In
populated areas, the best idea seems to be the use of seawalls in front of
ports and cities. In Patong Beach in Thailand during the 2004
Indian Ocean tsunami, the seawall in front of the beach dissipated much of
the energy of the tsunami and prevented the city from being destroyed. Even
though the flooding because of a rise in sea level wasn’t stopped by
the seawall, the force of the tsunami was, and very few casualties resulted
in the area. The only areas of the city that were seriously damaged were the
areas directly behind openings in the seawall designed to allow access to
the beach 6. The conclusions from this report indicate
that it is best to have walls offshore, with continuous protection and no
holes. One design for a wall that could be implemented in ports and coastal
cities is the design used in Providence, RI for the Fox Point Hurricane Barrier.
This wall has three openings for ships to pass that can be closed with little
warning for the protection of the harbor. Fox Point has protected the city
of Providence from the floods that used to ensue destruction every time a
hurricane struck, but since the barrier was built,
the problem has been alleviated 21. A wall that both
allows the free flow of marine traffic into and out of the port and protects
the city from floods and tsunamis serves as a good balance between the necessity
for protection and the need for accessibility. While the walls do not need
to be taller than the tsunami to be effective, the taller a wall is, the larger
the column of water stopped will be. Seawalls do not, however, completely
protect a city 11 and should be used in conjunction
with other methods of protection, especially trees on the coastline and dikes
in rivers.
One
of the most effective methods of protection from a tsunami is trees. Some
villages in India, for example, had minimal casualties in the 2004 tsunami
because they had planted trees along the coastline. The village of Naluvedapathy,
for example, was protected by about a kilometer of trees and suffered no direct
damage from the tsunami 17. Even though this would
be too many trees for many areas of the coastline, a moderate thickness of
trees, especially those with deep roots and dense coverage, can protect effectively
against tsunamis. Mangroves, it appears, are especially
good at protecting areas from tsunamis 22, so a beach
with mangroves on the shore and rows of trees behind it would be well-suited
to withstand a tsunami. Our plan is to plant and help sustain mangroves along
empty coastlines where there is little tourism. In areas where there is tourism,
the plan is to encourage the planting of low trees
in a band that extends virtually uninterrupted throughout
the entire shore. While
these trees do not protect as effectively as mangroves, planting these would
be a compromise between having accessible beaches for tourists and having
protected coasts. This band of trees would have a positive effect on tourism
too, for it adds to the natural beauty of the areas and provides shade. Another
mechanism for preventing a tsunami from exerting its full force on the coast
is to encourage the growth of coral reefs directly offshore from coasts in
a way that they form an undersea wall of coral. While this is not completely
effective, it has been shown to reduce the impact force of the tsunami 22.
While this would only be applicable to certain parts of Peru where the water
is warm enough, it would make a great method of protection for Micronesia,
as well as an extra attraction for tourists.
