T188 Role of Geology in Planning and Mitigation of Natural Hazards

Wednesday, 31 October 2007
8:00 AM - 12:00 PM

VOLCANIC RISK MAP FOR TUNGURAHUA, ECUADOR: WHAT CAN RISK MAPS CONTRIBUTE TO VOLCANIC HAZARD COMMUNICATIONS?

Paper number: T188-10
Program: Technical Sessions
Time: 10:20 AM – 10:35 AM

Authors

Abstract

More than 250 volcanoes are exposed in the Ecuadorian part of the Northern Andean Volcanic Zone. Tungurahua located in the eastern volcanic cordillera, is one of the 17 considered active volcanoes and remained dormant until 1993. Since 1999, after eighty years of relative inactivity Tungurahua entered into a new eruptive phase. In May of 2006 a new cycle started with ash showers and a high frequency of phreatic and strombolian explosions of which one reached a height of 19 km. Shortly after an apparent calmness, first pyroclastic flows erupted on the western flank reaching small villages. The strongest observed eruption occurred in 2006 producing ~20 pyroclastic flows along the western flank, killing 7 people in a previously stated safe zone, affecting some 1.5 million citizen and devastating at least five small villages, destroying ~20,000 ha of cultivated land and had a very high social and economic impact. As result authorities changed frequently the alert levels based on little scientific observation, which lead since 1999 almost annually to various evacuations of several thousands from the close but due to natural barriers protected city of Baños and of other nearby minor villages in the volcano area.

To assess the volcanic danger of the area a GIS array for the Tungurahua and its surroundings had been carried out. The array combines volcanic hazard zonation with four layers of economic and population data (population, infrastructure, land use, and standard of living). The goal is to present on a single map, the risks of volcanic activity in terms that the public can better understand. The map, which shows the cost of the volcano to the Ecuadorian government, it's developed and shared using an World Wide Web vehicle, which facilitates some complex overlays. Although volcanic hazard maps are now available at many hazardous volcanoes, volcanic risk maps are very rare and may offer some special advantages in Volcanic Hazard Communications efforts. They can be used to forecast the cost of volcanic activity, which may be helpful in securing budgeting for mitigation efforts. They may be used for planning mitigation expenditures, because sensitivity analysis of uncertainties in hazard zonation or recurrence intervals of various types of activity can be tested against economic and population data for cost effectiveness.