How important are America's coastlines?

If you go by land area, the coasts are significant enough, but if you go by head count, coastal zones are even more important. The National Oceanic and Atmospheric Administration (NOAA) keeps tabs on coastal areas, publishing information at its "State of the Coast" website. According to the agency's 2013 "National Coastal Population Report," shoreline counties make up about 10% of the nation's 3 million square miles of land; but they are home to 39% of the nation's 313-million-person population. Broaden the definition of "coastal" to include nearby "watershed" counties, and the included land area increases to 20% — but the population who call those counties home jumps to 52% of the nation's people.

"Within the limited space of the nation's coast, population density far exceeds the nation as a whole, and this trend will continue into the future," the NOAA report says. "This situation presents coastal managers with the challenge of protecting both coastal ecosystems from a growing population and protecting a growing population from coastal hazards."

One example of that growing population, says the Reuters news agency, is former Arkansas governor and Presidential candidate Mike Huckabee. Reuters focused on Huckabee's case recently as part of a long analysis of coastal development trends (see "Water's Edge: Why Americans are flocking to their sinking shores even as the risks mount," by Deborah J. Nelson, Ryan McNeill, and Duff Wilson).

According to the Reuters report, Huckabee and an associate bought two shorefront parcels in Santa Rosa Beach, Florida, after three hurricanes in succession had severely eroded the beach at that location, leaving existing houses perched precariously on a fragile, disappearing dune. A contractor placed sand in front of the existing lots, called that the dune line, and applied for permits. When agency staff at the Florida Department of Environmental Protection (DEP) were reluctant to okay construction, Huckabee's engineer went over their heads, appealing to then-agency director Michael Sole.

Huckabee got his permit. And although Huckabee is far from a typical citizen, Reuters reports that his case in not so unusual. Says Reuters: "Accommodating the two politicians was nothing out of the ordinary. The way they got their permits is standard operating procedure along much of Florida's besieged shoreline … The ease with which Huckabee and his neighbors have been able to work around some of the most restrictive beach development laws in the country is indicative of a problem that only worsens as rising seas gnaw at U.S. shores: Americans are flocking to the water's edge, as they have for decades, even as the risks to life and property mount. And government is providing powerful inducements for them to do so."

The mounting risk, according to the Reuters report, is the incidence of tidal flooding — increasing for a century, and accelerating in recent decades. Reuters analyzed data from hourly readings at 25 government tide gauges with data going back at least 50 years. "During that period," Reuters reports, "the average number of days a year that tidal waters reached or exceeded flood thresholds increased at all but two sites and tripled at more than half of the locations. Since 2001, water has reached flood levels an average of 20 days or more a year in Annapolis, Maryland; Wilmington, North Carolina; Washington, D.C.; Atlantic City, New Jersey; Sandy Hook, New Jersey; and Charleston, South Carolina. Before 1971, none of these locations averaged more than five days a year. Annapolis had the highest average number of days a year above flood threshold since 2001, at 34. On the Delmarva Peninsula, the annual average tripled to 18 days at the Lewes, Delaware, tide gauge." With the more frequent flooding comes more rapid erosion of fragile shorelines, undermining homes at the same time as the rising waters threaten roads and public facilities.

For Grayson Chesser, a resident of tiny Saxis, Virginia, on the Chesapeake Bay shore, the handwriting is on the wall. Hard pressed to compete with more populous communities in the fight for government funds to hold out the sea, Saxis is facing a shortening future. Says Chesser: "You just can't beat the ocean. You're going to lose every time."