To delineate flood risk zones in Abakaliki Local Government Area, a hydrological model (modified rational model) was integrated into the GIS environment by the arithmetic overlay operation method, using operators such as addition and division. The results show that the delineated areas however experienced same rainfall intensity of 414.2 mm/hr yet the flood intensities of these areas differ. For instance, the very high flood risk zone covers about 22.8 percent of the study area while the low risk zone covers about 44.3 percent. And the potential areas likely to experience periodic floods with a given input of rainfall are mostly below 40m elevation. This study analyzed time series land use/land cover imageries (1986-2016) and 30 years rainfall data to examine land use/ land cover changes and rainfall variability as underlying causes for flood risk hazards on downstream community. The LULC change detection showed that out of the four identified land use classes (Forest, Agricultural lands, Bare lands, and Settlements), only settlements changed significantly (5% to 12%). The available rainfall record for 30-year period of 1986 to 2016 was analyzed to examine the trends of rainfall in the study area and to provide evidence of climate change. Time series graph was constructed to illustrate the changing trends within the months and years. Statistical analysis was performed and the result shows low monthly precipitation changes throughout the years under study. When the standard deviation values are examined, it is observed that the standard deviation values of most months (March, April, May, June, July, August, September and October) are lower than the mean values of these months indicating that the deviation from the normal distribution is not significant. Qualitative validation of the modeling results obtained through focus group discussions (FGDs) with local communities and experts shows that the flood modeling method accurately classified most communities deemed to be highly susceptible to flood hazard.