Investigation Into The Causes Of Blocked Drainage, Canal And Culvert In Ilorin-west Local Government Area
[A CASE STUDIES OF AGBO-OBA, OJA-TUNTUN AND SAWMILL]

Appropriateness of the drainage system                         The engineers’ indicated that the drainage system provided for some area in Ilorin-west local government road was inadequate and therefore inappropriate. The magnitude of the water from the surrounding the area in which the road is situated was overlooked during design. They also indicated that studies that were carried out before designing the road were not sufficient to satisfactorily ascertain the amount of water that would cross the road at a point in time and therefore the design lacked capacity to adequately drain the runoffs which hindered debris causing the drainage, canal and culvert to block during the storm.    However, poor workmanship (seen through poorly worked stone pitching, embankment, non channelized drainage and gabions) by the contractor during construction and poor maintenance also contributed to the drainage problems in Ilorin west local government drainage, canal and culvert system.
State of the drainage facilities
The engineers were in consensus that the drainage facilities were in a poor state and therefore needed action with immediate effect. The works department in charge of Ilorin west local government road reported that the authority carried out inspection of the road and its drainage facilities yearly but that emergency inspection was carried out when a problem occurred to ascertain its extent and to carry out required action.
Bitto consultants have carried out a study on the effect of blocked drainage system on the surrounding environment. They both agreed that though there was need for the removal of debris, redesigning and reconstruction of the drainage system, there was also need to carry out maintenance on the existing drainage facilities to increase their efficiency and effectiveness. They reported that redesigns and reconstruction have not been implemented, due to lack of resources and commitment by the government. Farming practices in the area according to the engineers cannot be blamed for the erosion of the road and drainage features but instead the small capacity of the drainage system provided.
The damage on the road was severe especially in May 2012 when some parts of the road were washed away. This showed the dangers that motorist were exposed to and therefore necessitated a move to correct the drainage system. Combined system was specifically cited as the appropriate drainage system, however; separate system, open channel system and subsurface drainage system were also recommended by the engineers for the different parts of the road. The engineers responded that it is not with enough capacity to satisfactorily drain away water during a heavy downpour.

4.2.2          Results from questionnaire type two: Response from the respondents and road users
    The analysis of result collected from the questionnaire in Agbo-Oba, Oja-Tuntun and Sawmill.