Abstract:
The main metropolitan region of Islamabad-Rawalpindi (twin cities) in Pakistan has experienced rapid urbanization since the 1990s due to rural-urban migration and drastic developmental projects. This change has lead towards increased urban expansion in the region, noticeably impacting the local temperature and consequently creating the phenomenon of Urban Heat Island (UHI) effect. This study estimates the surface UHI effect and relates the changes in land use land cover (LULC) types in these twin cities with land surface temperature (LST) during the summer season. Landsat TM 5 and ASTER LIB imageries from 1991 to 2006 were utilized for the retrieval of LST and LULC types. Normalized Difference Vegetation Index (NDVI), Normalized Difference Bare Index (NDBal) and Normalized Difference Built-up Index (NDBI) were used to extract LULC attributes for quantitative and qualitative image analysis
Results indicated that variation in LST for both the cities was affected fundamentally by the spatial distribution and areal extent of LULC type. Changes in LULC types modified the reflectance of the land surface and thus affected the heat and moisture fluctuations Quantitative analysis between LST and indices showed great temperature differences within a LC type apart from variations among different LC types. Stronf positive correlation between NDBI and NDBal index with LST ilhastrated significant contribution of built-up and bare land types towards the rise in urban temperatures, thus creating the UHI effect. The observed changes in LULC of the twin cities were mainly attributed to poor land use planning and inconsistent government policies, the results of which were clearly evident through high saban temperatures in the city of Rawalpindi as compared to Islamabad
