Toward Natural Shoreline Infrastructure to Manage Coastal
Transcript Of Toward Natural Shoreline Infrastructure to Manage Coastal
TOWARD NATURAL SHORELINE INFRASTRUCTURE TO MANAGE COASTAL CHANGE IN CALIFORNIA
A Report for:
California’s Fourth Climate Change Assessment
Prepared By:
Sarah Newkirk1, Sam Veloz2, Maya Hayden2, Bob Battalio3, Tiffany Cheng3, Jenna Judge4, Walter Heady1, Kelly Leo1, Mary Small5
1 The Nature Conservancy 2 Point Blue Conservation Science 3 Environmental Science Associates 4 National Oceanic and Atmospheric Administration 5 California State Coastal Conservancy
DISCLAIMER
This report was prepared as the result of work sponsored by the California Natural Resources Agency. It does not necessarily represent the views of the Natural Resources Agency, its employees or the State of California. The Natural Resources Agency, the State of California, its employees, contractors and subcontractors make no warrant, express or implied, and assume no legal liability for the information in this report; nor does any party represent that the uses of this information will not infringe upon privately owned rights. This report has not been approved or disapproved by the Natural Resources Agency nor has the Natural Resources Agency passed upon the accuracy or adequacy of the information in this report.
Edmund G. Brown, Jr. Governor
August 2018 CCCA4-CNRA-2018-011
ACKNOWLEDGEMENTS
This project was supported by many advisors, who were very generous with their time and expertise. Specifically: Andrea Pickart, Humboldt Bay National Wildlife Refuge; Brenda Goeden, San Francisco Bay Conservation and Development Commission; Michelle Orr, Environmental Science Associates; Damien Kunz, Environmental Science Associates; Eric Joliffe, United States Army Corps of Engineers; Christina McWhorter, Hamilton Wetlands Plant Nursery; Jeff Melby, California State Coastal Conservancy; Louis White, Environmental Science Associates; Paul Jenkin, Surfrider Foundation; Evyan Sloane, California State Coastal Conservancy; Rick Nye, Seal Beach National Wildlife Refuge; Marilyn Latta, California State Coastal Conservancy; Kathy Boyer, San Francisco State University; Su Corbaly, California State Coastal Conservancy; Elizabeth Gagneron, California State Coastal Conservancy; Mary Matella, California Coastal Commission; Jennifer Mattox, State Lands Commission; Laura Engeman, San Diego Climate Collaborative; Dani Boudreau, Tijuana River National Estuarine Research Reserve; Joel Gerwein, California State Coastal Conservancy; David Behar, San Francisco Public Utility Commission; Jack Liebster, Marin County Planning; Leslie Ewing, California Coastal Commission; Juliette Hart, United States Geological Survey; Amber Parais, San Diego Climate Collaborative; Sara Hutto, Greater Farallones National Marine Sanctuary; Natalie Cosentino-Manning, National Oceanic and Atmospheric Administration National Marine Fisheries Service; Jeremy Lowe, San Francisco Estuary Institute; Kif Scheuer, Local Government Commission; George Domurat, U.S. Army Engineer Institute for Water Resources; Ken Schreiber, Land Use Planning Services, Inc.; Bruce Bekkar, City of Del Mar; Joseph Tyburczy, California Sea Grant Extension; Brian Brennan, Beach Erosion Authority for Clean Oceans and Nourishment; Luisa Valiela, Environmental Protection Agency; Christina Toms, San Francisco Bay Regional Water Quality Control Board; John Rozum, National Oceanic and Atmospheric Administration Office for Coastal Management; Becky Lunde, National Oceanic and Atmospheric Administration Office for Coastal Management; Deborah Ruddock, California State Coastal Conservancy; Chris Williamson, City of Oxnard; Edward Curtis, San Francisco State University; Sergio Vargas, Ventura County; Dean Kubani, City of Santa Monica; Jenny Dugan, University of California Santa Barbara; Maren Farnum, State Lands Commission; Patrick Mulcahy, State Lands Commission; Madeline Kinsey, California State Parks; Andrew Gunther, Center for Ecosystem Management and Restoration; Kristen Goodrich, Tijuana River National Estuarine Research Reserve; Monique Myers, California Sea Grant Extension; Warner Chabot, San Francisco Estuary Institute; Alex Westhoff, Marin County.
ii
PREFACE
California’s Climate Change Assessments provide a scientific foundation for understanding climate-related vulnerability at the local scale and informing resilience actions. These Assessments contribute to the advancement of science-based policies, plans, and programs to promote effective climate leadership in California. In 2006, California released its First Climate Change Assessment, which shed light on the impacts of climate change on specific sectors in California and was instrumental in supporting the passage of the landmark legislation Assembly Bill 32 (Núñez, Chapter 488, Statutes of 2006), California’s Global Warming Solutions Act. The Second Assessment concluded that adaptation is a crucial complement to reducing greenhouse gas emissions (2009), given that some changes to the climate are ongoing and inevitable, motivating and informing California’s first Climate Adaptation Strategy released the same year. In 2012, California’s Third Climate Change Assessment made substantial progress in projecting local impacts of climate change, investigating consequences to human and natural systems, and exploring barriers to adaptation.
