Nigeria has a history of collapsed dams

Concerned residents of Maiduguri, Borno State, have expressed worry about the recent flooding in the state and described it as devastating.

They note that the occurrence is the fallout of a system failure in public infrastructure, including dams across the country.

They also observe that, due to system failures in the Alau dam in the Alau community of Konduga Local Government Area of Borno, the dam’s collapse has caused massive displacement and destruction in the city.

They express regret that many residents have been displaced from their homes and means of livelihood while a lot of property, including farm produce, has washed away.

Observers note that the flooding has affected many sectors of the economy and environmental lifestyles, including the zoological garden, where animals, including wild ones, were thrown into the city in the flood.

Research has shown that the Alau dam, located 20 kilometres outside Maiduguri, was constructed in 1986 during the military regime of General Ibrahim Babangida for irrigation purposes, flood control, and water supply. It had previously collapsed.

The first collapse occurred in September 1994, displacing more than 4,000 people and destroying much property.

The case of the Alau dam is not isolated; in the early 1990s, the Bunkure dam in Kano also collapsed and destroyed farm produce on its bank.

More than 200 dams, holding more than 31 billion cubic litres of water, are spread across the country, largely for irrigation, power generation, water supply, flood control and fisheries and they ought to be effectively maintained to check system failure, analysts observe.

However, it is a regret that Alau dam, which has the capacity to store 112 million cubic litres of water, failed in spite of the N400 million budgeted for its rehabilitation in the last four years, an unconfirmed source notes.

The dam got N285 million in 2020, N80 million in 2021, N37.5 million in 2023, and N30 million in 2024.

The Minister of Water Resources, Joseph Utsev, however, justifies why the dam emptied its massive water content to the street, saying “the dam did not collapse but struggled to handle the excess water from nearby tributaries causing overflow into surrounding areas.

“Government officials confirmed that climate change has intensified rainfall leading to excess water that many dams are struggling to manage, and as temperature rises, we expect increased rainfall, leading to higher water volumes in our rivers and channels.”

The minister also announced measures to prevent a recurrence of the incident, noting that “proactive measures are crucial to preventing future escalations; long term solutions are underway with budgetary allocation in 2024/ 2025 specifically targeting dams rehabilitation.”

Raising more concerns about dam collapse, Simon Joshua, a water resources engineer, listed problems of dams in the country to include inadequate spillway flood capacities, loss of reservoir capacity due to sediment accumulation, and seepage.

“There is also absence of downstream release facilities for either irrigation or water supply, lack of hydrological information and monitoring, absence of reservoir operation rules and inadequate instrumentation,’’ he said.

Another engineer, Lawrance Ekpo, however, said that dam failure could be naturally triggered or caused by the failure of the engineering sub-system that might cause instability of the dam or its operation.

“Dam failure in Nigeria is caused by a combination of many factors, including flood events, inadequate spillways, resulting in substantial or large consequences,’’ he said.

Apart from the Alau dam, available documents and records show that other dams, such as the Bagauda dam in Kano, failed due to similar factors that triggered the collapse of the Alau dam.

The Bagauda dam was constructed and designed as a zoned earth-filled dam in 1969 and 1970 by direct labour.

The dam was constructed mainly for the Kadawa irrigation site and to provide water to the Kano metropolis and surrounding villages.

The dam failed on 16 August 1988 after two days of intense rainfall, which added about 10 cubic litres of water to the already-full reservoir. It overtopped the embankment and collapsed.

Similarly, Cham Dam in Gombe failed on 1 September 1998, after being overtopped by floods caused by 13 hours of continuous rainfall. The incident involved not only the embankment’s overflow but also the overflow without a gate spillway.

Goronyo Dam in Sokoto failed twice; the first was on 15 August 1984 and second in 2018. It was built in 1983 by the Shehu Shagari administration.

The Bagoma dam incident in Kaduna State was no different. It failed on 10 September 1994 due to piping through its foundation. The treatment and power houses were flooded, so also the access roads to nearby villages.

The same incident was recorded in Cross Rivers when the Obudu dam failed on 3 October 2003, when 16 hours of excessive rain overfilled its reservoir, and with the spillover structurally inadequate to accommodate the volume of water, the channel was eroded completely.

Waya Dam in Bauchi State also failed on 15 May 1997. Waya dam is a homogenous earth dam with reservoir capacity of 30 million cubic litres of water.

The major cause of the failure was poor construction from the onset. The effect was the erosion of the inadequate spillway channel and flooding of the dam embankment.

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The dam spillway was designed to discharge 150 cubic metres, but the flood that undermined the dam was recorded at 250 cubic metres.

It is clear that the immediate and remote causes of dam failure in Nigeria are almost the same; as such maintenance must be given top priority.

The government also needs to redesign, maintain, and transform multi-purpose dams into more viable facilities, engage in massive advocacy, and raise water users’ and communities’ public awareness of risks and emergency actions to be adopted in case of flooding or any disaster.

Since dams can fail due to overtopping caused by floods, acts of sabotage, or structural failure of materials used in dam construction, dam experts suggest that dam operators should perform routine maintenance.

They also suggest that staff should undergo regular training to ensure they are fully prepared for a possible failure event.

(NANFeatures)