My impression is that the economy of Sri Lanka depends partly on tourism that is closely related to the beautiful beaches and wonderful tropical setting. Like other coastal areas of the world, there are certain inherent risks associated with natural coastal hazards, but having an awareness of those hazards and developing plans that would mitigate the impacts of those hazards have allowed development to proceed in other coastal areas. Societies around the world are achieving a higher tolerance for loss of property associated with natural hazards (because people tend to live in hazardous areas) but we still have a very low tolerance for loss of life. In order to allow coastal development in hazardous areas, plans need to be formulated by local and central governments that recognize the hazards and provide for hazard mitigation and evacuation.

Where I live in Florida, which is at high risk each year from hurricanes, the general population is assigned to evacuation shelters that are located near their homes but in relatively safe areas and where there are provisions available for those who evacuate their homes. In the US, many states have coastal construction setback lines that are used to prevent construction in the most hazardous areas. Destruction of coastal property is inevitable where construction is allowed in hazard prone areas. Unfortunately we, as scientists, are incapable of predicting when that will occur.

It seems to me that in Sri Lanka, multi-story public or commercial buildings that are capable of withstanding the forces of tsunami waves could be designated as shelters for local residents. Vertical evacuation is crucial in those areas where the terrain is flat for long distances and the primary roads are parallel to the coast. Vertical evacuation allows for rapid response to a warning with minimal distances of travel. Clearly there would need to be enough designated shelters to accommodate the entire resident population as well as the staff and guests, if they were beach-front hotels. Concrete pilings to support the structures are necessary because the rapidly flowing water can create deep scour pits around and beneath foundations and cause the buildings to collapse. However, reinforced concrete pilings set well below the surface can be built to withstand the scour and not fail. The depth of the pilings depends on the load (mass of the building) and the soil conditions. Geotechnical firms and engineers would be able to design the buildings.

Finally, it is my opinion that education is the most important component of the early warning system and evacuation plans. There were early warning signs that could have saved many lives if they were heeded. Because the history of tsunami inundation had been lost over time, the population was not prepared to respond appropriately. My hope is that the schools will educate future generations about the tsunami hazard and how to recognize possible inundation by a tsunami wave even without a sophisticated network of seismic stations and ocean buoys.

Please feel free to share these thoughts with others.

Robert Morton

U.S. Geological Survey