Morphometric Analysis of Apena and Itori Rivers in Abeokuta, Ogun State, Nigeria

Abstract

This study was carried out to estimates the watershed characteristics for peak discharge of each watershed drained by Rivers Itori and  Apena which are tributaries to Ogun River in Abeokuta South East. The method adopted for this research was to use the map of Abeokuta  South East (SHEET 260 S.E) to estimate the number of tributaries that can be found within rivers Itori and Apena in such way  that the area calculated from the square method of the discharge basin in km² using the stream order and mean length of all first order  streams can be determined. Also, to examine the estimation of watershed characteristics using the two specified rivers to know the stream density, drainage density, average catchment slope, form factors and compactness coefficient, elongation ratio, circulatory ratio,  the concentration time for the basin and the time from peak to recession. The experimental results obtained showed that the two rivers  are dendritic in pattern with a bifurcation ratio of 1.733 and 1.853 for rivers Itori and Apena respectively. The two drainage areas fall into  the fourth order. Itori river from 1.1- 10.2 in its first order, 1.2-4.8 in second order, 0.6-3.8 in the third order and 0.8-5.2 in the fourth order  while Apena river, the first order lies between 0.7-6.7, 1.1-7.1 for second order, 0.4 – 4.5 for third order and 0.4 – 5.8 in the fourth order  respectively. This means that the range between two rivers shows that river Itori has higher range in first order than Apena but Apena  has higher range in the second order. Moreover, River Apena has higher ranges than river Itori and river Itori has more ranges than  Apena River. The result of the peak discharge for the two rivers indicated that river Apena was estimated at 83.667m³⁄s and that of River  Itori was at 79.997m³⁄s respectively and this means that River Apena has the higher discharge compared to that of River Itori which has  the lowest discharge and the higher discharge has more benefit in water resources planning and development for future purposes.