ing Alaska) is significantly higher than the national average—300 versus 98 persons per square mile—reflecting the limited land area involved (Crossett et al. 2004). This population swells in the summer months, as beaches are the top tourist destination (Douglass et al. 2005). Coastal areas are projected to experience continued development pressures as both retirement magnets and tourist destinations. For example, many of the most populous coastal counties located in California, south Florida, and Texas (Harris County), which already experience the effects of hurricanes and other tropical storms, are expected to grow rapidly in the coming decades (Crossett et al. 2004). This growth will generate demand for more transportation infrastructure and increase the difficulty of evacuation in an emergency.

Sea level rise, which climate scientists now believe to be virtually certain, in combination with expected population growth, will aggravate the situation, making housing and infrastructure in low-lying coastal areas even more vulnerable to extensive flooding and higher storm surges. An estimated 60,000 miles of coastal highways is already exposed to periodic coastal storm flooding and wave action (Douglass et al. 2005).2 Those highways that currently serve as evacuation routes during hurricanes and other coastal storms could be compromised in the future. Although coastal highway mileage is a small fraction of the nearly 4 million miles of public roads in the United States, the vulnerability of these highways is concentrated in a few states, and some of these routes also serve as barriers to sea intrusion and as evacuation routes (Titus 2002).

Coastal areas are also major centers of economic activity. Six of the nation’s top 10 U.S. freight gateways (by value of shipments) (BTS 2007) will be at risk from sea level rise (see Table 3-1). Seven of the 10 largest ports (by tons of traffic) (BTS 2007, 30) are located in the Gulf Coast, whose vulnerability was amply demonstrated during the 2005 tropical storm season.3 The Gulf Coast is also home to the U.S. oil and gas industries, providing nearly 30 percent of the nation’s crude oil production and

2

These estimates were made by using geographic information systems to measure the length of roads in coastal counties, superimposing data from the Flood Insurance Rate Maps of the Federal Emergency Management Agency to indicate those roads along the coast or tidal rivers likely to be inundated by storm surge in a 100-year storm, and finally adjusting the estimate to eliminate flooding from rainfall runoff.

3

The Port of South Louisiana is the nation’s largest port by tonnage and the largest agricultural export facility in the United States (Mineta 2005). Fortunately, it suffered only minor structural damage from Hurricane Katrina.



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