Table of Contents 2.13.18 Planning Commission Agenda 2 1.9.18 Planning Commission Draft Minutes 5 PC Staff Report_Adaptation Plan 2.13.2018.pdf 8 City of Del Mar Planning Commission Agenda Del Mar (Temporary) City Hall 2010 Jimmy Durante Boulevard, Suite # 100, Del Mar, California 6:00 P.M.
Tuesday, February 13, 2018
Agenda Ted Bakker Chair It is the intention of your Planning Commission to be receptive to your concerns about your community. Your participation in Nate McCay local government will assure a responsible and efficient City of Del Mar. Vice Chair Regular Meetings of the Planning Commission are generally Philip Posner held on the second Tuesday of the month, beginning at 6:00 Commissioner p.m. For further information regarding the scheduling of meetings or meeting agendas, check the City’s web-site at Don Countryman www.delmar.ca.us, or call the Planning Department’s office at Commissioner 858-755-9313. A full Planning Commission agenda packet with all backup information is available at City Hall, the Del Mar Carmel Myers Library, and on the City’s web site the Friday before each Commissioner Planning Commission meeting.
Unless otherwise noted, for items on the agenda, applicants Kathleen A. Garcia and their team of representatives shall limit their [total] Planning & Community presentations to 10 minutes or less. Other speakers may Development Director address the Planning Commission for three minutes each. Please submit a “Request to Speak” form to the staff member Amanda Lee prior to the Chair announcing the agenda item. The forms are Principal Planner located near the door at the rear of the Meeting Room. The Agenda item number being addressed should be indicated on the speaker slip. The Chair will call you forward at the appropriate time. The applicant or authorized representative must be present in order to ensure action by the Commissioners.
Meeting will end at 11:00 p.m. unless extended by a majority vote of the Commissioners. If all the items on the agenda are not heard, the remaining items will be heard the following Tuesday (if facilities are available) at 2010 Jimmy Durante Boulevard, Suite # 100.
When addressing the Planning Commission, please step forward to the lectern and state your name and address for the record. Whenever possible, lengthy testimony should be presented to the Commissioners in writing and only pertinent points presented orally.
Consent Calendar: The Consent Calendar is considered by the Planning Commission near the beginning of the agenda. Items placed on the Consent Calendar will be approved in accordance with the staff recommendations for the item unless removed from the Consent Calendar by Commissioners, staff, or a member of the public. If you wish to keep an item from being placed on the Consent Calendar, please submit a “Request to Speak” form to the staff member prior to the meeting or be prepared to indicate an objection to the placement on the Consent Calendar when the Chair or staff asks if there are any objections to approval of the Consent Calendar.
City of Del Mar, 2010 Jimmy Durante Blvd, Del Mar, CA 92014 Phone: 858-755-9313 Fax: 858-755-2794
Planning Commission Meeting February 13, 2018 Agenda Page 2 of 3
This notice will be the only written notice sent. Items, which are continued by the Planning Commission from one Planning Commission meeting to another “date certain” meeting date, will not be re-noticed through the mail.
Final action - the decision of the Planning Commission is final unless a written appeal is filed with the City Clerk, accompanied with a processing fee, within ten (10) working days from the date of notice of the action taken on the application. An approved permit shall not be valid until the 10-day appeal period has expired. The appeal is then forwarded to the City Council, which determines at the Initial Consideration whether to reject the appeal, thereby upholding the Planning Commission’s decision, or to set the matter for a subsequent date for a new (de novo) public hearing review. If a de novo public hearing is set by the City Council, an additional fee will be required.
Special Needs: In compliance with the Americans with Disabilities Act, if you need special assistance to participate in this meeting, please contact the City Clerk’s office at 858-755-9313. Notification 48 hours prior to the meeting will enable the City to make reasonable arrangements to ensure accessibility to this meeting.
As a courtesy to all meeting attendees, please set cellular phones and pagers to silent mode and engage in conversations outside the Commissioners Chambers.
Meeting Decorum: All persons attending the Planning Commission meeting shall conduct themselves in a courteous and respectful manner. Comments shall be directed to the members of the Commission, rather than to others in attendance at the meeting. The Chairperson (or Vice Chair or Chair pro-tem in their absence), is designated as the parliamentarian for the meeting. As deemed appropriate, they may interrupt a speaker with instruction to redirect their remarks to relevant points on the agenda item before the Commission. They may also terminate a speaker's oral presentation if comments continue to be non-relevant or become disrespectful.
Note: The entirety of the City of Del Mar is located within the Coastal Zone. Some of the development projects listed on this agenda, as noted, require the receipt of a Coastal Development Permit. Some of these projects may also lie in what is known as the “Coastal Development Appeals Area”. For the projects located in the appeals area, the City’s action on the requested Coastal Development Permit may be appealed to the California Coastal Commission. An appeal may be filed with the Coastal Commission within the ten calendar days following the Coastal Commission’s receipt of a notice from the City of its final action on the Coastal Development Permit application. However, before an appeal may be filed with the Coastal Commission, the City’s action on the CDP application must be final, meaning that all of the City’s [separate and internal] appeals processes must first be exhausted.
ROLL CALL
APPROVAL OF MINUTES
1) Approval of January 9, 2018 Planning Commission Meeting Minutes
UPDATE
PLANNING COMMISSION/STAFF DISCUSSION (Non-Application Items)
1) 2018 City Council goals and priorities update
HEARING FROM THE AUDIENCE ON ITEMS NOT LISTED ON THE AGENDA (Oral Communications)
DISCUSSION AND BRIEFING (Application Items) Planning Commission Meeting February 13, 2018 Agenda Page 3 of 3
CONSENT CALENDAR
NEW APPLICATION(S):
ITEM 1 Project: Del Mar Coastal Resiliency/Sea Level Rise Adaptation Plan LCPA 16-005 Location: Citywide Applicant: City of Del Mar Environmental Status: The project is exempt from preparation of an environmental document pursuant to CEQA Guidelines (14 CCR Section 15265 Statutory Exemption: Adoption of Coastal Plans and Programs), which states that CEQA does not apply to activities and approvals pursuant to the California Coastal Act by any local government as necessary for the preparation and adoption of a Local Coastal Program. The CEQA Guidelines shift the burden of CEQA compliance for this action from the City to the Coastal Commission. The proposed Adaptation Plan does not authorize or facilitate any development construction or grading to occur and would not have a significant effect on the environment. Staff Contact: Amanda Lee, Principal Planner Description: A request for a recommendation to the City Council regarding the proposed Local Coastal Program Amendment relating to the City’s coastal resiliency and sea level rise planning work program. The Adaptation Plan would be established as a new land use plan and incorporated in the City’s Local Coastal Program. The Adaptation Plan was prepared in response to the vulnerability and risk assessment of local hazards relating to sea level rise, storm-surge, coastal flooding, and erosion. The Adaptation Plan will serve as the City’s toolbox to help property owners (public and private) plan for and address local hazards. The proposed adaptation strategies are required by State law (Senate Bill 379).
ADJOURNMENT
I, Jennifer Gavin, Associate Planner for the City of Del Mar, certify that a copy of the foregoing was posted at the Del Mar City Hall on Thursday, February 1, 2018.
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Jennifer Gavin, Associate Planner Planning and Community Development Department CITY OF DEL MAR PLANNING COMMISSION REGULAR MEETING MINUTES January 9, 2018 City Council Chambers 2010 Jimmy Durante Blvd., Suite 100, Del Mar, California
The minutes set forth the actions taken by the Planning Commission on the matters stated. Audio/video recordings of the Planning Commission proceedings are retained for a period of ten years, in accordance with the City's Records Retention Schedule. Audio/video recordings, as well as written materials presented to the Planning Commission, including Red Dots (materials provided to the Planning Commission after the agenda has published), are available on the City’s website at www.delmar.ca.us/AgendaCenter or by contacting the Administrative Services Department at (858) 755-9313.
CALL TO ORDER Chairperson Bakker called the Regular Meeting to order at 6:00 p.m.
ROLL CALL All Commissioners Present: Chairperson Ted Bakker, Vice Chair Nate McCay, Commissioners Don Countryman, Carmel Myers and Philip Posner
Staff Members Present: Principal Planner Amanda Lee, Associate Planner Jennifer Gavin
APPROVAL OF MINUTES
The motion by Commissioner Posner, second by Commissioner Countryman to approve the meeting minutes for October 10, 2017, was unanimously approved.
The motion by Commissioner Posner, second by Commissioner Countryman to approve the meeting minutes for November 7, 2017, was unanimously approved.
The motion by Commissioner Countryman, second by Commissioner Myers to approve the meeting minutes for December 5, 2017, was unanimously approved.
STAFF UPDATE
Principal Planner Lee shared that the December 5, 2017 Planning Commission approval of the Conkwright Site Specific Parking Management Plan/Parking Agreement P17-002 was appealed by the project applicant. The initial consideration of the appeal is scheduled for City Council on Tuesday, January 16, 2018, at which time the Council will decide whether to uphold the Planning Commission decision or set the matter for a de novo hearing.
Principal Planner Lee also announced that the Del Mar Adaptation Plan relating to the City’s sea level rise planning is scheduled for the February 13, 2018, Planning Commission hearing. For planning purposes, this item is expected to be well attended and is likely to take several hours. Planning Commission Regular Minutes January 9, 2018 Page 2 of 3
PLANNING COMMISSION/STAFF DISCUSSION (Non-Application Items)-
Commissioner Bakker recommended that the City review applicable Fire Codes in light of the recent California wildfires and consider whether additional local fire resistive building requirements should be adopted.
COMMISSION UPDATE None
HEARING FROM THE AUDIENCE ON ITEMS NOT LISTED ON THE AGENDA (Oral Communications) None
DISCUSSION AND BRIEFING (Application Items)
Principal Planner Lee identified there was only one item on the agenda (Item 1) and that it was eligible for the consent calendar.
CONSENT CALENDAR
ITEM 1 APN: 290-230-26-00;299-230-25-00 CUP17-002 Location: 1658 Coast Boulevard, Powerhouse Park CDP17-014 Owner/Applicant: City of Del Mar Zone: PP (Public Parkland) Overlay Zones: Beach, Historic Preservation, Coastal Bluff, Open Space Environmental Status: This project is listed among the classes of projects determined to have less than significant adverse effect on the environment and therefore, is exempt from the provisions of the California Environmental Quality Act (CEQA) pursuant to CEQA Guidelines Section 15303 Class 3 (e) - New Construction. Staff has further determined that none of the six exceptions to the use of a categorical exemption would apply to this project (CEQA Guidelines Section 15300.2). Staff Contact: Jennifer Gavin, Associate Planner Description: A request to construct a new shade structure over existing park furniture at the Tot Lot and to install new path lighting within Powerhouse Park.
Note: This project is located within the appeal jurisdiction of the California Coastal Commission.
IT WAS MOVED BY COMMISSIONER COUNTRYMAN, SECONDED BY COMMISSIONER MYERS TO APPROVE ITEM 1 ON CONSENT TO MAKE A RECOMMENDATION TO THE CITY COUNCIL FOR APPROVAL OF CONDITIONAL USE PERMIT 17-002 AND COASTAL DEVELOPMENT PERMIT 17-014 (Vote 5-0)
Ayes: Chair Bakker, Vice Chair McCay, Commissioners Countryman, Myers, and Posner Noes: None Planning Commission Regular Minutes January 9, 2018 Page 3 of 3
Absent: None
ADJOURNMENT Chairperson Bakker adjourned the meeting at 6:07 p.m.
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Jennifer Gavin, Associate Planner
City of Del Mar
PLANNING COMMISSION STAFF REPORT February 13, 2018
APPLICATION: Local Coastal Program Amendment LCPA 16-005 – Del Mar Coastal Resiliency/Sea Level Rise Adaptation Plan
REQUEST: That the Planning Commission adopt a Resolution (Exhibit A) to recommend that the City Council establish a Del Mar Coastal Resiliency/Sea Level Rise Adaptation Plan and incorporate the new land use plan into the Del Mar Local Coastal Program via the requested Local Coastal Program Amendment LCPA 16-005.
APPLICANT: City of Del Mar
BACKGROUND:
The City of Del Mar is actively planning to protect its beach, coastal bluffs, and environmental resources and minimize potential impacts to residents, businesses, visitors, public property and property owners in areas identified as vulnerable to damage from projected storms, flooding, erosion, and sea level rise. The City is working with technical consultant, Environmental Science Associates (ESA) and the Sea Level Rise Technical Advisory Committee (STAC) to address State law (California Senate Bill 379 and the Coastal Act), which requires that all local agencies prepare vulnerability assessments and establish climate adaptation and resiliency strategies to address local hazards.
The City’s Adaptation Plan will serve as a “toolbox” to help owners (public and private) plan for and address local hazards and will help the City to manage its shoreline and coastal resources for future generations. The Planning Commission is being asked to review the draft Adaptation Plan/Local Coastal Program Amendment (Exhibit B) and provide a recommendation to City Council per Del Mar Municipal Code (DMMC) Section 2.34.040. The City’s Local Coastal Program (LCP) applies citywide and includes the City’s certified land use policies, zoning ordinances (DMMC Chapter 30), and zoning maps. The proposed Adaptation Plan would be a new land use plan in the City’s LCP. Therefore, any evidence of a potential conflict with the existing certified LCP or State Coastal Act goals (referenced in the staff report) should be identified as part of the Planning Commission’s recommendation to City Council.
What is Sea Level Rise?
Sea level rise is the thermal expansion and rising of ocean water caused by global warming (melting ice) and tectonic movement and slippage of land mass into the ocean. As such occurrences increase on a global scale, sea level rise is expected to continue to accelerate.
1050 Camino Del Mar, Del Mar, California 92014 -2698. Telephone: (858) 755-9313.Fax: (858) 755-2794 www.delmar.ca.us
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Over time, the effect of sea-level rise will be more apparent locally as the width of the beach narrows, coastal bluffs erode, and the threat to people and property increases.
According to overwhelming scientific consensus, the sea level rose nearly 7 inches world- wide over the past 100 years and will continue to rise. Without local action to prepare, significant portions of Del Mar’s beach, coastal bluffs, and lagoon habitat may be lost. The Adaptation Plan will help the City plan ahead to address the identified vulnerabilities.
Technical Basis for the City’s Adaptation Planning Approach
The Adaptation Plan was prepared using best available science, guidance from the Coastal Commission, regional cost benefit and legal risk analysis studies, and context-specific, local data and technical studies. At the state level, the best available science on sea level rise is considered to be the National Research Council’s “Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future” (2012).
