Erosion Might Create Most Sand

The report, unveiled Wednesday by UC San Diego researchers, studied the craggy shoreline from Dana Point to La Jolla and concluded that as much as 68% of the region's beach sand comes from the coastal bluffs and cliffs, which have been steadily developed over the years.

Many of the area's bluffs and promontories are protected by seawalls that have been constructed to prevent the ocean from chewing away at the hillside. But, the study indicates, seawalls may actually reduce an important seashore ingredient -- sand.

The loss of sand is an important issue along the California coastline, where beach cities spend millions of dollars replacing sand that has been swept away.

The study was immediately challenged by coastal engineers and seawall advocates who argued that, ultimately, it might be easier to replace beach sand than allow cliff erosion to go unchecked. The findings stand in stark contrast to a long-held assumption that most beach sand comes from rivers and other tributaries that drain into the sea.

Environmentalists cheered the report, citing it as further proof that seawalls are a detriment to sandy beaches. State law currently allows beachfront property owners to protect their homes from erosion with seawalls, large boulders and other means of holding back the sea.

"I hope it raises the bar to qualify for a seawall," said Chad Nelsen, environmental director for the Surfrider Foundation, an environmental group that has sued developers to stop seawalls.

"There's only so many houses on this front row on the bluffs and, compared to the millions [of people who]

The report gives ammunition to environmentalists who believe that property owners whose homes are threatened should retreat from coastal bluff areas rather than fight nature. Areas with long-standing erosion problems include north San Diego County, Santa Cruz and Pacifica, south of San Francisco.

But critics say this study doesn't change the seawall debate. Eroding bluffs make up a bigger percentage of beach sand simply because the region's urbanized rivers carry less sediment, said David Skelly, a coastal engineer who designs seawalls. The study was also done over a very dry six-year period ending in 2004, which meant there was less rainfall to carry sediment down rivers.