Mitigation involves taking action to reduce risk. Mitigation is a long-term planning activity, unlike preparedness, response, and recovery, which are more immediately part of the emergency itself. But mitigation can begin following a disaster, during recovery, to mitigate the effects of any future disaster. In the mitigation phase of the emergency management cycle, activities aimed at decreasing the likelihood of disaster or reducing its negative impacts can either be structural or non-structural. Examples of structural mitigation activities include building physical infrastructure such as sea walls or retrofitting existing buildings to withstand the hazard, or to serve as shelters. Instances of non-structural mitigation activities include developing storm surge warning systems, post-disaster recovery plans, and educational programs. Other non-structural mitigation measures include flood insurance programs (although some consider this as part of preparedness), and land use planning activities like zoning. As you can see, mitigation activities are wide-ranging and can overlap with other phases of the emergency management cycle.
Please take a few minutes to think about what you just learned and answer the question below.
Constructing levees and seawalls is probably the most obvious mitigation measure to protect a community against disaster. Seawalls can be very effective in physically impeding the progress of a tsunami and are common in tsunami-prone parts of the world, such as Japan. However, as the case of the Fukushima Daiichi disaster, which we covered in Module 11) demonstrates, cost considerations or inaccurate estimates of potential tsunami heights may result in seawalls of insufficient height to serve their intended purpose. Additionally, structures like levees require maintenance, and it was a lack of attention to the structural integrity of the levees protecting New Orleans that lead to the disaster of Katrina’s flood there.
In Module 8, we looked at the various hard structures and their designs for protecting coastlines and communities. In Module 10 we looked at smart building measures – both traditional and newly innovative. These measures are all methods for mitigation, and many have been used for centuries. The managed retreat strategies we explored in Module 9 are also considered mitigation measures.
Another structural mitigation measure is constructing or retrofitting buildings for use as shelters. As hurricane storm-surge risk zones expand as sea levels rise, 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. On the northeastern coast of Japan, for example, residents may have only minutes to respond between the time of the earthquake and the arrival of the tsunami.
Developing effective warning systems is an essential non-structural mitigation activity. Hurricane forecasts typically provide a few days’ advance notice of the potential for a hurricane affecting a particular area; While not perfect, storm surge forecasts can provide enough time for emergency managers to issue warnings. After Superstorm Sandy, a storm surge warning system was developed for the Meadowlands District in New Jersey that can provide storm surge forecast maps at least three hours in advance. When a hurricane is approaching the shoreline of the U.S. the National Hurricane Center issues regular advisories which give graphic information about storm surge, as well as estimates of the height of the storm surge for an area (form of estimates for certain stretches of coastline). Local authorities can take this information and use it to warn residents, for example, if a certain roadway is likely to flood, or if a levee is likely to be topped. Each storm is unique and, due to the many factors driving the impacts in a particular location (say, your house), storm surge forecasting is still tricky to predict on a small scale, especially because it is affected by even small changes in the landfall location as was the case in Hurricane Laura in August 2020. On a neighborhood or larger scale, the National Storm Surge Hazard Maps [2] provide an interactive mapping tool to estimate storm surge based on the hurricane category on the Saffir-Simpson Scale.
Establishing detection and warning systems are particularly essential to tsunami policy, as we have mentioned in previous modules. After a 1946 tsunami killed 160 people in Hilo, Hawaii, and 5 in Alaska, the United States established its first tsunami warning center in Ewa Beach, Hawaii. This center, now known as the Pacific Tsunami Warning Center (PTWC), is responsible for issuing most tsunami warnings for areas bordering the Pacific Ocean. A center in Palmer, Alaska, currently known as the National Tsunami Warning Center, provides warnings for Alaska, the Pacific coast of Canada, and the Pacific coast of the continental United States.
Following the 2004 Indian Ocean tsunami, which cost hundreds of thousands of people their lives, the United States spearheaded an effort to establish regional warning systems worldwide for coastal regions vulnerable to tsunamis. Initial responsibility for managing the Indian Ocean and Caribbean Sea systems fell to the PTWC, but the Indian Ocean system is now administered by national government organizations in Australia, India, and Indonesia, while a Caribbean Sea center opens in Puerto Rico in early 2021. Together with the North Atlantic and Mediterranean Tsunami Warning System, a European partnership, these organizations provide critical early warnings for tsunami events that serve an important preparedness function for regions exposed to tsunamis. See more details about the Global Tsunami Warning and Mitigation System in the Banda Aceh Case Study in this module.
In addition to having a sophisticated warning system in place and multiple ways to communicate warnings to residents, including phone texts, email, local TV news, as well as announcements via other broadcasting methods such as mosque loudspeakers in Islamic communities, and community group messenger networks, public education about what to do when an alert is broadcast is essential. This need is articulated in the case study in this module on the 2004 Indian Ocean tsunami and its impacts in Banda Aceh, Indonesia.
After disasters occur, the recovery process can be complex and overwhelming, so a post-disaster recovery plan is another helpful non-structural mitigation measure put in place by community-level government agencies. There are many aspects of recovery – economic, housing, environment, and social recovery – that should be considered. There are also many stakeholders who need to be involved in the recovery process. Developing a post-disaster recovery plan can identify and prioritize tasks and can recognize and engage stakeholders before an event takes place, thereby assisting recovery and minimizing chaos during a stressful time.
Another non-structural mitigation measure is zoning. Zoning enables local or regional governments to set restrictions on the types of structures that can be built in various locations within their jurisdictions. This tool can be used to prevent critical infrastructures such as power plants and hospitals from being built in tsunami or storm surge inundation risk zones. It can also be used in conjunction with development restrictions to prevent projects that would damage natural habitats, such as mangroves, that can mitigate tsunami or hurricane damage.
As we noted above, educating the public about mitigation measures are essential so that residents know what they can do to protect themselves, their families, and their property. So, education about tsunami and storm surge planning can fall under mitigation, but it is also part of preparedness.
Policies that promote mitigation are crucial to reducing the threat of disaster caused by natural hazards. In the United States, the National Tsunami Hazard Mitigation Program (NTHMP), run by NOAA in cooperation with USGS, FEMA, and the coastal U.S. states, has been developed to encourage tsunami mitigation practices. For more information, see the Tsunami Risk Reduction for the United States: A Framework for Action [7]. NOAA also manages the Storm Ready [8] and Tsunami Ready [9] programs, which recognize thousands of counties, communities, universities, and other members that meet a set of mitigation and preparedness criteria. Such programs and the policies advancing them are foundational to protecting people and places from disaster.
Links
[1] http://creativecommons.org/licenses/by-sa/3.0
[2] https://noaa.maps.arcgis.com/apps/MapSeries/index.html?appid=d9ed7904dbec441a9c4dd7b277935fad&entry=1
[3] https://www.usgs.gov/
[4] https://www.flickr.com/photos/trektrack/2859593228
[5] https://creativecommons.org/licenses/by-sa/2.0/
[6] http://earthobservatory.nasa.gov/Features/GlobalLandSurvey/sb3a.php
[7] https://www.sdr.gov/docs/Tsunami%20Risk%20Reduction%20for%20the%20US%20-%20A%20Framework%20for%20Action%202005-12-22.pdf
[8] https://www.weather.gov/StormReady
[9] https://www.ready.gov/tsunamis