The Long-Term Problem Facing California Beaches

California beaches are shrinking.

Over the past two centuries, the state has dammed about 500 streams. They don’t just trap water, they trap sand, which would otherwise flow down to replenish beaches.  Last week, a state Assembly committee examined the problem.

UC Santa Cruz professor Gary Griggs, who studies beach erosion, estimated that about a fourth of all the sand that rivers would otherwise carry to California beaches is trapped behind dams and reservoirs.

Federal, state and local agencies have undertaken projects along the California coastline to add more sand and mitigate the human causes of beach erosion.

Griggs says removing old dams, which no longer serve a purpose, can help, as can some renourishment and dredging projects. But Griggs says longer-term, beach erosion has less obvious solutions.

"The last ice age ended, ice began to melt — which has been happening ever since — the oceans filled back up, and the shoreline’s gradually moving inland," Griggs says. "It will push a beach along in front of it."

California has added seawalls and rocks to preserve its coastline. Griggs says that can protect development, but exacerbates the speed at which beaches disappear.

Caught between the ocean and a sea wall, "we lose the beach, we drown the beach, we flood the beach," Griggs says.

As sea level rises, Griggs says not just beaches, but coastal cities across the globe will have to retreat from the rising sea.