At the local level, ESA prepared a Coastal Hazards, Vulnerability and Risk Assessment using best available science to identify vulnerable areas in Del Mar that are subject to projected sea level rise, storm-surge, coastal flooding, river flooding, or erosion. The assessment identified vulnerable properties along the entire western boundary of the City, including properties on coastal bluffs (bluff erosion), at beach level (beach erosion/flooding from the ocean and river), and adjacent to the San Dieguito Lagoon (river flooding). Vulnerable City facilities/infrastructure include the fire station, public works yard, sewer lift station, beach access points, public roads, sewer lines, and stormwater systems.
Conservative projections indicate the City could be effected by a 5-inch increase in sea level rise by 2030, increasing to 12 inches by 2050, 1.7 feet by 2070, and 3.1 feet in 2100. Increased frequency and intensity of storms is also projected. For comparison, the extreme flooding Del Mar experienced during the historic floods of 1980 and 1983 are considered to have a 1% to 5% chance of occurrence in a given year. Extreme flooding is projected to increase to a 15% chance by 2030 to 2050, a 50% chance by 2070, and up to 100% chance each year by 2100. These projections are consistent with best available science, and will be re-examined on a periodic basis. If global efforts are successful to significantly reduce greenhouse gases and fossil fuel consumption, it may help to reduce the effects.
At the regional level, the San Diego Regional Climate Collaborative provided additional key resources, including a cost benefit analysis prepared by Nexus Planning & Research (2017) and a legal risk analysis prepared by the Environmental Law Institute (2017). Nexus Research’s cost benefit analysis evaluated the cost of “no action” versus various adaptation scenarios to protect, adapt, or abandon vulnerable properties. The study concluded that the highest cost to the City would be a choice to take no action at all; and that the highest return on investment may be realized if beach nourishment is used in the near term and paired with sand retention (i.e. groins). Similarly, the Environmental Law Institute’s analysis
2 February 13, 2018 Item 01 PLANNING COMMISSION STAFF REPORT: LCPA 16-005 February 13, 2018 Page #3 of 7 concluded there are potential legal risks if the City were to instead choose to take no action in regards to adaptation. More detailed cost benefit and legal risk analysis will occur at the project level when specific adaptation projects are contemplated.
Reference links to the technical documents referred to in this report are provided below:
1. National Research Council. Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future. (2012) http://www.delmar.ca.us/DocumentCenter/View/1879
2. California Coastal Commission. California Coastal Commission Sea Level Rise Policy Guidance: Interpretive Guidelines for Addressing Sea Level Rise in Local Coastal Programs and Coastal Development Permits. (2015) http://www.delmar.ca.us/DocumentCenter/View/1878
3. Environmental Science Associates. Del Mar Coastal Hazards, Vulnerability and Risk Assessment. (2016) http://www.delmar.ca.us/DocumentCenter/View/2455
4. Nexus Planning & Research. Comparing Sea Level Rise Adaptation Strategies in San Diego: An Application of the NOAA Economic Framework. (2017) http://docs.wixstatic.com/ugd/f0db5c_38386002d94b4417b21f4a77a8c76b33.pdf
5. Environmental Law Institute. Legal Risk Analysis for Sea Level Rise Adaptation Strategies in San Diego. (2017) http://docs.wixstatic.com/ugd/f0db5c_fbae0a9c4e984bfc952664735d274996.pdf
Coastal Resiliency/Sea Level Rise Planning Work Program
To help property owners plan ahead for the projected local hazards, the City’s Local Coastal Program is proposed to be amended to incorporate community policies, objectives, and implementation measures for adaptation. One challenge of this type of planning is that best available science can only predict a range of time in which future sea-level rise effects may be realized based on certain assumptions. There is no exact time table on which to base the plan. Therefore, the proposed approach would involve monitoring changes in conditions (i.e. extent of flood damage, storm frequency, sandy beach width, landward shift in mean high tideline, and erosion of coastal bluff edge) and potential risk over time, and would involve re-evaluation and updates in subsequent phases (similar to statewide housing program management).
Del Mar received two state grants (California Coastal Commission and Ocean Protection Council), which have helped the City gain access to key technical resources to tackle this complex planning topic. In accepting the grant funds, the City committed to prepare a Coastal Hazards, Vulnerability and Risk Assessment (completed 2016), Adaptation Plan
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(in process), Sediment Management Plan (in process), Lagoon Habitat Migration Assessment (in process), and implementing regulations/maps for incorporation in the City’s certified LCP (as part of work program scheduled through summer 2018). The Adaptation Plan is the land use plan currently before the Planning Commission. The Sediment Management Plan, Lagoon Habitat Migration Assessment, and implementing ordinance are separate documents that will be presented to Planning Commission in future hearings.
Del Mar’s Sea Level Rise Technical Advisory Committee
The Sea Level Rise Technical Advisory Committee (STAC) was created by the City Council in 2015 as an advisory Council Committee to provide guidance on the coastal resiliency planning process. STAC is an 11-person committee with two Council liaisons (currently Dwight Worden and David Druker). STAC felt the City’s initial draft Adaptation Plan (2016) was not nuanced to Del Mar; and therefore created a subcommittee to recommend revisions. The subcommittee put a tremendous amount of work to help tailor it to Del Mar. On January 25, 2018, STAC unanimously recommended approval of the Adaptation Plan with recommended revisions. (See Exhibit C for a summary of the STAC membership and recommendations provided.)
Significant public outreach has been conducted in a variety of public forums since 2015, including public meetings, workshops, and neighborhood forums. Over 20 public meetings were held to discuss the City’s coastal resiliency planning and Adaptation Plan. This included 17 STAC meetings/workshops since September 2015, three public forums focused on affected beach and coastal bluff neighborhoods, and additional subcommittee and neighborhood specific meetings. (See Exhibit D for the public outreach summary.)
ANALYSIS:
The Adaptation Plan will serve as a “toolbox” to help owners (public and private) plan for local hazards. Adaptation examples for private owners include measures to flood proof and strengthen structures, to engineer structures for protection (i.e. seawalls), to develop above projected flood elevations, and to locate development outside of bluff or flood hazard areas.
The toolbox also includes a range of options for larger scale adaptation including natural or green approaches for protection (i.e. beach nourishment, submerged reefs, and dunes), hard armoring approaches (i.e. seawalls, revetments, groins, breakwaters), and elevating or relocating road/utility infrastructure. Flexibility is desired because the type of strategies suitable for a location will differ based on context. For example, the approach for habitat resiliency may differ from strategies to protect buildings or infrastructure. Also, the choices will likely change over time as some become infeasible due to changing environmental conditions and others become available with new advances in engineering and science.
STAC recommended the following as principles to help guide future adaptation strategies:
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Limit the risk of extreme coastal and river flooding and damage. Maintain a walkable beach for recreational use, economic benefit, and reduce flooding. Maintain continuous horizontal coastal access and vertical water access points to North and South Beach. Maintain continuous coastal access from North Beach to South Beach. Maintain San Dieguito Lagoon wetland habitat functions.
The complete Adaptation Plan as recommended by STAC is in Exhibit B. Staff collected additional edits (to address technical inconsistencies and minor corrections) for Planning Commission to consider for recommendation to City Council (Exhibit E). The proposed Adaptation Plan is consistent with Del Mar’s existing certified LCP policies and regulations, and the California Coastal Act.
Managed Retreat
In accordance with Coastal Commission guidance, the City evaluated retreat as an adaptation strategy, which proved to be the most controversial issue relating to adaptation. Retreat is considered in cases where there is opportunity for a greater public benefit or as a worst case scenario to be considered when it becomes unsustainable to maintain development in a certain location (i.e. access and/or utilties are lost and serial reconstruction becomes cost prohibitive). Examples in Del Mar where retreat could be a viable option include relocation of City facilities and infrastructure and planning for long- term wetland habitat resiliency adjacent to the San Dieguito Lagoon.
Managed retreat is particularly controversial in regards to private property. After considering existing conditions in Del Mar versus projected risks, STAC recommended that managed retreat not be included in the Adaptation Plan at this time. Unlike the adaptation examples provided by Coastal Commission (i.e. Surfers Point in Ventura, CA), there is no contiguous open space or habitat for the ocean and beach sand to connect to in Del Mar. Instead, the associated costs (public and private) of retreat at a neighborhood scale in Del Mar would be significant, and appear to have limited opportunity, if any, for public benefit. The argument is that, contrary to the guiding principles for adaptation, retreat would actually increase the risk of flooding and damage to the public infrastructure and hundreds of homes adjacent to the beach front development with no public benefit. (See Exhibit G for the white paper by Walt Crampton for the Beach Preservation Coalition.)
In consideration of the STAC recommendation, managed retreat is intentionally not identified as an option in the “toolbox” for private property in Del Mar. Any retreat of Del Mar’s century-old beach level neighborhood should occur only as a last resort scenario with extreme hazardous conditions and only after all feasible alternatives have been exhausted. Due to the more imminent hazards and safety priorities to be addressed in the near term, managed retreat under worst case conditions is not a scenario that needs to be resolved
5 February 13, 2018 Item 01 PLANNING COMMISSION STAFF REPORT: LCPA 16-005 February 13, 2018 Page #6 of 7 now. However, as stated in the plan, the City will continue to reevaluate adaptation options (including retreat) as the projections are updated and environmental conditions change. (See Exhibit F for the STAC Summary Memo of their perspectives on Managed Retreat.)
Coastal Commission Authority: The City is required to comply with the Coastal Act. The Coastal Commission decision (whether to certify the City’s Adaptation Plan as a Local Coastal Program Amendment) will be based on Coastal Act Chapter 3 (Coastal Resources Planning and Management Policies): https://www.coastal.ca.gov/coastact.pdf
As declared by the State legislature (Coastal Act section 30001.5), the basic goals are to:
Protect, maintain, and where feasible, enhance and restore the overall quality of the coastal zone environment and its natural manmade resources. Assure orderly, balanced utilization and conservation of coastal zone resources taking into account social and economic needs of the state. Maximize public access to and along the coast and maximize public recreational opportunities in the coastal zone consistent with sound resource conservation principles and constitutionally protected rights of private owners. Assure priority for coastal-dependent development over other development on the coast. Encourage state and local initiatives and cooperation in preparing procedures to implement coordinated planning and development for mutually beneficial uses, including educational uses, in the coastal zone.
During the outreach process, the question was raised as to what happens when there are competing goals (i.e. private property rights versus public access). Per Coastal Act section 30007.5, in case of a conflict between Coastal Act policies, conflicts are to be “resolved in a manner which on balance is the most protective of significant coastal resources.” The Coastal Act does not define “significant coastal resources”, but does define “sensitive coastal resource areas” (Coastal Act section 30116) as including: “(a) Special marine and land habitat areas, wetlands, lagoons, and estuaries as mapped and designated in Part 4 of the coastal plan; (b) Areas possessing significant recreational value; (c) highly scenic areas; (d) Archaeological sites referenced in the California Coastline and Recreation Plan or as designated by teh State Historic Preservation Officer; (e) Special communities or neighborhoods which are significant visitor destination areas; (f) Areas that provide existing coastal housing or recreational opportunities for low- and moderate- income persons; and (g) Areas where divisions of land could substantially impair or restrict coastal access.”
The proposed Adaptation Plan/Local Coastal Program Amendment is subject to certification by the Coastal Commission and will be submitted to the Coastal Commission after City Council action. City staff has been coordinating with the San Diego District Coastal Commission staff throughout the process. Their comment letter is expected to be submitted as a “red dot” communication.
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ENVIRONMENTAL STATUS:
The Adaptation Plan is required by State law (Senate Bill 379). Pursuant to the California Coastal Act and State Guidelines for coastal jurisdictions, the Adaptation Plan policies are required to be incorporated into the City’s Local Coastal Program. The proposed Local Coastal Program Amendment is exempt from preparation of an environmental document pursuant to CEQA Guidelines (14 CCR Section 15265 Statutory Exemption: Adoption of Coastal Plans and Programs), which states that CEQA does not apply to activities and approvals pursuant to the California Coastal Act by any local government as necessary for the preparation and adoption of a Local Coastal Program. The CEQA Guidelines shift the burden of CEQA compliance for this action from the City to the Coastal Commission. The Adaptation Plan does not authorize or facilitate any construction or grading to occur and would not have a significant effect on the environment.
PUBLIC NOTICE:
A Notice of Availability/Notice of Public Hearing was published and distributed per the Coastal Act requirements. Additional courtesy notice was mailed to residents and property owners in potentially vulnerable areas. Notice was also distributed via email blast to the City’s “notify me” interested persons list.
RECOMMENDATION:
The Planning Department recommends the Planning Commission adopt the Resolution in Exhibit A and make a recommendation to the City Council.
Respectfully submitted,
Amanda Lee Principal Planner
Exhibit A – Draft Planning Commission Resolution Exhibit B – Draft Adaptation Plan Exhibit C – STAC Membership and Recommendations Exhibit D – Outreach Summary Exhibit E – Additional Adaptation Plan Revisions for PC Consideration Exhibit F – STAC’s Managed Retreat Summary Memo Exhibit G – White Paper by Walt Crampton for the Beach Preservation Coalition
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RESOLUTION NO. PC 2018-xx
A RESOLUTION OF THE PLANNING COMMISSION OF THE CITY OF DEL MAR, CALIFORNIA, PROVIDING A RECOMMENDATION TO THE CITY COUNCIL REGARDING THE PROPOSED LOCAL COASTAL PROGRAM AMENDMENT (LCPA 16-005) THAT WOULD ESTABLISH A CITY OF DEL MAR COASTAL RESILIENCY/SEA LEVEL RISE ADAPTATION PLAN AS A NEW LAND USE PLAN IN THE CITY’S LOCAL COASTAL PROGRAM IN ACCORDANCE WITH STATE LAW.
