Abstract
With urbanization impervious surfaces increase, drainage pattern changes, overland flow becomes speedy, flooding and environmental problems such as land degradation increases. The objective of this study is to evaluate the hydraulic performance of storm water drainage system of the study area. The drainage channels are filled with or blocked by silt and garbage, the blockage of drainage structures is due to flat areas and siltation of drainage system which leads to failures on roadways. Spatial analyses were conducted using Arc GIS, Bentley Flow master, Google Earth pro and Auto CAD software’s as analytical tools. The hydrological analysis was computed by rational method. The existing depth and width of the storm water drainage channel were measured for all sub catchments of the town and used to determine the existing drainage capacity using Bentley Flow master. The existing condition drainage channel depths of sub-catchments 6,7 and 8 increased by 68.40%, 160.20% and 121.07%; and the widths by 55.44%, 116.83% and 100.98%, and the design discharge was also 9.29m3/s, 16.47m3/s and 9.13m3/s, respectively. Therefore, this study recommends improvement in the integration of road and drainage structure; integration of solid waste management system in order to prevent the over flowing of storm water as a result of blockage of drains; the stations of the road requires proper maintenance and suitable measures should be taken in order to make the road and storm water drainage structures serve for the intended purposes sustainably to the stakeholders.
Highlights
Urbanization is characterized by a marked increase in built structures [1] such as streets, walkways, parking lots and rooftops creating sealed surfaces
The design capacity of the sub catchments of the town was calculated by taking the intensity for 25-year return period from the IDF was determined by rational formula. This discharge was compared with existing discharge of the town was determined from the measured depth and width of the storm water drainage channel for all sub catchments of the town
The drainage system provided along the local streets of this area doesn’t consider this slope character of the area. Storm water in this area flows with high velocity in the provided drainage systems
Summary
Urbanization is characterized by a marked increase in built structures [1] such as streets, walkways, parking lots and rooftops creating sealed surfaces. Storm water drainage system is designed to drain excess rain and ground water from impervious surfaces such as paved streets, car parks, parking lots, footpaths, sidewalks, and roofs [5]. The most important use of the storm water drainage system is to carry the excess rain water in the monsoon season from the roads, streets and roofs and make the city free from the problems of back flow and from the flood. The pattern of urbanization and modernization Ethiopia has meant increase densification along with urban infrastructure development This has led to deforestation, use of corrugated roofs and paved surfaces. Due to inadequate integration between road and urban storm water drainage, infrastructure provision and poor management significant proportion of the area is exposed to flooding hazards/risks. Appropriate design of the surface drainage system is an essential part of road design [8]
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