Assessing the Impacts of Urban Green Areas on Mitigating Urban Heat Island Effect: The Case of Addis Ababa, Ethiopia
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Date
2016-06
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Addis Ababa Universty
Abstract
Several studies have been conducted on analyzing the land surface temperature since
1970’s other than Ethiopia in detail. Urban Heat Island (UHI) is the variation in Land
Surface Temperature (LST) between the urban realm and the surrounding rural areas.
Urban areas are experiencing large population density, an increase surface temperature
and expansion of builtup
environment, which this intern affects the microclimate
of the
city and develops UHI. With regard to surface temperature, different parameters and
data’s were used to understand the situation, to examine its effect and for determining a
solution to overcome the consequences. Input data’s such as Landsat TM (Thematic
Mapper), ETM+ (Enhanced Thematic Mapper Plus) and Landsat 8 OLI – TIRS
(Operational Land Imagery – Thermal Infrared Sensor) images, after conducting
radiometric and geometric corrections, were used to produce results for analysis. For
generating LST of the study area, using Landsat Satellite data, Single and Split Window
Algorithms were applied. Measurement techniques, NDVI (Normalized Difference
Vegetation Index), LST (Land Surface Temperature), NDBI (Normalized Difference
Builtup
Index) and Landuse/
Landcover
were produced to examine the UHI effect and
the positive influence of green areas. The result in correlating the LST and NDVI
indicates that, more than 76% of the variability of the LST is due to the distribution of
NDVI throughout the study area. Therefore, NDVI as indicator to LST is acceptable,
because, it results in strong correlation. The maximum LST in the four base years (1985,
1995, 2006 and 2015), with slight decrease in 1995, it shows a gradual increment in the
measured LST and area coverage. In 1985, the area under 17⁰�� surface temperature
covers 0.95km2, 17–21⁰���������������������������� km2 and 61.6% of the area received temperature
between 27–31⁰���� The result also shows, the higher the value of the NDBI is the higher
the LST. A dramatic landuse/
landcover
change exhibited from 1985 to 2015. In 1985
the builtup
covers 25.7%, in 1995 about 40.8, in 2006 was 48.31 and in 2015 become
59.64%. On the other hand, vegetation cover is decreasing from 16.6% to 9.54% for the
year 1985 and 2015, respectively. Measured temperature in the selected public parks and
surroundings, indicates that, there is a maximum of 5⁰�� temperature increment. Urban
Public Parks plays a major role in mitigating the Urban Heat Island Effect. Therefore, a
proper planning should be considered by government and stakeholders for administering
and developing green areas and individuals keep the surrounding green.
Key words: NDVI, NDBI, LST, UHI, Land-use/Land-cover.
Description
Keywords
NDVI, NDBI, LST, UHI, Land-use/Land-cover