Journal of Emerging Trends in Engineering and Applied Sciences: Research Areas

Abstract:
This research aims at analyzing the variability of rainfall over Osogbo between 1960-2010 and the associated impact on the design of road projects within Osun State. While Mann Kendall analyses showed a positive trend in annual rainfall, ANOVA tests showed that the inter-annual variability of rainfall was not statistically significant. Rainfall variability of 15.6% was obtained for the study area while the mean annual Standardized Precipitation Index value of -0.1198 indicated that the inter-annual variation of rainfall was near normal. In terms of coefficient of variation, monthly rainfall was majorly seasonal and slightly moderately seasonal, with the highest and least coefficient of variations of 3.81 and 0.30 obtained in April and June respectively. The significance of this research was that it was able to reveal both increasing monthly rainfalls as well as increasing mean decadal annual rainfall in the study area. Furthermore, hydrologic modelling of runoff from Osogbo watersheds revealed that out of the seven culverts that were investigated, four were grossly inadequate which require upgrade while the remaining three culverts require regular desilting maintenance. The potential benefit of this research is that it has revealed that utilization of non-certified professionals by the State Government in the design and execution of road and drainage projects often leads to ill-conceived and poorly executed projects which does not justify the huge expenditure on such projects and further exposes the populace to more catastrophic flooding incidences. Engagement of certified engineering professionals in the design, construction and supervision of road and drainage projects guarantees best value for money. In addition, it is recommended that rainfall variability and climate change impacts must be factored in the design of drainage systems in order to increase their resilience to climate variability and the associated negative impacts such as flooding.

Keywords: climate change; culvert capacities; rainfall variability, hydrologic and hydraulic analyses

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