A THESIS SUBMITTED TO THE FACULTY OF WATER SUPPLY AND ENVIRONMENTAL ENGINEERING, ARBA MINCH WATER TECHNOLOGY INSTITUTE SCHOOL OF POST GRADUATE STUDIES ARBA MINCH UNIVERSITY IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN WATERSUPPLY AND ENVIRONMENTAL ENGINEERING

Abstract

In last few years Arba Minch has been doing different urban development activities like construction of streets, new settlement and others. Those urban development activate leads to produce higher amount of runoff by increasing imperviousness of the town. As the result of these the town faced different problem during the rainy season that affect the human activities, wealth and health. To overcome those problems this research aims to investigate the impact of urbanization on storm water drainage system by considering land use/land cover change using SWMM 5.2.4.To achieve the aim of study: area characteristics, land use land cover change, rainfall intensity and existed drainage characteristics were analyzed. The total catchment is delineated by using Digital Elevation Model (DEM) data from Alaska satellite facility and sub divided in to different sub-catchments and analyzed their characteristics on ARC GIS10.8. The land use land cover classification analyzed using Google Earth Pro collaborating with ARCGIS for detail calcification on three consecutive periods which are 2003, 2013 and 2023.The existing drainage network characteristics were done by field survey that used as an input data for the model to simulate. The rainfall intensity was analyzed using frequency analysis of 32 years rainfall data obtained from Ethiopian meteorological agency. The result showed that the impervious surface and water body increase by14.1 % and1.5% respectively within 20 years interval. The increment of impervious surface caused by expansion of institutions and commercial area, formation of new settlements, construction of new asphalt roads and cobble stones. The main factor for water body increment is the expansion of Lake Abay that serves as reservoir for some portion of the town runoff. In contrast to impervious and water body the pervious surface decreased by 15.6% that caused by reduction in bare land and farmland. Land use Land Cover change have great impact on the existing drainage system by 8.4 % peak runoff increment on sub-catchments and 10.84% increment maximum flow in the outfalls within 20 In last few years Arba Minch has been doing different urban development activities like construction of streets, new settlement and others. Those urban development activate leads to produce higher amount of runoff by increasing imperviousness of the town. As the result of these the town faced different problem during the rainy season that affect the human activities, wealth and health. To overcome those problems this research aims to investigate the impact of urbanization on storm water drainage system by considering land use/land cover change using SWMM 5.2.4.To achieve the aim of study: area characteristics, land use land cover change, rainfall intensity and existed drainage characteristics were analyzed. The total catchment is delineated by using Digital Elevation Model (DEM) data from Alaska satellite facility and sub divided in to different sub-catchments and analyzed their characteristics on ARC GIS10.8. The land use land cover classification analyzed using Google Earth Pro collaborating with ARCGIS for detail calcification on three consecutive periods which are 2003, 2013 and 2023.The existing drainage network characteristics were done by field survey that used as an input data for the model to simulate. The rainfall intensity was analyzed using frequency analysis of 32 years rainfall data obtained from Ethiopian meteorological agency. The result showed that the impervious surface and water body increase by14.1 % and1.5% respectively within 20 years interval. The increment of impervious surface caused by expansion of institutions and commercial area, formation of new settlements, construction of new asphalt roads and cobble stones. The main factor for water body increment is the expansion of Lake Abay that serves as reservoir for some portion of the town runoff. In contrast to impervious and water body the pervious surface decreased by 15.6% that caused by reduction in bare land and farmland. Land use Land Cover change have great impact on the existing drainage system by 8.4 % peak runoff increment on sub-catchments and 10.84% increment maximum flow in the outfalls within 20In last few years Arba Minch has been doing different urban development activities like construction of streets, new settlement and others. Those urban development activate leads to produce higher amount of runoff by increasing imperviousness of the town. As the result of these the town faced different problem during the rainy season that affect the human activities, wealth and health. To overcome those problems this research aims to investigate the impact of urbanization on storm water drainage system by considering land use/land cover change using SWMM 5.2.4.To achieve the aim of study: area characteristics, land use land cover change, rainfall intensity and existed drainage characteristics were analyzed. The total catchment is delineated by using Digital Elevation Model (DEM) data from Alaska satellite facility and sub divided in to different sub-catchments and analyzed their characteristics on ARC GIS10.8. The land use land cover classification analyzed using Google Earth Pro collaborating with ARCGIS for detail calcification on three consecutive periods which are 2003, 2013 and 2023.The existing drainage network characteristics were done by field survey that used as an input data for the model to simulate. The rainfall intensity was analyzed using frequency analysis of 32 years rainfall data obtained from Ethiopian meteorological agency. The result showed that the impervious surface and water body increase by14.1 % and1.5% respectively within 20 years interval. The increment of impervious surface caused by expansion of institutions and commercial area, formation of new settlements, construction of new asphalt roads and cobble stones. The main factor for water body increment is the expansion of Lake Abay that serves as reservoir for some portion of the town runoff. In contrast to impervious and water body the pervious surface decreased by 15.6% that caused by reduction in bare land and farmland. Land use Land Cover change have great impact on the existing drainage system by 8.4 % peak runoff increment on sub-catchments and 10.84% increment maximum flow in the outfalls within 20nterval. The increment of impervious surface caused by expansion of institutions and commercial area, formation of new settlements, construction of new asphalt roads and cobble stones. The main factor for water body increment is the expansion of Lake Abay that serves as reservoir for some portion of the town runoff. In contrast to impervious and water body the pervious surface decreased by 15.6% that caused by reduction in bare land and farmland. Land use Land Cover change have great impact on the existing drainage system by 8.4 % peak runoff increment on sub-catchments and 10.84% increment maximum flow in the outfalls within 20 year gap from 2003 up to 2023. Those result indicated the existing drainage system needs additional network other ways the flooding event occur that can cause damage on existing drainage system and also public wealth and health. Most of the flooding problems are caused by sediment loads within the existing drainage system. Those sediments came from the mountain area that found at the upstream of town. To overcome this problem covering upstream mountain with trees by constructing terracing around the mountain is recommended