WHEREAS, State law requires that local agencies prepare vulnerability assessments and establish climate adaptation and resiliency strategies to address identified local hazards; and
WHEREAS, Environmental Science Associates prepared a Coastal Hazards, Vulnerability, and Risk Assessment for the City of Del Mar using best available science that identified vulnerable areas in Del Mar that are subject to projected sea level rise, storm surge, coastal flooding, river flooding, or erosion; and
WHEREAS, disclosure of the Coastal Hazards, Vulnerability, and Risk Assessment for the City of Del Mar has been posted on the City’s web page since May 12, 2016 when notification of its availability was publicly announced, widely distributed, and reported on by local media; and
WHEREAS, the best available science on sea level rise in the State of California is considered to be the National Research Council’s report titled “Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future” (2012); and
WHEREAS, the City’s Adaptation Plan was prepared using best available science, guidance from the California Coastal Commission, regional cost benefit and legal risk analysis studies, and context-specific, local data and technical studies including the Del Mar Coastal Hazards, Vulnerability, and Risk Assessment (2016); and
WHEREAS, Nexus Research’s cost benefit analysis titled “Comparing Sea Level Rise Adaptation Strategies in San Diego: An Application of the NOAA Economic Framework” (2017) evaluated the cost of “no action” versus various adaptation scenarios to protect, adapt, or abandon vulnerable properties and concluded that the highest cost to the City would be a choice to take “no action” in regards to adaptation; and
WHEREAS, the legal risk analysis prepared by the Environmental Law Institute (2107) identified that there are potential legal risks for the City if the City Council were to choose to take “no action” in regards to adaptation; and
WHEREAS, the City of Del Mar is seeking approval of a Local Coastal Program Amendment (LCPA16-005) to establish a City of Del Mar Coastal Resiliency/Sea Level Rise Adaptation Plan; and
WHEREAS, the Adaptation Plan is intended to serve as a “toolbox” to help owners (public and private) plan for local hazards and help the City manage its shoreline and coastal resources for future generations; and
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Resolution No. PC-2018-xx Regarding LCPA16-005 Page 2 of 3
WHEREAS, the Adaptation Plan is a policy document that does not include any regulations and does not in and of itself either authorize or preclude development construction or grading activity to occur; and
WHEREAS, in 2015 the City Council established the Sea Level Rise Technical Advisory Committee (STAC) as an advisory committee to provide guidance on the coastal resiliency/sea level rise planning work program, including the draft Adaptation Plan; and
WHEREAS, over twenty public meetings have been held to discuss the City’s coastal resiliency/sea level rise planning and draft Adaptation Plan for Del Mar; and
WHEREAS, the initial draft of the Adaptation Plan was first released for public review in September 2016; and
WHEREAS, STAC felt the initial draft Adaptation Plan (2016) was not nuanced to Del Mar and therefore established a subcommittee who put a tremendous amount of work into reorganizing and repackaging the Adaptation Plan to help tailor it towards Del Mar; and
WHEREAS, on January 25, 2018, STAC recommended approval of the Adaptation Plan as revised; and
WHEREAS, a noticed public hearing of the Planning Commission was conducted to provide the public an opportunity to comment on the Adaptation Plan and associated Local Coastal Program Amendment and for the Planning Commission to provide a recommendation to the City Council; and
WHEREAS, the Local Coastal Program Amendment is subject to certification by the California Coastal Commission; and
WHEREAS, the City of Del Mar posted, mailed, and distributed a Notice of Availability of the draft Adaptation Plan for public review prior to January 30, 2018, in accordance with California Code of Regulations Section 13515 requirements for public participation and agency coordination for Local Coastal Program Amendments; and
WHEREAS, the City of Del Mar provided additional mailed courtesy notice to all residents and owners within the areas identified as potentially vulnerable; and
WHEREAS, the Adaptation Plan is required by State law (Senate Bill 379) and must be incorporated into the City’s Local Coastal Program pursuant to the California Coastal Act and State guidelines for coastal jurisdictions; and
WHEREAS, staff determined that the proposed Local Coastal Program Amendment is exempt from preparation of an environmental document pursuant to CEQA Guidelines (14 CCR Section 15265 Statutory Exemption: Adoption of Coastal Plans and Programs), which states that CEQA does not apply to activities and approvals pursuant to the California Coastal Act by any local government as necessary for the preparation and adoption of a Local Coastal Program
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because per the CEQA Guidelines the burden of CEQA compliance for this type of action shifts from the City to the Coastal Commission; and
WHEREAS, on February 13, 2018, the Planning Commission of the City of Del Mar held a public hearing on the City’s application for LCPA16-005, at which time all persons desiring to be heard were heard; and
WHEREAS, evidence was submitted and considered to include without limitation:
a. The Staff Report to the Planning Commission dated February 13, 2018, including report attachments; and
b. “Red dot” correspondence submitted after the agenda and staff report were posted; and
c. Oral testimony from Staff and the public; and
c. Additional information submitted during the hearing.
NOW, THEREFORE, BE IT RESOLVED that the Planning Commission of the City of Del Mar does hereby recommend the following:
RESOLUTION PC-2018-xx PASSED AND ADOPTED by the Planning Commission of the City of Del Mar, this 13th day of February, 2018, by the following vote:
AYES:
NOES:
ABSENT:
ABSTAIN:
______TED BAKKER, Chair Del Mar Planning Commission
______Kathleen A. Garcia, Director of Planning and Community Development
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Executive Summary
The Adaptation Plan serves as the City’s “toolbox” to help property owners (public and private) plan for and address future sea-level rise, storm surge, coastal flooding, and erosion. In 2016, the City of Del Mar prepared a Coastal Hazards, Vulnerability and Risk Assessment that identified the degree of vulnerability posed to City beaches, lagoons, coastal bluffs, visitor- serving amenities, public access areas, residential and commercial areas, and public infrastructure. In consideration of the vulnerabilities and risks, the Adaptation Plan provides tools for owners to manage risks and take actions based on measurable changes in conditions.
The Adaptation Plan provides flexibility for owners to choose from an array of adaptation options, rather than prescribing a specific plan of action. Project-level planning and approvals will be required to further develop and implement specific adaptation measures.
Adaptation measures are typically categorized within the following categories:
Protection strategies, which employ some sort of engineered structure or other measure to defend development (or resources) in its current location without changes to the development itself. Examples include “hard” armoring via structures such as seawalls, revetments, groins and breakwaters that defend against coastal hazards like wave impacts, erosion, and flooding; “soft” armoring using natural or “green” method like beach nourishment and artificial dunes to buffer coastal areas; and hybrid approaches using both hard and natural infrastructure.
Accommodation strategies, which modify existing development or design new development in a way that decreases hazard risks and thus increases the resiliency of development. Examples include elevating structures, retrofitting structures, using materials that increase the strength of development, or incorporating extra setbacks from hazards.
Retreat strategies, which relocate existing development as necessary out of hazard areas and limit the construction of new development in vulnerable areas. Examples where this strategy could be used for public property include relocation of public facilities, roads, and infrastructure.
Adaptation strategies should not be considered in isolation. Different types of strategies will be appropriate in different locations, and in many cases a hybrid approach with strategies from multiple categories will be necessary. Additionally, the suite of strategies chosen may need to change over time.
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The following principles were established to provide guidance for developing, evaluating, and analyzing adaptation measures:
Limit the risk of extreme coastal and river flooding and damage. Maintain a walkable beach for recreational use, economic benefit, and to reduce flooding. Maintain continuous horizontal coastal access and vertical water access points to North and South Beach. Maintain continuous coastal access from North Beach to South Beach. Maintain San Dieguito Lagoon wetland habitat functions.
In terms of City assets, the Adaptation Plan identifies high priority adaptation measures for which near term actions are recommended to reduce high vulnerabilities and risks. The Plan also discusses sediment management and sand retention measures and identifies potential adaptation measures to address the following areas and vulnerabilities:
San Dieguito Lagoon wetland adaptation for the River Valley San Dieguito River flooding adaptation for the North Beach and River Valley including the Del Mar Fairgrounds Bluff and adjacent beach erosion adaptation for the South Bluffs, and bluffs along South Beach and North Bluffs Beach erosion and flooding adaptation (north from 15th St to the San Dieguito River mouth)
The Adaptation Plan is based on the best science and adaptation practices available today. However, sea-level rise science and practices are evolving and environmental conditions along the beach, bluffs, and San Dieguito Lagoon are changing; therefore, it is anticipated that this document will be updated over time as needed.
The Sea Level Rise Technical Advisory Committee (STAC) evaluated retreat as an adaptation option and determined it is too early in the process to include retreat as an adaptation strategy in Del Mar. At this time, retreat is intentionally not included as an adaptation option for private property. STAC recommends that the City prioritize beach nourishment in conjunction with sand retention.
STAC recognizes that additional reports will be generated over time, including a Sediment Management Plan and a Wetlands Habitat Migration Assessment. Analyses of the financial and legal impacts of adaptation measures will be performed when any future project is initiated and details for a given project are available. It is expected that the City will reevaluate options, including retreat, as appropriate and using updated scientific and monitored data when amendments to the Adaptation Plan are considered at a future date.
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CHAPTER 1
Planning for Sea-Level Rise in Del Mar
1.1 About the City of Del Mar
Del Mar is a beach city in San Diego County, California. Del Mar is Spanish for "of the sea" or "by the sea," which reflects its location on the coast of the Pacific Ocean (Figure 1). Del Mar's climate is considered Mediterranean-subtropical with warm, dry summers and mild, humid winters. The city has a total area of 1.8 square miles (4.7 km2), where 1.7 square miles (4.4 km2) of it is land and 0.1 square miles (0.26 km2) of it (4%) is water. The entire western boundary of the city is on the oceanfront, from north to south, and includes bluff, lagoon river mouth, open beach and developed beach. Del Mar has a continuous wide beach stretching over two and a half miles from near the Los Penasquitos Lagoon on the south to San Dieguito Lagoon on the north, with additional walkable beach north of San Dieguito Lagoon rivermouth to Del Mar’s boundary with the City of Solana Beach. The beaches are walkable from end-to-end, especially in the summer when wider. The southern area of Del Mar is located atop and to the east of oceanfront bluffs, as is the area north of the San Dieguito lagoon. The northern area, known as North Beach, up to the river includes topography with oceanfront homes at a higher elevation than adjacent homes to the east, where the elevation declines eastward from the ocean front lots toward the LOSSAN rail line.
1.2 Planning Process and Goals Rising sea level increases the risk of hazards to coastal communities from storms, flooding, and erosion. In response to the increased risks of coastal hazards, the California Coastal Commission has a priority goal to coordinate with local governments, such as the City of Del Mar (City), to complete a Local Coastal Program (LCP) amendment that addresses the impacts of sea level rise. An updated LCP can help cities address new coastal management challenges that result from sea level rise and climate change.
Planning for sea level rise includes identifying and applying different adaptation mechanisms based on Coastal Act requirements, Del Mar’s voter-approved Beach Preservation Initiative (BPI) incorporated in the certified LCP, acceptable levels of risk, and community priorities. By planning ahead, communities can reduce the risk of costly damage from coastal hazards, can ensure the coastal economy continues to thrive, and can protect coastal habitats, public access and recreation, and other coastal resources for current and future generations. Adaptation strategies should be chosen based on the specific risks and vulnerabilities of a particular region or project site, in the context of applicable Coastal Act and LCP requirements.
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Figure 1 Del Mar Map
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1.3 Amending Del Mar’s Local Coastal Program
The California Coastal Act requires local governments, such as the City of Del Mar, in the state’s Coastal Zone to create and implement Local Coastal Programs (LCPs). Given that a majority of Del Mar lies within the Coastal Zone, the City’s LCP is an integral component of many planning processes. Each local government’s LCP consists of a Coastal Land Use Plan (referred to as LUP or General Plan) and an Implementation Plan (Zoning Code). Using the California Coastal Act, the California Coastal Commission (CCC) and local governments manage coastal development, including addressing the challenges presented by coastal hazards like storms, flooding, and erosion.
The purpose of this report is to complete some of the steps outlined in the CCC’s Sea Level Rise Policy Guidance document. These steps include the following:
Step 1. Establish the Projected Sea Level Rise Ranges Table 1.1 shows projected future sea-level rise from the National Research Council (NRC) study Sea-Level Rise for the Coasts of California, Oregon, and Washington (NRC 2012) for the mid-range and the high-range sea-level. The rate of sea-level rise is projected to accelerate in the future.
The low-range sea-level rise scenario is based on dramatic reduction of fossil fuel use, which has not yet occurred. The mid-range sea-level rise projections are based on reducing fossil fuel use, with a balance between fossil fuels and alternative energy sources; whereas the high-range sea-level rise projections assume intensive fossil fuel use will continue in the future. The NRC sea-level rise projections are considered “best available science” for/by the State of California.
Table 1.1 Sea level rise scenarios used in this Study 2030 2050 2070 2100
Low SLR 2in 5in 17in (1.4 ft)
Mid SLR 5 in 12 in 20 in (1.7 ft) 37 in (3.1 ft)
High SLR 12 in 24 in 38 in (3.2 ft) 66 in (5.5 ft)
The Del Mar Adaptation Plan acknowledges that the processes causing sea-level rise and the science of projecting sea-level rise are inherently uncertain. For example, the rate of sea-level rise is highly dependent on whether global greenhouse gas emissions will continue to increase or whether global emissions will be reduced. The rate of sea- level rise could be higher, or lower, than the above projections. Given the uncertainties, the Adaptation Plan is therefore not tied to specific timeframes or years, but rather uses thresholds based on amounts of sea-level rise of up to 5.5 ft and responses to climate change such as flood frequency and erosion.
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Step 2. Identify Potential Impacts from Sea Level Rise Based on available modeling from SPAWAR and USGS (CoSMoS 1.0 and 3.0 preliminary), the potential hazards for the City were identified and include storm induced dune erosion, coastal flooding from wave run-up, and tidal inundation. Given the boundaries and setting of the City, the most dominant hazards are the following: coastal flooding associated with major wave events, river flooding and coastal erosion.
Step 3. Assess the Risks and Vulnerabilities to Coastal Resources and Development The following sectors were determined to experience some form of existing or future risk and related vulnerability to sea level rise (e.g. bluff erosion and/or coastal flooding):
A. Land Use B. Roads C. Public Transportation D. Wastewater E. Storm water F. Parks G. Other Utilities (e.g. water, electricity, gas)
Per the City of Del Mar’s Coastal Hazards, Vulnerability, and Risk Assessment (ESA 2016,http://www.delmar.ca.us/DocumentCenter/View/2455), the City of Del Mar is currently vulnerable to river and coastal flooding and erosion, with significant damages in the recent past (late 1970s to present). Along the Del Mar bluffs (Figure 1), the cliff top has retreated to a point where it is a safety concern for the LOSSAN (Los Angeles- San Diego-San Luis Obispo) railroad along the bluff top, and the San Diego Association of Governments (SANDAG) and North County Transit District (NCTD) have responded by installing multiple bluff stabilization projects.
With future climate change and sea-level rise, studies suggest that the City of Del Mar’s current vulnerabilities are projected to increase in both frequency and intensity, resulting in increased damage to much of Del Mar including low-lying areas and areas near coastal bluffs, summarized as follows:
The beach above high tide will be lost to erosion with approximately 1 to 2 ft of sea-level rise, at which point beach erosion and coastal storms will threaten sea wall integrity, affecting the City’s North Beach District. Bluffs will erode and impact the LOSSAN railroad as well as the South Beach and South Bluff Districts; or, if the railroad were to be armored with a seawall, little to no beach will exist. San Dieguito River flooding will inundate the City’s North Beach and Valley Districts, including the Del Mar Fairgrounds, more frequently and with greater depths.
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The increased future sea-level rise and hazards will impact coastal resources and assets in Del Mar, including properties, roads and bridges, infrastructure, emergency services, coastal access, and San Dieguito River lagoon wetland habitats. The Coastal Hazards, Vulnerability, and Risk Assessment (ESA 2016, http://www.delmar.ca.us/DocumentCenter/View/2455) includes additional details, analysis, and discussion of Del Mar’s vulnerabilities to sea-level rise.
