Considerations for Management of the Mouth State of California’s Bar-built Estuaries

California has numerous rivers and creeks that meet the ocean in a small estuary that forms a sandbar during lower stream flow conditions. These bar-built estuaries face numerous management challenges that aim to balance developmental and recreational uses with the challenges of flooding, degraded water quality, fish passage, and more. Mechanical methods to open the sandbar are used to alleviate developmental and recreational needs in addition to increasing flow between freshwater and marine habitats. This breaching of the sandbar can have a range of effects on fish and their habitat conditions, making it complex to manage.

With support from NOAA’s National Marine Fisheries Service (NMFS), scientists at the Bodega Marine Lab and Moss Landing Marine Labs have authored, in collaboration with NMFS biologists in the West Coast Region, a report that presents an overview of considerations for managed breaching in California. It presents a synthesis of processes and phenomena related to bar-built estuary mouth closure and uses this to identify potential impacts of breaching. Three specific systems are reviewed as case studies: Los Peñasquitos Lagoon in San Diego County, Scott Creek Estuary in Santa Cruz County, and Russian River Estuary in Sonoma County. While there are fundamental similarities in the closure and breaching cycle across all bar-built estuaries statewide, there is also an immense diversity between these systems due to differences in watershed size, hydrology, development (rural, urban, agricultural, road/rail), and more.

Local communities challenged with the management of bar-built estuaries are likely to develop a management strategy where there is significant effort and experience in local monitoring, research, and informed stakeholder consultation. However, where there is limited monitoring, science, or consultation, the considerations outlined in this report provide preliminary guidance and a comparison with one of the study systems in this report may provide insight to the potential impacts of breaching management decisions.

For questions or comments please contact Brian Meux at 707 575-1253, brian meux@noaa.gov