Global Advanced Research Journal of Environmental Science and Toxicology (ISSN: 2315-5140) Vol. 2(3) pp. 086-092, March, 2013 Available online http://garj.org/garjest/index.htm Copyright © 2013 Global Advanced Research Journals Full Length Research Paper Spatial assessment of urban flood risks in Aba Metropolis, using geographical information systems techniques John D. Njoku 1* , Gordon T. Amangabara 1 , and Pat N. Duru 3 1 Dept of Environmental Technology, Federal University of Technology Owerri, Nigeria 2 Dept of Geography and Environmental Management, Imo State University, Owerri, Nigeria Accepted March 17, 2013 This study applied Geographical Information System Technology in the spatial analysis of flood risks in Aba metropolis. Data on spot heights and elevation were collected with Global Positioning System and used to produce digital elevation model map in a 2-D format; the aspect map showed the natural direction of storm water flow; the slope map was used to indicate the overall rate of downward movement of water and the contour map showed elevations at intervals of 10m. The digital elevation model presents the study area as ranging from 35 – 70m above sea level. Water flowed from areas 70m to areas 35m above sea level. Areas 35-39m and 43-48m are prone to flooding, as runoff from the areas of higher elevations tends to flow towards areas of lower elevations. The percentage slope variation showed that slopes which ranged from 38.26% - 46.88% and areas 55.50% - 64.12% are more vulnerable to erosion but flood free. The areas with slopes ranging from 64.12% - 72.74% and areas 81.36% - 89.98% have critical and steeper slopes and certainly produce flood of greater velocity than moderate or lower slopes. The aspect map showed that in areas of 0 - 22.5 and 337.5 - 360 water flows to the north, while 67.5 - 112.5 flows to the east. All areas of 157.5 - 202.5 water flows in the southern direction, while areas from 247.5 - 292.5 water flows in the western direction. Elevation in the area ranged from 72m to 36m with an average of 54m and must be considered in storm water channelization projects. Keywords: urban flood, geographical information system, spatial analysis, elevation INTRODUCTION Several manifestations and effects of climate change and variation have been studied (see for example, Ojo 1992; Obioh, 2002; FGN, 2003; NEST, 2003; Njoku, 2006). NEST (2004) indicated that current and future vulnerability include human settlements and health, water resources, wetlands, agriculture, food security, coastal *Corresponding Author E-mail: dr_jdnjoku@yahoo.com’ Mobile: +2348034016638 zones and land degradation. Land degradation reduces the quality and productivity of land. One of the causes of land degradation which has been on the increase as a result of climate change is erosion and flood. It is as a result of this and the rising spate of occurrence of urban flooding and inundation, especially in coastal and humid regions that this study was carried out. Ologunorisa, (2001) defined flood as any abnormally high water stage which may result in significant, detrimental effects such as property damage, traffic destruction, nuisance and health hazard. Flood also affects and damages agriculture, properties and public