DEVELOPMENT OF PEAK RUNOFF HYDROGRAPHS FOR OBA AND OTIN RIVERS IN OSUN STATE, NIGERIA
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Date
2016-06
Journal Title
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Publisher
International Journal of Latest Engineering Research and Applications (IJLERA)
Abstract
The unit and storm hydrographs for the catchments of Oba River and Otin River, Osun State, Nigeria were developed. Soil Conservation Service (SCS) and Snyder’s unit hydrograph methods were used to develop synthetic hydrographs for the two catchments, while the SCS Curve Number method was used to estimate excess rainfall values from rainfall depth of different return periods. The peak storm flows obtained based on the unit hydrograph ordinates using convolution procedures determined by SCS for rainfall events of 10yr, 20yr, 50yr, 100yr and 200yr return periods for Oba River and Otin River vary from 336.12 m3/s to 611.53 m3/s while those based on Snyder’s method vary from 142.31 m3/s to 283.34 m3/s for both Oba River and Otin River. The statistical analysis at 5% level of significance indicated that there were significant differences in the two methods. The analysis shows that the values of the peak flows obtained from SCS method is higher by about 58.11% and 54.08% than that of Snyder’s method for both the Oba and Otin rivers respectively. SCS method was recommended for use on the two watersheds since it incorporates most major hydrological and morphological characteristics of the basins like the watershed area, main channel length, river channel slope and watershed slope.