SPATIOTEMPORAL DYNAMICS OF URBAN BUILT-UP EXPANSION AND LAND SURFACE TEMPERATURE IN GUWAHATI MUNICIPAL CORPORATION, ASSAM

Abstract

In Guwahati, urban growth has increased over the past ten years, and the thermal imprint within the Guwahati Municipal Corporation (GMC) has evolved over the decade. The change in land surface temperature (LST) regime of GMC between 2013 and 2024 is reshaped by the growth of impervious surfaces. Late post-monsoon window Landsat 8 OLI/TIRS Image Collection 2 Level-2 imagery for the years 2013, 2018, and 2024 was processed in Google Earth Engine, with cloud-shadow masking, radiometric scaling, and emissivity-corrected LST retrieval using NDVI-derived vegetation fraction. The Built-up Index (NDBI) was used to map built-up intensity as both a continuous measure and a binary (classifier of urban extent) measure. LST was compared using zonal statistics and Pearson’s correlation of pixels at annual snapshots and inter-period change. The built-up area increased from 24.33 sq. km in 2013 to 40.12 sq. km in 2024, representing about a 65% expansion. The built-up zones were consistently warmer than the non-built-up areas, with the mean LST differences of approximately 1.5-1.98 °C. It shows that there is a consistent urban thermal penalty. The strong and significant within-year NDBI-LST correlations (r = 0.68-0.74) demonstrated that denser impervious cover is a reliable predictor of high surface temperatures. Conversely, relationships between the variations in NDBI and the variations in LST were weak to moderate (r = 0.26-0.31). It also points out the other contribution of interannual atmospheric variability, complicated topography, and mixed land cover at the urban fringe. The results indicate that a thermal difference exists between non-urban and urban surfaces in Guwahati. Although the areal coverage of the thermally stressed built-up land is still growing with the ongoing urbanisation.