Developing a drainage master plan for Lubigi Catchment using GIS and remote sensing.

Abstract

This report presents the results of a study to develop a drainage master plan for storm water, Drainage master plan involves drainage improvement plans, best management practices, focuses on the adequate surface drainage of the area as this will help in solving the, problem of floods in the area.

The study analysed the baseline information in chapter three which includes physical development of the catchment, rainfall pattern and the 'existing drainage channel. The prevailing conditions of the existing drainage system were observed and studied and it was found out that most of them 'ate covered' and some of them are blocked and-clogged in sections. Different data techniques were employed which. included field measurements and observations and oral interviews. It was found out that the ongoing physical development. topographic nature and the existing drainage system are the major causes of' floods in Lubigi catchment,

In this report, I present, a geographic Information System (GIS)' for hydrological data, development for a drainage master plan developed to reduce flooding in the catchment area Arc GIS and HEC-HMS to estimate area of the catchment (35.6m2), land use (which include commercial, wetland, residential, and peripheral residential), hydrological soil groups (the catchment belongs to group D), soil texture (i.e. clay and clay loam), and run-off curve numbers are also presented. Discharge was estimated using the rational method, the calculated values of mean discharge (1566-6m3/s), and standard deviation (176.92) were used to estimate the design discharge-for different return periods using Gumbel distribution method. The design discharge, (202S.3474m3/s) for a 50 year return period was 'used in the design because it is recommended in urban drainage manual for urban areas' the drainage channel was designed in Auto CAD with top width of 4 lm, bottom width of 35m, depth of3m free board of 1.5m and slope of 1:1, for levelling the slope of the channel, the volume of cut and fill was calculated and then the hydraulic behavior of the existing and designed channel was simulated by using HEC~RAS. This proved that according to discharge the channel Won't over flow.