Under the leadership of Governor Edmund G. Brown, Jr., a trio of state agencies jointly managed and supported California’s Fourth Climate Change Assessment: California’s Natural Resources Agency (CNRA), the Governor’s Office of Planning and Research (OPR), and the California Energy Commission (Energy Commission). The Climate Action Team Research Working Group, through which more than 20 state agencies coordinate climate-related research, served as the steering committee, providing input for a multisector call for proposals, participating in selection of research teams, and offering technical guidance throughout the process.
California’s Fourth Climate Change Assessment (Fourth Assessment) advances actionable science that serves the growing needs of state and local-level decision-makers from a variety of sectors. It includes research to develop rigorous, comprehensive climate change scenarios at a scale suitable for illuminating regional vulnerabilities and localized adaptation strategies in California; datasets and tools that improve integration of observed and projected knowledge about climate change into decision-making; and recommendations and information to directly inform vulnerability assessments and adaptation strategies for California’s energy sector, water resources and management, oceans and coasts, forests, wildfires, agriculture, biodiversity and habitat, and public health.
The Fourth Assessment includes 44 technical reports to advance the scientific foundation for understanding climate-related risks and resilience options, nine regional reports plus an oceans and coast report to outline climate risks and adaptation options, reports on tribal and indigenous issues as well as climate justice, and a comprehensive statewide summary report. All research contributing to the Fourth Assessment was peer-reviewed to ensure scientific rigor and relevance to practitioners and stakeholders.
For the full suite of Fourth Assessment research products, please visit www.climateassessment.ca.gov. This report is intended to facilitate the use of Natural Shoreline Infrastructure along California’s coast, improving the resilience of communities and habitats in the face of climate change.
iii
ABSTRACT
Flooding and erosion caused by rising sea levels and powerful storms threaten property throughout coastal California. To protect against these climate-change related threats, landowners will certainly take action, and the default industry standard response has been to try to “hold the line” against the encroaching sea by constructing seawalls, dikes, levees and other forms of coastal armoring. While armoring may in some cases provide acceptable shortterm protection, armoring also tends to accelerate shoreline erosion, exacerbating hazards to people and leading to the eventual loss of critical wildlife habitat and public beaches.
Natural Shoreline Infrastructure can be as effective as armoring, while having the added benefits of preserving coastal habitat and public access. Recognizing this, California agencies have mandated that decision-makers prioritize its use in planning and investment decisions. Yet, planners have encountered many stumbling blocks as they have tried to incorporate these approaches into coastal resilience plans. Major obstacles include: a lack of a common definition and shared terminology; lack of expertise; lack of precedent; and the absence of siting guidance and technical design standards.
Here, we set out to enable planners to adopt Natural Shoreline Infrastructure by filling in the missing information. With the input of dozens of coastal managers who served on our Technical Advisory Committee, we developed a definition and collected a list of case studies where Natural Shoreline Infrastructure has already been successfully deployed in California. Drawing from these and other projects, we collected into one place the first detailed technical guidance for implementation, including siting criteria and design thresholds. These criteria inform decisions about where and when to use six types of Natural Shoreline Infrastructure (e.g. sand dunes, seagrass beds). Using Monterey Bay and Ventura County projects as examples, we demonstrate how to use the technical guidance in tandem with spatial data to match a particular shoreline environment with appropriate Natural Shoreline Infrastructure options, creating “blueprints” for action.
The information in this report is intended to facilitate the use of Natural Shoreline Infrastructure along California’s coast, improving the resilience of communities and habitats in the face of climate change.
