Mapping and analyzing temporal variability of spectral indices in the lowland region of Far Western Nepal

Satellite imagery-based spectral indices are essential for monitoring natural resource changes and urban environments. Assessing these indices is vital for natural resource management and environmental sustainability. This study adopted geospatial techniques and satellite imagery (Landsat 5 TM and Landsat 8 OLI/TIRS) to analyze changes in key spectral indices, i.e. Normalized Difference Vegetation Index (NDVI), Normalized Difference Built-Up Index (NDBI), and Normalized Difference Water Index (NDWI) over the past three decades (1991–2022) in the low land region of Far Western Nepal. The study examined the temporal trends and intricate relationships between these indices during this time frame. The substantial changes in NDVI, NDBI, and NDWI within the study area have been quantified from 1991 to 2022. The findings revealed significantly elevated NDBI values in 1991, 2001, and 2013 compared to 2022, while NDWI and NDVI values were consistently lower in 1991,2001, and 2013 compared to 2022. Notably, a negative correlation was observed between NDVI and both NDBI and NDWI, contrasting with the positive correlation found between NDBI and NDWI. The study underscores the potential of combining these spectral indices to evaluate vegetated areas, built-up areas, and water bodies, providing valuable insights for effective land management, urban planning, environmental monitoring, and sustainable water resource management. HIGHLIGHTS Used geospatial techniques and Landsat imagery to explore variations in spectral indices.; Examined NDVI, NDBI, and NDWI trends and their interrelationships.; Significant changes in NDVI, NDBI, and NDWI from 1991 to 2022.; Observed negative correlation between NDVI, NDBI, and NDWI; and a positive correlation between NDBI and NDWI.; Highlighted the potential of indices for mapping land features and recommended considering various factors in future research.;