Global Journal of Environmental Science and Technology

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Development of a Rainfall-Runoff Model for the Calabar Metropolis Catchment Using the Differential Equation Approach

*1Antigha, Richard E.E, 2Ayotamuno, M.J., 3Akor, A.J. and 4Fubara-Manuel, I.




Accepted 9th June, 2015


Analytical approach involving differential equations was used to develop model that could predict the influence of some  hydraulic and hydrologic parameters on the rainfall-runoff processes in Calabar Metropolis. The model generation relied on some other existing one-dimensional flow models.. The model was validated using the MAtlab v7 (R2008a) program. The RMSE approach was employed to compare the measured with the calculated discharges. Eight out of the ten locations gave strong results with the measured which ranged from 0.0370 to 0.625. There was a very strong correlation between the cross sectional area of drain and discharge (r = 0.93, p<0.01) as well as the basin area (r = 0.76, p<0.05). Incorrect sizing and spread of drains as well as the existing slopes employed in the generation of the drains’ invert during construction have been seen as some of the key factors that foster flooding in the Metropolis. Misalignment of the drains with the existing outlet does not help the expected discharge of storm runoff to receiving bodies. Sequel to these, revisiting the Calabar Master Plan of 1972 with the original design for six drainage outlets is recommended. Designers and managers of the Calabar Metropolis catchment are strongly encouraged to make use of the developed model in the analysis of the rainfall-runoff processes within the Metropolis instead of the rule-of-thumb approach commonly employed.


Keywords: Rainfall-Runoff Model, Calabar Metropolis Catchment, Equation approach