Investigation of Drought on Vegetation Cover Change Trend Between 1998 - 2010 With Use of Landsat Satellite Images and SPI Index (Case Study: Birjand Plain)

Vegetation cover is one of the main indexes in environmental ecological life that is directly in relation with region humidity conditions. Comparing vegetation cover between two periods with different humidity conditions in a region can show the rate of stress nicely in a drought period on the green vegetation cover. The aim of this study was investigating the changing in birjand plain vegetation cover during the recent drought. This study was done whit the help of GIS and remote sensing technology and SPI drought index. For doing this research, these data were used: percentage vegetation cover data that obtained from the field visiting, rainfall data, satellite images from Landsat TM 1998 And 2010. All of the satellite images preprocessing and processing, making vegetation index and change detection procedure were done in Erdas 9.2 and Idrisi Kilimanjaro 14 software and for establish regression relation between vegetation cover percentage and vegetation index, the Spss software was used. In among of vegetation index, msavi2 showed the highest relation that this index was used to make ready vegetation cover percentage map for the years which these studies were going on. This with post classification changes detection procedure, the changes that occurred in vegetation cover percentage in the region were detected the result showed vegetation cover severely affected from drought. So that in occurrences of drought from 1998 until 2010, we observed decreasing in vegetation cover percentage on %29 area of the region.