Keywords: Natural Shoreline Infrastructure, living shorelines, green infrastructure, coastal protection, coastal resilience, sea level rise, coastal storms, flooding, erosion, coastal armoring, seawalls, hazard mitigation, case studies, vegetated dunes, wetlands, cobble berms, marsh sills, tidal benches, horizontal levee, oyster reefs, eelgrass beds, outer coast, estuaries, coastal ecosystems
Please use the following citation for this paper:
Newkirk, Sarah, Sam Veloz, Maya Hayden, Walter Heady, Kelly Leo, Jenna Judge, Robert Battalio, Tiffany Cheng, Tara Ursell, Mary Small. (The Nature Conservancy and Point Blue Conservation Science). 2018. Toward Natural Infrastructure to Manage Shoreline
iv
Change in California. California’s Fourth Climate Change Assessment, California Natural Resources Agency. Publication number: CCCA4-CNRA-2018-011.
v
HIGHLIGHTS
● Coastal planners have faced many stumbling blocks when attempting to incorporate Natural Shoreline Infrastructure strategies into climate-change adaptation plans, and have instead often implemented short-term solutions like coastal armoring, and will continue to do so until significant hurdles to implementing other strategies can be overcome.
● Two major hurdles for planners are a lack of precedent and a dearth of technical guidance applicable to California’s varied environmental settings. To begin to address the first, we’ve collected five detailed case studies where planners have already successfully implemented different types of Natural Shoreline Infrastructure.
● To address the second hurdle to implementation we provide detailed technical guidance information to direct planners in evaluating and deciding where, when, and how to use six types of Natural Shoreline Infrastructure (e.g. sand dunes, seagrass beds), for optimal results.
● Using Monterey Bay and Ventura County as examples, we demonstrate how to use this guidance in tandem with local spatial data to match a particular shoreline environment with appropriate Natural Shoreline Infrastructure options, creating “blueprints” for action.
● Going forward, state agencies and NGOs should support demonstration projects that include testing and monitoring, so that the community of practitioners may continue to improve upon Natural Shoreline Infrastructure approaches and so they can be applied on larger scales, to enhance resilience to climate-change related hazards and maintain public access to healthy shorelines long into the future.
WEB LINKS
http://coastalresilience.org/case-studies-of-natural-shoreline-infrastructure-in-coastalcalifornia/
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TABLE OF CONTENTS
ACKNOWLEDGEMENTS ..................................................................................................................... ii PREFACE .................................................................................................................................................. iii ABSTRACT .............................................................................................................................................. iv HIGHLIGHTS ......................................................................................................................................... vi TABLE OF CONTENTS........................................................................................................................ vii 1: Introduction ........................................................................................................................................... 1
1.1 Purpose of This Study ..................................................................................................................... 1 1.2 Overview ........................................................................................................................................... 1 1.3 Shoreline Protection Approaches .................................................................................................. 2 1.4 Natural Infrastructure Defined and Codified into State Law.................................................... 4 1.5 Creating a Shared Definition of Natural Shoreline Infrastructure Among Stakeholders...... 4 2: Case Studies ........................................................................................................................................... 5 2.1 Seal Beach National Wildlife Refuge Thin-layer Salt Marsh Sediment Augmentation Pilot Project ...................................................................................................................................................... 6 2.2 Surfers’ Point Managed Shoreline Retreat Project ...................................................................... 7 2.3 San Francisco Bay Living Shorelines: Nearshore Linkages Project .......................................... 8 2.4 Hamilton Wetland Restoration Project ......................................................................................... 8 2.5 Humboldt Coastal Dune Vulnerability and Adaptation Climate Ready Project.................... 9 2.6 Lessons Learned ............................................................................................................................... 9 3: Technical Guidance on Natural Shoreline Infrastructure........................................................... 10 3.1 Introduction and Appropriate Use.............................................................................................. 10 3.2 Vegetated Dunes ............................................................................................................................ 11
3.2.1 Setting ....................................................................................................................................... 12 3.2.2 Design Guidance ..................................................................................................................... 12 3.2.3 Dune Subtype and Vegetation .............................................................................................. 14 3.2.4 Construction and Monitoring................................................................................................ 16 3.3 Cobble Berms .................................................................................................................................. 16 3.3.1 Setting ....................................................................................................................................... 17 3.3.2 Design Guidance ..................................................................................................................... 18
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3.3.3 Construction and Monitoring................................................................................................ 19 3.4 Marsh Sills ....................................................................................................................................... 19
