A CHANGE VECTOR ANALYSIS METHOD TO MONITOR DROUGHT USING LANDSAT DATA
- 1Department of GIS/RS, Science and Research Branch, Islamic Azad University, Tehran, Iran
- 2Department of Geospatial Information Systems, Faculty of Geodesy and Geomatics Engineering, K. N. Toosi University of Technology, Tehran, Iran
Keywords: Drought, Evapotranspiration, Change Vector Analysis, SEBAL, Najaf Abad basin, Landsat
Abstract. Drought has always been a heavy financial burden on a country's economy. To mitigate the impacts of an ongoing drought, spatial information on high risk areas are required. Therefore, the aim of this study is to identify the areas prone to drought in order to minimize the damages through a proper management policy. To achieve this goal, the actual evapotranspiration is considered. The rate of actual evapotranspiration was measured in Najaf Abad using the Surface Energy Balance Algorithm for Land (SEBAL) on Landsat ATM+ images. To present and test the changes in drought, the Change Vector Analysis (CVA) technique was applied to multi-temporal data to compare the differences in the time-trajectory of the tasselled cap intestines and brightness for two time periods 1995 to 2008 – 2008 to 2015. The images were processed using ArcGIS 10.3 and ERDAS Imagine 8.6™ software. The results indicated that the changed area is 9691.41 hectare and the unchanged is 49335.2 hectare between 1995 to 2008. The area of the changed pixels between 2008 and 2015, 3% is higher than the area of the change pixels in 1995 until 2008. In more than 3-quarter of the study area, the value of evapotranspiration has not changed. The proposed method demonstrated immense potentials in monitoring drought change dynamics especially when complemented with field studies.