Step 4. Identify Adaptation Measures
The Del Mar Sea-Level Rise Adaptation Plan serves as the City of Del Mar’s long- range planning guide to address future sea-level rise and its effects on storm surge and coastal flooding and erosion. This Adaptation Plan will provide the basis for developing new sea-level rise policies that will be integrated into the City’s LCP via a LCP Amendment.
Preparation of the Adaptation Plan is funded by the City and a planning grant awarded to the City by the Ocean Protection Council and administered by the California Coastal Commission. This Adaptation Plan follows the California Coastal Commission’s (2015) Sea Level Rise Policy Guidance for addressing sea-level rise in LCPs. Additional information on the City’s sea-level rise LCP Amendment is available at: http://www.delmar.ca.us/sealevelrise.
The Adaptation Plan is consistent with the California Coastal Act and relevant City and State policy, plans, and guidelines (reviewed in Chapter 2).
1.4 Del Mar’s Sea-Level Rise Stakeholder Technical Advisory Committee (STAC) The City established the Sea- Level Rise Stakeholder Technical Advisory Committee (STAC) to provide oversight and ensure the LCP amendment process is open, inclusive, and develops consensus amongst the many stakeholders involved. (For more details on the STAC, see: http://www.delmar.ca.us/499/Sea-Level-Rise-Stakeholder-Committee.) STAC developed the following guiding principles for the development of the Adaptation Plan:
Limit the risk of extreme coastal and river flooding and damage to less than approximately a 5% chance of occurring in a given year. Maintain a walkable beach for recreational use and economic benefit, and to reduce flooding. (Economic benefit in this context includes both market and non- market value.) Maintain continuous horizontal coastal access and vertical water access points to North and South Beach. Maintain continuous coastal access from North Beach to South Beach. Maintain San Dieguito Lagoon wetland habitat functions.
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1.5 Summary of the Adaptation Plan The Adaptation Plan includes the following components and adaptation measures to reduce risks associated with future sea-level rise. Any adaptation measure when implemented may introduce new needs for additional mitigation.
Public Facilities, Infrastructure and Beaches: high priority sea-level rise adaptation measures for the City to begin planning for now include: Relocating the City of Del Mar Fire Station Relocating the City of Del Mar Public Works Yard Flood-proofing the sewer lift station along San Dieguito Drive Beach sand retention, replenishment, and management San Dieguito Lagoon wetland adaptation: Conversion of vegetated wetland to mudflat and open water habitats with sea- level rise could be partially accommodated and offset by allowing and facilitating the conversion of higher elevation area to tidal wetland habitat, such as the tern nesting island, adjacent upland habitats, and upstream riparian habitats. Placement of sediment to raise the elevation of the wetlands (e.g., “spraying” material dredged from the River channel as a thin layer of sediment across the vegetated marshplain) has the potential to reduce or slow wetland habitat conversion. Wetland expansion/restoration can create new wetlands with higher elevation areas that are more resilient to sea-level rise; wetland restoration is compatible with partial retreat and construction of “living” levees to reduce flood risks along the River. San Dieguito River flooding adaptation: San Dieguito River channel dredging and Lake Hodges reservoir management have potential to reduce river flood risks in the near- to mid-term. A hybrid approach with restoration of developed area adjacent to the River to expand the San Dieguito Lagoon wetland floodplain and construction of new levees between the wetlands and development can provide longer-term flood risk reduction; “living” levees can be designed to incorporate restored wetland transition and upland habitats that improve wetland resiliency to sea-level rise. If Lake Hodges reservoir management is not possible, the timeframe for other measures may be sooner. Bluff/beach erosion adaptation: Beach nourishment and sand retention strategies as well as installation of access paths down the bluffs (e.g., stairways) in conjunction with authorized pedestrian crossings at railroad under- or over-passes may provide some near-term reduction in bluff erosion; investigating whether landscape irrigation in City neighborhoods east of the bluffs is contributing increased groundwater flow and associated erosion and the potential to reduce irrigation affects may also be beneficial.
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Relocating the LOSSAN railroad will allow for continued landward bluff erosion, and thereby maintain a beach below the bluff and provide access along the bluff top. Removal of bluff top sewer lines, drainage ditches, and fiber optic cables will eventually be required as the bluff continues to recede inland. Beach coastal (ocean) flooding and beach erosion adaptation: Beach and dune nourishment and sand retention strategies may provide near- term protection, but their effectiveness is likely to decrease over time with higher amounts and rates of sea-level rise. Redevelopment policies and regulations can be developed for the LCP Amendment to make feasible the option of elevating structures. Sand retention measures such as groins or artificial reef may help maintain the beach, but would likely introduce need for additional mitigation. Raising/improving the existing sea wall and revetments (i.e., “holding the line”) would reduce flood risks with sea-level rise. Raising City infrastructure including buildings, utilities, and roads will likely be required to accommodate the increase in flood risk with sea-level rise.
1.6 Purpose of the Adaptation Plan This Adaptation Plan is a “toolbox” that will provide the basis for developing new sea-level rise policies that will be integrated into the City’s Local Coastal Program (LCP) via a LCP Amendment. The adaptation strategies included are based on the technical analysis from the Coastal Hazards, Vulnerability and Risk Assessment (ESA 2016) that used flood risk and shoreline change modeling. Preparation of the Adaptation Plan has been funded by the City and a planning grant awarded to the City by the Ocean Protection Council and administered by the California Coastal Commission. This Adaptation Plan follows the CCC’s (2015) Sea Level Rise Policy Guidance for addressing sea-level rise in LCPs. Additional information on the City’s sea-level rise LCP Amendment is available at: http://www.delmar.ca.us/sealevelrise.
This project will inform the City’s long-term effort to address a range of coastal and climate change hazards in planning and regulatory processes. This information will assist the City in making informed decisions regarding land use and development standards from the project level to the plan and policy level.
The guiding principles behind the Adaptation Plan seek to be consistent with the voter-approved BPI to regulate the uses of the Del Mar beach area, a distinct and valuable resource, for the benefit of present and future generations, so as to protect public access to and along the shoreline, while promoting public safety, health and welfare, and providing for the protection of private property; minimize risks to Del Mar’s assets, including property and infrastructure; and to protect Del Mar’s coastal resources. The California Coastal Act defines coastal resources to include coastal development and hazards; public access and recreation; coastal habitats; Environmentally Sensitive Habitat Areas and wetlands; water quality and supply; archaeology and paleontological resources; and scenic and visual resources. A key coastal resource is the sandy beach, both for public enjoyment and community wellbeing, and also for ecosystem
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services such as storm damage protection.
Consistent with the California Coastal Commission Sea-Level Rise Policy Guidance and current environmental practice, the Adaptation Plan includes hybrids between these approaches, nature based or green infrastructure solutions, and multi-objective measures that incorporate environmental considerations, rather than focusing on independent solutions to protection.
1.7 Definitions
Adaptation: means anticipating the adverse effects of climate change and taking appropriate action to prevent or minimize the vulnerabilities and reduce the fiscal impacts. (Fiscal impacts in this context includes tax revenue impacts and any operational, repair or maintenance costs to the City.)
Coastal Erosion: erosion of the coast caused by wave attack.
Coastal Flooding: flooding along the coast caused during a large storm wave event and typically includes wave uprush with momentum that can cause damages.
Tidal Inundation: flooding caused during predictable high tides that occur with some regularity.
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CHAPTER 2
Relevant Plans and Guidelines
2.1 California Coastal Act The Legislature declares that the basic goals of the state for the coastal zone are to:
1. Protect, maintain, and where feasible, enhance and restore the overall quality of the coastal zone environment and its natural and manmade resources; 2. Assure orderly, balanced utilization and conservation of coastal zone resources taking into account social and economic needs of the state; 3. Maximize public access to and along the coast and maximize public recreational opportunities in the coastal zone consistent with sound resource conservation principles and constitutionally protected rights of private owners; 4. Assure priority for coastal-dependent development over other development on the coast; 5. Encourage state and local initiatives and cooperation in preparing procedures to implement coordinated planning and development for mutually beneficial uses, including educational uses, in the coastal zone.
2.2 Del Mar Community Plan The City of Del Mar Community Plan (General Plan) establishes the community’s vision for future growth through goals, objectives, and policies that address the following topics: environmental management, transportation infrastructure, and community development, including land use and housing (City of Del Mar, 1976). The Community Plan also references specific provisions for 16 specific plans that apply to certain areas of the city, natural or hazardous features, and provision of certain infrastructure.
1.E.1 Preserve, as open space, areas such as the 100-year floodway and the beach bluffs west of the railroad tracks that are too hazardous to justify permanent construction.
1.E.7 Open space areas should be managed with erosion control and pollution prevention measures in the forefront.
1.H.1 Participate in regional and/or statewide efforts to evaluate and control beach and bluff erosion problems.
1.I.10 Maintain existing public uses of beaches.
From the guiding principles above, the adaptation plan recognizes that Del Mar’s beach,
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particularly North Beach but also including South Beach along the bluffs, provide significant recreational, economic, and flood and erosion protection values. The beach is walkable for most of the year and most stages of the tide, with the exceptions being particularly high tides occurring in the winter when seasonal erosion of the beach has occurred. The intent of this guiding principle is to maintain these values and the character of Del Mar’s beaches. Through adaptation, the goal is to avoid extended periods of time or successive years where these uses and values are significantly compromised (e.g., periods of days or weeks when the beach is not walkable or only walkable at the lowest tides). Given that the beach is continually changing throughout the year and from year to year, it is difficult to measure or specify a minimum beach width and this guiding principle is therefore focused on maintaining the beach’s values.
1.E.4 Preserve and where necessary acquire easements for the protection of access to the beach and other public open space.
2.A.5 Preserve and improve pedestrian access to and along beaches and sea cliffs by use of all public rights-of-way and prescriptive easements.
As an extension of the guiding principles above, the City’s adaptation goal is to maintain continuous horizontal coastal access along Del Mar’s North and South Beach between Solana Beach to the north and Torrey Pines State Beach to the south. The Adaptation Plan also seeks to maintain and provide vertical access down to the Del Mar beach at existing access points and potentially new controlled and legal railroad crossing(s) and access down the South Bluff.
1.J.1 Establish a comprehensive master plan and management program for the lagoon including biological productivity potential, health controls, future water supply, the preservation and enhancement of wildlife, and opportunities for educational and recreational enjoyment.
1.J.2 Land use policies established within the San Dieguito River Floodway and Lagoon Habitat should be consistent with the long-range goal of returning the entire area to the natural lagoon condition.
In regard to the above Del Mar Community Plan goal, the Adaptation Plan seeks to maintain San Dieguito wetland habitat functions for wetlands within the City limits and to provide guidance and coordination for maintaining the Lagoon ecosystem as a whole, including upstream wetlands in the City of San Diego. The Del Mar Coastal Hazards, Vulnerability, and Risk Assessment (ESA 2016) indicates that vegetated salt marsh habitat will convert to unvegetated mudflat and open water habitat with sea-level rise. The Adaptation Plan seeks to maintain a diverse array of wetland habitats including vegetated salt marsh habitat for critical salt marsh species, which could otherwise be lost. Southern California Edison (SCE) currently maintains the San Dieguito Lagoon Restoration as part of the mitigation program for the San Onofre Nuclear Generating Station (SONGS); however, SCE is not currently required to address the potential effects of sea-level rise and at some point in the future the management of the restoration may be transferred to another entity. The Adaptation Plan therefore seeks to improve the resiliency of the entire San Dieguito Lagoon wetland ecosystem to sea-level rise, including the San Dieguito Lagoon Restoration.
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2.3 Del Mar Local Coastal Program Del Mar’s Local Coastal Program (LCP) guides development and protects coastal resources within the Coastal Zone. LCPs must be consistent with the California Coastal Act of 1976, as amended. Del Mar’s LCP is made up of two parts: (1) the Land Use Plan (a compilation of goals, policies, and recommended programs), and (2) Implementing Ordinances (regulations that implement the provisions of the Land Use Plan and the California Coastal Act) (City of Del Mar, 1993; 2001).
Del Mar’s LCP establishes goals, policies, and regulations for the following four overlays: beach overlay, coastal bluff overlay, floodplain overlay, bluff, and lagoon overlay.
The Beach Protection Initiative (BPI) was adopted on April 12, 1988, by the Del Mar voters. It was subsequently certified as part of the City’s LCP and codified in the Del Mar Municipal Code (DMMC) LCP as the Beach Overlay Zone at Chapter 30.50. The stated purpose of the Beach Overlay Zone created by the BPI is “to regulate the uses of the Del Mar beach area, a distinct and valuable natural resource, for the benefit of present and future generations”. The regulations aim “to protect public access to and along the shoreline, while promoting public safety, health and welfare, and providing for the protection of private property”. On November 14, 1988 the City Council, as authorized by the BPI, adopted Guidelines to interpret the BPI.
Additional key policies and regulations relevant to the Adaptation Plan are the following: Beach Overlay Zone (Land Use Plan, Chapter III; Implementing Ordinances, Chapter 30.50): The purpose of this zone is to protect public access to and along the shoreline, while promoting public safety, health and welfare, and providing for the protection of private properties. The zone establishes a Shoreline Protection Area (SPA) line within the Beach Overlay Zone. Coastal Bluff Overlay Zone (Land Use Plan, Chapter III; Implementing Ordinances, Chapter 30.55): The purpose of this zone is to protect Del Mar’s fragile coastal bluffs as a visual resource and avoid the risks to life and property associated with bluff failure and shoreline erosion. Floodplain Overlay Zone (Land Use Plan, Chapter III, Implementing Ordinances, Chapter 30.56): The purpose of this zone is to promote public health, safety, and general welfare by ensuring that new development is appropriately sited and constructed so as to avoid hazards to those who will occupy the development, and to avoid damage or hazards to the surrounding area. The purpose is also to ensure development will not obstruct flood flow; will be designed to reduce the need for construction of flood control facilities that would be required if unregulated development were to occur; and to minimize the cost of flood insurance to Del Mar’s residents. Lagoon Overlay Zone (Land Use Plan, Chapter VI; Implementing Ordinances, Chapter 30.53): The purpose of this zone is to protect the wetland resources of the Los Peñasquitos and San Dieguito Lagoons and their sensitive upland habitats by requiring that all development activities are designed and implemented in a manner that is consistent with wetland habitat protection and enhancement.
