STORM WATER DRAINAGE SYSTEM ANALYSIS OF HAWASSA CITY, ETHIOPIA

Abstract

Intense rainfall and urbanization are the main factors that affect the storm drainage system. In addition to rainfall intensity and impermeable layers, system blockage by solid wastes is the common problem in Hawassa city. The study achieved the objective of storm water drainage system analysis of Hawassa city. To analyze the level of the problem models like Arc GIS10.2, Google earth Pro, Generalized Extreme Value distribution and rational method are used to delineate the drainage system, classify of the sub watershed, simulate the design rainfall depth and runoff volume estimation respectively. The peak discharge generated in 2002 was 54.45m3 /s. Due to both factors the peak discharge generated counts 102.80m3 /s in 2019. Following the drainage system networking capacity of 13drains (59.09%) exceeded by design discharge, 20(90.91%) by 25 years discharge and 21(95.45%) drains capacity exceeded by 100 years discharge that contributes to pedestrian mobility interruption, traffic congestion , chronic distress of asphalt road and environmental health problem due to over flooding. Communication between professionals responsible for storm water drainage system, collaboration of institutions such as water supply, sewerage and sanitation, solid waste management and infrastructure department should be maintained. SUDs measures such as sizing drain and retention pond strategies to cope with intense rainfall and urbanization impact on storm drainage system and environment were recommended.