SF's $175M Seawall is Stirring Up a Sand Mystery

San Francisco is planning one of the largest seawalls in California history to protect a sewage treatment plant at Ocean Beach, but scientists warn that hardening the coastline could accelerate the very erosion it's meant to stop. Nobody fully understands why sand has been migrating from the beach's south end to the north since the 1980s, and researchers argue that building a major structure without answering that question first is a significant gamble.