• Lagos urges developers to avoid wetlands, illegal structures

In the face of mounting apprehension among residents over the consequences of flooding in several cities, especially Lagos, town planners, architects and state officials have weighed in to examine the effect on properties and proffer solutions to forestall the most serious natural hazard faced by Nigerians.

According to the World Meteorological Organisation (WMO), floods are without doubt the most devastating natural disasters striking numerous regions in the world each year. Since the last decade, the trend in flood damages has been growing exponentially.

This is a consequence of the increasing frequency of heavy rain, changes in upstream land-use and a continuously increasing concentration of population and assets in flood prone areas. In general, less developed countries such as Nigeria are the most vulnerable to floods, causing damages that significantly affect national Gross Domestic Product (GDP).

The 2022 Seasonal Climate Prediction (SCP) by the Nigeria Meteorological Agency (NIMET) seem to fall short of what is happening in Lagos presently, with the increase in frequency and severity of flood events in the city, as several hours of rainfall last week left many homeless and caused devastation in several parts of the state, which also highlighted the question of the impact of flooding on the value of property.

One factor that has contributed to the rise in flooding, experts said is the increase in impermeable surfaces with rapid urbanisation. Higher impermeable cover leads to increased surface runoff, a driver of flooding. More and more houses being built will only increase the percentage of impermeable cover, which will continue to exacerbate the issue.

The land can no longer absorb rainfall if it is built over; instead, water runs off impermeable surfaces into drains, which can become overwhelmed and into rivers, increasing the flood risk in multiple areas. It is unlikely that old drainage systems will be able to cope with the increased burden, and thus sewer and surface water flooding will be more prevalent.

The National President, Nigerian Institute of Town Planners (NITP), Olutoyin Ayinde, blamed the recurring flood on the absence of a National Physical Development Plan (NPDP), which will establish the framework for national physical infrastructure. “NPDP would strategically identify natural drainage facilities – the rivers, streams, brooks and rivulets, which themselves are natural resources meant to be protected, while they also serve as basins and drainage facilities to which artificial drainage infrastructure (the gutters and canals) eventually empty.

“The process of preparing the National Development Plan serves as basis for having a national drainage system plan. It would show how our water resources, natural surface drainage, are interconnected and possibly enhanced to boost national economy. Physical development of structures shouldn’t take place if there’s no plan that has considered the drainage implications of the development,” he said.

Ayinde said town planners are pained and concerned about the resilience of Lagos to future floods. “However, resilience to floods is not about town planners. It is about the capacity of a system, a people, to recognise the need for preparing the requisite plans and readiness to fund the preparation,” he said.

He called for public awareness on bad habits that make the environment vulnerable. “There’s also the need for institutional structures to ensure monitoring and enforce regulations to curb activities that negatively impact the environment, he said.”

According to him, there are too many informal players and when government doesn’t step in to take leadership, all sorts of calamity will occur. “All kinds of estates are springing up without consideration for the preparation of building plans. They’re developing on land meant for agriculture, conservation and government is doing very little control. It’s happening everywhere and it’s a time bomb ticking and waiting to explode into more floods and disasters.

“We should employ world’s best practices in developing our environment so that our settlements will not only be functional, but also sustainable,” Ayinde added.

In his submission, President, Nigerian Institute of Architects (NIA), Enyi Ben-Eboh, said the issue goes beyond a change in planning policies as flooding is a natural phenomenon, which we have little control, especially in the advent of climate change and negative social behaviours.

He said: “We can reduce to the barest minimum, its adverse effect on the human population by putting in place early warning signals and installing systems that predict and mitigate these serious adverse consequences once they occur.

“It is common knowledge that when we fail to plan, we invariably plan to fail. By implication, government must begin to take seriously the issue of masterplans and layout designs that take into cognisance the topography and natural drainage routes for water, with a view to designing relevant schemes to address runoff from storm water, taking into consideration the worst case scenario of rainwater volumes and ensuring that people do not build in areas prone to flooding. This is in addition to strict enforcement of these master plans to ensure that people do not build on natural drainage routes.”

Ben-Eboh stressed that architects as major stakeholders in the urban design and sustainable cities have a major role to play in flood prevention and control through a number of design considerations. “Principal amongst which is to ensure that there should be proper landscaping with minimal hard surfaces that would ensure that surface runoff is reduced with the introduction of green spaces that can facilitate the absorption of water into the sub-soil and ensuring that proper drainages are provided within and around the site in addition to ensuring that all planning regulations and necessary approvals are obtained before construction can commence.”

He also emphasised the need to raise awareness amongst communities of the need to practice safe building development practices by strictly adhering to approved provisions in the layout designs and that they obtain approvals from the necessary physical planning authorities.

“They should also imbibe the habit of regular de-silting of drains and avoid the negative habit of disposing of their refuse into drainage channels. That way, flood water can easily and quickly be discharged to the required secondary drainage channels amongst other preventive measures.

Ben-Eboh observed that most parts of Lagos have extremely low water table. “Consequently, there is a very low percentage of surface water absorption during the seasonal high rainwater periods. It is therefore advisable that the finished ground level within the building and the ground level around the building and within the property boundaries are raised well above the road level to allow the site drain into the street drains which must be provided on both sides of the road as a matter of necessity.

“Secondly, enough provision should be made for green spaces within the property boundaries to ensure that excess surface water can percolate into the ground and reduce runoff.

“Thirdly, provision should be made for the collection of rainwater coming from the roof to be channeled into proper drainages that empty into street gutters or a central storm water drainage system as the case may be.

Lastly, municipal authorities and estate owners must ensure that roads and drainages are provided in new and emerging estates and neighbourhoods before actual construction of buildings commence, while ensuring that drainage channels are not built over by greedy and unscrupulous individuals.

The Vice Chairman, Nigerian Institution Estate Surveyors and Valuers (NIESV) Lagos State Branch, Mr. Gbenga Ismail, called for the integration of the local climate change policy with town planning policy. He also expressed the need for a drainage plan that is in tune with current master plan.

Ismail was skeptical about flooding affecting property values. “I don’t know if flooding has negatively affected values in Lekki, Parkview, Victoria Island and Opebi in Lagos, which still retain very high value because demand for these locations remain high, while the low demand areas have definitely been affected,” he said.

The Lagos State Commissioner for Environment and Water Resources, Mr. Tunji Bello, traced the problem to flash flooding. “Most part of the Southern part of Lagos are already below the sea level and when it rains persistently for a minimum of four hours, you will have flash flood.

“Coastal cities are more vulnerable to this due to high water table. However, few hours after the rain, the water will disappear because all through the persistent rain, the ocean will rise, lagoon that empties the water from our drainage canal will also not be able to discharge into the ocean and you then have back flow into the canal and into the streets.”

According to him, the government deserves more commendation for its persistent response to the issue of flooding in the state through several drainage constructions and clearings in the past few years, adding, “we are committed to educating and enlightening our people more on flooding in Lagos despite the past efforts.

He urged Lagosians to stop illegal construction or building houses and shanties, as well as dumping of refuse on the canals because “we are all punished for it when it starts to rain. It is therefore the responsibility of all of us to police ourselves and exercise caution.

Bello said: “There are areas outside the city, which drainges have not covered but which are regarded as wetlands which people have gone to settle such as in Alimosho, Ikorodu, Ojo, Ibeju Lekki among others. Such areas are flood prone and we advise people to avoid them.”