A Comparative Analysis of Remote Sensing Derived Spectral Indices of Valanchery Micro Watershed, Kerala, India

Abstract

Spectral indices derived from multispectral satellite data provide a useful means to assess the temporal dynamics of land surface features. The study on spectral indices is important to detect the Land use change and the trend of urbanization and vegetation pattern of the watershed. The Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), and Normalized Difference Built-up Index (NDBI), three important remote sensing-based spectral indices, were compared for the Valanchery micro-watershed of Kerala for the study period (2015-2023). This study area was specifically carried out in this study area, since the study area is majorly covered with vegetation and plantation land use, and the study area is undergoing rapid urbanization. Multi-temporal spectral analysis (2015–2023) revealed an increase in the vegetation, with NDVI range of 0.45 to 0.52. NDWI ranged between (-0.47 to 0.13), and there was an increase in NDWI of 0.13 in the year 2020, indicating temporal moisture variability. NDBI values ranging between (−0.27 to 0.22), maximum NDBI values of 0.22 were observed during the year 2023 and showed an increase in built-up, with urban land. The findings of the study show that over the research period, there was a visible increase in built-up areas combined with a steady increase in vegetation greenness, especially within plantation and thick vegetation classifications. Holistic Integrated analysis of the spectral indices, such as NDVI, NDWI and NDBI revealed an improvement of vegetation with an increase in urban expansion and a decline in surface moisture conditions. The study is an important for multi-temporal spectral indices analysis and cloud-based processing usage to monitor landscape changes in micro-watersheds that are undergoing rapid urbanization.