Nigeria: Nigeria Floods

There was severe flooding in Nigeria – the worst in a decade. Earlier this month, Nigeria’s Nationwide Emergency Administration Company warned of catastrophic flooding for states situated alongside the programs of the Niger and Benue rivers. It famous that three of Nigeria’s reservoirs have been anticipated to overflow. The company mentioned the discharge of extra water from a dam in neighbouring Cameroon had contributed to the flooding. Olayinka Ogunkoya unpacks Nigeria’s mismanagement of its dams.

What affect does poor dam administration have on flooding in Nigeria?

The operations administration of dams and reservoirs is dependent upon what objective the dam was constructed for. If a dam was constructed for water provide, irrigation or hydro-electric energy, the intention can be to maintain the dam as near full pool capability as attainable in order to maximise useful resource availability.

If the dam was constructed for flood management, then the intention can be to de-water the reservoir earlier than the flood season. For this reason flood management reservoirs and dams have short-term reservoir cupboard space for storing spate circulation to alleviate downstream flood injury.

The water is subsequently launched downstream at charges that won’t create flood situations.

Most dams serve a number of functions. For instance, the dams on the River Niger, Kainji and Jebba, and its tributaries, Shiroro and Zungeru on the River Kaduna; and people on the tributaries of the River Benue – Dadin Kowa and Kiri on the River Gongola, and Kashimbila on the River Katsina Ala – have been constructed for hydro-electric energy era, fisheries and flood management.

Managing reservoirs for flood management requires preserving the utmost attainable empty house earlier than the flood season. Water storage is required for the remaining goals of water provide, irrigation and hydropower.

Within the Nigerian scenario, hydropower era dominates the capabilities of many massive dams. Which means the administration of reservoirs would concentrate on preserving the extent at full pool.

This runs towards the grain of what is wanted for flood management. If there isn’t any cupboard space then incoming flood waters will not be contained.

What measures ought to be in place to avert flooding?

Nigeria must create buildings alongside the River Benue and its tributaries that can serve primarily for flood management, and secondarily for hydro-electric energy.

Given the dearth of sources, it could be troublesome to construct dams for less than flood management. Efforts ought to due to this fact be made in the direction of the realisation of Seventies plans for the development of huge hydropower dams at Makurdi, Lokoja and Onitsha. These dams, aside from supplying electrical energy (3300 MW), would have vital flood management and mitigation functionality.

A couple of extra dams might be constructed upstream of Makurdi on River Benue. One is the Dasin Hausa Dam. This has been designed to detain extra spillage from the Lagdo Dam, and likewise generate 300 MW, irrigate 150,000 hectares, and make it attainable to navigate the River Benue all yr.

Many flood management dams and reservoirs ought to be constructed alongside the tributaries of River Benue since these are additionally high-discharge rivers and contribute to the flooding potential of their principal.

Flood management buildings present for short-term storage of flood waters upstream in order that downstream areas are protected towards inundation. The flood waters are steadily launched when the specter of flooding has declined.

Secondly, city and settlement progress involving constructing on decrease mendacity areas that obtain runoff ought to be zoned off except the areas are reclaimed and considerably elevated.

How can affected communities be higher protected?

Abatement measures. These contain implementing insurance policies and the development of buildings that inhibit flooding – or in any case considerably cut back its affect. Such measures embody zoning regulation, catchment afforestation, desilting of channels, and development of flood management reservoirs.

Safety measures also needs to be taken. These embody strengthening the pure levees or development of synthetic levees (flood embankments). A levee is a “dike” alongside the banks of a river shaped by sediments deposited throughout flood occasions. The crest of the levee is greater than the floodplain, and thus protects the floodplain from inundation or flooding the place the levee is sturdy.

Flood embankments or synthetic levees are normally constructed of alluvial materials dug out of pits on web site. Different kinds of embankments are flood partitions fabricated from strengthened concrete, sheet pile and masonry.

Throughout exceptionally extreme flood occasions, embankments could also be steadily elevated in top, as an illustration by sand-bagging, to forestall them from being overtopped and broken. Nevertheless, flood embankments can have plenty of adverse results. They’ll:

• cut back storage capability of the river channel and flood plains by proscribing circulation from the channel to the flood plain
• defend solely towards reasonable floods, since excessive floods may readily over-top the partitions
• inhibit the persevering with build-up and nutrient enhancement of the floodplain, which might have occurred naturally on account of inundation and siltation.

What can Nigeria do to make higher use of its dams?

Giant dams in Nigeria are totally owned by the federal government. The states and federal governments could make higher use of their dams by making certain that the dam construction, reservoir and associated gear and canals are maintained correctly.

At present, most vegetation and gear have damaged down or are functioning properly beneath put in capability. It’s because dam administration would not adhere to operation manuals.

Many dams in south-western Nigeria have been so uncared for that mature bushes are rising on their faces.

All dam tasks below development have to be urgently accomplished. There are dams uncompleted for the reason that Eighties.

A primary problem in Nigeria is coverage discontinuity by successive governments. The result’s the buildup of deserted tasks in all spheres of nationwide improvement: dam, energy, water provide and irrigation, metal business and roads.

It seems it’s but to be appreciated that authorities is a continuity, whether or not it’s the inexperienced or crimson occasion that’s in management, and all tasks initiated by the earlier administration must be accomplished by succeeding administrations.

Olayinka Olatokunbo Ogunkoya, Professor of Geomorphology, Obafemi Awolowo College