Normalized Difference Vegetation Indexand Hotspot Analysisin Guwahati Municipal Corporation Area, Assam, India
Of all the vegetation indices developed for satellite images, Normalized Difference Vegetation Index (NDVI) is one of the most widely used vegetation index for assessing vegetation health. The study is focused on observing the changes in NDVI values, processed in ENVI 5.3. Spatial clustering analysis of NDVI values was achieved by using the Getis-Ord Gi* tool for hot spot analysis (HSA) in ArcGIS 10.2 for the years 1996, 2000, 2004, 2008 and 2015 in the Guwahati Metropolitan Corporation (GMC) area. The results reveal that the NDVI values of the study area have been showing a declining trend with the lowest value of NDVI for the year 1996 being -0.43 and the highest being 0.5, while the lowest value of NDVI in 2015 was -0.17 and the highest was 0.32. This declining trend in the NDVI values over the years has been attributed to the decrease in NDVI hot spots and an increase in NDVI cold spots. The hot spots are scattered in clustered patches over the area while the cold spots have increased drastically as a result of rapid expansion of the built-up areas in the GMC area. The increasing NDVI cold spots is a matter of grave concern as it affects the sustainability of the area under study by dwindling the vegetation cover present and therefore, requires the immediate shift in focus of the stakeholders and the authorities concerned.