Application of geospatial techniques in the analysis and mitigation of the flood risk : Case study : R. Nyamwamba.

Abstract

This project report presents research conducted during my stay at Busitema University while pursuing a BSc, in Water Resources Engineering scoping at applying geospatial techniques to GIS and RS to delineate the 100year flood plains of Nyamwamba River in Kasese district. The research was started with the-planning phase which involved studying various literature and collecting ancillary data in form of journals and reports. This broadened the researcher's knowledge about flood plain delineation as well as GIS. hydraulic, modelling and to formulate the methodology for the whole project. It was followed by the modelling stage. This started with data collection from various sources both from offices and field surveys. Data collected included: DEM. Topo Shecrs, river map, imageries, flow data, stage data, land, use maps, rainfall data and soil maps. These datasets were conditioned and processed in the GIS environment using the ATCGIS software, later 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 floodplain map which was over laid to a Google image to determine high risk areas. They included among others: -SAEMS offices, Kilembe mines. hospital, All saints church, Kilembe senior secondary school premises, Kyanzuki, Bulembja and katiri primary schools, Lastly, was the model validation phase, in which a confusion matrix was computed. A source river how map of Nyamwamba catchment was crossed with the model-output map, a confusion matrix table with pixels of Hooded, and non-flooded areas was output, by this; the values of reliability arid accuracy of the model were calculated in the ILWIS software. The model gave an accuracy of 79%, With a reliability value of 78%. This proved that the model can be used for flood mitigation in the project area. Data consisting specialty form UNMA and CAA inadequate flow data of Nyamwamba River and absence of a high resolution DEM were my challenge in this project. A geo-spatial planning support system should be developed for the area and the contribution of glaciation to the flow of the Nyamwamba river should be researched about to ascertain flow predictions of the river.