Performance improvement of an urban storm water management system :

Abstract

The hydraulic incompetence of storm water drainage systems in developing towns like Kasese municipality is the problem at hand. This is mainly due to increased paved surfaces, under designing of some sections, inadequate maintenance and poor solid waste management. Therefore, rainfall frequency analysis has been carried out as well as the hydraulic competence of the existing drainage structures in Kasese municipality. Rainfall frequency analysis was carried out using the Gumbel distribution after best fit tests and the design storms that correspond to the 10, 25, and 50-year return periods were computed. Using a high-resolution Digital Elevation Model (DEM) of 12.5m, a watershed delineation was carried out and the sub-basin parameters calculated accordingly. A total of eighty-two (82) watersheds fourteen and sub watersheds were obtained in project area. Using the watershed parameters obtained, the design storm and the hydraulic properties of the existing drainage network collected from the field as inputs to PCSWMM, runoff simulations were caried out. This simulation was carried to assess the hydraulic competence for the existing drainage structures for 10-year and 25-year return period for all drains and 25-year and 50-year return periods for the culverts. Some sections of the network were found to be hydraulically competent, along the Kamulinkwizi, others incompetent; most part of the Kasese primary drain while some sections were under designed. Integration of sustainable development options in the drainage design, use of silt traps, better solid waste management and regular maintenance of the drainage system have been recommended KEY WORDS: Stormwater drainage system Hydraulic competence, PCSWMM