GIS in Hazard Mapping and Vulnerability Assessment on Montserrat
Ryan, Lavern, URISA Journal
The British Government, the United Nations Development Programme (UNDP), and other international organizations have cooperated with the government of Montserrat in its massive efforts to rebuild socially and economically after its volcanic destruction in 1995.
In this connection, the Physical Planning Unit (PPU), in collaboration with the Department of Lands and Survey (L&S), has developed a GIS-based Land Information System (LIS) for effective planning and better management of land resources. LIS provides the basis for the development of a National Data Warehouse (NDW), which is effectively utilized for the better management of various public utility services and other resources of the country.
Moreover, GIS based LIS has proved to be an effective tool in disaster management. It is needed at all stages of disaster management, particularly mitigation, preparedness, response, and recovery. The demand for quick and accurate information and mapping where hazards exist can be met by the LIS. It allows for the analysis and visualization of a disaster situation, effectively reducing the loss of life and property.
This paper describes how GIS based LIS was implemented in hazard mapping and vulnerability assessment on Montserrat. It demonstrates the overall methodology adopted to achieve these objectives and gives an idea of the future potential of its application in the management of catastrophes.
Montserrat, part of the Leeward Islands in the eastern Caribbean and overseas territory of the United Kingdom, is approximately 39.5 square miles in area. It lies approximately 27 miles southwest of Antigua (see Figure 1) and 1,150 miles north of the equator. This volcanic island is approximately 12 miles long and seven miles wide at its broadest point, with geographic coordinates of 16[degrees] 45' N, 62[degrees] 12' W.
[FIGURE 1 OMITTED]
Montserrat has severely suffered in the recent past, particularly when a major volcanic eruption in June of 1997 completely destroyed nearly two-thirds of the island, including its airport, seaport, and the capital, Plymouth. Such devastation has had an unfavorable impact on its economic, social, environmental, and institutional infrastructures, resulting in an immediate migration of nearly 62 percent of its population to the United Kingdom, the United States, and other countries (see Figure 2).
The island has since been divided into two zones (see Figure 3): the safe area (1) and the unsafe area. (2) The safe area has been undergoing rapid development in terms of expanding road networks and the construction of buildings, all in an effort to provide facilities for the steadily re-increasing population. The unsafe area however, has been excluded from all development and human activities.
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
VOLCANIC HAZARD ON MONTSERRAT
Based on the seventh meeting of the Scientific Advisory Committee (SAC) (3) on Montserrat Volcanic Activity that took place on August 28 to 30, 2006 (MVO 2006), it was concluded that the continued rapid growth of the lava dome posed a serious hazard to the nearby occupied communities. These hazards were pyroclastic flow from dome collapse and column collapse, rock avalanches from the collapse of the crater walls, and explosions with ash and rock fallout (see Figure 4).
The SAC advised that "the likelihood of these hazards is strongly controlled by the rate of extrusion, with high rates more likely to initiate both collapses and explosions." In this particular setting, a large dome almost reached the point where it was capable of overtopping the crater rim, and potentially being able to send pyroclastic flows in multiple directions. Figure 5 shows populated areas [1-3] at risk. The dashed line is the estimated southern boundary that can be reached by a pyroclastic surge produced by a collapse of 12 million cubic meters of dome material; the northern boundary of this is the solid line between Areas 1 and 2. …