Dimension 2: Sensitivity
Sensitivity is the degree to which people and the things they value could be harmed by exposure to a hazard.
Sensitivity to coastal hazards is more difficult to assess than exposure, particularly before a disaster occurs.
In 2011, a 9.0 magnitude earthquake off the Pacific coast of the Japanese island of Tōhoku caused a massive tsunami that killed more than 15,000 people and destroyed or damaged hundreds of thousands of buildings. It also caused a nuclear disaster in the form of meltdowns at three reactors of the Fukushima Daiichi Nuclear Power Plant. However, other nuclear reactors within the path of this event’s tsunami waves were essentially unaffected.
Why did the Fukushima Daiichi plant experience catastrophic meltdowns while other reactors exposed to the tsunami did not? One explanation is that Fukushima Daiichi reactors were more sensitive to tsunamis than other reactors. Sensitivity, as defined earlier in this module, is the degree to which people and the things they value could be harmed by exposure to a hazard. It is important to assess sensitivity to a hazard before an event occurs to more fully understand the potential for adverse impacts. It is also important to assess sensitivity after an event has occurred to locate where the worst effects were felt and to identify lessons that might be applied to future hazard events.
Sensitivity to coastal hazards is more difficult to assess than exposure, particularly before a disaster occurs. Hurricanes and associated storm surge exposure are generally only possible in particular coastal areas globally, and are much more common in some areas than in others. Likewise, tsunamis are generally caused by undersea or volcanic seismic events, which limits the number of places they can physically occur. Because we have much historical experience and physical science knowledge about these hazards, we can often predict with reasonable accuracy which places might be exposed.
Sensitivity, however, is not always as clear. As depicted in the vulnerability scoping diagram presented earlier in this module, one needs to consider both the components of sensitivity to a hazard and measures of that sensitivity. Two components of sensitivity often considered to be important to understanding vulnerability to coastal hazards are infrastructure and demographics. Of these, infrastructure is the more straightforward of the two to assess. Typically, information is readily available on infrastructure’s date of construction, materials used, ability to withstand various hazards, and so on, particularly in developed countries. Understanding the condition and quality of infrastructure enables assessment of its sensitivity to hazards, and consequently the sensitivity of populations that rely on the infrastructure.
Demographic factors such as race, gender, and socioeconomic status can also play an important role in assessing sensitivity to coastal hazards. However, these factors are highly context-specific, and can also interact with one another.
The two aspects of a community most often considered in sensitivity assessments are the demographics of the population and the infrastructure of the built environment. Of these, infrastructure is the more straightforward of the two to assess.
Let’s think of an example we are already familiar with. With Hurricane Katrina, the infrastructure designed to protect the city of New Orleans from storm surges (the levee system) was not strong enough to withstand the surge and therefore failed and the city flooded. Many people living in the city had characteristics that lead to high levels of sensitivity. Poverty, sickness, and old age are three characteristics that were shared by many of the people who suffered the most as a result of Katrina’s flooding. This led to the shocking human catastrophe we witnessed, with thousands of people unable to evacuate and trapped, and some dying for lack of medical help or basic human needs. The city displayed a high level of sensitivity. This became painfully obvious after the storm, but was, perhaps, harder to assess before Katrina happened (although there had been many attempts to draw attention to the issue prior to the storm).
Similarly, but with far less impact on human suffering, with Sandy in New York, the infrastructure of Lower Manhattan, including the subway, was not designed to withstand a storm surge. This became painfully obvious after the storm, too. These lessons in sensitivity are (or should be) what drive communities to improve their resilience to coastal hazards by working to strengthen their adaptive capacity, as we will see in the next section.