Excerpt:
Carlsbad, unlike many other seaside communities, might just have the time, space and resources to get ahead of coastal erosion. 

As Tom Frank walks down the shoulder of an oceanside highway in Carlsbad, California, he finds signs everywhere that this stretch of iconic highway will not last as it is much longer.

The sandy bluffs underneath roadside parking lots have completely given way in some spots, sending slabs of asphalt tumbling over the cliffs and leaving hollowed-out voids under the remaining pavement. Fences keep visitors from getting too close. But there are other “hot spots” where erosion has exposed abandoned drain pipes and forgotten curbs from an earlier era, when the highway was even closer to the ocean.

“This coastline’s eroding about six inches to a foot a year,” said Frank, Carlsbad’s transportation director and chief engineer. “There used to be roads along the coastline that are no longer there.”

Carlsbad, a suburban community 30 miles north of San Diego, has deployed a wide variety of innovative traffic designs to make its streets safer and more walkable. But perhaps no project on the city’s to-do list is bigger than determining the future of this stretch of Carlsbad Boulevard, a divided highway along beaches and bluffs that was once part of California’s famed Highway 101.

The most immediate threat is to a one-mile segment of the highway between two hills near Encinas Creek where the road gets within just a few feet of the crashing waves at high tide. Local officials call it “The Dip.” Already, saltwater spills onto the pavement during winter storms or “king tides.” A decade ago, the city placed boulders known as rip rap along the lowest point to secure the highway. But armoring the infrastructure only delays the inevitable — nobody is quite sure for how long — and will likely speed the process of sand on the beach disappearing.

“No matter what your perspective is on climate, the coastline is eroding, and it is coming in,” said Frank…