A GIS – Based Flood Risk Mapping: A Case Study of Pru District in the Brong Ahafo Region of Ghana

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Pru District of Ghana has been experiencing yearly flooding that affects properties and lives. But the floods of 2010 brought a lot of difficulties and untold hardships on the affected victims in the District. Hence there was the need to find a new method of identifying and mapping potential flood risk zones, determining the extent of land cover and land use changes, and determining the effects of flood on affected victims. Geographic Information System (GIS) and Remote Sensing were integrated to map out the flood risk zones and also determined the land use and land cover changes. A total of 226 household heads and 11 officials of National Disaster Management Organization, District Assembly, Environmental Health and Sanitation Department, District Agricultural Development Unit and the District Health Directorate in the District were interviewed. In determining the flood risk zones, the Shuttle Radar Topographic Mission 90 meters Digital Elevation Model was used to produce the flood risk map of the District and classified the flood risk zones into high, medium and low. It was realized that 3,246.26 km² (52.68%) of the land areas fall within the high flood risk zone, 754.54 km² (12.24%) fall within medium flood risk zone and 2,161.79 km² (35.08%) fall within the low flood risk zone. The Landsat Thematic Mapper and Enhanced Thematic Mapper plus images of 1990 and 2006 of the study area were used to determine the land cover and land use changes. It was shown that between 1990 and 2006, the vegetative cover decreased by 17.25%, built up / bare surfaces increased by 18.50% and water bodies decreased by 1.25%. About 283 houses got submerged by the flood at Banyawaya, Fante Akura and Yeji Nsuano with another 69 submerged at Kobre. About 68.53% of the farmers had their farms totally or partially inundated by the floods in 2010 resulting in food insecurity, psychological problems for farmers, and increase in the prices of some food commodities. The integrated use of GIS and Remote Sensing serve as valuable tool in identifying and monitoring flood risk zones.
A Thesis Submitted to the Department of Environmental Science of the Kwame Nkrumah University of Science and Technology in Partial Fulfillment of the Requirements of Master of Science Degree in Environmental Science, May-2013