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Journal of Environmental Hydrology
ISSN 1058-3912 |
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Electronic Journal of the International Association for
Environmental Hydrology
JEH Volume 16 (2008), Paper 15 Posted April 30, 2008 RETURN PERIOD ANALYSIS AS A TOOL FOR URBAN FLOOD PREDICTION IN THE ACCRA PLAINS, SOUTHERN GHANA
Seth Xeflide ABSTRACT Return period analysis is a common statistical approach used for predicting flooding in urban centers. It is a very important tool for building and designing the safest possible flood control structures. The analysis provides information about when a flood of a given magnitude is expected to occur, be equaled, or exceeded. Flooding is common in urban cities as a result of unplanned development and poor drainage systems and recent flooding in the Accra, Ghana, metropolitan area has been attributed largely to these factors. In this study return period analysis of annual rainfall and maximum 1-month rainfall has been conducted for 30 years of data for the Accra plains. The analysis used the Weibull plotting position. The prediction equations were used to forecast flood magnitudes for return periods of 5, 10, 20, 25, 50 and 100 years. The highest rainfall occurred between May and June. Annual rainfall of 1223.5 mm and maximum 1-month rainfall of 420.6 mm are expected to occur every 31 years. Extrapolation of the return period based on a linear regression model suggests that a maximum 1-month rainfall and maximum annual rainfall of 550.5 mm and 1612.98 mm is expected to occur every 100 years, respectively. The study recommends that urban planners and structural engineers take into account all necessary statistically derived flood magnitudes as inputs during the design of drainage systems in the region. Reference: Xeflide, S., and D. Ophori. 2008. Return period analysis as a tool for urban flood prediction in the Accra Plains, southern Ghana. Journal of Environmental Hydrology, Vol. 16, Paper 15. CONTACT: Duke U. Ophori Dept. of Earth & Environmental Studies Montclair State University Upper Montclair, NJ 07043 USA E-mail: ophorid@mail.montclair.edu |
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