Vertical Evacuation Structures for Tsunamis
Time frame: 2009 - 2014
GHI staff in the field with Patra Dewi, Director of KOGAMI (Tsunami Alert Community), and community leaders in Padang.
The southwestern coast of Sumatra and the Mentawai Islands offshore face the world’s highest risk from tsunamis and a significant risk from earthquakes. The magnitude 9.1 December 26, 2004 earthquake, which occurred on the northern part of the Sunda megathrust offshore of Banda Aceh and generated the great Indian Ocean tsunami, increased stress on the southern part of the fault system, making this segment of the fault closer to failure and the likelihood of future earthquakes in that location even higher.
Coastal communities urgently need to prepare for the expected earthquakes and tsunamis. Yet most of the vulnerable coastal communities in the area are unaware of their risk and of possible mitigation options. Some of these communities have launched preparedness and awareness efforts, but much work remains to be done.
GHI and its project partners, Geoscientists Without Borders and Engineers for a Sustainable World, conducted a feasibility study of vertical evacuation structures as a key component of tsunami preparedness in Sumatra. A vertical evacuation structure is a building or earth mound that is specially designed to resist earthquake and tsunami forces, and its height allows people to evacuate above the level of tsunami inundation. The main purpose of vertical evacuation structures is to provide protection during a tsunami. These buildings are especially important where high ground does not exist or where local earthquake sources do not allow people enough time to evacuate, between the moment when an earthquake strikes and the time when the first tsunami wave reaches the shore. Vertical evacuation structures are a fairly new concept that has proven effective; some survivors of the 2004 Indian Ocean tsunami were saved because they evacuated to multi-story reinforced concrete buildings.
In this project, an interdisciplinary team developed a conceptual design for a vertical evacuation structure in Padang, West Sumatra, Indonesia. This project could serve as the first step toward making vertical evacuation structures a major element of tsunami safety efforts in this vulnerable region, potentially saving thousands of lives. U.S. and Indonesian students and professors, governmental agencies, and NGOs have committed to take part in this hands-on, cross-disciplinary collaboration.
For example, Padang, West Sumatra, Indonesia, has mapped evacuation routes and carried out evacuation drills, but unfortunately, the city’s topography makes high ground especially difficult for much of the population to reach in the time between the tsunami warning and the arrival of the tsunami wave. Bengkulu, a coastal city to the southeast of Padang, has not even begun to make evacuation plans. An estimated 800,000 people in Padang and 300,000 people in Bengkulu live in tsunami risk areas.