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2.4 Del Mar Climate Action Plan
The Del Mar Climate Action Plan provides a roadmap for the Del Mar community to reduce greenhouse gas emissions. The Climate Action Plan includes a greenhouse gas emission inventory for 2012 (defined as the baseline) and emission reduction targets for 2020 and 2035. Actions to meet emission reduction targets are grouped by the following community sectors: energy and buildings, water and waste, transportation, and urban tree planting. The Climate Action Plan identifies the process for implementing and monitoring success of the reduction measures included in the plan. Adaptation strategies to help the city reduce vulnerabilities and build resilience to the anticipated effects of climate change are also included. Adaptation strategies that relate to the measures identified in this Adaptation Plan include:
Coastal Flooding Conduct a sea-level rise study to understand the risks and cost/benefits of development within flood hazard zones and potential long term mitigation recommendations. Explore protecting existing and construct new natural buffers to protect the coastline from flooding. Explore preservation of shorelines through beach replenishment and nourishment to address impacts of sea-level rise on shorelines. Natural Systems and Wildlife Monitor the health of coastal wetlands/river habitats that filter polluted runoff. Protect, preserve, and restore native habitats.
2.5 CCC Sea-Level Rise Policy Guidance In 2015, the California Coastal Commission (CCC) adopted the Sea Level Rise Policy Guidance document to aid jurisdictions in incorporating sea level rise into LCPs, Coastal Development Permits, and regional strategies. The document outlines specific issues that policymakers and developers may face as a result of sea level rise, such as extreme events, challenges to public access, vulnerability and environmental justice issues, and consistency with the California Coastal Act. It organizes current science, technical, and other information and practices into a single resource to facilitate implementation of the Coastal Act by coastal managers at the state and local level. The policy guidance document also lays out the recommended planning steps to incorporate sea level rise into the legal context and planning strategies to reduce vulnerabilities and guide adaptation planning. The policy guidance has a strong emphasis on using soft or green adaptation strategies.
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CHAPTER 3 (move to APPENDIX A)
Coastal Processes and Human Adaptations
As STAC evaluated Del Mar’s vulnerabilities and adaptation options, committee members collected and summarized reference materials to provide context specific to Del Mar. Particular emphasis was placed on the need for references relating to the movement of sand along the Del Mar shoreline in the interim while the City’s consultant, Environmental Science Associates, performed the data collection, analysis, and preparation of a Sediment Management Plan specific to Del Mar. Sand replenishment and beach nourishment emerged as high priorities during STAC’s nearly three-year evaluation (see Chapter 5 for more detail). This Appendix summarizes reference materials on the Oceanside Littoral Cell and the implications of human intervention, including sediment management, beach nourishment and the construction of groins, breakwaters, and seawalls. References are provided at the end as pointers to supplementary materials for readers of the Adaptation Plan. The material summarized here provided background and context for STAC during Phase 1 of the STAC process.
3.1 Oceanside Littoral Cell Coastal processes drive the movement of littoral sediment, leading to beach erosion, beach stability, or beach accretion. Coastal erosion and accretion has always existed and these Coastal processes have long contributed to the present coastline. The California coast can be separated into discrete geographic areas called littoral cells. Littoral cells are the areas where sediment moves in various directions along the coast. Other features such as submarine canyons and headlands are also part of the coastal environment. The littoral cells within San Diego County (Figure 3.1.1) are the Oceanside Littoral Cell to the north, the Mission Bay Littoral Cell, and the Silver Strand Littoral Cell. Patsch et al (2007) provides a broad overview the Oceanside littoral coastal processes as follows:
“The Oceanside littoral cell extends approximately 50 miles from Dana Point Harbor south to La Jolla and Scripps Submarine Canyons. The large Oceanside Littoral Cell is artificially divided by Oceanside Harbor’s north jetty, which effectively eliminates significant transport of littoral sand from the northern portion of the littoral cell to down coast of the Harbor. The shoreline of this cell consists of a continuous, narrow beach backed by sea cliffs or bluffs with the exception of the mouths of coastal rivers, streams, and harbors. Rocky headlands form the northern and southern boundaries of this cell. Sand entering the Oceanside littoral cell moves southward in the direction of the net alongshore transport and eventually enters the heads of La Jolla and Scripps submarine canyons, which are within a few hundred yards of the shoreline, just offshore from Scripps Institution of Oceanography. These canyons extend offshore in a southwesterly direction for approximately 33 miles, eventually depositing sediment into San Diego Trough, although it is widely believed that La Jolla Submarine Canyon is not a functioning sink for beach sand at the present time.”1
25 February16 13, 2018 Item 01 Chapter 3 Draft Adaptation Plan 2/2/2018 "San Juan Creek and the Santa Margarita, San Luis Rey and San Dieguito rivers are the major sources of fluvial sand to the Oceanside littoral cell. San Juan Creek and the Santa Margarita and San Luis Rey rivers each contribute on average ~40,000 cubic yards/yr of sand, while the San Dieguito River contributes an average of ~12,500 cubic yards/yr of sand to the littoral budget(sediment coarser than 0.0625 mm). The Santa Margarita, San Luis Rey and San Dieguito rivers have had their natural sand yields reduced by 31%, 69% and 79%, respectively, (a reduction of ~154,000 cubic yards/yr) through damming. Fluvial sources originally provided ~66% of the sand to this littoral cell. Post-damming, the rivers now provide only ~33% of sand to the overall littoral cell budget." 1
26 February17 13, 2018 Item 01 Figure 3.1.1
Littoral Cells within San Diego County
Large portions of the Oceanside littoral cell consist of sea cliffs and bluffs that range in height from 25 to 100 feet. The Torrey Pines area has cliffs and bluffs which reach heights of over 300 feet. In the Oceanside cell, approximately twenty percent of the sea cliffs have some type seawalls or revetments. Up to 80% of the sand from the erosion of sea cliffs and bluffs is of the grain size or that contributes directly to the coastal beaches. Table 3.1.1 from Patsch et al (2007)1 provides details on cubic yards (cy) of sand per year (yr) contributed to the Oceanside littoral cell from major sources. The difference in contribution from rivers indicates reductions in sand sources to the Oceanside littoral are due to the damming of rivers and the armoring of sea cliffs. As described by Leighton and Associates (2001), “Since 1919, dams have been built across all the major rivers systems in San Diego County that provides sediment to the beaches. With the construction of Lake Hodges in 1919, the effective sediment producing area of the San Dieguito River watershed was reduced from 346 square miles to 43 square miles. We can conclude that the beach width generally ha[s] been reduced since 1910 when the railroad was placed on the bluffs”.
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Table 3.1.1 Overall sand contributions and reductions since 1910 to the Oceanside littoral cell 1 Oceanside Littoral Cell Inputs Natural (cy/yr) Actual (cy/yr) Reduction (cy/yr) Rivers 286,500 (66%) 132,500 (33%) 154,000 (54%) Bluff Erosion 118,000 (27%) 100,000 (25%) 18,000 (15%) Gully/Terrace Erosion 31,500 (7%) 31,500 (7%) 0 Beach Nourishment 138,000 (34%) + 138,000 (0%) Total Littoral Input 435,700 (100%) 401,700 (100%) 34,000 (8%)
Patsch et al (2007) provides a description of the reductions in the sand budget in the Oceanside littoral as follows: “’Actual’ sand yield refers to the estimated volume of sand reaching the coast under present day conditions taking into account reductions in sand supply from dams and sea cliff armoring as well as additions (e.g., sand provided by the dredging of Oceanside Harbor) to the budget from beach nourishment. In total, beach nourishment (not including bypassing from Oceanside Harbor) has provided approximately 7.2 million cubic yards of fill on the beaches in this cell, which is approximately 138,000 yd3/yr over the last 65 years (1940-2005), representing 34% of the sand in the overall littoral budget. There appears to be a significant reduction in sand input to the cell compared to the original natural conditions as a result of most of the historic sand nourishment took place several decades ago.”1
“Loss of sand from the region’s beaches has occurred continually since: Implementation of flood control and other infrastructure throughout the coastal watersheds that reduces supply of sand from rivers; Construction of Oceanside Harbor in the early 1960s (which added sand to the regionover the short-term, but significantly interrupted sand delivery from upcoast over the long-term); Proliferation of hard structures (e.g., seawalls) that prevent bluff sand from being deposited on the beach; Natural change to a more energetic wave climate since 1978; Reduced rates of beach nourishment since the 1960’s; and Dense urbanization in the coastal zone.”6
In the Moffatt & Nichol (2009) study for SANDAG, they noted the following recent SANDAG beach nourishment effort as follows: “SANDAG performed beach nourishment from September to December 2012, including placements at Solana Beach. According to SANDAG, it is estimated that the southern Oceanside Littoral Cell needs 25 million cubic yards of sand nourishment for restoration and 320,000 of cubic yards of sand nourishment for maintenance” 6.
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3.2 Sediment Management As described in section 3.1, the Oceanside littoral has a problem inadequate sediment delivery to the coast. Using sand from offshore deposits can serve to nourish stripped sand beaches as a public benefit. The objective would be to use sediment that is presently trapped upstream or up coast, or sequestered in offshore and terrestrial sand deposits. This may be effective for offsetting existing sediment losses from the coastal zone. In addition, the removal of existing surplus sediment from impacted areas such as clogged harbor entrances, lagoon mouths, and degraded wetlands can also benefit these natural features. Moffatt & Nichol (2009), evaluated Oceanside Harbor’s northern jetty sediment transport impacts for SANDAG as follows:
“The interruption of sediment transport by Oceanside Harbor’s northern jetty has created an extensive deposit of high quality sand up coast of the jetty, representing a large potential nearshore source if SANDAG and MCB Camp Pendleton can reach agreement on the procurement of that sand. This material would have naturally migrated to the southern portion of the Oceanside littoral cell had the jetty not halted its migration. Therefore, it represents a sediment sink, and restoration of natural littoral cell dynamics could provide a large-scale source of “new” sediment for the southern littoral cell. Sediment bypassing from this fillet represents one, if not the most potentially productive contributions to the coastal sediment budget for the San Diego region. SANDAG investigated this potential source in late 2008 and found it suitable for nourishment, but concluded that additional investigation is needed to better define the highest quality portions of the deposit.” Restoration of sediment movement past the Oceanside Harbor jetty would contribute significantly to the region’s sediment budget. Bypassing of sediment from up coast of Oceanside Harbor is recommended to increase sediment volumes along North County beaches. Oceanside Harbor jetty retains a wide sandy fillet formation extending several miles north of the jetty into MCB Camp Pendleton (DBW/ SANDAG 1994)” 6.
The objective should be that nourishment rates at least equal loss rates. This rate should serve as the target for nourishment for future inputs to the region. Nourishment rates that exceed the loss rates should promote beach widening. Implementation of groins, breakwaters, and reefs to retain sand along the coastline should be investigated as a means to reduce the on-going need for sand nourishment. A Del Mar Sediment Management Plan will be prepared as a next step to further study and detail beach and dune nourishment as an adaptation measure.
3.3 Del Mar Shoreline Change Analysis In Del Mar, approximately 66% of sediments in the sea cliffs have a grain size that is large enough to contribute to the beaches. Table 3.3.1 summarizes the quantity of beach-sand-sized material, based on the grain size that contributes to the beach. These sand volumes were averaged over a 6-year time span to calculate average annual sediment volumes of beach- sand-sized materials.
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Table 3.3.1 Average annual eroded volumes (m3/yr) - April 1998 to April 2004
Beach-Sand Content (total reduced for Total Eroded Sediment grain size1) Section Name Gully Seacliff Gully Seacliff Torrey Pines 8300 26,400 3500 11,100 Del Mar 600 4900 500 3700 Solana Beach 0 8300 0 6200 Cardiff 0 5800 0 4600 Leucadia 0 5900 0 4700 Carlsbad 0 4000 0 3200 Camp Pendleton 7600 5500 4100 2900 San Onofre 16,700 57,100 11,900 40,500 Oceanside Littoral Cell 33,200 117,900 20,000 76,900
San Clemente2 4700 7600 3800 6100 2 Dana Point 0 4500 0 3600 2006 - Adam P. Young and Scott A. Ashford 1 Grain size of sediments in the sea cliffs large enough to contribute to the coastal beaches. 2 The total for the Oceanside Littoral Cells excludes the San Clemente and Dana Point sections.
Table 3.3.2 summarizes calculated south bluff retreat rates for the Del Mar area. A high percentage of the bluff erosion and retreat results from periods of substantial rainfall which tend to saturate portions of the bluffs and weaken the bluff materials to the point of failure. One can anticipate that similar magnitude of retreat rates of up to 12 feet of bluff erosion may occur in the next 20 years. Therefore, in several sections along the tracks, bluff retreat may impact the existing rails if mitigation measures are not implemented. The North County Transit District (NCTD) determined that installing soldier piles was the least environmentally damaging feasible alternative for an interim approach to track bed stabilization. Soldier piles can be considered to be underground, reinforced concrete columns. In the SANDAG Del Mar Bluffs Stabilization Project 3 (2010) submission to the California Coastal Commission, SANDAG defined soldier piles as follows: “Soldier piles are essentially underground, reinforced concrete columns. Spacing the soldier piles along a bluff provides improved support, provided that the soldier piles are anchored in a relatively stable geological formation”. 10
Table 3.3.2 Historical Del Mar calculated south bluff retreat rate 2,9 Del Mar Calculated Bluff Retreat Rate Report Years Bluff Retreat Rate AT&SF 1943-78 0.14 ft/yr L&A 1978 0.22ft/yr Benumof & Griggs 1999 0.4 to 0.6 ft/yr FEMA 2000 < 1ft/yr
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Figure 3.3.1
Beach width history from 1978-2015 for monitoring point 15
Figure 3.3.2
Beach width history from 1978-2015 for monitoring point 25
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The underlying structure of the beaches in most northern San Diego County is a rock platform with a very thin coating of sand and sometimes cobble. Many of the northern San Diego County beaches have very little sand depth because of sand undernourishment caused by the reductions of sand from inland sources and local geology. Figures 3.3.1 and 3.3.2 show the average decline in Del Mar beach width just south of the San Dieguito river mouth from two monitoring stations since 1978. As outlined by Elwany, Hany of Coastal Environments (2016) in the annual the San Dieguito Lagoon Restoration Project Report, “A study conducted in 2010 concluded that the rate of beach width decrease is about 2.0 ft/yr to 4.5 ft/yr.” 5
3.4 Human Alterations to the Shoreline
3.4.1 Beach Nourishment
Beach and dune nourishment is an adaptation strategy that provides protection against coastal storm erosion while maintaining the natural condition, beach habitat, and processes (such as the ability of the beach to erode in response to winter storms and build up sand in response to summer wave conditions). Beach nourishment refers to placement of sand to widen a beach, which can be accomplished by placing a sediment-water slurry directly on the beach and/or mechanical placement of sediment with construction equipment (Figure 3.4.1.1). Sand can be obtained from inland sources (e.g., sand trapped in dam reservoirs, construction projects) and can be dredged from offshore.
