Resilient engineering is design of infrastructure to withstand and recover from such major hazard events as earthquakes, hurricanes, floods, and wildfires. It goes beyond design for life safety. It also looks beyond historic hazards such as the 100-year flood or the 500-year seismic event to anticipate hazards that increase with changes in climate and effects from the built environment.
For example, the city of Houston, Texas, experiences “500-year floods” year after year. Clearly the historic definition of flooding no longer reflects the current or prospective situation. Designing to withstand historic floods does not serve the community well.
Resilience is the capacity of individuals, communities and systems to survive, adapt and grow in the face of stress and shocks, and even transform when conditions require it. Building resilience is about making people, communities and systems better prepared to withstand catastrophic events–both natural and man made–and able to bounce back more quickly and emerge stronger from these shocks and stresses.–The Rockefeller Foundation
The National Institute of Building Sciences reports that every $1 invested in disaster mitigation saves $6.
Administrative measures for resiliency
Low-probability, high-impact events are a fact of life. Individual humans look for protection from them to governments and, if they can afford it, insurers. Humanity, at least as represented by the world’s governments, reveals instead a preference to ignore them until forced to react–even when foresight’s price-tag is small. It is an abdication of responsibility and a betrayal of the future.–“The next catastrophe,” The Economist, June 25, 2020
Resilient engineering is only part of what it takes to make a resilient community. Some aspects of resiliency have more to do with administration than engineering. In “The rising cost of catastrophes,” The Economist outlines several steps governments can take to make communities more resilient:
- Preparation. Instead of concentrating on rescue and repair after the fact, governments can designate buildings to serve as emergency shelters. Buildings such as school cafeterias or public libraries that are already part of the community are best, as they’ll be maintained and ready when needed.
- Protection of natural defenses. Instead of allowing private owners to drain swamps, pave large areas, and build on flood plains at will, governments can enact and enforce environmental regulations and zoning laws. For example, the city of Edmonton, Alberta, prohibits building on land that is prone to landslides. The city of Toronto, Ontario, prohibits building in ravines that are subject to occasional flooding. In both cities these areas have become parks–amenities for local residents–rather than disasters waiting to happen.
- Elimination of perverse incentives. Instead of paying to rebuild on the same land after a flood or subsidizing insurance for buildings on unsuitable sites, governments can remove such perverse incentives. For example, a city council could buy and demolish homes in a flood plain.
Community resilience planning
The National Institute of Standards and Technology (NIST) has prepared a two-volume guide for community resilience planning. The guide outlines a six-step process for setting priorities and allocating resources to improve resilience. It also shows how to characterize the social and economic dimensions of the community, dependencies and cascading consequences, and building and infrastructure performance. Planning includes government officials, business leaders, community members, and other stakeholders. Implementation takes place over several years to keep the costs manageable.
The interstate highway system contributes to resilience by facilitating evacuation in advance of floods, fires, and other calamities. After the event, it permits ready transport of supplies and assistance from other parts of the country.
Resilience planning can make a community better able to recover and even thrive after a catastrophe. It can also make it a more attractive place for individuals and businesses. For example, the Big U is a large-scale project that provides flood control for Lower Manhattan while also providing recreational opportunities. And good transportation is essential to running a successful business.
The extent of recovery and the ultimate outcome depend upon the nature and severity of the event and the community’s preparedness to prevent incidents, mitigate risk, protect assets, respond in a timely and coordinated way, and recover community functions. Together, these measures determine the community’s resilience.–Community Resilience Planning Guide for Buildings and Infrastructure Systems, Vol. I and II
Planning for resilient engineering in Minnesota
The State of Minnesota assessed two types of buildings, a library and an apartment building, for vulnerability to a disaster. The library would serve as an emergency community hub, while the apartment building would allow residents to shelter in place. Rather than specify the type of disaster, the study concentrated on the type of service disruption that would result. In this case, it considered disruptions to the energy supply (natural gas and electricity), water and sanitation, and vehicle transportation. The study assumed that the disruptions would last for 10 days, with supplies of food and water arriving after 4 days.
For the energy system, the study considered how to maintain acceptable temperatures, store energy, and operate at reduced power. The strategies included passive ventilation, heating, and cooling; insulation and thermal mass; solar panels with battery backup; and hookups for generators. Even if the solar array generates more power than the building uses in low-power mode, a generator may be necessary if a storm damages the solar array.
The overall, annual energy use increases very slightly…over the predicted 50-year period. The end uses, however, shift. As the outdoor temperature rises across the year, heating demand is reduced (21% to 16%) while cooling demand increases (15% to 20%). This may have implications for sizing heating and cooling equipment…Energy models…[predict] an overall energy demand increase of 14% from present day to 2040. This modeling indicates that energy conservation measures taken now to reduce energy use and ensure resilience also contribute to “future-proofing” the building against a changing climate.–Resilience Adaptation of Sustainable Buildings
Minnesota also regulates its utilities to encourage them to prepare for extremes of weather.