3.4.1 Setting ....................................................................................................................................... 20 3.4.2 Design Guidance ..................................................................................................................... 20 3.4.3 Construction and Monitoring................................................................................................ 21 3.5 Tidal Benches .................................................................................................................................. 22 3.5.1 Setting ....................................................................................................................................... 23 3.5.2 Design Guidance ..................................................................................................................... 23 3.5.3 Construction and Monitoring................................................................................................ 25 3.6 Native Oyster Reef ......................................................................................................................... 25 3.6.1 Setting ....................................................................................................................................... 26 3.6.2 Design Guidance ..................................................................................................................... 27 3.6.3 Construction and Monitoring................................................................................................ 28 3.7 Eelgrass Beds .................................................................................................................................. 29 3.7.1 Setting ....................................................................................................................................... 30 3.7.2 Design Guidance & Implementation.................................................................................... 30 3.8 Other Considerations for Natural Shoreline Infrastructure..................................................... 32 4: Development of Blueprints for Deploying Natural Shoreline Infrastructure ........................ 33 4.1 Overview ......................................................................................................................................... 33 4.2 Methods ........................................................................................................................................... 33 4.3 Preliminary Results........................................................................................................................ 36 4.3.1 Suitability of Vegetated Dunes in Monterey Bay and Ventura County .......................... 36 4.3.2 Suitability of Cobble Berms in Monterey Bay and Ventura County................................ 36 4.4 Discussion and Anticipated Products ......................................................................................... 38 5: Conclusions and Future Directions ................................................................................................. 38 6: References............................................................................................................................................. 40 APPENDIX A: Technical Advisory Committee Membership ......................................................A-1 APPENDIX B: Literature Defining Natural Shoreline Infrastructure ........................................ B-1 APPENDIX C: Common Native Plants for Restoration in California Coastal Habitats ......... C-1
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APPENDIX D: Detailed Methods of Blueprints for Deploying Natural Shoreline Infrastructure ........................................................................................................................................ D-1
D.1 Spatial Data Inputs .....................................................................................................................D-4 D.2 Application of Thresholds to Outer Coast Measures.............................................................D-4
D.1.1 Sand Dunes ...........................................................................................................................D-4 D.1.2 Cobble Berms........................................................................................................................D-4 D.1.3 Opportunities to Improve Location Suitability Through Managed Retreat................D-5 D.2 Application of Thresholds to Estuary Measures ....................................................................D-6 D.2.1 Marsh Sill ..............................................................................................................................D-6 D.2.2 Tidal Bench ...........................................................................................................................D-7 D.2.3 Oyster Reefs and Eel Grass Beds .......................................................................................D-7
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1: Introduction
1.1 Purpose of This Study
This report aims to provide crucial information and guidance, so that in response to the threat of shoreline flooding and erosion—exacerbated by climate change—California planners can curtail their reliance on coastal armoring and can instead begin to more widely deploy Natural Shoreline Infrastructure solutions.
Currently, planners interested in using Natural Shoreline Infrastructure approaches face a host of obstacles (Caldwell et al. 2015). In consultation with our Technical Advisory Committee (Section 1.5, Appendix A), we identified four major obstacles that we could feasibly tackle and begin to overcome: (1) a lack of clarity over what Natural Shoreline Infrastructure entails; (2) a perceived lack of precedent for Natural Shoreline Infrastructure in California; (3) a lack of technical guidance for siting and design to help planners pinpoint which methods to use and where; (4) and a lack of examples demonstrating the application of siting guidelines to evaluate suitability of Natural Shoreline Infrastructure in specific locales.
Here, we address each of these challenges. First, we develop a shared definition of Natural Shoreline Infrastructure with stakeholders (Sections 1.4, 1.5). We then present five case studies where Natural Shoreline Infrastructure has been used successfully in California (Section 2, Appendix E). We also provide detailed technical guidance for deciding where, when and how to use Natural Shoreline Infrastructure approaches, according to local conditions (Section 3). Last, we demonstrate how the technical guidance can be applied using spatial data to evaluate suitability of these approaches in Monterey Bay and Ventura County (Section 4, Appendix F).
1.2 Overview
California’s iconic coast links together thousands of miles of coastal habitats which are foundational to the high biodiversity unique to the coast and provide benefits to millions of people (Heady et al. 2018). Cliffs, dunes, wetlands, estuaries, and beaches provide critical habitat to fish, endangered plants, marine mammals, and birds travelling along the Pacific Flyway. (Neuman et al. 2008; Hughes et al. 2014; Heady et al. 2018).
It is impossible to overstate the importance and irreplaceability of these habitats, which serve as essential nursery, feeding and resting areas for both terrestrial and marine species. California’s coastlines are also critical habitat for people. Millions flock to the coast annually, to fish, swim, surf, rest, honor sacred traditions and to be surrounded by nature (NOAA 2015, Heberger et al. 2009). Beach-goers in California spend approximately $3 billion annually, and the non-market benefits of coasts, when translated into dollar figures, are greater than $2 billion per year (Kildow and Colgan 2005).
