The news about climate change all over the world and the devastating flood in Nigeria, especially in Lokoja and other parts of Kogi State has created numerous concerns and raised many questions in the minds of people, Students inclusive.
We are aware that the situation has generated debates and lots of academic discourse elicited by the trouble Nigerian people are currently facing as a consequence of the flood.
Ultimatums have been issued, and many directives are given to address them. Are we going to get it right this time and bring to a complete halt the damage the flooding constantly brings to the people of Nigeria?
In 2012, exactly 10 years ago, Nigeria witnessed a traumatizing situation that left many families depleted, with many deaths resulting from the River Niger and Benue overflowing. The effects of that flood on the lives of many people, infrastructure, roads, farms, and businesses are still being nursed by many.
They have wondered why the flood has continued to ravage the nation unabated almost every year with consequences too disturbing for most Nigerians, especially those within the riverine areas.
Again, it is no news that economic activities were grounded for many weeks as the usually very busy roads linking the North from most Southern states were overflooded when the Rivers Niger and Benue opened their bowels on the city, Lokoja, with a driving distance of 201 kilometers to the Federal Capital Territory.
In this interview with a Hydro-geologist, the Public Affairs Unit of the Vice-Chancellor’s Office, Federal University Lokoja, tried to make sense of the consequences of the flooding and the dead weight it left on the Muritala Mohammed Bridge, (Jamata bridge) for weeks.
We spoke with Professor Abdullahi Emmanuel Bala, Deputy Vice-Chancellor, Administration, Federal University Lokoja who was the former Dean of the Faculty of Science, and the pioneer Head of the Department of Geology.
Here is what he said, it is very revealing, savour it.
Professor Bala Speaks:
We are very much aware that the world is experiencing climate change. Climate change is not an entirely new phenomenon, as it has occurred several times in Earth's history. Over time, the change had been due primarily to minimal variations in the Earth’s orbit, which alter the amount of solar energy reaching the Earth. Temperature changes are the causative agents of climate change.
The world in post-industrial revolution times is witnessing increased release or production of carbon dioxide, methane, nitrous oxide, and water vapor, all of which are greenhouse gases whose presence over the earth’s surface restricts the escape of radiations from the surface into the atmosphere, thus keeping the surface warm. This has manifested in the global rise in temperature, warming of the ocean surface, decrease in snow cover in the Northern Hemisphere, glacial retreat, increased ocean acidification, and the rise in sea level. These greenhouse gases are of anthropogenic origin.
Climate change is linked to the environmental conditions of killer heat waves, wildfires, aridity, desertification, erosion, and flooding, all of which are closely interconnected, or are responsible for the temporal and spatial fluctuations in the amounts and trends of rainfall.
The climatic conditions of Nigeria have two seasons annually, the dry, and the wet season with the latter dominated by rainfalls, and it is in this season that flooding is experienced. Therefore, another flooding should be expected next year during the rainy season and its magnitude will be known when the time comes. Flooding is the accumulation of a large amount of water in an area that is usually dry, or of a river, containing more water in it than normal as a result of rainfall. Whereas flooding is triggered in the hinterland along river channels, and in wetlands when the groundwater table in such areas rises substantially above the ground surface as a result of rainfall, it is boosted by the rise in ocean water level in the coastal areas.
Like in the year 2012, flooding ravaged many parts of Nigeria in 2022. Many people believe that it was caused by the release of the reservoir water from the Lagdo dam in Cameroons. However, the Executive Director of NIHSA has stated clearly that the flooding resulted principally from rainfalls within the country, a fact that is strongly supported by the Executive Director of the NWRI who has stated categorically even in 2012 that large volumes of floodwaters are generated by the major tributaries of River Benue within Nigeria.
The discharge of a river can be controlled by damming it. A dam is a peculiar linear engineering structure that is built inside a valley across the river channel to impound water for economic uses and to regulate the flow across it downstream. There are various types. Dams can be built on small, medium, and large rivers. Irrespective of the purpose(s) for which a dam is built, its design and construction must follow certain specifications and its life is preserved by certain operational practices when the water has been impounded by it. One of such is the release of the water from the reservoir behind it to relieve the pressure mounted by the water so that it does not fail and at the same time to control flooding behind the dam, and another is the de-silting of the reservoir from time to time for the reservoir to accommodate the amount of water based on the designed capacity and delay its rise above zero of gauge.
The release of water from the Lagdo dam was done essentially for the first reason given above. If only the Nigerian government had built another dam downstream of the Lagdo (the Dasin Hausa dam) as contemplated, the magnitudes of the flooding both in 2012 and in 2022 would have been less in Nigeria than were experienced. In Nigeria, the growth in population and occupational practices have made the people build and settle, farm, and rear livestock on the river flood plains. These activities have caused the removal of vegetation in the first instance, then trampling by cattle consolidates fine-grained soils and promotes rapid runoff as do built environments, or loosens coarse-grained soils rendering them vulnerable to erosion as does crop farming. During the rains, once the rainfall intensity exceeds the infiltration capacity of the soil, runoff commences and moves with it the loosed soil grains down the slope towards the river channels.
In addition, stream erosion occurs along river channels, and it becomes significant during times of flood when more and faster moving water is available to transport the sediment load. These sediments are eventually laid down in the river channels and on the flood plains when the rate of flow slows down. This will result in the river channel becoming shallow and therefore unable to accommodate large volumes of water in times of flooding.
One proof of the river channels becoming shallow was the excessive flooding of Lokoja township and downstream on the River Niger this year. This was confirmed by the submergence of the Murtala Mohammed bridge, which is about 20 nautical miles north of the confluence of the Rivers Niger and Benue. The bridge that was designed and constructed to operate under a projected live weight and to operate under the conditions of free air stood submerged and overloaded with motor vehicles and their contents over its entire length for weeks. The submergence could not have resulted from the release of water from the Lagdo dam lake alone, especially as the release from the Kainji, Jebba, or Shiroro dams was not reported to be of any consequence.
Have we seen the last of the devastating flooding? The answer is NO unless the following issues are addressed as quickly as possible.
i. Dredging of the River Niger Channel. As far back as 2008, it was observed that the river channel was becoming shallow due to the deposition of sediments within it. It was the reason that the dredging of the channel from Warri to Baro was contracted, but the job was not done. Dredging will provide more room for the flood waters to be accommodated within its channel and curtail the overflowing of the banks (the spread onto the land).
ii. Damming of certain critical rivers - draining the two major rivers in Nigeria especially the River Benue. The major tributaries of the River Benue include Rivers Gongola, Taraba, Donga, Katsina-Ala, Mada, Shemanker Ankwe, and the Wase. Damming these rivers, starting with the one with the highest discharge and subsequently in that order, should be considered. Apart from helping to control flooding by accommodating flood water behind it, the reservoir can provide some economic services. This applies to other parts of the country where necessary.
iii. De-silting of the existing reservoirs. This is a standard practice in the maintenance of dams and in maintaining the planned storage capacity of the reservoir behind the dam. De-silting will remove the excess sediments which had settled to the lake bottom from waters delivered to it, especially during the rainy season. This applies to other reservoirs in the country.
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