Addressing Coastal Vulnerabilities Through Comprehensive Planning: How RAND Supported the Development of Louisiana's Comprehensive Master Plan

According to the U.S. Census Bureau, U.S. coastal counties have grown by more than 45 percent between 1970 and 2010, amounting to 50 million new coastal residents and billions of dollars in additional assets (homes and businesses) in these areas.1 Coastal residents are vulnerable to many potential risks, including damage to human life and property that result from storm flooding. And the increasing concentration of people, property, and other activities in coastal areas can itself contribute to the problem by removing or diminishing wetlands, barrier islands, and other features that serve as natural buffers to storm surges. The Gulf Coast has borne a substantial portion of the damage from coastal storms in recent decades. For example, Hurricanes Katrina and Rita in 2005 and Gustav and Ike in 2008 collectively caused approximately $150 billion in damage to Louisiana, Mississippi, and other Gulf Coast states.2 But these coastal risks are also prevalent in other areas, as shown by the massive damage and disruption that “Superstorm” Sandy caused to the people, homes, businesses, and infrastructure of coastal communities along the Eastern Seaboard. Coastal risks may increase as the climate warms. Sea levels are anywhere from 6 to 12 inches higher now than a century ago and continue to rise at a rate of more than an inch per decade. Current projections suggest that the rate of sea-level rise will continue to increase because of warming oceans and melting glaciers, leading to sea levels from 8 inches to as much as 4–6 feet higher than 1990 levels by 2100.3 Such increases, when combined with coastal tides and storm surge, will likely dramatically increase the risk of floods to coastal residents and property. And warming sea surface temperatures and changing climate patterns could also either intensify future tropical storms and hurricanes or make large and powerful hurricanes more common.4 Reducing the vulnerability of coastal communities to these threats is challenging, given both the scale of the problem across broad geographic regions and uncertainty about the specific nature of the risk. Several restoration efforts in the United States have begun to take more-comprehensive planning approaches to addressing such challenges. Those in the Florida Everglades, Chesapeake Bay, and San Francisco Bay Delta regions are notable recent examples. But such efforts have not yet led to a broadly applicable methodology for identifying and reducing coastal vulnerabilities to climate change.