عنوان مقاله [English]
نویسندگان [English]چکیده [English]
One of the most important consequences of drought is reducing the amount of vegetation cover. Due to the Reduction of vegetation, the environmental conditions will be provided for the appearance of various problems such as soil erosion, surface runoff and increasing the flood risk and ….. Accordingly, evaluation of drought effects on vegetation cover is very important. In this regard, the use of reflective remote sensing techniques to evaluate the effects of drought has been known as one of the most efficient methods.
In this study, to evaluate the effect of drought on vegetation in Kurdistan province, meteorological data and remote sensing techniques have been used. Firstly, the standard precipitation index (SPI) for six Meteorological Stations during the years of 2000-2009 was calculated. Next, based on 40 sensing images from TERRA / MODIS 16-days, in months of August, September, October and November, the normalized difference vegetation index (NDVI) was calculated. With regard to this index, vegetation area was classified into 6 groups and the area of each class was calculated. Finally, SPI and NDVI indices were compared.
The results of this study indicate that between the mean indices SPI and NDVI, high correlation
(+ .77) with 0.01 significant level, are existing and reducing the amount of SPI index approximately -0.20, averaged 1.2 percent (equivalent to 350 kilometers) poor vegetation cover increases. The rate of decline for the NDVI index, is approximately 0.01. Results obtained from the index SPI, showed that in 2001 and 2008 the moderate drought occurred in the province of Kurdistan. NDVI index calculated in the two years showed that poor vegetation cover, noticeably increased (respectively 80.6% and 76.6%) while in 2007 almost as a normal year, the amount of poor vegetation based on NDVI index, approximately 69.7% was calculated. Comparison between the years 2001 to 2007 (approximate change of 11 percent poor vegetation), well represents the effect of drought on vegetation in the province of Kurdistan.