Natural Hazard Observer Nov 2005

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Living on the Edge: The Coastal Collision Course ®How should society reduce the inevitable risks of liv- ing near the shore? Obviously, we cannot expect people to leave the coasts, but we can expect sound government policies that protect their long -term sustainability and di- minish damage to the built environment through mitiga- tion. Hurricanes are a regular occurrence along the East and Gulf coasts of the United States; 167 tropical storms made landfall during the twentieth century. We are in a new cycle of increased Atlantic hurricane activity, and at the same time there is a continuing coastward migration of Americans. Coastal watershed counties already account for about 50 percent of the population. It seems that eve- ryone wants a waterfront view, and beachfront property has become some of the most expensive real estate in the country. Small beach cottages have given way in recent decades to luxurious, multistory houses, and in South Florida, high -rise condominiums are approaching $500 million valuations. The "Gold Coast" of Florida, which runs along the southeastern coast between Palm Beach and Miami, has an appraised value exceeding $1.3 trillion that is highly vulnerable to hurricanes. Any erosion of the beach that takes place, of course, increases the exposure of fixed structures to the impact of coastal storms. �, I Coastal erosion is a national problem; best estimates are that almost 90 percent of the nation's sandy beaches are receding.' This nearly ubiquitous beach erosion prob- lem is particularly troublesome in that the rate of coastal erosion is about two orders of magnitude greater than the rate of sea level rise (SLR), so that even small changes of SLR result in significant land loss.' Since one of the most certain consequences of global warming is an increase in the rate of global SLR, the already severe coastal erosion problems witnessed in the twentieth century will be exac- erbated in the coming decades. Growing populations and concomitant beachfront de- velopment in the face of rising sea levels and shoreline recession defines a coastal collision course. There is also a collision of management philosophy and policies of the three principal federal agencies with statutory authority: the U.S. Army Corps of Engineers, the Coastal Zone Management (CZM) Program administered by the Na- tional Oceanic and Atmospheric Administration, and the Federal Emergency Management Agency's (FEMA) Na- tional Flood Insurance Program. The Corps of Engineers has been criticized for its role in encouraging coastal development and poststorm redevelopment through its subsidized sand pumping pro- jects, which renourish beaches. Beach nourishment is seen by an increasing number of coastal communities as a panacea even though many renourished beaches have lasted only a few years rather than decades.' In contrast, the CZM Program offers states an incentive to better manage beachfront development. Unfortunately, best management practices have rarely been exercised. Most of the burden of managing coastal development has fallen upon FEMA because of its national flood insur- ance, which is sought after by homeowners and communi- ties that are literally "living on the edge." FEMA has done an excellent job by providing incentives to build new structures above the storm surge elevation and to strengthen existing structures against windstorm damage, but there has been no direct consideration of horizontal shoreline movement, specifically coastal erosion.' The lack of coordinated federal erosion programs and policies is abundantly evident as the coastal building boom continues. Nationwide, coastal erosion may be responsible for approximately $500 million of property damage each year,' including loss of structures and land. Within the highest risk flood hazard areas (called V -zones by FEMA) of the Atlantic and Gulf coasts, the risk of damage from erosion is almost equal to (and added to) that from flood- ing. If the present trend continues, it is estimated that one of four buildings located within 500 feet (152.4 m) of the U.S. shoreline will be claimed by coastal erosion during the next 60 years.' These estimates do not assume any additional beach hardening, nor do they make assumptions about future beach nourishment projects. In actuality, more and more coastal communities are seeking beach nourishment projects funded by the Corps of Engineers. Through these Corps- authorized beach fill projects, the federal government is making 50 -year commitments with little to no regard for global change impacts. Estimates of erosion damage do not include the ef- fects of accelerated SLR due to climate change because projections of future shoreline positions are based on his- torical observations. If SLR during the next 50 years is 3.9 inches (10 cm) greater than during the past half cen- tury, erosion rates would average 11.8 inches (30 cm) per year faster than observed historically. This would increase Natural Hazards Observer November 2005