STORMWATER ANALYZING URBAN FLOOD IN CASE OF DUKEM TOWN USING THE STORMWATER MANAGEMENT MODEL (SWMM)

Abstract

Urban floods are caused due to increase population density in urban areas and the development of urban infrastructure without consideration to drainage aspects. Due to inadequate provision of conveying the runoff to the outlet properly runoff through the town can destruct the structures. The well-connected drainage network and maintenance of the existing stormwater drainage facilities are the mitigating measures of the prevailing drainage problems. This study is concerned stormwater drainage system analysis of Dukem Town focusing on the Southern part around Tedecha area. Recorded rainfall data from 1987 to 2017 years were obtained from NMSA which is used for the hydrological analysis. The catchment area and upper catchment were delineated by using Arc GIS 10.4.1 tool. The rainfall frequency analysis was conducted by identifying the best-fit probability distribution with different return periods. This enables to develop the Intensity-Duration-Frequency (IDF) curve. The intensity duration frequency curve was developed by using the General Pareto Distribution method. Estimation of peak-rate discharge was carried out by using Rational and SCS methods. Hydraulic parameters were determined after measuring the dimension of existing canals by using a tape meter. The total simulated runoff flow from the design period was found to occur 32m3 /s from the twenty sub catchments. The adequacy of the existing drainage systems was checked by comparing the estimated runoff with the existing drainage capacity. However, it was observed that most of the drainage lines were inadequate to safely dispose runoff. The problem of existing drainage systems was lack of a well-connected drainage lines net-work, inappropriate maintenance of drainage facilities, and unavailability of drainage line at the proper place. The major portion of the drainage system performs poorly; e.g. at SC 19, 48.8%, Oda Nabe Secondary School 12.8%, Kera 28.8%, SC11, 30.3%, and SC13, 46% drainage system were severely degraded. This result shows the majority of the drainage system is not adequate to carry the design flood. To overcome the prevailing issues, the major portion of the drainage system is required to be re-constructed and maintain properly to safely pass the generated runoff, and also giving awareness to the community about such an issue is essential