Influence of Urban Sprawl on Microclimate of Abbottabad, Pakistan

Abstract

Urban centers are expanding rapidly due to quickly-increasing population which results in microclimate change due to lack of urban planning. Factors like degradation of green areas, trees, and vegetation are defining a new regime of urban environment giving rise to a lack of drinking water and lowering water tables. Consequently, unplanned urban sprawl with all its varied facets is having adverse impacts on the environment. Rapid variations in some of its climatic factors in the immediate vicinity are alarming and need to redress at war footings. This paper is an endeavor to present a hypothesis that urban sprawl plays a vital role in impacting and the influencing the microclimate of the city or the area. In this research, geospatial approaches were adopted to identify urban sprawl. Rise in land surface temperature (LST) for the last 25 years (from 1990 to 2016) has been highlighted using Landsat (5 TM, 7 ETM+ and 8 TIRS) satellite images. Weather data collected from Meteorological Department is used to identify temperature rising trends. Result of the research clearly indicates that rapid urban sprawl has adverse impacts on microclimate by increasing LST. Built-up area has been changed from 178 to 477 sq. km within the years of 1990 to 2016. Vegetated area has decreased from 770 to 602 sq. km. Water areas have been decreased from 524 to 360 sq. km within the span of last 26 years. The bare land has increased from 494 sq. km to 742 sq. km. LST in winters has risen from 17 °C to 23 °C and at times shot up to 31 °C, which is alarming. Annual mean air temperature increased by 3 °C to 4 °C from the 1980s to 2016. During summers, the average air temperature rose to a startling 33 °C from 28 °C and LST has had a steady rise from 28.4 °C to 35 °C. The alarming urban sprawl in relation to temperature rise warrants measures which are required to plan the urban planning, forestation, and ecological measures to mitigate the disastrous trends which may result in flash floods, landslides, soil erosion and sediment transport endangering downstream reservoirs, water quality and depletion in ground water table in the valley.