City of San Clemente Sea Level Rise Vulnerability Assessment Prepared with assistance from: October 2019 City of San Clemente Sea Level Rise Vulnerability Assessment | Page ii Table of Contents Acronyms and Abbreviations ............................................................................................................................................................ v Executive Summary ......................................................................................................................................................................... vii 1. Introduction and Approach ........................................................................................................................................................ 1 1.1 Study Approach ......................................................................................................................................................... 1 1.2 Existing Coastal Setting ............................................................................................................................................ 2 1.3 Study Area ................................................................................................................................................................ 2 1.4 Coastal Resources .................................................................................................................................................... 5 1.5 LOSSAN Rail Corridor .............................................................................................................................................. 6 2. Coastal Processes .................................................................................................................................................................. 12 2.1 Littoral Processes and Sediment Supply ................................................................................................................ 12 2.2 Shoreline Change ................................................................................................................................................... 14 2.3 Water Levels ........................................................................................................................................................... 16 2.4 Wave Climate .......................................................................................................................................................... 17 2.5 History of Coastal Storm Damage ........................................................................................................................... 19 3. Sea Level Rise (SLR) Projections ........................................................................................................................................... 22 3.1 Projections and Probability ...................................................................................................................................... 22 3.2 General Overview of SLR Scenarios Evaluated in this Study: ................................................................................ 24 4. Evaluation of Sea Level Rise and Related Hazards ............................................................................................................... 26 4.1 CoSMoS 3.0 Sea Level Rise Scenarios .................................................................................................................. 26 4.2 Coastal SLR-Related Flooding ................................................................................................................................ 27 4.3 SLR- Related Shoreline Erosion Projections .......................................................................................................... 29 4.4 Sea Level Rise Exposure – North Reach ................................................................................................................ 29 4.5 Sea Level Rise Exposure – Central Reach ............................................................................................................. 33 4.6 Sea Level Rise Exposure – South Reach ............................................................................................................... 36 5. Sea Level Rise Vulnerability Assessment ............................................................................................................................... 40 5.1 Public Beaches and Public Trust Resources .......................................................................................................... 42 5.2 Coastal Public Access Points .................................................................................................................................. 44 5.3 California Coastal Trail ............................................................................................................................................ 46 5.4 Public Restroom and Picnic Facilities ..................................................................................................................... 47 5.5 San Clemente Marine Safety Division Headquarters .............................................................................................. 48 5.6 City of San Clemente Municipal Pier ....................................................................................................................... 49 5.7 Historic and Cultural Resources .............................................................................................................................. 50 5.8 Surfing ..................................................................................................................................................................... 53 5.9 Critical Public Infrastructure and Public Facilities ................................................................................................... 54 5.10 LOSSAN Rail Corridor ............................................................................................................................................ 55 5.11 Blufftop Residential and Commercial Development ................................................................................................ 56 5.12 Transportation Infrastructure / Public Roadways .................................................................................................... 61 5.13 Environmental Resources/Environmentally Sensitive Habitat Areas (ESHA) ......................................................... 62 5.14 Scenic Resources ................................................................................................................................................... 63 5.15 Saltwater Intrusion .................................................................................................................................................. 64 5.16 Socioeconomic Impacts and Environmental Justice ............................................................................................... 65 6. Range of Adaptation Strategies .............................................................................................................................................. 66 6.1 Hold the Line (Protect) ............................................................................................................................................ 66 6.2 Managed Retreat .................................................................................................................................................... 67 6.3 Beach Nourishment ................................................................................................................................................. 70 7. Building Resiliency: Recommendations and Next Steps ........................................................................................................ 72 8. List of Report Preparers and Contributors .............................................................................................................................. 76 9. References .............................................................................................................................................................................. 77 City of San Clemente Sea Level Rise Vulnerability Assessment | Page iii Appendix A – Existing Coastal Access Points (Public and Private) ................................................................................................ 79 TABLE OF TABLES Table 1: Coastal Resource Inventory in San Clemente .............................................................................................................. 5 Table 2: Annual Maximum Significant Wave Height near San Clemente Municipal Pier, 1983-1998 (USACE, 2012) ............. 18 Table 3: Summary of CoSMoS Version 3.0 Phase 2 Scenarios ............................................................................................... 26 Table 4: Blufftop Parcels Vulnerable at 4.9 feet SLR* .............................................................................................................. 56 TABLE OF FIGURES Figure 1: Illustration of Coastal Squeeze in front of a Non-erodible Structure ............................................................................ vii Figure 2: Key Questions for a Vulnerability Assessment ............................................................................................................. 2 Figure 3: Study Reaches .............................................................................................................................................................