Watershed Assessment 2008
Introduction
Pescadero Marsh is an approximately 340-acre coastal wetland formed at the confluence of
Pescadero Creek and Butano Creek in San Mateo County, California. It is located about 12 miles
south of the City of Half Moon Bay, at the intersection of State Highway 1 and Pescadero Road
(Figure 1). Pescadero Marsh (the Marsh) encompasses Pescadero Lagoon, the lower courses of
the two creeks, and some adjacent upland areas (Figure 2). The Marsh is within Pescadero State
Beach; a 225 acre section of the Marsh is classified as Pescadero Marsh Natural Preserve.
Pescadero Marsh offers a diversity of habitats, including salt marsh, fresh water marsh, sand
dune, riparian forest, and coastal scrub. The Marsh changes seasonally from an open, tidal estuary
to a closed lagoon, the result of a sandbar that forms across the mouth of Pescadero Creek during
the spring, summer, or fall, and that persists usually until late fall or early winter. After formation
of the sandbar, the water level in the lagoon and throughout the Marsh rises, inundating the
lowland areas of the Marsh.
Pescadero Marsh provides habitat for a wide variety offish, birds, amphibians, reptiles,
invertebrates, and plants. Over the course of the twentieth century, much of this habitat was
degraded or eliminated, due to diking and draining of most of the marsh areas, and their
conversion to agricultural uses. In addition, the construction of State Highway 1 across the
western edge of the Marsh; the construction of Pescadero Road and the bridge over Butano
Creek; and alterations in the watersheds of Pescadero and Butano Creeks that led to a huge
increase in the sediment load carried by the two streams (ESA, 2004) and a decrease in dry
season flows – all wrought major changes on the Marsh.
The California Department of Parks and Recreation (DPR) began purchasing land for Pescadero
State Beach in 1958, and completed acquisition of the currently-held parcels in 1979.1 Since DPR
took ownership of the Marsh, it has engaged in a series of studies to better understand Marsh
dynamics and past conditions, and has undertaken a series of actions to restore the natural
hydrologic functions and biological productivity of the Marsh. This report represents the latest
effort in this series.


