Improving the Hydraulic Capacity of the Namakwekwe Drain

Abstract

Kiteso Cell, located in Mbale city, is experiencing rapid urbanization. This growth has led to more surface water runoff overwhelming the existing drainage system. The primary drainage channel, the Namakwekwe Drain (also known as Ngabito), is roughly 755 meters long and has uneven sections. Some parts are lined with stone, while others are simply earthen ditches. To understand the flooding problem, an investigation was carried out to assess the drainage channel's condition and surrounding area. Analyses of the rainfall patterns in the area (hydrological characteristics) were also carried out to determine the amount of runoff generated during heavy rain events. The runoff generated in the area was determined by analysing the hydrological characteristics of the catchment. The 50-year return period design storm was used to analyse the hydraulic capacity of the Namakwekwe drain to determine the inadequacies of the channel. To address the flooding issue, the research proposes modifying the channel's geometry using modelling software. This involved reshaping the channel into a trapezoidal shape and lining it with concrete. While the estimated cost of this project is UGX 1.25 billion, the economic benefits are expected to outweigh the cost. The project is estimated to have a benefit-cost ratio of 1.1, meaning the benefits gained will be slightly higher than the initial investment. Additionally, these benefits are expected to be realized within a ten-year timeframe, making it a financially sound solution.