The Volcanic Eruption of La Soufriere lowered from Red to Orange Alert

Mudflows Protection against Lahars or Mudflows

By April 22nd La Soufriere had exploded 32 times leaving heavy layers of ash everywhere making buildings collapse and sending pyroclastic flows down the volcano sides destroying everything in its wake.

On April 15th the West Indies Seismic Research Center was further able to measure the Sulphur Dioxide (SO2) flux from La Soufriere dispersing with the Jetstream across Africa, the Arabian Peninsula and Asia.

On May 5th the Government of St Vincent and the Grenadines after advice from the West Indies Seismic Research Centre decided to lower the Red hazard alert to Orange. This decision was made after discussion and consultation about monitoring techniques, data, and the current state of the volcano.
In order to verify the status of matters, the scientists will have to take a look in the crater, using a helicopter, under controlled conditions.

Professor Richard Robertson, explained that: “In St Vincent the alert levels are the mechanism by which we could respond as scientists that also indicates to the authorities and to the public what we think is happening to the volcano.
And there has to be such a mechanism where they go up and down if necessary, otherwise it may make it difficult to respond to changes when needed”.

He noted, “...in red we say it’s erupting, it’s explosively erupting, it’s doing a lot of nasty things. Once it stops doing that then we have to decide what are the chances of it going to stay in that state.”

Residents of communities in the Orange zone can return home, access to the Red zone remains restricted due to the dangerous threat of lahars.

Because this threat may continue for some time, scientists have advised that certain measures be put in place to safeguard lives, livelihoods and property of persons who occupy the Red zone. These dangerous threats have been continuously recorded on the flanks of the volcano as the rain falls, and occurrences of these lahars are not expected to end in this rainy season.

Protection against Lahars or Mudflows

“The best protection is to stay out of the valleys, don’t put any kind of major assets in it because of the fact that, in the case of St Vincent, it’s going to happen so fast that it’s difficult to provide a warning,” Professor Richard Robertson

The flows, which can be warm from hot deposits left on the volcano, are particularly dangerous for the fact that they contain ash, and debris such as boulders and trees. This week, scientists observed boulders up to 5m (15 feet) in diameter coming down lahars in Wallibou. (A boulder is a rock fragment with a size greater than 256 millimeters in diameter).

Robertson said “your warning would essentially be that you’re either hearing or seeing the stuff come towards you so it means that you really, if there’s any indication of something coming down that valley, you just simply have to get out of that valley and secondly, you have to make sure you don’t have something in it like a house for example or farm lands, which will cause you to have to go there regularly and stay there and not focus on the fact that you could get knocked out by a lahar”.

The scientist said it was important that government agencies and those responsible for planning to be forceful in their advice to persons who may put themselves in harm’s way by trying to build in the valleys below the volcano.
He added that there should be a proactive strategy where prepositioned assets and material are in place to facilitate the clearing away process.

Another suggestion was that a “lahar-ready” programme be implemented to help persons in the communities better understand the hazard so they are ready in the event of lahars taking place following heavy rains.

Else Marie Pedersen, St Vincent and the Grenadines

 

Evacuation and relief efforts