Assessing the performance of the drainage system in Kansanga, Kampala

Abstract

This study examined the hydraulic performance of the main drainage channel in Kansanga catchment area. The areas along the main channel flood during high precipitation conditions despite the existence of the open drainage channel, thus triggering the conductance of this study. In addition, solid waste collection and disposal catchment area is dismal due to people using the existing drainage channel as a disposal point hence posing an immediate health hazard to the inhabitants. The first objective of the study was to undertake a hydrological study of the main channel in the Kansanga catchment area and determine the peak runoff of the catchment. Other objectives of the study included building a hydrologic and hydraulic model of the main channel in suitable software to assess the hydrologic and hydraulic performance of the channel. We found it befitting to come up with an appropriate assessment of the channel to examine its hydraulic performance using performance indicators. A reconnaissance survey was conducted which involved visiting the site and interactions with the community about the main channel. Importation of coordinates into ArcGIS enabling the generation and measurement of the watershed of the main drainage channel. The 10-year return-period design storm was determined with the aid of rainfall data from Makerere University Meteorological department and the time of concentration calculated and estimated at 81 minutes, the critical rainfall intensity read off from the developed intensity-duration-frequency curves as 45 mm/hr. and the peak flow calculated from EPA-SWMM as 60.84 m3/s The report shows detailed hydraulic calculations using Hydraulic toolbox software with volumes from EPA-SWMM with results deducing that the hydraulic properties of the channel rendered unsuitable for their purpose of drainage. The report also included determination of the extent to which the solid waste in the channel contributed to flooding using a simple solid waste desk study. Findings showed that solid waste was indeed a contributor to the channel capacity reduction thus increasing the prospects of flooding.