Unfortunately, more than 90% of coastal wetlands, beaches, and estuarine intertidal lands have already been converted to agriculture or development (Dahl 1990, Zedler 1996). The remaining 10 % will likely continue to shrink from climate change-induced hazards. Coastal bluffs are already eroding at a rate of 0.30 m (1 ft) per year in many places, and that rate of change will likely increase over the coming decades as sea levels rise and Pacific storms intensify (Hapke and Reid 2007, Vitousek et al. 2017). By the turn of the century, projections of 1 to 2 m (3 to 6 ft)
1
A Report for:
California’s Fourth Climate Change Assessment
Prepared By:
Sarah Newkirk1, Sam Veloz2, Maya Hayden2, Bob Battalio3, Tiffany Cheng3, Jenna Judge4, Walter Heady1, Kelly Leo1, Mary Small5
1 The Nature Conservancy 2 Point Blue Conservation Science 3 Environmental Science Associates 4 National Oceanic and Atmospheric Administration 5 California State Coastal Conservancy
DISCLAIMER
This report was prepared as the result of work sponsored by the California Natural Resources Agency. It does not necessarily represent the views of the Natural Resources Agency, its employees or the State of California. The Natural Resources Agency, the State of California, its employees, contractors and subcontractors make no warrant, express or implied, and assume no legal liability for the information in this report; nor does any party represent that the uses of this information will not infringe upon privately owned rights. This report has not been approved or disapproved by the Natural Resources Agency nor has the Natural Resources Agency passed upon the accuracy or adequacy of the information in this report.
Edmund G. Brown, Jr. Governor
August 2018 CCCA4-CNRA-2018-011
ACKNOWLEDGEMENTS
This project was supported by many advisors, who were very generous with their time and expertise. Specifically: Andrea Pickart, Humboldt Bay National Wildlife Refuge; Brenda Goeden, San Francisco Bay Conservation and Development Commission; Michelle Orr, Environmental Science Associates; Damien Kunz, Environmental Science Associates; Eric Joliffe, United States Army Corps of Engineers; Christina McWhorter, Hamilton Wetlands Plant Nursery; Jeff Melby, California State Coastal Conservancy; Louis White, Environmental Science Associates; Paul Jenkin, Surfrider Foundation; Evyan Sloane, California State Coastal Conservancy; Rick Nye, Seal Beach National Wildlife Refuge; Marilyn Latta, California State Coastal Conservancy; Kathy Boyer, San Francisco State University; Su Corbaly, California State Coastal Conservancy; Elizabeth Gagneron, California State Coastal Conservancy; Mary Matella, California Coastal Commission; Jennifer Mattox, State Lands Commission; Laura Engeman, San Diego Climate Collaborative; Dani Boudreau, Tijuana River National Estuarine Research Reserve; Joel Gerwein, California State Coastal Conservancy; David Behar, San Francisco Public Utility Commission; Jack Liebster, Marin County Planning; Leslie Ewing, California Coastal Commission; Juliette Hart, United States Geological Survey; Amber Parais, San Diego Climate Collaborative; Sara Hutto, Greater Farallones National Marine Sanctuary; Natalie Cosentino-Manning, National Oceanic and Atmospheric Administration National Marine Fisheries Service; Jeremy Lowe, San Francisco Estuary Institute; Kif Scheuer, Local Government Commission; George Domurat, U.S. Army Engineer Institute for Water Resources; Ken Schreiber, Land Use Planning Services, Inc.; Bruce Bekkar, City of Del Mar; Joseph Tyburczy, California Sea Grant Extension; Brian Brennan, Beach Erosion Authority for Clean Oceans and Nourishment; Luisa Valiela, Environmental Protection Agency; Christina Toms, San Francisco Bay Regional Water Quality Control Board; John Rozum, National Oceanic and Atmospheric Administration Office for Coastal Management; Becky Lunde, National Oceanic and Atmospheric Administration Office for Coastal Management; Deborah Ruddock, California State Coastal Conservancy; Chris Williamson, City of Oxnard; Edward Curtis, San Francisco State University; Sergio Vargas, Ventura County; Dean Kubani, City of Santa Monica; Jenny Dugan, University of California Santa Barbara; Maren Farnum, State Lands Commission; Patrick Mulcahy, State Lands Commission; Madeline Kinsey, California State Parks; Andrew Gunther, Center for Ecosystem Management and Restoration; Kristen Goodrich, Tijuana River National Estuarine Research Reserve; Monique Myers, California Sea Grant Extension; Warner Chabot, San Francisco Estuary Institute; Alex Westhoff, Marin County.
ii
PREFACE
California’s Climate Change Assessments provide a scientific foundation for understanding climate-related vulnerability at the local scale and informing resilience actions. These Assessments contribute to the advancement of science-based policies, plans, and programs to promote effective climate leadership in California. In 2006, California released its First Climate Change Assessment, which shed light on the impacts of climate change on specific sectors in California and was instrumental in supporting the passage of the landmark legislation Assembly Bill 32 (Núñez, Chapter 488, Statutes of 2006), California’s Global Warming Solutions Act. The Second Assessment concluded that adaptation is a crucial complement to reducing greenhouse gas emissions (2009), given that some changes to the climate are ongoing and inevitable, motivating and informing California’s first Climate Adaptation Strategy released the same year. In 2012, California’s Third Climate Change Assessment made substantial progress in projecting local impacts of climate change, investigating consequences to human and natural systems, and exploring barriers to adaptation.
