Water Supply and Environmental Engineering

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Browsing Water Supply and Environmental Engineering by Author "Ashenafi, Zinabie"

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    Performance Assessment of Stormwater Drainage System in Alamata Town
    (Addis Ababa University, 2018) Ashenafi, Zinabie; Geremew, Sahilu (PhD)
    Urbanization of an area invariably leads to increase in overall imperviousness of the area. When land becomes impervious,stormwater will stagnate on the surface thereby affecting the infrastructure, transportation and causing inconvenience to general populace. Stormwater drainage problem is one of the major challenges facing many countries in Ethiopia in general and Alamata town also faced the problem. This study has investigated the overall challenges of the stormwater drainage system in Alamata town.Rapid expansion of built environment, poor urban drainage managements and location of Alamata town being at the foothills of mount Gra-Kahsu are the major problems in the study area. The objective of this study is to evaluate the current stormwater drainage systems and associated problems. This research involves collection of both primary and the secondary data and the collected raw data was edited, coded, classified, and tabulated in order to make it ready for analysis. Furthermore, spatial analyses was conducted using Arc GIS, Bentley Flow master, Google Earth pro, and Auto CAD software’s as analytical tools. The land use land cover image was processed for the years 2008 and 2018 by using Arc GIS.10.4.1 and Google earth pro then for each land use/land cover, annual stormwater runoff volume was calculated and digital change detection were evaluated. The results indicate that Annual runoff volume of Built -up area in the study area has increased from 162129.6m in 2018 which accounts for 13.35% of the total Annual runoff volume. The Vegetation has decreased from 15616.8m 3 in 2008 to 183772.8 m 3 in 2008 to 4568.4m 3 in 2018 which accounts for 70.75%. The Bare Land area has increased from 8286.3m 3 3 in 2018 which accounts for 153.08%. The existing depth and width of the stormwater drainage channel were measured for all sub catchments of the town and used to determine the existing drainage capacity using Bentley Flow master. The hydrological analysis was computed by the SCS method and rational method. The computed discharge values, which were determined by both SCS method and rational method, were compared by dividing the watershed area according to their area of application. The existing condition drainage channel depths of sub-catchments 6,7 and 8 Increase 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 9.29m in 2008 to 20970.9m 3 /s and 9.13m 3 3 /s, 16.47m 3 /s respectively.