Dune restoration would include placement of sand, grading, and planting to form “living” back beach dunes. Dune restoration is recognized as a natural way of mitigating backshore erosion as well as maintaining a wider beach through sacrificial erosion of the dunes. Dune restoration can provide aesthetic, ecology, and recreation benefits. A variant includes placement of cobble (rounded rock), which is often naturally present as a lag deposit1 below beaches in California (Figure 3.4.1.2). Burying a layer of cobble provides a “backstop” that is more erosion resistant and dissipates waves to a greater degree.
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Figure 3.4.1.1 Beach Sediment Placement at Carlsbad
Figure 3.4.1.2 Beach Nourishment, Dune Restoration, and Cobble Placement Illustration
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Table 3.4.1.1 Beach and dune nourishment benefits and constraints summary Benefits Constraints
! Preserves beach • Limited sand sources
Less effective over time with increasing sea- "Living shoreline" provides beach and dune habitat level rise
! Reduces flood and erosion risks • Transportation of sediment to receiver sites
! Short-term beach use and ecology impacts
Table 3.4.1.1 summarizes benefits and constraints of beach and dune nourishment. Potential problems with beach nourishment include loss of beach use during construction and impact to beach ecology11,12, which are generally considered short term negative effects. Beach nourishment can also change beach conditions (e.g., texture and slope), if and when the placed sand is different than the “native” beach sand, which typically occurs due to the difficulty in finding sand with the same grain sizes. The success of the nourishment depends on the volume of nourished material, the grain size, and the proximity or use of sand retention measures (discussed separately in the next section).
Placement of sand typically provides a temporary benefit until the sand erodes and migrates away from the placement area. It is therefore important to consider the fate of the sand and implications of deposition in other areas. In general, increased sand supply is considered beneficial to most beach areas, but can be problematic at lagoon inlets and storm drain outlets. Sand deposition on rocky substrate may also adversely affect habitat and recreation such as surfing.
Key feasibility constraints to beach nourishment and dune restoration include the availability of appropriate sand sources and the required amount and frequency of nourishment. With a certain amount or rate of sea-level rise, the amount and frequency of nourishment may make the measure unsustainable. For the purposes of the Adaptation Plan, it is assumed that beach nourishment will be effective with up to 1 ft of sea-level rise based on the results of the Coastal Hazards, Vulnerability, and Risk Assessment and is, therefore, not included as an adaptation measure for sea-level rise above 1 ft.
Monitoring plays an important role in identifying the need for re-nourishments. Monitoring is typically focused on the annual maximum and minimum beach width and minimum dune width. The minimum dune width should provide an acceptable buffer for storm erosion (e.g., 2- to 5- year storm). At any time, beach nourishment may be required in response to erosion from a major storm event.
If beach-sized material becomes available via construction or other activity, the City will consider whether the material could be beneficially re-used on the Del Mar beach. Southern California Edison placed sand dredged from the San Dieguito Lagoon on the northern portion of
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North Beach in 2011 (40,000 cubic yards) and 2014 (15,000 cubic yards). Similarly, beach and dune nourishment can be combined with dredging of sediment from the San Dieguito River as a future adaptation measure to reduce river flood risks. SANDAG has conducted beach nourishment in San Diego County through the Regional Beach Sand Project. SANDAG performed beach nourishment from September to December 2012, including placements at Solana Beach. The City of Del Mar did not participate in the SANDAG Program, but could consider participating in any future nourishment to implement this adaptation measure. Additional information on regional sand management can be found via the Coastal Sediment Management Workgroup (CSMW, http://www.dbw.ca.gov/csmw/).
According to Van Rijn et al (2007), “Overall, it is concluded from field practice that shore face nourishments have an efficiency (defined as the ratio of volume increase of the nearshore zone and the initial nourishment volume) of 20% to 30% after about 3 to 5 years” 7. This seems consistent with studies of nourishment projects in Californian which have shown that about 20% of the projects survived less than 1 year, 55% lasted only 1 to 5 years and about 20% survived over 5 years.
3.4.2 Groins The principle objective of groins is sand retention. Groins are thin and long structures perpendicular to the shoreline extending into the surf zone. Groins typically extend slightly beyond the low water line. Groins are used to reduce the longshore currents and littoral drift in a surf zone and to retain the beach sand between the groins. Groins are used to stabilize and widen the beach or to extend the lifetime of beach fills. A groin field is a series of similar groins that may be constructed to protect a stretch of coast against erosion. Groins should be prefilled with sand upon construction, otherwise the groins will have adverse impacts when a structure- retained beach is allowed to develop with sand from the littoral system.
Van Rijn et al (2007) define two major types of groins, as follows: ”impermeable, high-crested structures: crest levels above +1 m above MSL (mean sea level); sheet piling or concrete structures, grouted rock and rubble-mound structures (founded on geotextiles) with a smooth cover layer of placed stones (to minimize visual intrusion) are used; these types of groins are used to keep the sand within the compartment between adjacent groins; the shoreline will be oriented perpendicular to the dominant wave direction within each compartment (saw-tooth appearance of overall shoreline); permeable, low-crested structures: pile groins, timber fences, concrete units, rubble- mound groins, sand-filled bags are used; permeability can increase due to storm damage; these types of groins are generally used on beaches which have slightly insufficient supplies of sand; the function of the groins is then to slightly reduce the littoral drift in the inner surf zone and to create a more regular shoreline (without saw- tooth effect); groins should act as a filter rather than as a blockade to longshore transport.” 7
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3.4.3 Detached Breakwaters and Reefs Breakwaters are parallel structures that are used to protect a section of the shoreline by forming a buffer or barrier to the waves. Breakwaters obstruct the wave energy. There are two major categories of breakwaters: those that are positioned above the still water level (emerged); and breakwaters below the still water level (submerged Van Rijn et al (2007) define the various variants of breakwaters, as follows:
“There are many variants in the design of detached breakwaters, including single or segmented breakwaters with gaps in between, emerged (crest roughly 1 m above high water line) or submerged (crest below water surface), narrow or broad-crested, etc. Submerged breakwaters are also known as reef-type breakwaters and are attractive as they are not visible from the beach. A reef (hard or soft) is a relatively wide, submerged structure in the shallow nearshore zone.
Submerged structures cannot stop or substantially reduce shoreline erosion (dune-cliff erosion) during storm conditions, as most of the waves will pass over structure to attack the dune or cliff front. Supplementary beach nourishments are required to deal with local storm-induced shoreline erosion (especially opposite to gaps). Down drift erosion generally is manageable as longshore transport is not completely blocked by low-crested structures. A major problem of submerged breakwaters and low-crested emerged breakwaters is the piling up of water (wave- induced setup) in the lee of the breakwaters resulting in strong longshore currents when the breakwater is constructed as a long uninterrupted structure (no gaps) or in strong rip currents through the gaps when segmented structures are present. Other disadvantages of detached breakwaters are the relatively high construction and maintenance costs, inconvenience and danger to swimmers, and small boats and aesthetic problems (visual blocking of horizon).” 7
3.4.4 Seawalls and Revetments Seawalls and revetments are structures to armor the shore to protect the land behind it. They are shore-parallel structures that protect against storm-induced erosion and/or long-term chronic erosion by the sea. These structures have various shapes such as vertical, concave or sloping designs. When natural beaches can no longer prevent erosion due to high waves, seawalls are typically built along a limited section of the shoreline as a last defense line against the waves. If no other solution helps to solve the problems of erosion or flooding during high surge levels, the building of seawalls or revetments is considered to be a necessary and "end of the line" solution. Van Rijn et al (2007) define the various variants of breakwaters, as follows:
“A seawall is a vertical (or almost) retaining wall with the purpose of coastal protection against heavy wave-induced scour; it is not built to protect or stabilize the beach or shore face in front of or adjacent to the structure. Thus, chronic erosion due to gradients of longshore transport will not be stopped or reduced. A revetment is an armor protection layer (consisting of light to heavy armor layer, underlying filter layer and toe protection) on a slope to protect the adjacent upland zone against scour by current and wave action. To reduce scour by wave action and wave reflection at the toe of the structure, the slope of the revetment should be as mild as possible
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(not steeper than 1 to 3). The crest of the revetments should be well above the highest storm surge level resulting in a crest level at +5 m above mean sea level along open coasts and up to +7 m at locations with extreme surge levels.
Seawalls and revetments are very effective in stopping local shoreline erosion (dunes and soft cliffs), but these types of structures hardly change the longshore transport gradient often being the basic cause of chronic erosion. Hence, erosion of the beach and shore face in front of the structure will generally remain to occur. Down drift erosion will usually occur at locations where no structures are present. Continuing shore face erosion may ultimately lead to an increased wave attack intensifying the transport capacity and hence intensified erosion (negative feed- back system). Groins are often constructed to reduce scour at the toe of the revetment by deflecting nearshore currents”. 7
Table 3.4.4.1 Effectiveness of Hard Structures (adapted from Van Rijn et al, 20107)
Effectiveness Type of Stop shoreline Structure Reduce shoreline erosion Beach width erosion Seawall none or very yes yes Revetment small no, dune and cliff wider for narrower yes, especially at beaches erosion will continue cells; smaller and Groins of relatively coarse sediment during major storms saw tooth effect (0.3 to 1 mm) with high water for wider cells no, dune and cliff yes, especially at very erosion will T-head Groins exposed, eroding beaches of continue during medium wide fine sand major storms with high water levels no, dune and cliff Submerged erosion will detached yes, but minor continue during small breakwater/reef major storms with high water levels no , dune and cliff Emerged erosion will medium to wide at breakwater yes at lee side continue during lee side (low crested) major storms with high water levels no, dune and cliff Emerged erosion will medium to wide at breakwater yes at lee side continue during lee side (high crested) major storms with high water levels
Table 3.4.4.1 provides a comparison of hard shoreline protection measures and their effectiveness to reduce or stop shoreline erosion and their impacts on beach width. As described by Everts Coastal (2002), “In Southern California, the most effective shore-connected sediment- blocking structures, such as groins, are located where the bearing of the open coast shoreline is between 240 and 310-320 degrees and there is a substantial net longshore sand transport rate.”13 It should be noted that Del Mar’s bearing averages 348 degrees, and
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therefore is not optimum for groins, since the length of the groins would need to be relatively long to be effective. In summary, beach nourishment in conjunction with detached breakwaters or reefs that retain sand might warrant further investigation by the City of Del Mar.
3.5 References 1. Patsch, Kiki, and Gary Griggs. Development of Sand Budgets for California’s Major Littoral Cells. Institute Of Marine Sciences, University of California, Santa Cruz, California Department of Boating and Waterways, California Coastal Sediment Management Workgroup, Jan. 2007. 2. Leighton and Associates, Inc. Del Mar Bluffs Geotechnical Study, Part 1. Geotechnical Evaluation, Volume 1, North County Transit District, 2001. 3. Scott, Alan, and Jane E. Smith. Shoreline Protective Structures. Staff Report to the California State Lands Commission, Apr. 2001. 4. Young, Adam P., and Scott A. Ashford. Application of Airborne LIDAR for Seacliff Volumetric Change and Beach-Sediment Budget Contributions. Journal of Coastal Research, Mar. 2006., 22:307-318. 5. Elwany, Hany of Coastal Environments. San Dieguito Lagoon Restoration Project, 2015 Beach Data Annual Report, City of Del Mar, California. Southern California Edison, February 5, 2016. 6. Moffatt & Nichol, Coastal Regional Sediment Management Plan for The San Diego Region, SANDAG and California Coastal Sediment Management Workgroup, Mar. 2009. 7. Van Rijn, Leo. Coastal erosion control based on the concept of sediment cells. Concepts and Science for Coastal Erosion, Conscience for the European Commission, Contract 044122 - D13a, Jan. 2010. 8. Adam P. Young, Jessica H. Raymond, John Sorenson, Elizabeth A. Johnstone, Neal W. Driscoll, Reinhard E. Flick, and Robert T. Guza, Coarse Sediment Yields from Seacliff Erosion in the Oceanside Littoral Cell, Journal of Coastal, May 2010, Volume 26, Issue 3, pg(s) 580- 585. 9. Hapke, C.J., and Reid, D., 2007, National Assessment of Shoreline Change, Part 4. Historical Coastal Cliff Retreat along the California Coast, U.S. Geological Survey Open-file Report 2007-1133 10. CC-020-10, SANDAG, Del Mar Bluffs Stabilization Project 3. 11. Charles H. Peterson and Melanie Bishop. Assessing the Environmental Impacts of Beach Nourishment, BioScience, Volume 55, Issue 10, 1 October 2005, Pages 887– 896. 12. Schlacher TA, Thompson L. Beach recreation impacts benthic invertebrates on ocean-exposed sandy shores. Biological Conservation. 2012;147:123–32. 13. Everts Coastal. Impact of Sand Retention Structures on Southern and Central California Beaches. California Coastal Conservancy, June 2002. CCC Contract Number: 00-149.
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CHAPTER 4
About this Adaptation Plan This Adaptation Plan draws on the City of Del Mar’s Coastal Hazards, Vulnerability, and Risk Assessment (ESA2016, http://www.delmar.ca.us/DocumentCenter/View/2455) and guidance provided by the STAC. This Adaptation Plan was developed over a series of public STAC meetings in which the STAC and public provided input and feedback.
4.1 Adaptation Plan Overview and Process The recommended approach for the City of Del Mar planning for sea level rise involves phasing in short and long term adaptation strategies. This phased approach provides a structure for sequencing adaptation measures using expected sea-level rise thresholds, and provides a way to manage uncertainty in timing and extent of sea level rise impact. Thresholds guide in the planning and implementation stages of adaptation strategies. For example, thresholds related to the extent of flooding or frequency of damages might be used to initiate new adaptation options. The process should involve the local community, and reflect the Del Mar community’s risk tolerance, local conditions, and adaptation vision.
The Adaptation Plan provides a framework for the City to manage risks (Section 4.2), to monitor effects of sea-level rise (Section 4.3), and choose from a toolbox of adaptation options (Section 4.4). The Adaptation Plan provides flexibility for the City to choose from an array of adaptation measures over time as specified thresholds are met. The Adaptation Plan therefore provides potential adaptation options for managing risks, to be incorporated into specific plans of action when needed. The City will choose among adaptation options as the projected effects of sea- level rise are realized. Project-level planning and approvals will be required to further develop and implement the adaptation measures included in the Adaptation Plan (Section 4.5). The Adaptation Plan identifies the lead times for project-level planning of adaptation measures so that the City can begin planning the implementation of adaptation measures in advance of when implementation is needed.
The Adaptation Plan is based on the best science and adaptation practices available today; however, the Adaptation Plan acknowledges that sea-level rise science and practices are evolving and the intent of the Adaptation Plan is that the City will evaluate future decisions and take action based on the best-available science and technology at the time.
The Adaptation Plan includes a range of sea-level rise adaptation measures within the three general categories of adaptation defined by the California Coastal Commission (CCC) in 2016: Protect, Accommodate, Retreat.
