Communities as Systems

Infrastructure is the backbone of our communities, providing not only critical services but also the means for health, safety, and economic growth. Virtually everything we do from phoning a friend, to sending an e-mail at work, to making our evening dinner relies on a web of interconnected infrastructure assets and systems. Given the vital importance of infrastructure to our social and economic well-being, it is imperative we ensure these systems are strong, secure, and resilient.

Essential Community Functions


One or more local jurisdictions or special districts, including a region or shared infrastructure corridor.

The NIST Community Resilience Planning Guide is one resource that outlines a series of basic societal functions that communities provide, such as economic growth, education, and public health. In every community, both urban and rural, these societal functions are enabled by infrastructure assets and systems working together to provide critical services. For example, the public health function relies on electric power to run lights and hospital equipment, clean water for sanitation, emergency services and transportation infrastructure to transport patients and healthcare providers, and many other infrastructure sectors.

A functional approach begins with understanding what functions are critical to a community or region's success and examines how those functions can be made more resilient. Importantly, this approach does not mean protecting individual assets and systems but instead encourages users to think about how a function can be preserved. For example, while hardening electric grid infrastructure can improve the resilience of community functions, a similar result may be achieved through deploying generators to critical facilities. Ultimately, the goal is to limit disruptions to the delivery of essential community functions, whether by reducing the likelihood of infrastructure systems disruptions or reducing their consequences.


A combination or group of components that interact with each other to perform a function.

Importantly, infrastructure assets and systems not only support societal functions but are also interconnected with and reliant on one another to operate. For example, a community’s water system is almost certainly dependent on electricity to manage filtration processes and power pumps. And electric power generation and transmission systems rely on communication networks to manage, monitor, and control the flow of electricity. Moreover, many of these systems are large and geographically dispersed, crossing local jurisdictions and state lines and requiring coordination with many partners to enhance resilience.

Taking a big-picture view of your community can help you identify fundamental functions and recognize all the interconnected assets and systems that are truly essential to maintaining its vitality.

Critical Infrastructure Systems


The collection of interrelated physical, cyber, and organizational assets and systems that provide products and services essential for the operation of society.

Infrastructure systems are the backbone of communities. While all infrastructure plays a role, some infrastructure systems are more critical than others. Critical infrastructure are those infrastructure systems and assets that are so vital that their incapacitation or destruction would have a debilitating effect on security, the economy, public health, public safety, or any combination thereof.

The U.S. Department of Homeland Security has defined 16 sectors or categories of infrastructure that are considered critical to the nation. At the local level, some of these systems may be owned or operated by local government partners and many of them will be vital to the health, economy, and security of the community or region.Each critical infrastructure system is made up of individual assets that work together as an integrated network.

Chemical: Manufactures, stores, uses, and transports chemicals. Food & Agriculture: Farms, restaurants, and food manufacturing, processing, and storage facilities.
Commercial Facilities: Facilities with open-access to the public for shopping, business, entertainment, or lodging Healthcare & Public Health: Healthcare facilities, research centers, suppliers, manufacturers, and information technology systems.
Communications: Interconnected physical and cyber networks that enable voice, video, and data transmission. Financial: Credit and financing organizations, depository institutions, providers of investment products, and insurance companies.
Critical Manufacturing: Industries that produce primary metals, machinery, equipment, and components essential to other critical infrastructure. Government Facilities: Buildings owned or leased by federal, state, local, and tribal governments including everything from courthouses to schools to the post office.
Energy: Provides electric power and fuels. Information Technology: Produces and provides hardware, software, and information technology systems and services, and the Internet.
Emergency Services: Services that protect property and the environment, save lives, assist communities impacted by disasters, and aid recovery during emergencies. Nuclear Reactors, Materials & Waste: Nuclear reactors that produce power, fuel, and medical or industrial isotopes, as well as shipments and users of radioactive materials.
Dams: Delivers critical water retention and control services. Transportation Systems: Aviation, highway, maritime, mass transit, freight rail, postal/shipping, and pipeline systems.
Defense Industrial Base: Enables research and development, design, production, delivery, and maintenance of military weapons systems. Water: Drinking water and wastewater systems.

These critical infrastructure sectors are related to and resemble the "community lifelines" FEMA uses to discuss essential systems within response and recovery operations. Both the sector and lifelines constructs can be used to consider infrastructure dependencies. Within this tool, we will take a closer look at several infrastructure systems that are key to resilience whether looked at through a sector-based or "community lifelines" lens.

Each critical infrastructure system is made up of individual assets that work together as an integrated system. The figures below illustrate the networking of assets using four of the most important critical infrastructure systems as examples. These four infrastructure sectors - Energy, Communications, Water, and Transportation - are critical to the operations of almost all other sectors, as well as each other, and are fundamental to the delivery of the basic societal functions communities seek to provide. While each figure only depicts a single, simplified system within each sector (there are many, and many variations!), they should help illustrate the interconnected nature of those systems and their reliance on many individual assets.

Communication Icon

Common communication sector assets include telephone lines, fiber optic lines, cell towers, switching stations, and data hubs.

Energy Sector Icon

Energy Sector Assets include the electric grid--power generation, transmission, and distribution, as well as fuel refineries, pipelines, and terminals.

Water Sector Icon
Water & Wastewater

The water sector include water and wastewater treatment facilities, pipes, pumping stations, and storage.

Transporation Icon

The Transportation sector includes roads, rail, trucking, airports and supporting infrastructure, ports and port infrastructure, as well as intermodal facilities and pipelines and pumping stations

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