Wednesday, June 19, 2013

Hazard level system

Guillaume Levieux
Published on 23 March 2009
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The Hazard Level System was updated on 4 November 2011.

The Government of Montserrat, the Disaster Management Coordinating Agency (DMCA) and the MVO have adopted a Hazard Level System which has been used at the Soufrière Hills Volcano, Montserrat since August 1, 2008. The purpose of the system is to improve management of the ongoing eruption and to provide important information to the residents of Montserrat.

The Hazard Level System has replaced the Alert Level System. The Hazard Level is not related to the old Alert Level.

The Hazard Level System divides the southern two-thirds of Montserrat into five zones, with two Maritime Exclusion Zones. Access permission for each of these zones is dependent on the Hazard Level. The Hazard Level, which ranges from 1 to 5 is set by NDPRAC on the advice of MVO.

Leaflets and posters explaining the Hazard Level System are available from the offices of the DMCA, MVO, airport and many other locations in Montserrat. They can also be downloaded as pdf files in the download area.

 

Access restrictions

Unrestricted Daytime access Daytime access to some areas Daytime transit Controlled access Essential workers
Ashfall and lahars can be significant hazards in all areas, and require appropriate precautions. Access is permitted from 8:00 am until 4:00 pm. Access gates will be locked at all other times. Areas will be defined depending on state and location of the volcanic activity. Boats permitted to travel through the MEZ without stopping from 6:30 am until 5:30 pm. No access without approval from NDPRAC. Approval considered on a case-by-case basis. Gates will be locked at all times. No access apart from MVO and associated staff. Access for essential maintenance only with approval from NDPRAC. Gates will be locked at all times.
Hazard level or access restrictions may be changed for severe weather such as unusually high rainfall, storms or hurricanes.

Hazard Level System

Hazard Level1 1 2 3 4 5
Typical Activity2 More than one year with no measured activity. No activity that threatens the north or west.3
Low measured activity.4		 Mild activity that threatens the west.5
Significant change of measured activity.6
High measured activity.7		 Lava extrusion that threatens the north or west.
Large unstable dome to the north or west.		 Threat of large pyroclastic flows to the north or northwest.
Threat of lateral blast or sector collapse.
Zones map Hazard Level 1 20111025_hl_2 20111025_hl_3 20111025_hl_4 20111025_hl_5
Zones A Unrestricted Unrestricted Unrestricted Unrestricted Controlled access
B Unrestricted Unrestricted Unrestricted Controlled access Controlled access
C Unrestricted Daytime access Controlled access Controlled access Essential workers
F Unrestricted Daytime access Daytime access Controlled access Controlled access
V Daytime access to some areas Essential workers Essential workers Essential workers Essential workers
Maritime Exclusion Zones W Unrestricted Daytime transit Daytime transit Essential workers Essential workers
E Unrestricted Essential workers Essential workers Essential workers Essential workers
1 The Hazard Level is not related to the Alert Level used prior to 1 August 2008.

 

2 The descriptions of types of volcanic activity are indicative only. The level will be set by the MVO based on assessment of the actual activity.

 

3 For example, growth contained by the crater or non-growing lava dome contained by the crater.

 

4 Measured activity refers to all the monitoring techniques used by the Montserrat Volcano Observatory (MVO) including seismic, ground deformation, gas measurements and visual observations.

 

5 For instance, mild ash venting from vents located on the northern or western side of the crater with no measured activity that might be a precursor to larger activity.

 

6 Any change in measured activity which may be the precursor to an eruption caused by a sudden rise of magma beneath the dome. This may, or may not, be accompanied by surface activity such as explosions or dome growth.

 

7 A high level of measured activity which may be the precursor to an eruption caused by the steady rise of magma within the volcano. This may, or may not, be accompanied by surface activity such as explosions or dome growth.

Hazard zones

Download the fullsize hazard zone guide here.

Zones

 

Zone A South of Nantes River, including, Salem, Hope, Frith, Flemmings, parts of Olveston and Old Towne, the upper part of Happy Hill and extending 500 m out to sea.

 

Zone B Iles Bay, Belham, Waterworks, parts of Old Towne, the lower part of Happy Hill and extending 500 m out to sea.

 

Zone C Cork Hill, Weekes, Foxes Bay, Richmond Hill, Delvins and extending 500 m out to sea.

 

Zone F Corbett Springs, Locust Valley. This zone is dedicated to farming and is defined by NDPRAC.

 

Zone V St George's Hill, Soufrière Hills, South Soufrière Hills, Plymouth, Lee’s, Harris, Spanish Point.

 

Maritime Exclusion Zones

 

Zone W Approximately 2 km offshore between Sturge Park and O’Garro’s.

 

Zone EApproximately 4 km offshore between Roches Yard and Spanish Point, decreasing to 2 km offshore from Spanish Point to Pelican Ghaut.
Category: Hazard level system