Cases and Precedents : emergency shelters | community rebuilding | ecology restoration | disaster prevention



Tsunami Mitigation and Prevention

Tsunamis, like most natural disasters, are beyond human control. There are, however, a number of techniques that can minimize the harmful effects of tsunamis to the physical environment (including built structures) and to individuals and communities. Accompanied by an effective warning system, thoughtful design and strong community organization can reduce harm from Tsunamis and other natural disasters.

Mitigation and prevention through: site strategies | community development | ecology

Site Strategies

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The US National Tsunami Hazard Mitigation Program’s publication Designing for Tsunamis stresses the importance of understanding site conditions. Through zoning, creation of open space and not allowing new development in potential tsunami areas, safer land use will be better able to protect people and buildings. In redevelopment of high risk areas four basic site planning techniques need to be considered. Please refer to page 4-11, Table 4-1.Mitigation Methods for Selected Types of Development which gives a variety of building solutions based on the four basic site planning techniques listed below.


Specific Site Planning Strategies to Reduce Tsunami Risk

1. Avoid Inundation Areas: Site Buildings or infrastructure away from hazard area or locate on a high point.

2. Slow Water: Forests, ditches, slopes, or berms can slow down waves and filter out debris. The success of this method depends on correctly estimating the force of the tsunami.

3. Steering: Water can be steered to strategically placed angled walls, ditches and paved roads. Theoretically, porous dikes can reduce the impact of violent waves.

4. Blocking : Walls, hardened terraces, berms and parking structures can be built to block waves.he house and household in a wide community context such as whether it is a majority or minority situation, the conflict situation and ownership issues.


Case Study: Hilo, Hawaii was hit by a tsunami in 1960 and created widespread damage. The downtown area was rebuilt according to the Hilo Downtown Development Plan which was passed in 1974. The plan determined safe areas to build based on both the 1946 and 1960 tsunamis that affected the downtown area. All new buildings had to conform to urban design and building design standards. Any building built below the 20-foot elevation contour line had to be able weather the force of a major tsunami. Parking structures were also designed to block the water from buildings farther inland.

Source: Hilo Downtown Development Plan. Credit: County of Hawaii

Buildings made of concrete, masonry and heavy steel frames tend to withstand a tsunami if it is unaccompanied by an earthquake. Houses made of wood, manufactured houses and light steel frame structures did not fare well.

Please see page 27 of Designing for Tsunamis for a case study of a Hilo downtown development plan and to the table on page 35, Tsunami Effects and Design Solutions for a list of design solutions that may withstand a tsunami based on local hazard mapping.

Community- Based Prevention

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The Philippines has been termed a “laboratory for new approaches in disaster mitigation” due to the large number of disasters that have occurred there. Community based disaster preparedness endeavors initiated by the Phillipines National Red Cross are briefly described and analyzed in the publication:

Case Study: Risk reduction in practice: a Philippines case study

A study by the International Federation of Red Cross and Red Crescent Societies in the Philippines found that community-based disaster action teams are an important element in disaster relief.Volunteering is a kind of grass roots organization which views the local community as the primary actors who have a good sense of what needs to be done and needs to be involved to make the changes that are needed. Working together on building mitigation structures, such as seawalls and evacuation centers, creates a sense of control over the environment after a disaster and builds a sense of community among workers. Volunteers working on disaster preparedness are able to make connections between local villages and the larger disaster agencies.

Community-Based Approaches to Disaster Mitigation

This paper discusses the importance of community as a part of disaster mitigation. Locally involved people know what the needs are, are able to define the problems. The disaster survivors themselves are knowledgeable about local resources and can use their skills and knowledge so that costs are kept low. The advantage of the community-based approach is that projects can combine projects involving for example, housing and agriculture or health and agriculture. This kind of grassroots organizing emphasizes solutions rather than law and order issues.In addition,local peole can easily identify who are the natural leaders.

In Cambodia in 2001 local workers repaired dams and dikes; cleaned irrigation ditches, culverts, and water gates; and constructed small bridges.

Case Study: Sustainability in Grass-Roots Initiatives - U.N. Center for Regional Development

In Bangladesh a community-based program worked to reduce damage from flooding. Projects undertaken involved raising homestead yards so that cattle, poultry, feed and other possesions would be place above flood level. Other projects included building latrines and tube wells above the flood level. Shelters and community space were constructed as well as raised roads with culverts.

A 1988 project in Guagua, Indonesia focused on community-based projects that included building spur dikes, unclogging important waterways, dredging and building dikes.

Source: Sustainability in Grass-Roots Initiatives, U.N. Center for Regional Development Source: Sustainability in Grass-Roots Initiatives, U.N. Center for Regional Development