Communities in Lagos, Nigeria’s commercial capital, are reporting increasing incidents of floods and rising flood waters threatening their livelihoods and homes.
The estimated 22 million residents of the state are however oblivious of the reasons why: which is that Lagos is sinking.
This is in addition to the rising sea level that is blamed on global warming.
Land subsidence is a gradual settling or sudden sinking of the earth’s surface due to removal or displacement of subsurface earth materials.
This occurs when large amounts of groundwater have been withdrawn from certain types of rocks, such as fine-grained sediments.
Research by the University of Lagos and a thesis titled, ‘Evaluation of Induced Seismicity and Liquefaction Potential of Coastal Sands Using Integrated Method in Part of Lagos Wetlands’, point to an increased threat to many inhabitants of the state.
Prof Lukumon Adeoti, the principal investigator, Earth Signature Research Group, Department of Geosciences, in the University of Lagos stated that beyond the report, there are evidences that subsidence rate in many cities in Nigeria is increasing.
Their research also give credence to a 2022 published research by three US scientists, Peo-Chin Wu, Meng Wei and Steven DiHondt, all of the Graduate School of Oceanography, University of Rhode Island, USA. They measured the subsidence rater of 99 coastal cities around the world between 2015 and 2020.
Based on the published research of the US scientists, satellite data indicate that land is subsiding faster than sea level is rising in many coastal cities throughout the world and if subsidence continues at recent rates, these cities will be challenged by flooding much sooner than projected by the sea level rise models.
The report by the US scientists identified Lagos, an area of 5 × 10 km in the center of Lagos, as subsiding faster than 2 mm/yr.
The report recommended expanded monitoring and policy interventions to reduce subsidence rates and minimize the consequences. It also suggested that Permanent Global Navigation Satellite System (GNSS) stations can provide accurate measurements of coastal subsidence (mm/yr) but are limited in their spatial coverage and spatial resolution.
Interferometric Synthetic Aperture Radar (InSAR), it said, can provide much greater spatial resolution with reasonable accuracy (a few mm/yr).
The absence of GNSS data, according to the report, is even more pronounced for cities in many less-developed nations.
Although InSAR data indicate that a large portion of the coastal area of Lagos is subsiding more rapidly than sea level is rising, there is no openly accessible GNSS data for any apparently subsiding locations in this region.
It further said that in cities where openly accessible GNSS data are not available, true subsidence rates may be even higher than we have estimated from InSAR data, if the reference area is subsiding.
On his part, Prof Adeoti who is a professor of Applied Geophysics urged the media to help in the campaign to sensitise the public in protecting the earth surface from increased land subsidence which if the effect is not tackled, can portend danger and expose the community to danger.
He stated that before human activities, be it building, sourcing for water and others are carried out, it is of importance that Geotechnical Method should accompany Geophysical Method in testing the soil of earth sub-surface and determine the type of foundation to be deployed.
Adeoti noted that, as the chairman of building code in Lagos, he has worked with Lagos State Building Control Agency (LASBCA) that regulates development of buildings in the state.
He said, “The problem we are facing in Nigeria is that we don’t make use of the right method sometimes in finding the nature of the sub-surface before building. There is the Geophysical Method, Geotechnical Method and Multichannel Analysis of Surface Waves (MASW).
“Based on my own finding, one of my Phd students has worked on that and we have it documented. In fact we have more information than that. Information you are giving us is not up to what we have. The topics of research carried out by my Phd students is, ‘Evaluation of Induced Seismicity and Liquefaction Potential of Coastal Sands Using Integrated Method In Part Of Lagos Wetlands’.
“Most of those facing the challenge of land subsidence will be around Lekki. Anywhere you have a high water table will be problematic. Coastal cities like Warri, Calabar, Port Harcourt will be affected.
“We need advocacy and partners with the media. A lot of research is being done that has proffered solutions to issues but is the government or agencies concerned aware or ready to make use of it ? One doctor can kill one person at a time but engineers and we in the building environment can kill many people if we don’t do the right thing. By the time we have building collapses, many people are affected and there are loss of lives. Any sub-surface that is not properly defined and we build on it we will face problems and that is what we call subsidence”.