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The CCC further guides, after evaluating vulnerability and establishing policies to be used throughout hazardous areas, communities can begin the process of evaluating and choosing adaptation strategies for specific areas. In most cases, especially for LCP land use and implementation plans, multiple adaptation strategies will be needed and every community will need to assess their risks and their potential options. There are a number of options for how to address the risks and impacts associated with sea level rise. Choosing to “do nothing” or following a policy of “non-intervention” will likely lead to unacceptable exposure to hazards and impacts to coastal resources, so the strategies for addressing sea level rise hazards will require proactive planning to ensure protection of coastal resources and development. Figure 4.1 illustrates the process of selecting and implementing proactive adaptation strategies.
Figure 4.1 Process to Evaluate, Select and Plan Adaption Options
1. Evaluate 2. Identify Assets at Risk
3. Analyze alternative adaption strategies
Protect Accommodate Retreat
4. Apply Legal Framework
5. Identify Preferred Strategies
Consistent with the California Coastal Commission Sea-Level Rise Policy Guidance and current environmental practice, the Adaptation Plan includes hybrids between these approaches, nature based or green infrastructure solutions, and multi-objective measures that incorporate environmental considerations while also remaining consistent with the relevant plans and guidelines listed in Chapter 2, rather than focusing on independent solutions to protection.
4.2 Risk Management The goal of the Adaptation Plan is to manage sea-level rise-related risks by keeping these risks within an acceptable limit. Table 4.1 summarizes risk for extreme (infrequent) and significant (more frequent) flooding from the Coastal Hazards, Vulnerability, and Risk Assessment (ESA 2016). “Low, moderate, and high” risks are defined for the purposes of the Risk Assessment and Adaptation Plan as follows:
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● Low: 0% - 5% chance of occurrence in a given year ● Moderate: 5% - 30% chance ● High: 30% - 100% chance
A guiding principle of the Adaptation Plan is to limit the risk of extreme flooding and damage to a low risk level (i.e., less than 5% chance of occurrence in a given year).
TABLE 4.1 Summary of North Beach Asset Vulnerability to Flooding and Damage
Risks to Del Mar’s assets increase with sea-level rise. The goal of the Adaptation Plan is to plan a sequence of adaptation measures that can be taken to reduce the risk of extreme flooding, thereby maintaining the risk at a low or acceptable level (Figure 4.2).
Figure 4.2 Concept of Adaptation to Manage Del Mar’s Risks with Increasing Sea Level Rise
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The Adaptation Plan includes accommodating some increase in flood risks. For significant flooding (i.e., flooding that occurs more frequently than extreme flooding, but is still significant), the current low – moderate risk will increase to moderate – high levels with 1 ft of sea-level rise or more (Table 4.1). Thus, the Adaptation Plan focuses on limiting extreme flood risks to low levels, but an increase in significant flooding is expected with sea-level rise.
4.3 Monitoring Change The Adaptation Plan includes measurable thresholds that, if and when they occur, call for the implementation of adaptation measures to limit risks. The Adaptation Plan sets conceptual planning-level adaptation thresholds such that adaptation measures can be implemented to reduce risks before the acceptable target level of risk is exceeded. The City will need to monitor and evaluate the trajectory towards these thresholds to track whether and when these thresholds are met. The Adaptation Plan thresholds and monitoring are summarized below.
Amount of sea-level rise (e.g., 1 ft, 2 ft, and 3 ft of sea-level rise). Certain adaptation measures will need to be taken when sea-level rise has risen by a certain amount. To monitor sea-level rise and progress towards the sea-level rise amount thresholds, the City will follow sea-level rise reports from the State and Scripps Institute of Oceanography (SIO) and sea level rise data from the nearby NOAA tide gage at Scripps Pier at La Jolla Shores (Figure 4.3). Sea level is inherently variable in response to predictable astronomical tides and less-predictable atmospheric events such as El Nino and individual storms; however, given that extreme flooding occurs infrequently, sea-level rise may be realized before extreme flooding occurs. Tracking sea-level rise may therefore allow the City to anticipate and act in advance of the projected effects of sea level rise. Figure 4.3 Sea Level Rise Trend at La Jolla Tide Gage
SOURCE: NOAA
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Flooding and storm damage frequency. In addition to the amount of sea-level rise, the frequency or risk of flooding and storm damage is used as a threshold in the Adaptation Plan. To monitor the frequency of flooding and storm damage, the City will track and keep records of coastal and River flooding and storm damage events and information. This could be a collaborative effort between City staff and residents in which reports, pictures, and videos are collected. The date, type, location, and severity of flooding (e.g., depth, duration, wave height), and damages can be collated into a file. The intent will be to track the frequency, extent, and severity of flooding to assess if and how the frequency of flooding is increasing. If significant and/or extreme flood events occur, then storm data (e.g. water levels, wave conditions) can be collected and storm frequencies can be recalculated to quantify the increase in flood risk for comparison against risk- based thresholds.
Beach width. Given that a guiding principle is to maintain a walkable beach, beach width is used as a metric for considering when beach adaptation measures would be implemented. Specific beach width thresholds are discussed in Chapters 8 and 9 and will be further detailed as part of subsequent analyses including the preparation of a Sediment Management Plan. Southern California Edison and SANDAG currently perform beach profile surveys to monitor beach width. Southern California Edison is required to maintain a minimum beach width of 32.4 ft to 180.0 ft (depending on the location on the beach) at least through 2025, assuming no adverse impacts from the project are found, as part of the California Coastal Commission Coastal Development Permit for the San Dieguito Lagoon Restoration; however, this requirement and Southern California Edison’s beach maintenance program do not account for future sea-level rise. SANDAG measures four profiles in Del Mar. Profiles are surveyed two times per year, from 1999 to present. The City will review the results of beach surveys from Southern California Edison and SANDAG, and assess the results against beach width thresholds. Supplemental and long-term beach monitoring programs, including all of Del Mar’s beaches, is recommended for consideration as part of the implementation of the Adaptation Plan.
Bluff top offset. The Adaptation Plan uses the offset or distance between the top of the bluffs and assets such as the LOSSAN railroad track, sewer line, and the edge of bluff top properties as a threshold for bluff adaptation measures. When the bluff top reaches the threshold set based on the distance at which the safety of the asset is at risk, the Adaptation Plan calls for implementation of bluff adaptation measures. The North Coast Transit District and SANDAG currently monitor the condition of the bluff relative to the safety of the railroad track. Dr. Adam Young of the Scripps Institute of Oceanography has also performed research on the erosion of Del Mar’s bluff. The City will review and track bluff-top erosion monitoring and results from NCTD, SANDAG, and/or Dr. Young. If and when the railroad is relocated off the bluff, the City will consider supplemental and long term bluff top erosion monitoring programs to track erosion towards the sewer line and property along the bluff against the offset threshold.
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San Dieguito River channel deposition. Per the Coastal Hazards, Vulnerability, and Risks Report (ESA 2016), the potential for increased deposition of sand in the San Dieguito River channel with sea-level rise is a significant factor in increasing the City’s risk of River flooding. The amount of channel deposition is therefore used as a threshold for River flooding adaptation measures in the Adaptation Plan. Southern California Edison currently surveys channel cross-sections and is required to maintain a certain tidal flow (tidal prism), but is not required to maintain a channel bed elevation for the purposes of reducing flood risk to Del Mar. The City will review and track Southern California Edison’s channel surveys and assess if deposition thresholds are reached and will consider supplemental channel monitoring if and when necessary.
San Dieguito Lagoon wetland conversion. The Adaptation Plan uses conversion of San Dieguito Lagoon wetland habitats with sea-level rise (e.g., conversion of vegetated wetland habitat to mudflat and open water habitat) as a threshold for wetland adaptation measures. As part of the San Dieguito Lagoon Restoration, wetland habitat acreages are monitored by UC Santa Barbara on behalf of the California Coastal Commission, and Southern California Edison is required to maintain certain wetland acreages; however, these requirements and maintenance do not account for future sea-level rise. The City will review and track the Restoration habitat monitoring and coordinate with the California Coastal Commission and Southern California Edison on evaluating thresholds and the process for implementing adaptation measures when thresholds are reached. The City will also consider monitoring of wetland areas outside of the Restoration and coordination with the City of San Diego on upstream wetland habitat monitoring and adaptation.
The City will consider preparation of a sea-level rise Adaptation Plan Monitoring and Thresholds Assessment Report on a regular cycle, recommended to be annual. The City will use the report to identify significant changes or progress towards thresholds. The City will evaluate if and when thresholds are reached and identify and plan next steps towards implementing adaptation measures. The City may conduct this process in consultation with technical experts and will seek public input and review. The City will also consider participating in regional efforts, if initiated, to monitor and track sea-level rise and related effects.
4.4 Analysis of Adaptation Options The adaptation plan identifies near-term measures for City assets and addresses specific vulnerabilities and risks for the City District areas illustrated in Figure 4.4. Each chapter presents a range of adaptation options with the benefits, constraints, limitations, and potential impacts for each. A figure for each of the four City areas (beach, bluff, river, and wetlands) illustrates available adaptation measures together with criteria to be monitored to assess rate and amount of change, lead times and anticipated time ranges when each measure would be effective. The plan has the following five parts:
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Chapter 5 - High Priority Measures for Public Resources: High priority measures to relocate and flood-proof public safety and public works facilities, and plan for beach nourishment and sand retention. Chapter 6 - San Dieguito Lagoon wetland adaptation: Relevant to the river valley and San Dieguito lagoon. Chapter 7 - San Dieguito River flooding adaptation: Relevant to the river valley, Del Mar Fairgrounds, and North Beach (north from 15th St to the San Dieguito river mouth). Chapter 8 – Bluff and adjacent beach erosion adaptation: Relevant to the South Bluffs, bluffs along South Beach, bluffs along Powerhouse Park, and the North Bluffs. Chapter 9 - Beach erosion and flooding adaptation: Relevant for North Beach (north from 15th street to the San Dieguito River mouth)
Criteria for considering an adaption measure include degree of loss of beach, bluff, or wetland, frequency of damaging storms, and river channel deposits. As discussed in Section 4.3, “Monitoring Change”, as changes happen and progress, full evaluation of design, environmental impacts, and costs of any given adaptation measure will require additional studies. Adaptation strategies also need to be evaluated for conformance with the relevant City and state policy, plans and guidelines detailed in Chapter 2, which include the following:
Del Mar Community (General) Plan Del Mar Local Coastal Program Del Mar Climate Action Plan California Coastal Commission Sea Level Rise Policy Guidance Safeguarding California Plan
Coastal Development Permit review and approval for adaptation measures will fall within the California Coastal Commission and/or the City’s coastal permitting jurisdiction and, depending on the jurisdiction, may be processed through either the City of Del Mar’s LCP and/or pursuant to the California Coastal Act. For the four City areas listed above (beach, bluff, river, and wetlands), a table at the end of each Adaptation Plan chapter summarizes the likely coastal permitting mechanisms for available adaptation measures. These tables provide information for the development of the LCP Amendment as a next step. Other approvals and permits beyond those listed in Chapters 5 - 9 may also be required and would need to be addressed separately.
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Figure 4.4 City Districts in Del Mar
4.5 Project-Level Planning and Lead Times The Adaptation Plan identifies adaptation measures at a conceptual planning-level of detail and discusses potential benefits and effects of adaptation measures. Additional detailed project-level
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planning and design would be required to implement adaptation measures. For adaptation measures involving construction, the project-level planning and design may include: Feasibility study including additional technical analyses, development and assessment of project alternatives and details, conceptual and preliminary engineering design, and cost estimating CEQA and possibly NEPA environmental review and regulatory permitting Final engineering design.
Lead time is required to perform project-level planning, secure funding, and implement or construct an adaptation measure. All adaptation options discussed in the Adaptation Plan require substantial lead time. For example, levees, comprehensive sea wall strategies, sand retention strategies, and wetland management strategies can require significant lead time. With anticipated lead times the City will be able to begin advance planning before adaptation measures could be in place to limit risk.
4.6 Re-Evaluation The Adaptation Plan is intended to establish a process in which new data and information are assessed as needed to inform adaptation decisions and actions. As such, it is anticipated that the Adaptation Plan may be re-evaluated and updated.
After much discussion, STAC determined that it is too early in the process to include managed retreat as an adaptation option for Del Mar.
Each Adaptation Plan chapter for Lagoon, River, Bluff and Beach includes a final section that summarizes anticipated permitting requirements. Overall, the next steps in the Sea-Level Rise Adaptation Plan and LCP Amendment process, which include the development of LCP policies and regulations and additional studies that will provide further detail on adaptation measures and their implementation
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CHAPTER 5
High Priority Measures for Public Resources High priority sea-level rise adaptation measures for the City to begin planning now include relocating or otherwise flood adapting the City’s Fire Station and Public Works Yard on Jimmy Durante Boulevard, as well as flood-proofing the sewer lift station along San Dieguito Drive (Figure 5.1). These facilities already have a medium to high risk of San Dieguito River flooding (i.e., 5% annual chance of flooding) or greater, as evidenced by the San Dieguito River flooding the fire station and public works yard in February 1980 (see the Coastal Hazards, Vulnerability, and Risk Assessment (ESA 2016) for additional information). It is recommended the city should immediately begin evaluation of beach nourishment and sand retention strategies to maintain recreational opportunities for the citizens of Del Mar as well as enhanced protection of public infrastructure and private property. Beyond the vulnerabilities addressed in this chapter, the City should evaluate and monitor risks to all other public resources including roads, bridges, sewer lines, water supplies, storm drainage systems, parks, and public structures.
Figure 5.1 High Priority Infrastructure
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City of Del Mar fire station. The fire station is an essential services building that should be operable during flooding in order to respond to flood-related calls and other emergencies. Given that flood risk has the potential to increase with sea-level rise, the adaptation plan calls for beginning a process to relocate the fire station to a location that is not anticipated to flood and would still allow the fire department to respond to an emergency. The alternative is to flood proof the facility, for example through berms, elevation, or other strategies, so it can continue to operate on a fully functional basis. Moderate exposure of the fire station to flooding will make emergency services highly vulnerable with 1 ft of sediment deposition because the fire station will be impacted when flooding is occurring and emergency response is needed, as occurred in the 1980 flood. Some flood-proofing could be accomplished by raising facilities above the 100- year flood level (12.8 ft NAVD per FEMA 2016) with an allowance for future sea-level rise (e.g., to an elevation of 15.8 ft NAVD with a 3 ft of sea-level rise allowance above the current 100- year flood level). Other flood proofing options include enclosing and water-proofing vulnerable equipment.