Under the leadership of Governor Edmund G. Brown, Jr., a trio of state agencies jointly managed and supported California’s Fourth Climate Change Assessment: California’s Natural Resources Agency (CNRA), the Governor’s Office of Planning and Research (OPR), and the California Energy Commission (Energy Commission). The Climate Action Team Research Working Group, through which more than 20 state agencies coordinate climate-related research, served as the steering committee, providing input for a multisector call for proposals, participating in selection of research teams, and offering technical guidance throughout the process.
California’s Fourth Climate Change Assessment (Fourth Assessment) advances actionable science that serves the growing needs of state and local-level decision-makers from a variety of sectors. It includes research to develop rigorous, comprehensive climate change scenarios at a scale suitable for illuminating regional vulnerabilities and localized adaptation strategies in California; datasets and tools that improve integration of observed and projected knowledge about climate change into decision-making; and recommendations and information to directly inform vulnerability assessments and adaptation strategies for California’s energy sector, water resources and management, oceans and coasts, forests, wildfires, agriculture, biodiversity and habitat, and public health.
The Fourth Assessment includes 44 technical reports to advance the scientific foundation for understanding climate-related risks and resilience options, nine regional reports plus an oceans and coast report to outline climate risks and adaptation options, reports on tribal and indigenous issues as well as climate justice, and a comprehensive statewide summary report. All research contributing to the Fourth Assessment was peer-reviewed to ensure scientific rigor and relevance to practitioners and stakeholders.
For the full suite of Fourth Assessment research products, please visit www.climateassessment.ca.gov. This report is intended to facilitate the use of Natural Shoreline Infrastructure along California’s coast, improving the resilience of communities and habitats in the face of climate change.
iii
ABSTRACT
Flooding and erosion caused by rising sea levels and powerful storms threaten property throughout coastal California. To protect against these climate-change related threats, landowners will certainly take action, and the default industry standard response has been to try to “hold the line” against the encroaching sea by constructing seawalls, dikes, levees and other forms of coastal armoring. While armoring may in some cases provide acceptable shortterm protection, armoring also tends to accelerate shoreline erosion, exacerbating hazards to people and leading to the eventual loss of critical wildlife habitat and public beaches.
Natural Shoreline Infrastructure can be as effective as armoring, while having the added benefits of preserving coastal habitat and public access. Recognizing this, California agencies have mandated that decision-makers prioritize its use in planning and investment decisions. Yet, planners have encountered many stumbling blocks as they have tried to incorporate these approaches into coastal resilience plans. Major obstacles include: a lack of a common definition and shared terminology; lack of expertise; lack of precedent; and the absence of siting guidance and technical design standards.
Here, we set out to enable planners to adopt Natural Shoreline Infrastructure by filling in the missing information. With the input of dozens of coastal managers who served on our Technical Advisory Committee, we developed a definition and collected a list of case studies where Natural Shoreline Infrastructure has already been successfully deployed in California. Drawing from these and other projects, we collected into one place the first detailed technical guidance for implementation, including siting criteria and design thresholds. These criteria inform decisions about where and when to use six types of Natural Shoreline Infrastructure (e.g. sand dunes, seagrass beds). Using Monterey Bay and Ventura County projects as examples, we demonstrate how to use the technical guidance in tandem with spatial data to match a particular shoreline environment with appropriate Natural Shoreline Infrastructure options, creating “blueprints” for action.
The information in this report is intended to facilitate the use of Natural Shoreline Infrastructure along California’s coast, improving the resilience of communities and habitats in the face of climate change.
Keywords: Natural Shoreline Infrastructure, living shorelines, green infrastructure, coastal protection, coastal resilience, sea level rise, coastal storms, flooding, erosion, coastal armoring, seawalls, hazard mitigation, case studies, vegetated dunes, wetlands, cobble berms, marsh sills, tidal benches, horizontal levee, oyster reefs, eelgrass beds, outer coast, estuaries, coastal ecosystems
Please use the following citation for this paper:
Newkirk, Sarah, Sam Veloz, Maya Hayden, Walter Heady, Kelly Leo, Jenna Judge, Robert Battalio, Tiffany Cheng, Tara Ursell, Mary Small. (The Nature Conservancy and Point Blue Conservation Science). 2018. Toward Natural Infrastructure to Manage Shoreline
iv
Change in California. California’s Fourth Climate Change Assessment, California Natural Resources Agency. Publication number: CCCA4-CNRA-2018-011.
v
HIGHLIGHTS
● Coastal planners have faced many stumbling blocks when attempting to incorporate Natural Shoreline Infrastructure strategies into climate-change adaptation plans, and have instead often implemented short-term solutions like coastal armoring, and will continue to do so until significant hurdles to implementing other strategies can be overcome.
