The Nigeria Hydrological Services Agency (NiHSA) has warned that Nigeria could experience more severe flooding over the next 12 weeks, with the worst impacts expected between August and September if urgent preventive measures are not taken.
Director-General and Chief Executive Officer of NiHSA, Umar Mohammed, said the devastating floods that recently affected Lagos and several other states were accurately predicted by the agency long before they occurred, but many of its warnings were ignored.
According to him, the current flooding marks only the beginning of the peak rainy season, stressing that conditions could deteriorate significantly in the coming months.
“What we are witnessing now is just the beginning. If nothing is done, flooding between July and September could become much worse, especially around August and September,” Mohammed warned.
NiHSA says floods were anticipated
Mohammed explained that NiHSA had used various scientific forecasting models to predict the flooding well before the rains intensified.
He said the agency consistently alerted relevant authorities about the looming danger but lamented that many of its forecasts were not taken seriously.
“We saw this coming. Our predictions were based on scientific analysis, but unfortunately many of the warnings were disregarded,” he said.
Lagos vulnerable to three different types of flooding
Speaking through the agency’s Head of Geographic Information System (GIS) and Remote Sensing, Emmanuel David Tuna, the NiHSA boss explained that Lagos faces unique flooding challenges because of its geographical location.
According to him, the state is vulnerable to three different forms of flooding simultaneously:
- Urban flooding caused by heavy rainfall overwhelming drainage systems.
- Riverine flooding from overflowing rivers.
- Coastal or tidal flooding resulting from the Atlantic Ocean and rising sea levels.
He noted that when these three types occur at the same time, flooding becomes significantly more destructive.
“Lagos is a coastal state with a massive urban population, major rivers and direct access to the Atlantic Ocean. These factors make it susceptible to multiple forms of flooding occurring simultaneously,” he explained.
Areas below sea level face greater risk
Mohammed disclosed that field surveys conducted by NiHSA revealed that some parts of Lagos sit at or even below sea level, making floodwater difficult to drain naturally.
Using geographical surveying equipment, officials found that several communities recorded elevations equal to or lower than sea level.
He explained that these low-lying areas are particularly vulnerable because floodwater cannot easily flow away, forcing water to remain stagnant for extended periods.
Blocked drainages worsening flooding
The agency also blamed poor drainage maintenance for worsening the flood situation.
According to Mohammed, inspections carried out after previous rainy seasons showed that many drainage channels across Lagos were already filled with stagnant water before the latest rains began.
He said several drains were heavily blocked by refuse, sand, plastics and silt, preventing floodwater from flowing freely.
Instead of channeling water away from residential areas, many drainage systems had effectively become stagnant ponds.
“Our observations showed that many drainages were already full before the rains intensified. Most were blocked and filled with debris, preventing water from flowing as they should,” he said.
Ogun River contributing to Lagos floods
Mohammed further explained that the overflowing Ogun River is adding to the flooding in Lagos.
He said tributaries branching from the river enter several parts of Lagos before eventually emptying into the Atlantic Ocean.
Because urban flooding had already overwhelmed drainage channels, the additional river water intensified flooding in many communities.
He noted that Lagos has been fortunate that tidal levels have remained relatively low, warning that a combination of high tides and heavy rainfall could have produced even more devastating consequences.
Flooding may last for days or weeks
The NiHSA chief warned that floodwaters could remain in affected areas for prolonged periods because the ground has already become saturated.
With little capacity to absorb additional rainfall, he said future downpours could cause floodwaters to linger for several days or even weeks.
“If more rainfall occurs before existing floodwater drains away, flooding could persist for one or two weeks in some locations,” he warned.
Drinking water contamination feared
Beyond flooding itself, Mohammed expressed concern over the safety of drinking water across affected communities.
He revealed that NiHSA had begun testing water quality before the flooding in anticipation that boreholes and other water sources could become contaminated once floodwaters spread.
According to him, the agency intends to compare water quality before and after flooding to identify contamination sources and assess risks to public health.
He added that a technical team is expected to visit Lagos to carry out post-flood water quality assessments.
Floods expected to continue until October
Mohammed said flooding is expected to continue intermittently throughout July, August and September before gradually reducing in October.
Although rainfall intensity may decline later in the year, he cautioned that flooding could still occur until around November.
“We expect an on-and-off pattern of flooding from July through September. The rains should begin to reduce in October, but flooding may still occur. We are likely to be much safer around November,” he said.
Lagos battered by prolonged rainfall
The warning comes after Lagos experienced more than 12 hours of torrential rainfall that submerged roads, homes and businesses across the state.
The downpour disrupted commercial activities, left motorists and commuters stranded, and forced many parents to keep their children away from school due to safety concerns.
Some of the worst-hit locations included the Lagos-Oshodi Expressway, Abeokuta Expressway near Oshodi, Lekki-Epe Expressway, Victoria Island, Agege, Ikeja, Oworonshoki, Gbagada, Funsho Williams Avenue, Iwaya in Yaba, Lagos Mainland and several coastal communities.
Videos circulating on social media showed residents appealing to the Lagos State Government for emergency assistance as floodwaters overwhelmed major roads and residential areas.
States urged to take flood warnings seriously
Mohammed also criticised what he described as poor cooperation from many state governments regarding annual flood forecasts.
He said NiHSA regularly provides predictions and early warning information before each rainy season, but many authorities fail to act until disasters occur.
According to him, stronger collaboration between federal and state authorities is essential to reduce the impact of flooding and protect lives and property during the remainder of the rainy season.
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