Study: Millions of tons of sand and sediment are being washed into the Atlantic off Nigeria

Africa’s largest delta region, which forms the southern boundary of the oil-rich Niger Delta, has a problem people in the energy business ignore: It has turned into one of the most eroded parts of…

Study: Millions of tons of sand and sediment are being washed into the Atlantic off Nigeria

Africa’s largest delta region, which forms the southern boundary of the oil-rich Niger Delta, has a problem people in the energy business ignore: It has turned into one of the most eroded parts of the world, experts say.

Before oil was discovered in commercial quantities in the region in the 1960s, traditional agriculture and fishing were the region’s primary occupations. Farmers fertilized the land with sediments carried by the Niger River from wetlands. They grew cotton, oil palm and oranges.

Today, the 70 million people living in the region depend on oil, which may ultimately be produced out of the swampy Delta. Now, few crop crops.

“What we are losing are no longer yield-bearing seabeds because they are drowned and flooded,” said Professor Samuel Kazara, director of the Oil Geosciences and Marine Climate Change Laboratory at the University of Ibadan in southern Nigeria. “We are also losing water and salt deposits that are now changing the topography of the delta because we now have extensive salt marshes in areas once fertile.”

About 1 billion tons of sediment is carried into the Delta daily by the sands of the Atlantic Ocean. But some of that sediment ends up in the Niger River delta through massive dams built on the river and the seaward currents of the Gulf of Guinea. From there, it’s carried to an island basin, where it rains.

The rivers in the region are all large enough to form lagoons so that they can drain into the Atlantic. But in the ocean, sediments sink, naturally. Rivers in the Delta, by contrast, flow a normal river course, pulling silt in and leaving little or nothing to pull out.

“The rivers move slowly, and only about 500,000 of them flow from west to east every year,” Kazara said. “The Sodo Caves west of Port Harcourt represent more than 7 trillion tons of sand — that’s the equivalent of four New Pyramids of Giza.”

The Sodo Caves in this part of the Delta are similar to the Grand Canyon in the U.S. In fact, the driest part of the Delta suffers the worst erosion of all. Across the Delta, nine out of 10 of the 867 eroded caves is still visible.

“We are losing surface objects and canoes,” Kazara said. “The loss of docks and bottom aids like those dredged up by the oil companies are also being lost in the delta.”

With no natural defences, the sediment starts to subside into the ocean. As it sinks, natural currents compress the sediment at a rate faster than the sediment can compact. As a result, over time, surface sediment gets jaggedly fractured and winds up sinking a long way from its original place. The Gulf of Guinea is now an arc of disturbed islands running across the area.

Many stretches of the degraded delta are no more than a few miles wide and cut off by towered hills. The history of the area’s sea routes has now been subsumed into these towering rock formations.

“Nigeria’s most deltas are still to be developed,” Kazara said. “This is something that people in the energy industry still fail to see as a primary threat. There are major strategic interests in the area and there is no current word on how to defend them against the erosion and loss of the Delta.”

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