Dr. Akintola Omigbodun

There are two flood types observed in Lagos, the first is when there is rainfall over an extended period of time.

*Community sacked by flood in Bauchi. INSET: Motorcycles and tricycles wading through a flooded road

Water flows towards lower ground and with the build up of water volumes, water may enter the premises of persons along its path. Pools of water also accumulate and wherever these pools reach a critical depth they become a barrier to the movement of vehicles.

The second flood type is from the River Ogun system whenever there are huge water releases from a dam on the River Ogun System. The resulting flood path affects communities along the River Ogun in Ogun State and Lagos State. The flood path is over 27km long and up to 4km wide in places.

We shall consider the risks associated with first flood type. Essentially, the probability of an event occurring multiplied by the consequence of the event equals the risk that can be assigned to that event, i.e. Probability X Consequence = Risk. Risk management therefore sets out to minimize both the probability and the consequence.

There is increasing recognition that floods are avoidable in Lagos State. For example, the Lagos State Government, LASG, through its agency the Lagos Metropolitan Area Transport Authority, LAMATA, is building a deep buried drainage channel along ACME Road, Ogba to take flood waters from the Agege/Ogba area into the gorge below Lateef Jakande Road and Omole Phase I Estate.

Another example is the Eko Atlantic City which is an ongoing sand-filled addition of about 900 hectares to the existing land mass of Victoria Island at Bar Beach.

The developers of this land mass expect to provide 18m wide canals running west to east across the land mass to remove storm waters and keep the land mass dry.

There was an exceptional rainfall event in the Lagos area on 10 July 2011 when there was about 260mm of rainfall in an 18-hour period. How prepared are we for a repeat rainfall event? The LASG has a system of drainage canals that discharge into the Lagos Lagoon.

These canals should take flood water below our roads and the bridges across the canals. However, our roads near the canals were covered with water after the rains of 10 July 2011.

The day after and 15 hours after the rains had stopped, cars and Volkswagen buses on Funsho Williams Avenue approaching Alaka Estate from Costain had to switch off their engines.

The vehicles had to be pushed through the flood waters and past the canal at Alaka as such vehicles stalled when there were attempts to drive them through the flood waters. Should we make our drainage canals bigger, or if this is not feasible, should we have areas where flood waters are temporarily stored and pumped out when the floods subside?

Flood waters on our highways create traffic delays, gridlocks and generally 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.

Ikorodu Road is the main arterial route into Lagos and for at least 15 days each year, traffic flow is severely restricted by flood waters at certain locations on the south bound lanes between Maryland and Onipanu.

The water that accumulates on the road comes from areas to the west, Ilupeju, Palmgrove and Mushin. What is astonishing is that areas to the east of the road, Somolu and Obanikoro are at a lower level than Ikorodu Road and water should readily pass through.

The obstructions to water flow should be removed and the next [email protected] should take this matter up with the federal authorities.

Next week, we continue with the second flood type.