● Two major hurdles for planners are a lack of precedent and a dearth of technical guidance applicable to California’s varied environmental settings. To begin to address the first, we’ve collected five detailed case studies where planners have already successfully implemented different types of Natural Shoreline Infrastructure.
● To address the second hurdle to implementation we provide detailed technical guidance information to direct planners in evaluating and deciding where, when, and how to use six types of Natural Shoreline Infrastructure (e.g. sand dunes, seagrass beds), for optimal results.
● Using Monterey Bay and Ventura County as examples, we demonstrate how to use this guidance in tandem with local spatial data to match a particular shoreline environment with appropriate Natural Shoreline Infrastructure options, creating “blueprints” for action.
● Going forward, state agencies and NGOs should support demonstration projects that include testing and monitoring, so that the community of practitioners may continue to improve upon Natural Shoreline Infrastructure approaches and so they can be applied on larger scales, to enhance resilience to climate-change related hazards and maintain public access to healthy shorelines long into the future.
WEB LINKS
http://coastalresilience.org/case-studies-of-natural-shoreline-infrastructure-in-coastalcalifornia/
vi
TABLE OF CONTENTS
ACKNOWLEDGEMENTS ..................................................................................................................... ii PREFACE .................................................................................................................................................. iii ABSTRACT .............................................................................................................................................. iv HIGHLIGHTS ......................................................................................................................................... vi TABLE OF CONTENTS........................................................................................................................ vii 1: Introduction ........................................................................................................................................... 1
1.1 Purpose of This Study ..................................................................................................................... 1 1.2 Overview ........................................................................................................................................... 1 1.3 Shoreline Protection Approaches .................................................................................................. 2 1.4 Natural Infrastructure Defined and Codified into State Law.................................................... 4 1.5 Creating a Shared Definition of Natural Shoreline Infrastructure Among Stakeholders...... 4 2: Case Studies ........................................................................................................................................... 5 2.1 Seal Beach National Wildlife Refuge Thin-layer Salt Marsh Sediment Augmentation Pilot Project ...................................................................................................................................................... 6 2.2 Surfers’ Point Managed Shoreline Retreat Project ...................................................................... 7 2.3 San Francisco Bay Living Shorelines: Nearshore Linkages Project .......................................... 8 2.4 Hamilton Wetland Restoration Project ......................................................................................... 8 2.5 Humboldt Coastal Dune Vulnerability and Adaptation Climate Ready Project.................... 9 2.6 Lessons Learned ............................................................................................................................... 9 3: Technical Guidance on Natural Shoreline Infrastructure........................................................... 10 3.1 Introduction and Appropriate Use.............................................................................................. 10 3.2 Vegetated Dunes ............................................................................................................................ 11
3.2.1 Setting ....................................................................................................................................... 12 3.2.2 Design Guidance ..................................................................................................................... 12 3.2.3 Dune Subtype and Vegetation .............................................................................................. 14 3.2.4 Construction and Monitoring................................................................................................ 16 3.3 Cobble Berms .................................................................................................................................. 16 3.3.1 Setting ....................................................................................................................................... 17 3.3.2 Design Guidance ..................................................................................................................... 18
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3.3.3 Construction and Monitoring................................................................................................ 19 3.4 Marsh Sills ....................................................................................................................................... 19
3.4.1 Setting ....................................................................................................................................... 20 3.4.2 Design Guidance ..................................................................................................................... 20 3.4.3 Construction and Monitoring................................................................................................ 21 3.5 Tidal Benches .................................................................................................................................. 22 3.5.1 Setting ....................................................................................................................................... 23 3.5.2 Design Guidance ..................................................................................................................... 23 3.5.3 Construction and Monitoring................................................................................................ 25 3.6 Native Oyster Reef ......................................................................................................................... 25 3.6.1 Setting ....................................................................................................................................... 26 3.6.2 Design Guidance ..................................................................................................................... 