Geospatial Mapping and Analysis of the 2012 Nigeria Flood Disaster Extent in Yenagoa City, Bayelsa State, Nigeria

摘要

This article provides a spatial analytical framework for using Geographic Information Systems (GIS) technology in flood mapping. It examines the geospatial mapping and analysis of the 2012 Nigeria flood disaster extent in Yenagoa city, Bayelsa State. Landuse map of 2012 was generated from the imagery of the study area sourced from Google Earth 2012 version. The imagery was geo-referenced and geo-processed in ArcGIS 9.3 to world coordinate system while the flood extent map was generated from the Radarsat of October 2012. The extent of flood in each landuse was determined by overlaying the flood extent map on the landuse map of 2012 using INTERSECT operator. Findings show that the 2012 flooded area extent was 64.42 sq km and 7.0% of total land area of Yenagoa LGA. The built up area had the highest spatial coverage which was 355.90 (38.68%) of the total land area in 2012. The flood affected area was also highest in the built up area as 18.88 sq km was covered which was 9.16% of the built up area and 50.62% of the entire flood extent. The correlation coefficient of the relationship between size of landuse and flood extent within each landuse was 0.487 and r2 was 0.237 suggesting that the coefficient of determination was 23.7%. The relationship was direct but low correlation coefficient and students’ t- test proved that there was no significant relationship between flood extent in the landuse and size of the landuse at p=0.05. The article recommends periodic flood hazard and risk mapping to reduce flood damages in the flooded areas of Yenagoa LGA and construction of dams across the major rivers to regulate the volume of water. Key words: Geospatial, Mapping, 2012 Nigeria Flood, Disaster Extent