Structural Mitigation Activities

Construction of infrastructure, such as levees and seawalls, is an important structural measure to mitigate disaster. For example, seawalls can physically impede the progress of a tsunami and are therefore sometimes used to protect residences and infrastructure in tsunami-prone parts of the world, such as Japan. However, as the case of the Fukushima Daiichi disaster demonstrates, cost considerations or inaccurate estimates of potential tsunami heights may result in seawalls that are insufficient to serve their intended purpose.

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Figure 11.4: Seawall in Taro, Iwate, Japan.
Credit: By Kihkyef (Own work) CC-BY-SA-3.0, via Wikimedia Commons

Another structural mitigation measure is constructing new buildings or retrofitting existing structures for use as shelters. It is obvious that shelters must be outside the flood risk zone, but hurricane storm surge risk zones are expanding as sea level rises, so the location of existing shelters in hurricane-prone regions must be reevaluated over time. It is also important to note that tsunami shelters are only useful if a community is far enough from the tsunami source to allow sufficient warning for residents to get to the shelter. This is not the case in numerous tsunami-prone locations, such as the northeastern coast of Japan, where the distance from the offshore subduction zones that generate the tsunami to the adjacent coastline is measured in tens of kilometers, thus providing scant minutes between the geophysical event and the tsunami coastal strike.