27 3.6.3 Construction and Monitoring................................................................................................ 28 3.7 Eelgrass Beds .................................................................................................................................. 29 3.7.1 Setting ....................................................................................................................................... 30 3.7.2 Design Guidance & Implementation.................................................................................... 30 3.8 Other Considerations for Natural Shoreline Infrastructure..................................................... 32 4: Development of Blueprints for Deploying Natural Shoreline Infrastructure ........................ 33 4.1 Overview ......................................................................................................................................... 33 4.2 Methods ........................................................................................................................................... 33 4.3 Preliminary Results........................................................................................................................ 36 4.3.1 Suitability of Vegetated Dunes in Monterey Bay and Ventura County .......................... 36 4.3.2 Suitability of Cobble Berms in Monterey Bay and Ventura County................................ 36 4.4 Discussion and Anticipated Products ......................................................................................... 38 5: Conclusions and Future Directions ................................................................................................. 38 6: References............................................................................................................................................. 40 APPENDIX A: Technical Advisory Committee Membership ......................................................A-1 APPENDIX B: Literature Defining Natural Shoreline Infrastructure ........................................ B-1 APPENDIX C: Common Native Plants for Restoration in California Coastal Habitats ......... C-1
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APPENDIX D: Detailed Methods of Blueprints for Deploying Natural Shoreline Infrastructure ........................................................................................................................................ D-1
D.1 Spatial Data Inputs .....................................................................................................................D-4 D.2 Application of Thresholds to Outer Coast Measures.............................................................D-4
D.1.1 Sand Dunes ...........................................................................................................................D-4 D.1.2 Cobble Berms........................................................................................................................D-4 D.1.3 Opportunities to Improve Location Suitability Through Managed Retreat................D-5 D.2 Application of Thresholds to Estuary Measures ....................................................................D-6 D.2.1 Marsh Sill ..............................................................................................................................D-6 D.2.2 Tidal Bench ...........................................................................................................................D-7 D.2.3 Oyster Reefs and Eel Grass Beds .......................................................................................D-7
ix
1: Introduction
1.1 Purpose of This Study
This report aims to provide crucial information and guidance, so that in response to the threat of shoreline flooding and erosion—exacerbated by climate change—California planners can curtail their reliance on coastal armoring and can instead begin to more widely deploy Natural Shoreline Infrastructure solutions.
Currently, planners interested in using Natural Shoreline Infrastructure approaches face a host of obstacles (Caldwell et al. 2015). In consultation with our Technical Advisory Committee (Section 1.5, Appendix A), we identified four major obstacles that we could feasibly tackle and begin to overcome: (1) a lack of clarity over what Natural Shoreline Infrastructure entails; (2) a perceived lack of precedent for Natural Shoreline Infrastructure in California; (3) a lack of technical guidance for siting and design to help planners pinpoint which methods to use and where; (4) and a lack of examples demonstrating the application of siting guidelines to evaluate suitability of Natural Shoreline Infrastructure in specific locales.
Here, we address each of these challenges. First, we develop a shared definition of Natural Shoreline Infrastructure with stakeholders (Sections 1.4, 1.5). We then present five case studies where Natural Shoreline Infrastructure has been used successfully in California (Section 2, Appendix E). We also provide detailed technical guidance for deciding where, when and how to use Natural Shoreline Infrastructure approaches, according to local conditions (Section 3). Last, we demonstrate how the technical guidance can be applied using spatial data to evaluate suitability of these approaches in Monterey Bay and Ventura County (Section 4, Appendix F).
1.2 Overview
California’s iconic coast links together thousands of miles of coastal habitats which are foundational to the high biodiversity unique to the coast and provide benefits to millions of people (Heady et al. 2018). Cliffs, dunes, wetlands, estuaries, and beaches provide critical habitat to fish, endangered plants, marine mammals, and birds travelling along the Pacific Flyway. (Neuman et al. 2008; Hughes et al. 2014; Heady et al. 2018).
It is impossible to overstate the importance and irreplaceability of these habitats, which serve as essential nursery, feeding and resting areas for both terrestrial and marine species. California’s coastlines are also critical habitat for people. Millions flock to the coast annually, to fish, swim, surf, rest, honor sacred traditions and to be surrounded by nature (NOAA 2015, Heberger et al. 2009). Beach-goers in California spend approximately $3 billion annually, and the non-market benefits of coasts, when translated into dollar figures, are greater than $2 billion per year (Kildow and Colgan 2005).
Unfortunately, more than 90% of coastal wetlands, beaches, and estuarine intertidal lands have already been converted to agriculture or development (Dahl 1990, Zedler 1996). The remaining 10 % will likely continue to shrink from climate change-induced hazards. Coastal bluffs are already eroding at a rate of 0.30 m (1 ft) per year in many places, and that rate of change will likely increase over the coming decades as sea levels rise and Pacific storms intensify (Hapke and Reid 2007, Vitousek et al. 2017). By the turn of the century, projections of 1 to 2 m (3 to 6 ft)
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