EVALUATING THE IMPORTANCE OF URBAN WETLANDS IN MONITORING MICROCLIMATIC ENVIRONMENT; A STUDY IN BOLGODA LAKE IN SRI LANKA AND ITS SURROUNDING

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Year:
2016
Type of Publication:
Proceedings
Keywords:
Urban wetlands, UHI, LST, population density distribution
Authors:
Samarasinghe, Y. M. P.; Dayawansa, N. D. K.
Abstract:
Urban heat island effect is one of the serious environmental consequences which alter the microclimatic environment of urbanized areas by resulting relatively high air temperature compared to the surrounding non-urbanized areas. Wetlands within urban territory play an important role by regulating the microclimatic environment. This study was conducted in Bolgoda Lake and surrounding Divisional Secretariat Divisions (DSD) located in Colombo District, Western Province of Sri Lanka to identify the land use changes, Urban Heat Island (UHI) distribution, Microclimatic effect of UHIs and the relationship between population distribution pattern and the UHI distribution in 2001, 2005 and 2014. Landsat ETM+ (2001), Landsat TM (2005) and Landsat OLI/TIRS (2014) satellite imageries and population statistics (2001 and 2011) were analyzed with Remote Sensing and GIS techniques. Land use change detection revealed that area covered by paddy and other vegetation have reduced by 30% from 2001 to 2014 whereas densely urban/ construction sites have increased by 60%. A good relationship was identified between urbanization pattern and urban heat island (UHI) distribution while an expansion of heat islands was noticed in 2001, 2005 and 2014. Western side of the Bolgoda Lake and the coastal belt are critically affected by UHI effect resulted by elevated urbanization. It was observed that the land surface temperature (LST) is less closed to the wetland and increases with the distance from the wetland indicating the microclimatic regulation effect of wetlands. Low mean LST values were identified in water bodies and paddy/other vegetation land use classes whereas highest was reported for densely urban/construction sites. The study identified that the population density is increasing over time and the pattern of population density distribution follows the pattern of UHI distribution. Comprehensive analysis of satellite derived LST can be used to demonstrate the impact of urban wetlands on regulation of microclimatic environment and to encourage the protection of wetlands in urban areas
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