EVALUATION OF DRAINAGE CONDITION AS A CAUSE OF PAVEMENT DETERIORATION ON SELECTED ROADS IN ILORIN, NIGERIA

Abstract

Poor drainage is an important factor associated with pavement deterioration in urban road networks. This study evaluated drainage condition and its relationship with pavement deterioration along five selected road corridors in Ilorin, Kwara State, Nigeria. Field assessment covered drainage geometry, slope, blockage, structural condition and flow behaviour, together with pavement distress, chainage and hydraulic performance. Drainage Condition Index (DCI) and Pavement Deterioration Index (PDI) were used for comparative assessment, while estimated runoff was compared with drainage conveyance capacity. DCI ranged from 25 to 78 and PDI from 25 to 85. Akerebiata–Sobi recorded the poorest drainage condition (DCI = 25), highest deterioration (PDI = 85) and about 60% affected pavement area. Fate Roundabout–Sango recorded the best drainage condition (DCI = 78), lowest deterioration (PDI = 25) and about 15% affected area. Potholes and cracking accounted for 25% and 20% of observed distress types, respectively, while poor maintenance and siltation/sediment deposition represented 25% and 20% of identified drainage deficiencies. Hydraulic comparison showed inadequate capacity on Sango–Kwara Polytechnic Gate, Royal Valley–Akerebiata, Akerebiata–Sobi and Maraba–Fate Roundabout roads; Fate Roundabout–Sango was adequate. The findings indicate an association between poorer drainage and greater pavement deterioration, but drainage is not the sole cause of failure. Integrated drainage rehabilitation, routine desilting, hydraulic upgrading, culvert/outfall maintenance and chainage-based monitoring are recommended.