Prof Adeoti advocated for synergy between town and town – the academia and the practitioners should synergize in implementing best standards to prevent what will lead to disasters.
But according to Prof Ife Adewunmi, Civil Engineer and Professor of Water Resources and Environmental Engineering, not only Lagos is sinking in Nigeria, as parts of other coastal cities in Bayelsa State and Ayetoro in Ondo State are also sinking.
Prof Adewunmi who spoke to LEADERSHIP in a phone interview noted that the report was true and efforts must be made by everyone to reduce environmental pollution caused by anthropogenic activities.
Prof Adewunmi who is now based at Redeemers’ University of Nigeria said, “The focus on Lagos. It is not only Lagos that is sinking. Ayetoro in Ondo State is also affected by human activities. Lagos is only the focus as the commercial capital of Nigeria.
“They didn’t look at Bayelsa, Rivers State where all these soils come from. I worked in Bayelsa for eight years and day and night, they flare gas. Out of all these gases flared is what contributes to global warming. Global warming leads to subsidence that you are talking about. And this has affected the whole world.”
“Looking at the report; it’s not just the things that were itemized. Who are those contributing to the impact? We don’t have many industries here compared to developed countries that are involved in greenhouse gas emissions that reduce the ozone layer causing global warming. The Polar areas are affected and when the ice melts, it increases the water level.
“In Nigeria, incineration, burning of refuse is another contributory factor and we are wasting money instead of recycling. We don’t do proper incineration in this country. We still do open burning of refuse which is also a harmful practice that we do here and it should be curbed. Anthropogenic activities are contributing to pollution. All these should be stopped with proper sensitization.
“In Lagos, we have the highest number of cars and traffic in Nigeria, and fumes are released that heat up the environment and this has health implications. So, we need to manage this and have the right policy in place that will reduce carbon fuel,” Adewunmi added.
He advocated good governance which will make the government and agencies make good policies, just as he said the private sector should be allowed to get into management as the government cannot do it alone.
Prof Adewunmi noted that polluters, who are the developed countries and foreign organizations, must pay as they are the major culprits of pollution.
“The federal and state governments should provide an enabling environment for the private sector to give solutions to these issues. I gave a report in Redeemers’ University during World Environmental Day and I focused on plastic pollution which was the theme for the year.
“I spoke on how to convert plastic products to building materials as this burning and burning of plastic materials is releasing toxic substances into the atmosphere. We can derive energy from some of our wastes – not just plastic wastes but organic wastes. We don;t need to incinerate.
“So efforts should be made to promote conversion of our wastes to energy. We have some inventors in this country that have done it and they should be encouraged,” he further said.
Some Lagos residents who spoke with LEADERSHIP Weekend in separate interviews lamented the effects of the increased flooding as a result of rainfall in different parts of the state, saying some of the buildings in their areas are being submerged.
A resident of Lekki areas of the state, who identified himself as Chidi Afam, lamented the impact of heavy rainfall and the attendant floods that affected several parts of Nigeria’s commercial nerve centre.
“In my area of the state, the situation almost turned tragic as many people were trapped when a building started sinking there.
“It took a combination of emergency workers to get them to safety. That is why I believe that Lagos may be sinking. These influential residents must reach out to the state government for a solution to the perennial problem.’’
Another resident, Mrs Vivian Adeyanju, noted: “The early morning rainfall on Thursday, which lasted about six hours, caused floods in many Lagos communities and forced motorists and road users to wade through gridlock and flooded roads to get to their respective destinations and handle their businesses that tells you something is wrong.
“They will say its flash flood. This flood remains on the roads for a very long time, even till the next day. People find it difficult to pass through some roads due to potholes covered by the flood.”
She said such roads in Lagos include the Marina road on Lagos Island, the Pen Cinema area of Agege, the Aboru-Iyana-Ipaja-Ile-Epo area, streets of Dolphin Estate in highbrow Ikoyi area, amongst other areas.
“Another problem in Lagos is that of blocked drainage and gutters. This has degenerated and led to chaos everywhere in the state”, she concluded.
Meanwhile, efforts by this paper to get a reaction from the Lagos State government did not turn out, as the commissioner for Information and those for the ministries directly involved in the management of the issue at stake are yet to be appointed.
