Developing a GIS functional Extension for automated Environmental Impact Assessment (Degradation Model)

Generally, general Geographical Information Systems (GIS) has brought a great change in the Environmental data analysis, but a big volume of spatial data and relative complexity of common Environmental Models, make the analysis process time consuming. Goals of this study include: investigating the possibility of automatic execution of Degradation Model in the GIS environment and programming of user friendly software in GIS-ArcView.By Avenue language, required scripts for executing of degradation model were programmed.All scripts constituted a unit set called Degradation Model (IRAN) Extension. This Extension consist of one menu (involving 15 submenu) and two tools in tools bar. The first and second parts of menu are for input data. Third part of menu consist for storing data analyzing. In the forth part, degradation model coefficient is calculated according to the model for each unit. After classification of degradation coefficients, susceptible area to development, undevelopable areas and sensitive areas are determined. Tools of this extension are used for drawing of grid on study region and inputting degradation factors intensity.To verify this extension, environmental impact assessment process was executed in an area (320983 hectare) with both manual and automatic methods.Comparison of results of two methods showed that automatic method decreases required execution time considerably and increases accuracy of model execution by 13/4 percent.