Mitigating the effects of floods on agricultural production in Awoja sub catchment.

Abstract

Throughout the human history floods have been an integral part of the civilization. Still men have not quite coped well to live with floods. Flooding is the most frequent global natural disaster, rural areas are becoming more vulnerable to flooding due to effect of climate change. Flash flood is the common phenomena caused by heavy rains. Drainage channels is common strategy used for flood control. The failure of preventive measures has led to researchers to advocate a shift in thinking from preventive measures to flood risk and structural management measures. Recently, the advancement in computer-aided technology has been extensively used in formulating models used for flood calculation and hazard analysis. This study focuses on using a hydraulic model HEC-HMS and HEC-RAS in a GIS environment for the affected areas of Awoja, generates the flood area and the return period for the specified flood events. This project involved. studying various literature and collecting ancillary data in form of journals and reports. This helped to formulate the methodology for the whole project. It was followed by the modelling stage. This started with data collection from various sources i.e. from offices. Data collected included: DEM, discharge flow data; land use/land cover data, rainfall data and soil data. These datasets were conditioned and processed in the GIS environment using the ArcGIS software. Land use and soil data was used to generate Curve number grid. and later geo-hms was used to set up a project which involved basin characteristics and processing and exported into HMS to generate hydrograph (peak discharges) to be used in the HECRAS. The IDF curves were generated for a return period of 50 years that gave peak intensity of 19.5m/s and therefore aided in calculating the design flood. The GeoRAS file was exported to the HEC-RAS program to compute for a steady flow simulation. The RAS mapper export from HEC-RAS program was then imported in to ArcMap to delineate a flood plain map which was overlaid to a Google image to determine flood prone areas. The drainage system was then designed with the design parameters already generated.