Butano Creek Channel Reconnection and Resilience Project
This multi-objective project addresses critical fish passage, water quality and flood risk challenges affecting Butano Creek, Pescadero Marsh and Lagoon and the surrounding community of Pescadero in unincorporated San Mateo County.
Anthropogenic disturbances to the watershed have significantly increased sediment delivery to Butano Creek and the Pescadero Marsh. In large portions of the project reach, the creek channel no longer existed due to sediment accumulation filling the channel to the top of its banks, and subsequent establishment of vegetation on top of the accumulated sediment. The resulting condition was nearly impassable for anadromous salmonids and other native fish species. The limited fish passage through this reach was of particular concern for populations of endangered Central California Coast Coho Salmon (Oncorhynchus kisutch) and threatened Central California Coast Steelhead (O. mykiss). Compounding these challenges were the regular development of high levels of anoxia in Butano Marsh which caused devastating annual fish fills in Pescadero Lagoon during natural breaching events in late fall and early winter. The loss of Butano Creek’s conveyance capacity also caused chronic flooding of Pescadero Creek Road, disconnecting the town from its main access route and emergency services following even small rain events.
To address these problems, the project excavated accumulated sediment from the Butano Creek channel to re-establish fish passage between the estuary and the watershed, and to reduce flooding of Pescadero Creek Road during low magnitude, frequently occurring flood events. The excavated sediment was beneficially re-used to selectively fill portions of Butano Marsh including relic agricultural ditches, borrow pits, and other man-made low spots that generated anoxic conditions and allowed the anoxic water to rapidly drain from the marsh into the lagoon during breaches. These actions restored salmonid access to the watershed’s spawning habitat, providing escape and refuge during times of low water quality in the marsh, and reduced the conditions that create anoxic water and drive fish kills. cbec served as the prime consultant on the project, managing efforts of four other entities. cbec’s field reconnaissance team conducted extensive topographic and bathymetric surveys, then leveraged this data to develop a 2-D hydrodynamic and sediment transport model to inform restoration designs. Other efforts included development of plansets, basis of design reports, and cost estimates, permitting support and bid support, and construction supervision. Construction was completed in 2019 with monitoring ongoing.