Impact of Flood in Urban Drainage System and Identifying Cause of Storm Water Flooding: - The Case of Gurd Shola Area
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Date
2021-03
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Addis Ababa University
Abstract
Disasters like flooding have changed dimensions of urban areas. The urban flooding in cities is mainly
in the form of flash floods and water logging of streets due to high intensity short spell rainfall. But the
levels of damage to these disasters have increased over time in the urban areas because of increased
rainfall runoff volume. However, it is clearly evident that different level of exposure and different
extents of flood hazard characteristics vary the urban flood risk nature from city to city. Addis Ababa
is one of the fastest growing cities in Africa and urbanization is known to increase the amount of runoff
generated from the urban catchment. Due to urbanization and lack of proper design and management,
the city’s’ transport infrastructure has experienced frequent flooding.
The objective of this research is to identify the drainage condition of Gurd shola area, which is one of
the villages found in in Addis Ababa with respect to the hydrology, hydraulic and operation and
maintenance features. In this study, the impacts of important factors on flooding in urban drainage
system of Gurd Shola area were evaluated using primary and secondary data collection systems. For
the analysis of rainfall data and their probability distribution Gumbel and log Pearson’s III distribution
statistical methods were used. In order to see the impact, runoff coefficient for different time interval
year 2004 and 2019 was used and also the rainfall intensities for different duration was analyzed for a
period of 1988-2017.
The rational formula and Bentley Civil Storm software were used to compute the peak flood estimation
for (T= 10 years) and to determine the hydrological peak flow respectively. The analysis from the
frequency distribution indicates that Gumble Extreme Value distribution was to be a good fit. The
finding of the study shows that, the flooding problem mainly arises due to improper cleaning and storm
water management. Slops also should be clearly checked in order avoid unwanted storm water
accumulation on the road surface.
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Keywords
Urban drainage, Storm water, hydraulic, hydrology, flooding