Watershed Assessments >>
Watershed Assessment 2008
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.
Watershed Assessment 2004
The Pescadero-Butano Watershed Assessment was undertaken to assess current habitat conditions
for Coho salmon and Steelhead trout in the watershed, and to identify factors limiting the quality
and extent of salmonid habitat. The overall goal of the project is to develop a scientific basis for
future management plans and actions related to restoration of the watershed and the salmonid
fishery. The specific objectives of the project are as follows:
1. Characterize the watershed and identify the areas of remaining high quality salmonid
habitat, that should receive high priority for conservation and restoration treatments;
2. Identify the factors and anthropogenic processes limiting the quality of salmonid habitat in
the watershed, and water quality generally.
3. Identify the most cost-effective treatments for improving salmonid habitat, and the areas
where these should be employed.
Historically, both Pescadero Creek and Butano Creek, as well as several tributary streams,
supported runs of Steelhead trout and Coho salmon. Steelhead are still present, but there have
been only sparse reports of Coho salmon in the watershed in recent years. Both streams are listed
under the federal Clean Water Act as impaired water bodies for sediment. It should be noted that
this assessment is not intended to substitute for, nor to form the basis for the development of
Total Maximum Daily Loads (TMDL) for the basin, though the study may be useful to others
undertaking their development.
The Pescadero-Butano watershed has been the subject of several past studies, as well as actions
and efforts by local residents to investigate and solve problems associated with the streams,
including flooding, landsliding, impaired water quality, and the declining fish population. The
Pescadero-Butano Watershed Assessment builds on past studies, and includes several discrete
new studies. These include a land use history (Chapter 3); a hydrologic analysis of the watershed,
focusing on the USGS stream gauging record (Chapter 4) and a study of the changes in stream
bed elevation at several County road bridges (Chapter 5); a geomorphic study of the watershed,
including an analysis of sediment sources and erosion rates since 1937 (Chapter 6) and current
geomorphology of stream channels (Chapter 7); and an assessment of current ecological
conditions, focusing on the quality of salmonid spawning and rearing habitat, and specific
impairments to salmonid habitat (Chapter 8). All of these studies are synthesized and conclusions
are presented in Chapter 2……….