"Strengthening the resilience of regions and their critical infrastructures is essential for achieving national resilience. Over the past decade, adjacent regions and infrastructures have become more interconnected, enabling local disasters to ripple across multiple jurisdictions and sectors, causing disruption and damage over large geographic areas. Resilience is especially important in the lifeline sectors -- energy, communication, water, and transportation -- because they underpin the most essential functions of business, government, and communities. Much has been done to build partnerships and improve resilience nationwide . But when disaster strikes, the biggest hit is felt by the regions and local communities that must respond and confront the immediate consequences. [...] This study focuses on the resilience of 'lifeline sectors' (energy, communications, water, and transportation) within regions that have complex multistate, multijurisdictional, and cross-sector interdependencies, and which would have large national impacts if they were to fail catastrophically. Interdependencies among lifeline sectors create a risk environment in which a disruption in one infrastructure or region can spread to other sectors and regions, often in unexpected ways."
Department of Homeland Security: https://www.dhs.gov/