Africa's Biggest Dam Is Eating Away Its Own Foundation
Downstream Dead
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In late 2023 a team of engineers stood on dry bedrock eighty metres below the Zambezi, directly underneath the Kariba Dam, at the bottom of a hole that nobody had dug.
Kariba was designed in 1955 by André Coyne, who had already built more than fifty arch dams and was the most trusted man alive in that field. He set six radial floodgates high in the wall of a 128 metre double curvature arch. Structurally that is clean. Hydraulically it means the water leaving those gates never shoots outward. It falls, almost vertically, into the river at the foot of the dam.
Between 1962 and 1981 the Zambezi ran high and Kariba spilled often. A riverbed that sat at roughly 10 metres deep on the drawings became a crater about 80 metres deep, described by the consultancy that later designed the repair as no less than 90. And it was not simply deepening. It was working backwards, along a fault and seam zone in the gneiss, toward the dam's own foundation.
In 2012 a modelling team at the Swiss Federal Institute of Technology in Lausanne, working with AquaVision Engineering, called the scour hole unprecedented in dam history, and named the cause as the position of the gates.
What followed is one of the strangest civil engineering operations of the last twenty years. A concrete cofferdam across the Zambezi. Roughly 550,000 cubic metres of water pumped out, about 99 percent of the pool. A dry rock amphitheatre eighty metres deep, sitting directly beneath a live dam holding back 181 cubic kilometres of water. Then the blasting started.
This is the story of the 1955 drawing that pointed a spillway at its own feet, the six decades of routine flood operations that did the damage, the 294.2 million dollar programme that went down into the hole to stop it, and the half of that programme still running today, because the concrete of the wall has been slowly swelling since it was poured and six sluice gates have to keep moving through it.
It also ends where André Coyne's reputation ends, at a 60 metre arch dam above a town in the south of France, and 423 people who had twenty minutes.
Downstream Dead investigates the deadliest floods, dam failures and water disasters in history. New investigations regularly. Subscribe so you don't miss the next one.
#KaribaDam #Documentary #Engineering #Zambezi #Zambia #Zimbabwe #DamSafety #Hydropower #CivilEngineering #Geology #Infrastructure #Africa #DamFailure #Disaster #DownstreamDead
Africa's Biggest Dam Is Eating Away Its Own Foundation
Downstream Dead
2,941 views
In late 2023 a team of engineers stood on dry bedrock eighty metres below the Zambezi, directly underneath the Kariba Dam, at the bottom of a hole that nobody had dug.
Kariba was designed in 1955 by André Coyne, who had already built more than fifty arch dams and was the most trusted man alive in that field. He set six radial floodgates high in the wall of a 128 metre double curvature arch. Structurally that is clean. Hydraulically it means the water leaving those gates never shoots outward. It falls, almost vertically, into the river at the foot of the dam.
Between 1962 and 1981 the Zambezi ran high and Kariba spilled often. A riverbed that sat at roughly 10 metres deep on the drawings became a crater about 80 metres deep, described by the consultancy that later designed the repair as no less than 90. And it was not simply deepening. It was working backwards, along a fault and seam zone in the gneiss, toward the dam's own foundation.
In 2012 a modelling team at the Swiss Federal Institute of Technology in Lausanne, working with AquaVision Engineering, called the scour hole unprecedented in dam history, and named the cause as the position of the gates.
What followed is one of the strangest civil engineering operations of the last twenty years. A concrete cofferdam across the Zambezi. Roughly 550,000 cubic metres of water pumped out, about 99 percent of the pool. A dry rock amphitheatre eighty metres deep, sitting directly beneath a live dam holding back 181 cubic kilometres of water. Then the blasting started.
This is the story of the 1955 drawing that pointed a spillway at its own feet, the six decades of routine flood operations that did the damage, the 294.2 million dollar programme that went down into the hole to stop it, and the half of that programme still running today, because the concrete of the wall has been slowly swelling since it was poured and six sluice gates have to keep moving through it.
It also ends where André Coyne's reputation ends, at a 60 metre arch dam above a town in the south of France, and 423 people who had twenty minutes.
Downstream Dead investigates the deadliest floods, dam failures and water disasters in history. New investigations regularly. Subscribe so you don't miss the next one.
#KaribaDam #Documentary #Engineering #Zambezi #Zambia #Zimbabwe #DamSafety #Hydropower #CivilEngineering #Geology #Infrastructure #Africa #DamFailure #Disaster #DownstreamDead