yellow River. The evaluation results of the units which have soil and water loss data are consistent with the actual situation, indicating that the results can basically reflect the characteristics and statue of soil and water loss in Jiangsu Province. The result can be used as an important basis for Soil and Water Conservation Planning in Jiangsu Province.