Tsunami research shows destructive path worse in developed areas

06/07/05

TEMPE, Ariz. -- Last December's tsunami was a destructive force of nature that swept entire villages away and resulted in the deaths of approximately 200,000 people. Now, a team of researchers including Arizona State University's Harinda Joseph Fernando reports that some areas of Sri Lanka were devastated more than others and that the increased destruction follows human development along coastal regions.

Fernando, director of ASU's environmental fluid dynamics program and a native Sri Lankan, spent six days in January with a team of eight colleagues measuring the waves' maximum heights, the heights of the water run-up on land, how far inland the tsunami came and the total area of inundation on land. The team also checked data they collected against computer model predictions.

They published their results in the June 10 issue of Science in an article, "Observations by the International Tsunami Survey Team in Sri Lanka."

Philip Liu, a Cornell University professor of civil and environmental engineering, is the team leader and primary author of the article. Other team members are Patrick Lynett, Texas A&M University; Bruce Jaffe and Robert Morton, United States Geological Survey; Hermann Fritz, Georgia Institute of Technology; Bretwood Higman, University of Washington; James Goff, National Institute of Water and Atmosphere Research, New Zealand; and Costas Synolakis, University of Southern California.

Eyewitness accounts of the event did not give the team quantitative depictions of the tsunami, so the scientists became detectives, looking at clues like the elevation of water marks on standing buildings, scars on trees and rafted debris to gauge the height of the water. Measurement marks were photographed and locations were obtained using a Global Positioning System.

Along the island's east coast, which suffered the direct brunt of the tsunami, waves averaged heights of 30 to 35 feet (10 meters). The west coast exhibited some areas with wave height similar to the east coast, but in other areas the wave height dropped off sharply to around 3 or 8 feet (1 to 2.5 meters). Inundation, or how far inland the tsunami came, was fairly uniform along the east coast, but on the west coast, the inundation distances varied greatly.

After comparing the data they collected with the computer model predictions, the group came up with mixed results.

"One of the things we discovered was that the computer model was pretty good for the east coast, but not for the island's west coast," says Fernando. "The patchiness we found on the west coast was a mystery."

The team then set out to determine why the west coast exhibited anomalous behavior. Over the course of their observations, the survey team noticed several instances in which human intervention seemed to have amplified the behavior of the swell's path when the waves rushed inland.

A specific instance is a derailed passenger train along the Sri Lankan west coast that killed more than 1,500 people. The beach area immediately adjacent to the railroad had been altered after years of coral poaching. Mining for coral is big business in Sri Lanka due to its use as a raw material for various products, says Fernando, and although the act is illegal, the Sri Lankan government is lax in its enforcement.

Removing the coral does more than hurt the natural beauty of the island and upset the ecosystem. The coral acts as natural coastal protection against waves by breaking up the current as it sweeps into the beach. With a substantial amount of the coral removed, the tsunami was free to tear further inland than it would have been able to do naturally.

Re-landscaping the natural terrain of the island for commercial purposes also lead to horrific results. In one case, a resort removed part of a sand dune to accommodate more scenic views for its guests. That resort was completely destroyed when the tsunami hit, while neighboring areas located behind unaltered dunes were less damaged.

Fernando feels that the team's findings will have an impact on future research and policy concerning development and tourism.

"We'd like this report to sound an alarm that governments have to be more careful about enforcing coral poaching and destroying the beaches' natural defenses," says Fernando.

The tremendous carnage caused by the tsunami resulted in an emotional homecoming for Fernando.

"When I first saw it, it was a devastating experience," says Fernando. "But after a while, you get used to it because there was destruction everywhere."

To aid in future prevention of mass destruction caused by tsunamis, Fernando is working with Saman Samarawickrama from the University of Moratuwa in Sri Lanka. Samarawickrama, currently visiting ASU, and Fernando are studying the effects of corals on waves.

Fernando stresses that this research has applications almost anywhere in the world.

"The implications are applicable for any other tsunami," adds Fernando. "It should affect people's thoughts about tsunamis on any island or coastline."

Source: Eurekalert & others

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