Satellite-based application in drought disaster assessment using terra MOD13Q1 data across free state province, South Africa

Terra MOD13Q1 satellite data were used to assess drought disaster events and its spatiotemporal patterns over the Free State Province, South Africa between 2001 and 2019. Moderate Resolution Imaging Spectroradiometer (MODIS) products and climate data downloaded from Application for Extracting and Exploring Analysis Ready Samples” (AppEEARS) and NASA: Prediction of Worldwide Energy Resource databases, respectively were used in the study area. After acquiring MODIS data with the area of interest extracted using field sample and the layers of interest: using Enhanced Vegetation Index (EVI) and pixel reliability and defining the output as GeoTIFF with geographic projection, R programming was used for the analysis. This study also evaluated Standardized Precipitation Index (SPI) to further identify meteorological drought, computed at various time scales utilising information acquired from the Global Drought Observatory database. The results show and identify the years that are water-stressed in the study area, which indicated that low vegetation abundance and high temperature in the Free State Province occurred in 2000, 2008, and 2009. The result also shows that the summer season over large parts of the study region is characterized by moderate to extreme drought while winter seasons have light drought conditions during the same time. Seasonal and inter-annual comparisons of drought events outlined in the Vegetation Condition Index (VCI) provided a useful tool for analysing the temporal and spatial evolution of regional drought and for estimating potential environmental impacts. Drought events occurrence in the study area is less frequent and milder in winter months while summer droughts of different years were more severe. The results of this study can also be used as a tool for monitoring droughts and support for decision making in the evaluation and management of regional drought, for disaster preparedness.