Assessment of Drainage Structure by Using ArcGIS Software: The Case of Bale Robe Town, Ethiopia

Abstract

An increase in the frequency of extreme weather events such as heavy storms and floods has been reported in various parts of the world. Ethiopian cities at large, are troubled with storm water leading into floods especially during the rainy season due to inadequate installation of desired infrastructure. In the Robe town since the construction of impermeable surface like roads, sidewalks, buildings and others are highly increasing. They are reducing natural permeable surface that can infiltrate water into the ground. Those impermeable surface are create flooding and more storm water runoff in this town. In this town water flows through road especially during heavy rain are resulted in negative impacts on road pavement performance and on the overall situation of the town’s basic infrastructures. The objective of this research was to assess drainage structure in Bale Robe town by using ArcGIS software. The specific objectives of this study were; determining general characteristic of EDS, computing slope and capacity of EDS, identifying highly affected road segment due to improper drainage and recommending appropriate counter measure for identified defects. Majority of the data for the study were obtained from the field survey using surveying equipment and field observation, and some data were collected from concerned sectors. The population contains all existing drainage structures except earthen drainage structure. As a result of the study EDS have different types, and base widths, the capacity of some drainage structure are less than the required capacity while some of them are greater than the required capacity. There were both opened and closed drainage structures with slope of EDS between 0.1 percent and 1.96 percent. The terrain category of the town is flat and rolling. Generally, the EDS in the town has different general characteristics, capacities and different defects. The identified defects were due to different factors; like poor design, poor environmental assessment, and lack of maintenance were the main causes of street flood in the study area. In this town the following measurements should be taken to solve the identified defects, properly cleaning of drainage structure before and after rain, cover open drainage structure, improve the longitudinal gradient of drainage structure and improve the capacity EDS based on the ERA standard and causes of the defects.