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Bioshields
Research on Midwest shelterbelts studied for tsunami-hit areas
- Among the many hard-hit areas of the catastrophic 2004 western Pacific tsunami was Khao Lak, Thailand. Property was destroyed and hundreds of bodies washed ashore.
Nearly two years later, an Iowa State professor was in Khao Lak discussing how trees and other plants could mitigate damage from another tidal wave or devastating tropical storms.
Gene Takle, professor of geological and atmospheric sciences and professor of agronomy, represented a small team of ISU researchers at the Khao Lak conference last year sponsored by the United Nations' Food and Agricultural Organization (FAO). The objective was to improve understanding of the role of coastal trees and forests in protecting people and property. Takle was one of a number of international experts attended the meeting.
FAO officials became aware of research by Takle and others from Iowa State on shelterbelts for Midwest agricultural areas. These linear arrangements of trees act as windbreaks. The researchers use fundamental physics principles to understand how bioshields, as they are also called, deflect wind flow.
The FAO asked the ISU group to submit a paper on protecting coastal areas from tsunamis and typhoons using their knowledge of shelterbelt wind reduction.
A giant earthquake in the eastern Indian Ocean triggered the tsunami. A wall of water 30-foot high in some locales crashed ashore, killing some 230,000 people and leaving millions homeless. Damage was worst along shorelines where coastal forests had previously been destroyed, Takle said.
"There are clear examples in parts of India where the villages that had not taken out mangrove forests were not nearly as hard-hit," he said. "Natural barriers can help."
Mangrove forests are comprised of salt-tolerant tree and other plant species that grow along the coasts and in shallow water.
Takle worked with fellow meteorology faculty members Mike Chen and Xiaoqing Wu. They drew on their expertise of agricultural bioshields in the American Midwest and applied them to tropical coastal shelterbelts.
"We didn't have time for computer modeling specifically for the species and orientation with respect to coastal areas," Takle said. He added that their earlier work concentrated on trees such as cedar and white pine, not mangroves and palms.
The ISU researchers offered several suggestions for a coastal bioshield including the planting of trees as near to the ocean as possible with (moving inland) salt-tolerant plants next, followed by taller, wind-resistant plants.
Spacing of the plants is vital to correctly modify wind flow and speed. The bioshield has to provide protection during storms and allow cooling breezes at other times. Also, as bioshields slow wind speed, wind patterns change and can cause turbulence. Fluctuating wind, Takle explained, could be worse than a high wind at a consistent speed.
"You don't want to create turbulence in the wrong place. That kind of wind can shake apart a building," Takle said.
The FAO conference guidelines are a prelude to further suggestions coming from additional research by the team, which includes Sarah Schmidt, a graduate student in geological and atmospheric sciences and aerospace engineering.
"She's making more detailed analyses of the characteristics of the indigenous trees and shrubs from the coastal area," Takle said. "She's looking at various configurations. For example, do you use more palm trees? Or how do you alter the spacing of the plants?"
Takle said the researchers will publish this work in a scientific journal for general distribution and also share it with scientists and resource and land managers from Southeast Asia who are working to restore and protect these coastal areas.
According to the FAO, the use of bioshields should be considered within the framework of disaster management strategies, which also include effective early warning systems and evacuation plans.
Xiaoqing Wu, Gene Takle, Sarah Schmidt and Mike Chen.
Around LAS
October 1-14, 2007
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