Could Seawalls, Coastal Forests Reduce Japan's Tsunami Damage?

Frequently visited by natural disasters, Japan's tenacity and resiliency is well-known of. Now, Japan is intent to come up of ways to counter its next tsunami disaster by building seawalls and coastal forests.

Phys.org reports that the Japanese will conduct a 10-year reconstruction project, which includes the construction of tsunami seawalls along Tohoku's Pacific coast.

However, the project has received a lot of skepticism on its efffectiveness and price. Japan's reconstruction project reportedly costs about 31.5 trillion yen or about $255 billion.

Science Daily reports that there are new findings supporting the construction of seawalls and coastal forests. These are mentioned in a detailed research paper published in the journal PLOS ONE.

According to the study, researchers analyzed the history of tsunamis along the Pacific coast of Japan's Tohoku region. They found out that seawalls higher than five meters could reduce damage and death while coastal forests play an important role in protecting the public.

The heights and construction methods of seawalls vary widely from one community to another, even within the same town.

The paper's lead author, Roshnak Nateghi, said that there are many sub-municipalities that still don't have seawalls. But through analyzing four tsunamis in Japan (1896, 1933, 1960, 2011), they found that statistically, seawalls that are above five meters decreased the area's destruction rate.

Using a modeling method called Random Forest, Nateghi found that a 10-meter increase in the height of seawalls could yield to a 5 to 6 percent decrease in the destruction rate.

On the other hand, "tsunami control" forests showed that it could prove valuable in protecting areas and reducing damage. Areas with a lot of coastal forests have lower destruction rates.

The researchers determined the destruction rate by measuring the extent of flooding in their models. This is a critical factor in death rates and building damage rates and could lead to more understanding of possible safety measures such as multiple lines of defense and elevated topography..