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Heavy rains cause mudflows, flooding in St Vincent

Heavy rains cause mudflows, flooding in St Vincent
This screengrab shows the mudflows and damage to the railing of the Rabacca Dry River which was rebuilt at a cost of US $5 million. (GP)

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La Soufriere volcano is “quiet” but secondary hazards like lahar (mudflow), caused by heavy overnight and early morning rains, are posing a new kind of danger to the people of St Vincent and the Grenadines.

Speaking on the daily update on NBC Radio on Thursday, seismologist Roderick Stewart said the equipment that was monitoring the volcano indicated it was quiet and there were no tremors, but lahars were occurring in all of the major drainage valleys and these could have caused damage as they passed from the volcano to the sea.

Stewart, who is monitoring from the Belmont base, said this would lead to flooding because lahar tends to block existing culverts and drainage and cut new roads and paths.

“The actual danger from the volcano itself has lowered at the moment, but these sorts of secondary hazards – which are major hazards – are taking over for a while,” he explained.

“This may well be the picture we have throughout the next rainy season. We could have this sort of hazard happening all the time.”

Last week Tuesday on the same programme, volcanologist, Professor Richard Robertson of the University of the West Indies Seismic Research Centre warned of the possibility of lahar as the rainy season approached.

A lahar is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a river valley, and is extremely destructive, flowing tens of metres per second and tend to destroy any structures in their path.

Robertson, who was out in the field, reported seeing steam in some of the water.

Joining the discussion via telephone, Prime Minister Ralph Gonsalves sounded a warning to people in the communities in the hills and near the rivers. He said after the floods from 2010 to 2013, his government rebuilt five bridges, raising them higher, but was told by Robertson the engineering would be tested when the mudflows started.

One of those is the bridge by the Rabacca Dry River, and video circulating on social media showed part of the railing was damaged and the water was raging. Gonsalves said although the bridge itself, which was built at a cost of US $5 million with assistance from Mexico seemed to be holding, he was worried.

Stewart also warned people, especially those in SUVs who might be tempted, not to drive through the water even though it might be shallow. He said the water might only be six inches deep, for example, but it also contained material and was very powerful so it could wash away vehicles. (SAT)