Mophometric Description of Gullies Developing on Coastal Plain Formations around Yewa South and Ipokia in Ogun State South-West Nigeria

This study attempts to document morphometric parameters of some selected gullies in Owode, Ajilete, Oke-Odan and Idiroko areas of Yewa South and Ipokia Local Government Area (L.G.A) of Ogun State, Nigeria. Gully morphometric parameters and their interrelationships were examined in the coastal plain formation area of Ogun State. A total of thirty-two (32) gullies were sampled and the measurements of vital gullies parameters were taken in the field. These included; length (distance from Gully head), Gully depth, bed-width, and shoulder-width and slope angle. Others were shoulder-width/bed-width ratio, shoulder-width/depth ratio and cross sectional area were derived as the product of depth and width.

Descriptive statistical analysis was used to define the general morphometric characteristics of the sampled gullies. The mean, standard deviation, variance, coefficient of variation were determined for further works. The Pearson’s product moment correlation was used to explore the difference between the mean values of the parameters. The analysis of the correlation matrix computed reveals that 65% of the correlation coefficient have relationships that are significant at 0.05 significance level while about 25% of the correlation coefficients have relationships that are not significant at all. Only 10% were found to be at the 0.01 level of significance.

The result of the analyses shows that these gullies are simple in plan with more or less direct courses. In all, some has broad U-shaped form while others have V-shaped form. In the study, most of the correlation coefficient was strongly correlated.

In conclusion, the differences observed in the study are believed to be attributable, to a large extent, to variation in soil texture, micro-climate, farm operation, vegetation cover and some other cultural practices in some of the places where these gullies are currently developing.