Post-tsunami Thailand yields lessons for coastal construction
24 March 2005, CIESM News
According to researchers at John Hopkins University , inspections of Thai villages and ports stuck by the tsunami waves have uncovered some engineering lessons that might reduce casualties and destruction in the future. The team of experts toured Thailand , Sri Lanka and India in order to see which buildings and other structures held up against the waves—and which didn’t. From their personal observations the team compiled a list of general lessons for builders in coastal areas where future tsunamis may occur.
Elevated structures survive better. The waves were powerful enough to smash through a building’s ocean-facing wall and break out the opposite side, and high enough to inundate a second-story level. Elevated buildings that allowed the moving water to pass through the lower levels with little interference fared better than those with solid first-floor walls. Taller buildings that allowed people to reach heights above the wave’s crest helped reduce casualties. Materials matter, as reinforced concrete structures were more likely to survive the wave forces; in general masonry brink, and wooden structures did not fare as well. Orientation is important walls facing the ocean, allowing perpendicular impact from the waves, sustained more damage. Walls oriented in the direction of the flow sustained less damage. Strong foundations are necessary; in addition, landscaping or other features can protect the foundations against scouring, which is soil erosion caused by moving water. Seawalls can also be a very effective way to reduce wave damage. The structures must be continuous, however, with no gaps for pedestrian crossings. Also, such structures should not slope inland, allowing waves to slide up and over the walls like a skier.
Debris in the flow is hazardous. Many tsunami victims were injured or killed by debris pushed along by the powerful waves. Debris can be minimized if vehicles are parked and heavy items stored on the inland side of buildings. Ports are particularly vulnerable to tsunami waves. Boats and piers in a harbor hit by a tsunami have little protection. The beaches in Thailand recovered rapidly, within weeks of the disaster; natural ocean forces had returned the sandy beaches nearly to their pre-tsunami condition. Several questions raised during the trip require further research. These include why the height of the tsunami varied dramatically along the coast and how engineers can construct a mathematical model of wave forces as they pass through coastal structures.