| The Loess Plateau is located in the upper and middle reaches of the Yellow River in China. Especially, many cities, located in valley among the hill and gully area of Loess Plateau , are suffered by serious natural environment, meanwhile urban expansion has caused a lots of ecological environment problems. In this paper, the author takes Yan'an city as an example for exploration and research on geological problems, in order to build better geological environment for substantial development of the city. Due to powerful data process ability and spatial analysis function, Geographic Information System provides an advanced tool for solving problems of urban geological environment.In the paper, environmental quality of loess plateau valley-basin cities is assessed by GIS and geological method. In Yan'an city, for instance, main factor is analyzed which has influence on geological environment, meanwhile an index system of geo-environment quality assessment is set up. Assessment indexes are selected using correlation analysis tools. Appling principal component analyses, weight of indexes are determined. The author adopt GIS grid model in which cell size was defined as 8m* 8m. Fuzzy comprehensive assessment method has been chosen to establish mathematical model. Using of ARCGIS 9 software, the spatial database of Yan'an city is built, and some spatial operators and functions have been provided such as spatial query analysis, spatial analysis, digital elevation model analysis and three-dimensional vision. Through analysis operations in the grid result of Yan'an geo-environment quality is worked out. The results show that the geo-environment quality can be classified into four degrees: best, good, moderate, worst. It indicates that the system of quality assessment is both feasible and practical. At last, the geo-environment protective proposal of Yan'an city is put forward. |
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