Pescadero and Butano Creeks Watershed Sediment TMDL

Pescadero-Butano Watershed Sediment TMDL is fully approved and effective as of May 21, 2019. Here are final versions of relevant documents associated with this project.

TMDL Approval Process

  • U.S. EPA approved the Basin Plan amendment to establish the TMDL and the habitat enhancement plan on June 24, 2019
  • California Office of Administrative Law approved the regulatory action on May 21, 2019
  • State Water Board approved the Basin Plan amendment (Resolution No. 2018-0058) on December 11, 2018
  • Regional Water Board adopted the Basin Plan amendment (R2-2018-0027) to establish a TMDL for sediment in the Pescadero-Butano Watershed on June 13, 2018

Background

The Pescadero and Butano Creeks flow westerly and drain approximately 81 mi2of the Santa Cruz Mountains in western San Mateo and Santa Cruz Counties and enters the Pacific Ocean near the town of Pescadero. The watershed contains steep forested slopes, deep canyons with steep inner gorges, a coastal valley, and rolling hills and grasslands near the coast. While the Pescadero sub-watershed is 58 mi2, the Butano sub-watershed is 23 mi2. Pescadero Marsh, a 320 acre brackish and freshwater wetland at the confluence of Pescadero Creek and Butano Creek, is one of the most significant coastal wetlands on the central California.   It is composed of an estuary/seasonal freshwater lagoon, fresh and brackish water marshes, brackish water ponds, and riparian areas along stream channels. The watershed provides habitat for a diverse array of aquatic life, including steelhead trout, and in the recent past, coho salmon. Other listed species that are also dependent on habitats within the Pescadero marsh include tidewater goby, San Francisco garter snake, and California red-legged frog.

 

Due to land use changes in the watershed, sediment input to the channels doubled in the last 150 years and sediment storage along the channels and the valley has been eliminated. In addition, channel incision have disconnected the channels from their floodplains and converted sediment storage reservoirs into sediment sources. The zone of sediment storage in the western quarter of the watershed shifted from channels and the valley downstream to the lagoon and marsh. The lagoon, which is one of the most sensitive habitats for listed species, now receives more sediment. There is more sediment input to the channels, no storage, and a very efficient drainage system that transports all sediment eroded from the hills and channels downstream into the lagoon and marsh where most of it deposits.

Populations of steelhead and salmon in the Pescadero-Butano watershed have declined substantially over the last century due to progressive changes in land use resulting in excess sediment in the channels and degradation of channel habitat. Land clearing, timber harvesting, legacy grazing and agricultural practices, channel modifications, and roads have: i) increased hillslope erosion; ii) doubled annual sediment supply to channels; iii) resulted in deep incision of Pescadero and Butano creeks and their tributaries; and iv) eliminated sediment storage along the channel and on the floodplains. Habitat conditions are degraded by elevated concentrations of fine sediment in the streambed (primarily sand) – caused by pervasive alteration of sediment supply, transport, and storage- which further reduces juvenile salmonid growth and survival in all freshwater life stages. Channel incision has severely impacted the basic physical habitat structure of the channel and has caused habitat simplification expressed by a substantial reduction in the frequency and area of gravel bars, riffles, and side channels. Channel incision has also isolated channels from their floodplains: floodplains no longer function as sediment storage sites and are lost as excellent rearing and refuge habitats for juvenile salmon and steelhead. In addition, a substantial reduction in the amount of large woody debris in channels has greatly diminished the capacity for the creeks to store, sort, and meter sediment, as well as the quality and diversity of freshwater channel habitats. Lastly, significant and persistent increases in sediment supply and loss of floodplains have contributed to an order-of-magnitude increase in the sedimentation rate in the Pescadero lagoon and marsh, adversely impacting water quality.

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For more information contact:

Setenay Bozkurt Frucht
Water Resource Control Engineer
San Francisco Bay Regional Water Quality Control Board
1515 Clay St., Suite 1400
Phone: (510) 622-2388
Fax: (510) 622-2460
E-mail: setenay.frucht@waterboards.ca.gov