Bad Drainage and Its Effects on Road Pavement Conditions in Nigeria

This paper discusses the various effects of bad drainage on road pavement conditions in Nigeria. A lot of Nigerian roads across the country have inadequate drainage systems and deterioration often begins with the origin of cracks or pot holes on the road pavements either at the edges or along the drive way. This investigation looks into major Nigerian highways like the Lagos-Badagry expressway and municipal roads like the Siluko-Ring Road, Benin, Edo State. Having identified these two roads as case studies, on-site assessment of both roads were scheduled and visited with a view of investigating the possible causes of drainage deterioration and its subsequent effects on road pavement conditions. With the aid of a camera, pictures of the various degrees of drainage deterioration and its consequent effects on road pavement conditions were taken and labeled figures 1 to 11. Based on this investigation, it was discovered that adequate and proper maintenance cultures of drainages needs to be revived and strictly adhered to while carrying out enlightenment campaigns to residents where these drainage channels are situated towards creating an awareness that they need to keep these drainages clean and not use them as refuse dump sites. As a result of this investigation, it was discovered that road pavements needs to be designed and constructed to possess proper cross falls in such a way that they effectively drain off rain water from their surfaces into designated drainages. As such, effective drainage of the road pavement may be achieved by having a road cross fall of 4 - 6 % i.e. 145 – 195 mm fall from centre line on a 2-way cross fall pavement design. Even though many Nigerian roads are of poor conditions due to different reasons, Poor drainage constitutes a majority of those reasons. Keywords: Run-off, Surface Drainage, Sub surface Drainage, Blockage of drains, Moisture content, Water table.