Development of Storm Hydrographs for Three Rivers within Drainage Network in Kwara State, Nigeria using Snyder's Method

This paper presents the development of unit and storm hydrographs for Rivers Moro, Asa and Oyun catchmem. Snyder's method was used to develop the unit hydrographs; while the SCS Curve Number method was used to estimate excess rainfall values from rainfall depth of different return periods. The design storm hydrographs corresponding to the excess rainfall values were determined based on the unit hydrograph ordinates established through convolution. The design storm hydrograph obtained for Moro River catchment based on 5-yr, 20-yr, 50-yr, 100-yr and 200-yr return period ranged between 245.29 m3/s and 685.84 m3/s. Thai of Asa River catchment varied from 301.34 m3/s to 846.46 m3/s and the design storm hydrograph flows obtained for Oyun River catchment varied from 257.29 m3/s to 723.56m3/s. The design storm hydrograph flows obtained can be recommended for sizing hydraulic structures within Kwara State drainage network