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New Life for Eroding Shorelines: Beach and Marsh Edge Change in the San Francisco Estuary

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New Life for Eroding Shorelines: Beach and Marsh Edge Change in the San Francisco Estuary New Life for Eroding Shorelines: Beach and Marsh Edge Change in the San Francisco Estuary San Francisco SFEI Estuary Institute i New Life for Eroding Shorelines: Beach and Marsh Edge Change in the San Francisco Estuary A technical report associated with the New Life for Eroding Shorelines Project Prepared by SFEI In partnership with Julie Beagle Peter Baye (Coastal Ecologist) Katie McKnight Roger Leventhal (Marin Public Works) Ellen Plane Gloria Desanker Funded by Marin Community Foundation California Coastal Conservancy San Francisco SFEI Estuary Institute sfei publication #984 april 2020 SUGGESTED CITATION SFEI and Peter Baye. 2020. New Life for Eroding Shorelines: Beach and Marsh Edge Change in the San Francisco Estuary. Publication #984, San Francisco Estuary Institute, Richmond, CA. Version 1.0 (April 2020) REPORT AVAILABILITY Report is available at sfei.org IMAGE PERMISSION Permissions rights for images used in this publication have been specifically acquired for one-time use in this publication only. Further use or reproduction is prohibited without express written permission from the responsible source institution. For permissions and reproductions inquiries, please contact the responsible source institution directly. COVER and FRONT MATTER CREDITS Aerial imagery is of Whittell Marsh along Point Pinole Regional Shoreline (Courtesy of Google Earth) FUNDED BY The Marin Community Foundation and the California Coastal Conservancy ACKNOWLEDGEMENTS We thank the Marin Community Foundation and the California State Coastal Conservancy for providing funding for this project under the Advancing Nature-Based Adaptation Solutions in Marin County grant program. Marilyn Latta, Kelly Malinowski, and Linda Tong, our grant managers at the Coastal Conservancy, provided thoughtful feedback, review, and support throughout the project. This report benefited from a truly collaborative and interdisciplinary project team led by Dr. Kathy Boyer (San Francisco State University) along with several graduate students and technicians, including Melissa Patten and Kelly Santos, Peter Baye (Coastal Ecologist), Roger Leventhal (Marin County Public Works), and Marin Audubon Society staff. We are also grateful to our technical advisors for their review and guidance throughout: Stuart Siegel (San Francisco State University), Mike Vasey (SF Bay NERR), and Jeremy Lowe (SFEI). Technical review was also provided by Josh Collins (SFEI). Thank you to the many SFEI staff who contributed to this report: Ruth Askevold, Jeremy Lowe, Sam Safran, Micha Salomon, Pete Kauhanen and interns Kelly Santos and Jacob Kupperman. As this is just the first phase of deliverables for the New Life for Eroding Shorelines project, we are looking forward to integrating these results into the outcomes of the rest of the team’s work, and continuing to add to our understanding of physical and ecological shoreline processes towards the goal of greater shoreline resilience in the face of climate change. CONTENTS Glossary ......................................................................................................................viii Chapter 1. Introduction .................................................................................................. 1 Chapter 2. Marsh edge change .................................................................................... 11 Prepared by: Julie Beagle, Ellen Plane, Gloria Desanker, Micha Salomon Methods ...................................................................................................................................... 18 Results .........................................................................................................................................21 Patterns and examples ..............................................................................................................32 Discussion...................................................................................................................................40 Chapter 3. A technical introduction to beaches in the S.F. Estuary ........................... 47 Prepared by: Peter Baye Estuarine low energy beaches ..................................................................................................49 Estuarine beach planform and shoreline setting ........................................................................52 San Francisco Estuary beaches and sediment types .............................................................59 Estuarine beach and wetland interactions .............................................................................. 67 Wildlife habitat relationships ...................................................................................................70 Chapter 4. A remote sensing approach to evaluate beach change ............................ 85 Prepared by: Julie Beagle, Katie McKnight, Gloria Desanker Methods ......................................................................................................................................88 Results ........................................................................................................................................93 Discussion................................................................................................................................. 107 Chapter 5. Lessons learned in beach habitat pilot projects .......................................117 Prepared by: Peter Baye, Roger Leventhal Bay beach pilot restoration projects in Central SF Bay ......................................................... 117 Assessment of pilot project estuarine beach evolution, patterns, and processes ............. 126 Ecological processes and habitat evolution of bay beach pilot projects ............................144 Project planning and implementation ................................................................................... 156 Conclusions and recommendations .......................................................................................164 Chapter 6. Conclusion ............................................................................................... 171 GLOSSARY Accretion Berm crest The vertical accumulation of sediment causing growth of The linear break in slope marking the seaward limit of the a landform. berm and landward limit of the beachface (Komar 1976). Backwash Cusps The gravity-driven flow of water back down the slope of Regularly spaced shoreline landforms (spacing typically a beach after the swash of the preceding wave (Tarbuck between a few meters and a few tens of meters along and Lutgens 2008). the shore) consisting of small (< 1 m) embayments between protruding ridges. They are a common feature of Bar reflective beaches (Mangor 2019). Elongated intertidal or subtidal sand body with a wave or ridge form, deposited by (tidal) currents or waves; Drift aligned wave-deposited bars are generally aligned nearly parallel Drift alignments are found on beach-fringed coasts where with the shore (Price 1951, 1968). Bars deposited by the dominant waves arrive obliquely to the shore and swash and backwash of waves are termed swash bars. (with accompanying currents) maintain a beach parallel Large, persistent swash bars deposited at the limit of to the direction of the resulting longshore drift. They are constructive wave action at the backshore are also called typically found on straight coasts where the obliquely- beach berms (Pethick 1984, Davis and FitzGerald 2004). arriving waves move sediment alongshore (Bird 2019). Baylands Fringing beach General term describing areas around the margin of a A narrow strip of beach at the toe of a mainland bluff, bay, including mudflats, tidal marsh, and transition zone cliff, or levee. Narrow beaches along the outer salt marsh (Goals Project 2015). edge are termed marsh-fringing barrier beaches (Pilkey and Young 2009). Beach Deposit of unconsolidated sediment ranging from Groin/micro-groin cobbles to sand, formed by wave processes along the An artificially constructed obstruction to longshore shoreline. The beach extends from the landward limit drift of beach sediment, designed to cause local beach of wave action at the base of cliffs, bluffs, dunes, or a deposition. Micro-groins are short groins restricted to marsh platform, to the seaward or bayward limit of wave the beach berm and beachface, which allow significant action and beach sediment (Davis and FitzGerald 2004, bypassing of longshore drifted beach sediment. Pilkey and Young 2009). Lateral erosion Beach berm Landward movement of the shoreline. Also known as A nearly horizontal portion of the beach or backshore marsh edge retreat or recession. formed by the deposition of sediment by the receding Living shoreline waves (Komar 1976). A shoreline management system designed to protect or Beachface restore natural shoreline ecosystems through the use of The sloping section of the beach profile below the berm natural elements, and, if appropriate, manmade elements. where the swash and backwash of waves occurs at high Any elements used must not interrupt the natural water/ tide, eroding or depositing beach sediment (swash slope) land continuum to the detriment of natural shoreline (Komar 1976). ecosystems (Restore America’s Estuaries 2015). viii Low tide terrace (estuarine) Progradation The intertidal flats (sand, mud, or other mixed sediments) Lateral bayward or seaward growth and movement of the bayward of a low-energy beach, where wave action is shoreline; expansion of the marsh or beach edge. highly attenuated
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