San Gregorio Creek - Watershed

Watershed

The San Gregorio watershed is located approximately 11 miles (18 km) south of Half Moon Bay and covers approximately 61 square miles (160 km2). It is the second largest drainage in coastal San Mateo County, with approximately 45 miles (72 km) of "blue line" (perennial) streams. The mainstem of San Gregorio Creek begins at the confluence of Alpine Creek and La Honda Creek in La Honda, and flows 11.8 miles (19.0 km) to its mouth at San Gregorio State Beach in San Gregorio.

The creek ends in a lagoon primarily in the incised channel upstream from the Highway 1 Bridge. The lagoon at its seasonal largest, is about five acres and six feet deep, and serves as habitat for Tidewater goby (Eucyclogobius newberryi)) and rearing steelhead. Coho salmon do not rear in the lagoon but outgoing smolts use it to physiologically prepare for migration to saltwater.

This river floods occasionally on its path down CA Route 84 towards the Pacific Ocean, most famously during the 1997 El Niño.