Environmental and spatial assessment of urban heat islands in Qalyubia Governorate, Egypt

Present study is the first attempt to map Urban Heat Islands (UHIs) and assess the associated environmental characteristics in Qalyubia Governorate using remote sensing and GIS integrated with a field survey. A calibrated Landsat Operational Land Imager (OLI) acquired on July 22, 2018 was processed to calculate Land Surface Temperature (LST) and UHIs as well as to evaluate the environmental conditions through calculating the Land Use Land Cover (LULC) and the spectral retrieved indices. The investigated indices include Normalized Difference Built-Up Index (NDBI), Normalized Difference Vegetation Index (NDVI), Modified Normalized Difference Water Index (MNDWI), Normalized Difference Salinity Index (NDSI) and Normalized Difference Moisture Index (NDMI). Likewise, multispectral algorithm model was applied on the landsat calibrated image for mapping Particulate Matter of diameters lower than 10 micrometer (PM10) and characterizing its levels in the UHIs. The results demonstrated that the mean LST of each LULC class in Qalyubia Governorate followed this order; bare lands > urban > vegetation > water bodies. Most of bare land and built-up areas exist as heat island regions. The total area of UHIs was 397.5 km2; 119.8 km2 as bare land (30.2%), 201.2 km2 as built-up (50.6%), 0.2 km2 as water (0.05%) and 76.3 km2 as vegetation (19.2%). Low mean values of NDVI and MNDWI were observed in association with UHIs regions which confirmed the positive impact of green cover and water bodies in eliminating UHIs phenomena. On other hand, NDBI showed high mean level in UHIs comparing to its levels in the study area. The average value of PM10 over UHI (94.26 µg/m3) was more than that in the study area (81.07 µg/m3). It can be concluded that the decrease in green spaces and water bodies as well as the increase in urban density lead to increasing the intensity and widespread of UHIs phenomenon. Therefore, the study recommends the necessity to consider results of the present study for urban designers, planners, and architects in designing and planning urban communities.