Assessment of the effectiveness of the structural and non-structural mitigation measures of floods along the flood plains of river Manafwa :

Abstract

River Manafwa is a natural river found in Eastern Uganda. The river originates from Mount Elgon in eastern Uganda and traverses the districts of Bududa, Manafwa, Mbale, and Butaleja. It joins the Mpologoma River, which empties into Lake Kyoga. The river basin is prone to flooding, which disrupts transportation of goods and services between the Bududa and Manafwa districts and damages buildings with several deaths recorded. This study will focus on conducting assessing the effectiveness of the structural and non-structural mitigation measures through the utilization of software and these will be ArcGIS 10.8, HEC-HMS, and HEC-RAS. I will use ArcGIS 10.8 to delineate the catchment and Hydrological and Hydraulic models for the river catchment will be developed in HEC-HMS and HEC-RAS respectively. The curve number method was used as the loss method with the Muskingum method adopted as the routing method to simulate runoff from the catchment. I will simulate river flows for the different return periods of 10, 25, 50 and 100 years after which the basin model was calibrated and validated in HEC-HMS by using observed River flow data of River Manafwa from the DWRM, Ministry of Water and Environment. HECRAS 6.1.0 was used to carry out Hydraulic modeling for the river using simulated stream flow results from HEC-HMS 4.8. Effective mitigation measures and approaches were recommended to reduce the impact of floods on the communities living around the flood plains.