From: Tansa Musa, Reuters
Published August 19, 2005 12:00 AM

Cameroon Dam Nears Collapse, 10,000 Lives at Risk

YAOUNDE — A natural dam holding back a lake in Cameroon is on the verge of collapse, threatening to unleash a wall of water into neighbouring Nigeria and sweep away 10,000 people in its path, a scientist warned on Thursday.

Erosion has weakened the barrier holding back Lake Nyos in northwestern Cameroon, where a cloud of carbon dioxide that had accumulated under the water escaped in August 1986, killing 1,800 people in surrounding villages.

Doctor Isaac Njilah, a geologist at the University of Yaounde, said the region could soon face a much worse disaster if a volcanic tremor fractures the weakened dam, unleashing a torrent that would thunder downhill into Nigeria.

He said the wall of volcanic -- or pyroclastic -- rock had become so fractured that it could burst at any time.

"The natural pyroclastic dam holding back the millions of cubic metres of water in the lake is rapidly being deteriorated by mechanical and chemical agents of weathering and erosion and is at the point of collapse," he told Reuters after assessing the lake, 300 km (185 miles) northwest of Yaounde.


"If immediate action is not taken, the collapse of this dam will result in the deaths of thousands of people in the northwest province of Cameroon, and the Taraba and Benue states of Nigeria," he said.

He estimated that about 10,000 people in Cameroon and Nigeria would be drowned by a surge of 50 million cubic metres of water if the dam collapses.


Njilah said engineers from Cameroon and Nigeria should reinforce the damn and install a concrete spillway to drain excess water, as well as set up more tubes to release the carbon dioxide that has been collecting in the lake for centuries.

The 1986 catastrophe at Nyos -- which scientists say is the worst gas disaster on record -- focused international attention on the area, where experts recommended the controlled release of carbon dioxide dissolved in deep lake water.

Five pipes were to be installed to drain the gas, although only one was eventually built in the lake, which lies in the throat of an old volcano in the Oku volcanic field.

Scientists say Lake Nyos is one of only three lakes in the world known to be saturated with carbon dioxide -- along with Lake Monoun, also in Cameroon, and Lake Kivu on Rwanda's border with Democratic Republic of Congo.

During their investigations into the disaster, scientists discovered that a huge volume of water was being held back by the fragile natural dam, just 40 metres high and 45 metres wide at its narrowest point, which was rapidly eroding.

Potholes have gaped open in the harder, upper layer of the barrage, while water is trickling through the lower section.

"This leakage and the resulting erosion greatly threaten the stability of the dam," Njilah said.

The outflow of the water could also release pressure on the carbon dioxide at the bottom of the lake, leading to another gas disaster of even greater magnitude than that of 1986.

Beyond the human toll of that catastrophe, 3,500 livestock were killed and 4,000 people forced to flee, with many of the survivors suffering burns, respiratory disorders and paralysis.

"As of now, one can state without fear that the Lake Nyos dyke holds another disaster of greater magnitude in the making. If this occurs, there will be serious losses in human life, domestic and wildlife, and many natural ecosystems would be destroyed," Njilah said.

Source: Reuters

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