SIMULATION OF HYDROLOGICAL FLOOD ROUTING ALONG SPILL WAY CHANNEL OF RIVER ASA IN ILORIN KW AR;\ STATE.

Abstract

This report presents the hydrological flood routing along spillway channel of Asa dam. The storage constant K and a dimensionless weighting factor x were determined to be 0.92 and 0.2 respectively. Other constant Co , C1)C~ in Mukungum model are computed to be 0 . 2557 , 0.5534 and 0.1909 respectively. To perform the analysis , the spill way channel was divided into 15 reaches , each reach is 1Km long. The inflow into the reach at the beginning of the catachment area is the discharge from the spilling at Asa dam. The runoff from the basin areas of the reaches is computed and added to the main stream inflow to obtain the total inflow before routing was done to get the outflow. The outflow of the first reach serve as the inflow to the second reach and the process continue in that order. Also to depict the behaviour of the flowing water along the spillway channel , the outflow from each reach were plotted against the time (day) , thus established the form or shape of flood hydrographs at different points on the river at the downstream reach. This enable the prediction of the possibility of flood at downstream reach of the spillway channel. Based on this study, it was discovered that the construction of Asa dam across river Asa has changed the natural flood plains downstream to some extent because from the hydrograph it was observed that the effect of discharge from the dam was eminent at the upstream of the catchment area towards the city.