DEVELOPMENT OF PEAK RUNOFF HYDROGRAPHS FOR SELECTED RIVERS IN SOME PARTS OF NIGERIA

This paper presents the development of unit and runoffhydrographs for the Awun, Ogunpa and Wuruma Rivers. Unit hydrographs were developed based on the synthetic methods; Snyder, SCS and Gray. The SCS curve Number method was used to estimate the cumulative excess rainfall values for storm depth of different return periods. The peak runoffdetermined based on the ordinates from Snyder for 5-yr, 20-yr, 50-yr, 100-yr and 200-yr return period varies between 54.8m3/s and 746.3m3/s, the values of peak runoffbased on the SCS varies between110.8m3/s and 651.8m3/s and those obtained based on Gray method varies between 87.4m3/s and 453.1m3/s for the three watersheds. The statistical analysis and graphical comparison inferred that SCS method can be used to estimate flow ordinate required for the development of peak runoffhydrograph of different return periods for the three river watersheds. [PUBLICATION ABSTRACT]