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Elkhorn Slough Tidal Wetland Project

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the Tidal Wetland Project.




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Elkhorn Slough meandering creeks
Snowy plover © Matt Beals

The Elkhorn Slough Tidal Wetland Program has released a Request for Proposals (RFP) for final engineering, bid oversight and construction administration for the Elkhorn Slough Tidal Marsh Restoration Project. The RFP can be found here.


With fifty percent, or 1,000 acres, of Elkhorn Slough’s salt marshes being lost over the past 150 years and the ongoing marsh loss and habitat erosion, the Elkhorn Slough Tidal Wetland Project was formed. This unique program is a collaborative effort to develop and implement strategies to conserve and restore estuarine habitats in the Elkhorn Slough watershed. This collaboration, initiated in 2004, involves over 100 coastal resource managers, scientific experts, representatives from key regulatory and jurisdictional entities, leaders of conservation organizations, and community members.

Tidal Marsh Restoration Project
We are doing the first major salt marsh restoration project in Elkhorn Slough, by adding sediment to a subsided marsh, and are in the midst of thoughtful experimental design to ensure we have a high, sustainable marsh that will be more sustainable in the face of sea level rise than our other low marshes.
The Elkhorn Slough Tidal Marsh Restoration Project was a primary focus of TWP in 2014. Much of the year was spent evaluating the existing conditions and planning the project. This effort was led by ESA-PWA and included H.T. Harvey, Moffatt and Nichol, Moss Landing Marine Laboratories and ENGEO. Select the highlighted links to view the various reports. The Existing Conditions Report characterizes the current hydrology, water quality, geology, soils, biological resources, land use history and other environmental resources in and around the project site. This was pared down and formed the basis for the Restoration Plan. The Restoration Plan (5MB, and Appendices 18MB) covers a number of aspects of the project including; design criteria, project alternatives, sediment suitability, construction sequencing and methods as well as experimental design and adaptive management. We have enlisted a Salt Marsh Working Group, a group of scientists with expertise in marsh restoration both locally and worldwide. They have helped us with critical questions on the marsh elevation, slope and tidal channel configuration. CEQA is currently underway with the California Department of Fish and Wildlife (CDFW) as the lead. Two multi-agency meetings were held in 2014 (October and November) to gather agency input on regulatory compliance issues.

CDFW released the Initial Study Mitigated Negative Declaration. The public review period runs from July 10 - August 24, 2015. Permit applications are in preparation. It is anticipated that at least 10 permits will be needed from various regional, state and federal entities. Fundraising for construction is underway, we still need to raise about $2.5M. Construction is currently slated for 2016.


Tidal Wetland Project 5-year Plan
The strategic planning team decided that marsh restoration, improvement of water quality in stagnant areas behind water control structures, and supporting efforts to reduce nutrient loading are the top priorities for the coming decade.
The Strategic Planning Team and Science Panel met in early 2014 to identify and prioritize objectives focused around our core mission of conserving and restoring estuarine habitats and the processes that sustain them. Starting from the large-scale recommendations finalized by the group in 2012, the outcome of the 2014 meeting was a prioritized list of objectives for TWP partners to focus their efforts in Elkhorn Slough over the next five year period. The 5-year plan can be found here.

Parsons Slough Project Monitoring
The parsons sill project was successfully completed, the first project that will reduce tidal erosion in the estuary, and everything is going as expected. In response to questions about the Parsons Slough Project monitoring, we have posted two reports. One is an updated Parsons Slough Adaptive Management Plan, and the other is the 2014 Parsons Slough Project Annual Report (1.5MB) on the Parson monitoring submitted to the RWQCB and USACE. The Parsons Slough Adaptive Management Plan was developed collaboratively with smaller working groups composed of teams of scientists and resources agency personnel. They focused on identifying areas of positive and potential negative outcomes of the sill and developed monitoring strategies to identify changes. Under each objective is a brief summary of the outcomes to date. The areas of focus include: hydrodynamics and geomorphology, water quality, habitats, fish, invertebrates, waterbirds, and marine mammals.

Restoration recommendations for estuarine habitats of Elkhorn Slough
For the past several years, stakeholders and scientists participating in the Elkhorn Slough Tidal Wetland Project (TWP) have evaluated the pros and cons of different restoration alternatives for the estuary.  The main channel and tidal creeks in Elkhorn Slough have undergone extensive erosion due to tidal scour following the opening of an artificial mouth to the estuary in 1946 to accommodate Moss Landing Harbor.  The larger estuarine mouth also has contributed to dieback of salt marshes.  Tidal Wetland Project investigations explored whether a single large fix at the mouth of the estuary, effectively shrinking the mouth size, would benefit overall ecosystem health.  In November 2012, the TWP Strategic Planning Team, informed by the Science Panel, approved 10 recommendations for future action.  The decision, based on extensive interdisciplinary evaluations, was that no large scale action should currently be undertaken at the mouth of the estuary, because of potential risks to water quality, negative impacts to recreational boating, and uncertainty about benefits to salt marsh habitat. Instead, the Strategic Planning Team recommends a variety of other approaches to restoration be implemented over the coming decade, including a sediment addition project to restore subsided marsh, and enhancement of tidal exchange to selected wetlands behind water control structures.   The recommendations highlight the importance of reducing nutrient-loading and eutrophication in the estuary.  The recommendations also call for a collaborative approach to further science-based decision-making for the estuary.  The complete report summarizing the evaluation of different alternatives and the approved recommendations can be downloaded here (TWP_Recommendations_2012.pdf). In the coming years meetings with the Strategic Planning Team and Science Panel will focus on refining and prioritizing various approaches.


Restoration Plan for the Tidal Marsh Restoration Project at the Elkhorn Slough Reserve (24MB, PDF).

TWP Strategic PlanDownload the Elkhorn Slough Tidal Wetland Project Strategic Plan. This document describes Elkhorn Slough’s estuarine habitats, characterizes the main impacts causing loss and degradation of those habitats, and provides conservation and restoration recommendations.

The Elkhorn Slough Tidal Wetland Project is a collaborative effort led by the Elkhorn Slough National Estuarine Research Reserve. The Elkhorn Slough Reserve is owned and managed by the California Department of Fish and Wildlife in partnership with the National Oceanic and Atmospheric Administration and the Elkhorn Slough Foundation.

Grant funding for this project has been provided by the National Oceanic and Atmospheric Administration’s Coastal Impact Assistance Program, David and Lucile Packard Foundation, Resources Legacy Fund Foundation, U.S. Environmental Protection Agency, and the California Coastal Conservancy.


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This site is maintained by the Elkhorn Slough Foundation in partnership with the Elkhorn Slough National Estuarine Research Reserve