Heavy rainfall in Lagos often leads to slow movement of traffic. Pools of water accumulate at various locations on the highways and wherever these pools attain a critical depth, they become a barrier as motorists seek the shallowest parts for their safe passage.
Long lines of motorists build up behind these deep pools and in places where these lines meet, gridlock develops across the metropolis. Sometimes, some vehicles stall on moving through the pools of water and these vehicles become an obstruction to the movement of other vehicles.
Traffic delays, gridlocks and slow movement cause socio-economic losses which include additional fuel costs for vehicles that are delayed, wasted man-hours for persons delayed and increased charges for transportation of persons and goods.
The modern highway system in Lagos has a median that is raised above the road surface with kerbs and which median separates the main carriageways in places like Ikorodu Road, Funsho Williams Avenue, Mobolaji Bank-Anthony Way and Agege Motor Road.
There is also the alternative high and narrow reinforced concrete barrier separating the main carriageways on the Apapa to Oshodi to Oworonshoki Expressway. Service lanes on the highway system are separated from the main carriageways using kerbed traffic islands.
When it rains and water accumulates on the road surface, we should find out where the water is coming from and where it should go because highways are normally designed to be free from water on the road surface. As our first example, in the stretch of Ikorodu Road between Obanikoro Busstop and Palmgrove Busstop, rainwater comes from the drainage channels on Association Avenue and from the Palmgrove area to the west of Ikorodu Road. The water accumulates at the lowest point on the southbound service lanes, rises above the kerbs and flows unto the southbound main carriageway. The kerbs forming the median retain the water in the southbound carriageway.
If we examine the main carriage ways relative to the surrounding area, we find that the northbound service lanes and the adjacent Somolu area are about 2 metres lower than the main carriageways. Water from Association Avenue and the Palmgrove area should naturally flow across Ikorodu Road into Somolu.
The median should be reduced in level to the level of the road surface, the existing kerbs removed at the median and on the Somolu side of the northbound carriageway and the ground on the Somolu side shaped to allow the water to flow freely into the northbound service lanes. The existing kerbs should be replaced with kerbs having two legs with a crossbeam at the top such that large volumes of water can flow below the crossbeam.
Fortunately, the Lagos State Government, LASG, is currently carrying out a road project which includes the construction of drainage channels on both sides of the short link road joining the northbound service lanes to Shipeolu Street. It would be possible to take away water flowing into the northbound service lanes through the new drainage channels.
The situation described above also occurs between Palmgrove Busstop and Onipanu Busstop where the water is flowing from the Mushin side to the Somolu side. Another important location is the southbound service lanes between the junction of Ikorodu Road/Mobolaji Bank Anthony Way at Maryland and Onigbongbo Water accumulation in this area can be drained through the tunnel below the Maryland interchange.
There was an exceptional rainfall event in Lagos on 10 July 2011 when there was about 260mm rainfall within 18 hours. The day after and 15 hours after the rains had stopped, cars and Volkswagen passenger buses on Funsho Williams Avenue approaching Alaka Estate from Costain had to switch off their engines.
The vehicles had to be pushed through the floodwaters and past the canal at Alaka as such vehicles stalled when there were attempts to drive them through the flood waters. The canal at Alaka is part of the LASG System 4 drainage and this rainfall event highlighted the limitations of the drainage system that relies entirely on gravity flow.
The LASG is currently carrying out construction work on this System 4 drainage and it appears the LASG is reluctant to replace the culvert at Apapa Road where System 4 flows towards the National Theatre Complex. A bigger culvert at this location would provide greater relief to the areas served by System 4.
If one takes the exit ramp to the right from Eko Bridge into the Marina after heavy rainfall, one would run into a pool of water on the Marina. At this location, the road is adjacent to the Lagoon and ordinarily water should be able to flow from the land into the Lagoon. However, the earth on the Marina has been retained by sheet piles which have a reinforced concrete beam as cap.
A sump should be constructed from where the water would be pumped over the capping beam into the lagoon.
I hope the Federal Ministry of Works and the LASG will rise to the challenge of keeping traffic moving in Lagos after heavy rainfall. There are so many other locations in the Lagos area that are not mentioned in this piece.
Dr Akintola Omigbodun Click to signup for FREE news updates, latest information and hottest gists everyday
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pls govt should do somting to save d life of our people for raning season
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