Impervious surface growth and its inter-relationship with vegetation cover and land surface temperature in peri-urban areas of Delhi

Spatial changes in urban areas are closely associated with the increasing impervious land and thus, monitoring the spatio-temporal changes in impervious area is crucial for identifying urban growth. The capital city of India, Delhi has become one of the most populated cities of the world for its fast-growing economy and infrastructural development. Although the city is expanding since the last couple of decades, the rate of growth has become significantly high in the previous decade. This study aims to identify the spatio-temporal pattern of impervious surface growth in and around Delhi National Capital Territory (NCT) by using bi-temporal Landsat images of 2003 and 2014. The linear spectral unmixing (LSU) technique was employed for assessing the impervious surface growth over the megacity. To understand the associated changes of such growth, vegetation surface fraction (VSF), land surface temperature (LST) and normalized difference vegetation index (NDVI) were estimated and compared with the impervious surface fraction (ISF). Further, the fractional abundance of impervious surface was validated with built-up density, urban expansion and population density of the area. This study reveals the significant growth of impervious land in the peri-urban centres surrounding Delhi. The fractional abundance of impervious surface was found highly correlated with the vegetation surface fraction, LST and NDVI. The significant (p < 0.005) correlation coefficients prove good agreement among these variables. Strong negative correlation (r2 = 0.857) between ISF and urban expansion index (UEI) proves the potentiality for urban expansion in the less developed areas with abundant pervious surface. The study also reveals a significant polynomial relationship (r2 = 0.746) between impervious surface fraction and population density indicating high ISF (0.9-1.0) in the densely populated areas and vice-versa. The expanding impervious surface especially in the peri-urban centres along with the rising intensity of urban heat island (UHI) calling for suitable planning and strategies for sustainable urban growth.