A THESIS SUBMITTED TO THE DEPARTMENT OF WATER SUPPLIES, INSTITUTE OF TECHNOLOGY, SCHOOL OF GRADUATE STUDIES, ARBA MINCH UNIVERSITY IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN WATER SUPLIES JUNE, 2021 ARBA MINCH,

Abstract

This study presents an approach for stormwater runoff quantification from urban subcatchment through the developing drainage system model, applying Geographical Information Systems (GIS) and EPA SWMM modelling software. Satellite images for 2000, 2010 and 2020 of the urban catchment areas were selected based on the quality of data, also 24hr rainfall data were used. ArcGIS tool was used to extract hydrological parameters of the urban catchment by using (DEM), also the ‘EPA SWMM software’ was chosen for application in conducting this research. The Kinematic wave routing method was used to calculate the runoff and a green amt method was used for estimating the infiltration. The land use processing identified four major land use classes namely; Buildings, Roads, Green Areas and Open areas. These land use classes have been changed from 2000 to 2020. E.g., the open areas were reduced from 45.9% in 2000 to 2.62% in 2020. The green areas decreased from 15.32% in 2000 to 8.77% in 2020. The road developments have increased from 31.32% in 2000 to 34.95% in 2020. Where the building developments have increased from 7.47% in 2000 to 53.66% in 2020. The total computed peak discharge for 2000, 2010 and 2020 were 93.45 m3/s, 142.84 m3/s and 186.18 m3/s respectively, Which an increase about 99.1% from 2000 to 2020. Additionally, the hydraulic capacity of existing drainage systems was computed and inundation areas also were identified. This study definitely shows how the land use changes influences the peak discharge and capacity of drainage systems in study area. Further studies are needed to establish the effective flood modelling and mitigation measures. The outcome of this research is important and significant to water resource management authorities for estimating stormwater runoff from urban catchment. The work reported in this thesis significantly contributes to achieving environmental benefits through facilitating the storm water management in urban areas.