City of Del Mar public works yard. The City has an office building housing public works staff, a garage and work areas, and uses the public works yard for storage of City maintenance vehicles, equipment, and other supplies, some of which may be required to perform City services during or after flood and/or erosion events. The adaptation plan calls for beginning a process to relocate the public works yard to a location that is not flood-prone or to flood proofing it on its current site. Relocating or reconfiguring the public works yard also provides the opportunity to construct a portion of a new levee system south of the San Dieguito River to reduce flood risk in combination with restoring wetland and upland habitat on the public works yard as described as an adaptation measure in Section 5.4, San Dieguito River Flooding adaptation plan.
City of Del Mar sewer lift station. The sanitary sewer lift station along San Dieguito Drive is subject to extreme flooding with a 1% annual chance of occurrence. The potential consequences of flooding are high, as the flooding of the pump machinery could potentially cause pump failure. The adaptation plan calls for flood proofing the lift station as a near-term measure to reduce this risk, which will otherwise increase with sea-level rise. Flood-proofing could be accomplished by raising the lift station above the 100-year flood level (12.8 ft NAVD per FEMA 2016) with an allowance for future sea-level rise (e.g., to an elevation of 15.8 ft NAVD with a 3 ft of sea-level rise allowance above the current 100-year flood level). Other flood-proofing options include enclosing and water-proofing the pump motor and other vulnerable parts of the lift station.
City of Del Mar beach access points. Beach access points along the City’s beaches from 15th St north to San Dieguito Lagoon (North Beach) should be protected against storm surge and flooding.
Beach sand retention, replenishment, and management. The City’s beaches from 15th St north to San Dieguito Lagoon (North Beach) and all beaches adjacent to the bluffs provide a first line of protection against flooding and bluff erosion due to sea level rise.
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Flooding in the beach area could affect hundreds of homes (single family, duplex, and multi- family dwelling units), public recreation facilities (basketball and tennis courts), public roads, the railroad right-of-way, and the fairgrounds. Bluff erosion would lead to increased risk of damage to the City’s sewer, drainage, and fiber-optic cabling along the bluff-tops. Chapters 8 and 9 give details on vulnerabilities and adaptation options for both areas. A Sediment Management Plan is expected in early 2018 and will inform beach and sand management strategies.
Beach nourishment is a preferred adaptation option that can be acted upon as soon as possible based upon the findings and recommendations of the City’s Sediment Management Plan. It has the strongest potential to minimize damage risk while helping to maintain the City’s valuable broad beaches. Natural and non-structural sand retention strategies include adding berms in winter or establishing dune fields. Seasonal berming is a strategy the City has used for years with Coastal Commission approval. Sand is pushed into a berm in winter to help protect public and private property and to help protect sand by moving it out of the regularly active surf zone. These activities should be continued and possibly expanded where designed to minimize sand loss in accordance with the Sediment Management Plan. Sand retention strategies, including groins, breakwaters, dune fields, seasonal berming, and artificial reefs, have limitations that must be studied carefully in the context of their benefits and the risks to the City’s beaches. General benefits and limitations for these sand retention strategies are given in Chapter 9, Section 9.1.3 (Table 9.1.3).
Rather than wait until beaches shrink further due to changes in the river channels, flooding, erosion, and storm damage, the City should establish a Beach Retention Advisory Committee (BRAC). The committee would receive reports on monitored sand levels, beach width, and distance from bluff-top to infrastructure; assess adaptation options that replenish or retain sand; and recommend timely pro-active and, as needed, reactive actions. The committee would be further charged to study and report on the costs and expected lifespan of sand replenishment or retention interventions. Such a committee would be positioned to study the suitability of sand- retention strategies in the context of the City’s Community Plan and other relevant guidance documents reviewed in Chapter 2, and receive feedback and suggestions from City residents and property owners. The BRAC could be realized initially as a subcommittee of STAC.
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CHAPTER 6
San Dieguito Lagoon Wetland Adaptation This chapter includes a range of adaptation measures to address wetland habitat resiliency for the San Dieguito lagoon. This is relevant to the River Valley and San Dieguito lagoon. Permitting for some adaptation measures may be processed through federal, state or City entities as summarized in Section 6.3.
Vulnerability assessment: As sea level rises and flooding increases, the lagoon will experience “habitat creep” as the various habitat ranges are more frequently flooded. For example, as existing wetland habitats experience more frequent flooding, vegetated wetland habitats will be “drowned out” and convert to intertidal mudflats and subtidal habitat. Existing pickleweed marsh habitat could drown and be lost with 3 feet of sea-level rise unless the habitat bands are allowed and able to “migrate” upland as sea level rise and flooding increase Cordgrass low marsh habitat could be lost with 3 to 5.5 feet of sea-level rise, such that almost all of the San Dieguito Lagoon Wetland Restoration would be converted to intertidal mudflat and subtidal open water. Salt marsh habitats are expected to migrate upstream along the San Dieguito River with sea level rise; however, the River corridor is relatively narrow and the overall vegetated marsh acreage will be greatly reduced.
Wetland adaptation options: Allow/facilitate wetland conversion and transgression Sediment placement Wetland expansion/restoration
Wetland adaptation monitoring: Wetland habitat loss
6.1 Adaptation options
6.1.1 Adaptation option: allow/facilitate wetland conversion and transgression Allowing and facilitating wetland conversion and transgression is an adaptation strategy that would allow wetlands to grow into higher elevation areas as sea-level rises. Wetland vegetation establishes in areas of certain elevations relative to the tidal water levels to achieve a certain frequency of tidal inundation. As sea-level rises, the frequency of inundation increases and
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plants in these elevation ranges drown out. However, the seeds of the next generation of plants can survive if they establish at higher elevations. In this way, wetlands can “migrate” or transgress upslope. Allowing wetland transgression to happen naturally could be done in areas with existing transitional and upland habitat. In areas with development, wetland conversion could be facilitated by setting back infrastructure and development in certain key areas to leave room for marshes to migrate in the future. This could be done by setting policy that prevents any new development in the uplands surrounding wetland habitat.
Within the existing marsh basins in San Dieguito Lagoon, the salt marsh is expected to move upslope as water levels rise. However, the steep slopes will limit the amount of salt marsh in these areas. Salt marsh is also expected to move further upstream along the San Dieguito River to keep up with sea-level rise; however, the River corridor is relatively narrow and the overall vegetated marsh acreage will be greatly reduced. Acquiring upland areas near the existing marsh will be key to the sustainability of wetland habitat.
Table 6.1.1 summarizes benefits and constraints of allowing and facilitating wetland conversion and transgression. Creating space for wetlands to migrate will preserve wetland habitat until the rate of sea-level rise exceeds the migration rate. While allowing wetlands to migrate will provide more wetland habitat over time, this would come at the expense of transitional and upland habitats or developed areas. Wetlands also provide benefits such as flood and erosion protection and sequestration of greenhouse gases in the vegetation and wetted soils (see Appendix A for additional information).
Table 6.1.1 Wetland conversion and transgression benefits and constraints summary Benefits Constraints Preserves wetland habitat • Potential loss of upland and transitional habitat Reduces flood and erosion risks • Potential loss of development area Sequesters additional greenhouse Less effective over time with increasing rates gases in the new vegetation and soils of sea-level rise Limited existing areas for transgression
As a next step subsequent to this Adaptation Plan, a detailed San Dieguito Lagoon Wetland Habitat Migration Assessment should be performed in conjunction with the City of San Diego and other lagoon stakeholders to further assess the potential for San Dieguito Lagoon wetland habitats to migrate upstream and to upland areas adjacent to Lagoon to further develop adaptation measures that facilitate habitat migration. This assessment will include a spatial wetland migration analysis to identify areas where salt marsh habitats will or could migrate to. It will also identify and evaluate measures to preserve these potential habitat migration areas and corridors, including potential land acquisition, use designations, zoning buffers, setbacks, and conservation easements.
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6.1.2 Adaptation option: sediment placement Sediment placement on the marshplain is an adaptation strategy that would allow wetland accretion to keep up with sea-level rise. Wetland vegetation establishes in very specific elevation zones relative to tidal water levels. If/when the tidal water levels increase, the vegetation needs to establish at higher elevations as well. This can either be done through natural transgression if there is accommodation space or by placing sediment to actually raise the surface elevations.
Sediment placement in a marsh is a relatively new, but promising adaptation measure. The first sediment placement project on the West Coast was completed in April 2016 at the Seal Beach Wetlands in Huntington Beach. Clean dredged material from the Huntington Harbor was placed in an 8-10 inch layer over a roughly 7 acre area (USFWS 2016, Figure 6.1). Monitoring is being completed to track the outcomes of the project and inform future projects.
Figure 6.1 Sediment Placement on the Marsh at Seal Beach
SOURCE: USFWS 2016
Table 6.1.2 summarizes benefits and constraints for sediment placement. Sediment placement would allow marshes to keep up with sea-level rise, reduce flood and erosion risks, and provide an opportunity for beneficial reuse of sediment. However, because sediment placement is a relatively new method, there are still many unknowns related to the impacts to the marsh. Additionally, permitting is likely to be challenging until this becomes a more common practice. Placing sediment in wetlands requires careful and unique consideration, engineering, and construction. Over time, more and more sediment would need to be placed to keep up with sea-level rise, so sediment placement would become more expensive over time. Sediment placement has the potential to be compatible with River channel dredging as an integrated wetland/River flood management adaptation strategy
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Table 6.1.2 Sediment placement benefits and constraints summary Benefits Constraints
Preserves wetland habitat • Potential temporary impacts to the march
Reduces flood and erosion risks • Potentially challenging to permit Option for beneficial reuse of sediment • More expensive way to dispose of sediment More expensive over time as increasing rates of sea-level rise will require more sediment
6.1.3 Adaptation option: wetland expansion/restoration Wetland expansion or restoration is an adaptation strategy that increases the area of marsh. Restoration can range from planting native plants in upland or transition zones to significant grading of marshplain or channels to achieve the appropriate elevations for tidal inundation. Restoration can be combined with allowing wetland transgression (Section 6.1.1) as upland and transitional areas become available. For example, grading channels into a site might be necessary to bring tidal waters further back, but revegetation could occur through natural recruitment.
Wetland restoration is compatible with levees-with-partial-retreat adaptation measures for River flooding, for example as described in Chapter 5. In this scenario, the transition and upland habitat areas could be designed to allow for wetland habitat migration with sea-level rise, thereby increasing wetland resiliency to sea-level rise.
Table 6.1.3 summarizes the benefits and constraints of wetland restoration. Creating new wetlands through restoration will preserve wetland habitat until the rate of sea-level rise is faster than the rate at which marshes can migrate. While restoring wetlands will provide more wetland habitat over time, this would come at the expense of transitional and upland habitats or developed areas.
Wetlands also provide benefits such as flood and erosion protection and sequestration of greenhouse gases in the vegetation and wetted soils.
Table 6.1.3 Wetland expansion/restoration benefits and constraints summary Benefits Constraints
Creates new wetland habitat • Potential loss of upland and transitional habitats
Reduces flood and erosion risks • Potential loss of development area
Sequesters additional greenhouse Less effective over time with increasing rates gases in new vegetation and soil of sea-level rise
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6.2 Wetland adaptation monitoring The main criterion for initiating consideration and planning for wetland adaptation is habitat loss/conversion. With 2 ft of sea-level rise, existing high marsh (pickleweed) habitat is expected to drown out and move upslope into the existing transitional habitats. With 3 ft of sea-level rise, low marsh habitat (cordgrass) will move into areas that are currently mid marsh (pickleweed) and high marsh. As a result, mid and high marsh will be squeezed into the transition zone. With 5.5 ft of sea-level rise, all salt marsh habitat will be squeezed into the elevation band where transitional habitat occurs today, which is a smaller area than the existing wetland area.
Adaptation planning would be needed when existing high marsh converts to mid marsh and squeezes into the transition zone, which is likely to result in loss of high marsh habitat functions (e.g., loss of high tide refugia). As wetland conversion continues with sea-level rise, upland and transitional areas could be allowed to convert to marsh through wetland transgression. With enough sea-level rise (e.g., 1 ft of sea-level rise), this adaptation strategy is not expected to be effective and restoration in other higher elevation areas or placement of sediment in existing marshes would be needed. Table 6.2.1 presents monitoring criteria with wetland conversion thresholds to initiate consideration of adaptation measures. Table 6.2.2 provides lead times to begin advance planning before adaptation measures could be in place to limit risk.
Table 6.2.1 Wetland monitoring criteria to consider adaptation options Pickleweed / Cordgrass Criteria & Wetland Mudflat Cordgrass Mudflat Open Water Thresholds Conversion Open Water Mudflat Open Water Protect Sediment placement
Adaptation Conversion and Accommodate Options transgression
Retreat Wetland expansion, migration and restoration
Table 6 2.2 Possible lead times for planning wetland adaptation options Risk Actions Lead Times Adaptation Options Lagoon Protect 5-10 years Sediment placement wetlands Accommodate 5-10 years Wetland conversion and transgression Retreat 10-20 years Wetland expansion, migration and restoration
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6.3 Wetland adaptation coastal permitting The Coastal Development Permit review and approval for wetland adaptation measures may be processed by the City of Del Mar through the Local Coastal Program (LCP) and/or by the California Coastal Commission, pursuant to the California Coastal Act. Additional approvals may be required from the U.S. or California Fish and Wildlife Service, the U.S. Army Corps of Engineers, the California State Lands Commission, the U.S. Coast Guard, the California Department of Boating and Waterways, and California Regional Water Quality Control Boards.
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CHAPTER 7
San Dieguito River Flooding Adaptation This chapter includes a range of adaptation measures to address vulnerabilities from flooding along the San Dieguito River, including the river valley, Del Mar Fairgrounds, and North Beach (north from 15th St to the San Dieguito river mouth). Permitting for some adaptation measures may be processed through federal, state or City entities as summarized in Section 7.3.
The increased risk of San Dieguito River flooding is driven by changes in extreme precipitation and river discharge and increased deposition of sand in the river channel which would raise the elevation of the channel bed and the flood level. Increased channel deposition could occur as sea level rises, with waves driving an increase in sand transport “up” into the channel. The increase in channel depth could also increase deposition due to tidal flows into the San Dieguito River Lagoon and the interaction of river and tidal flows in the estuary. Increased precipitation and river discharge in the face of a rising sea level will also increase flood levels.
Vulnerability assessment: Roads and bridges, including Camino Del Mar road and bridge, Jimmy Durante Blvd. road and bridge, the railroad bridge, the North Beach District streets and San Dieguito Drive, will be highly vulnerable to flooding with 2 to 3 feet of deposition. Low-lying central portions of the North Beach District (blocks bounded by Camino Del Mar, 28th St, and Railroad; general vicinity of Coast Blvd. and Santa Fe between 17th St. and 23rd St.), which currently have low vulnerability to river flooding, would be highly vulnerable with 2 to 3 feet of deposition. The sewer lift station along San Dieguito Drive would be increasingly exposed to flooding and risk of failure. Other water and sewer infrastructure, coastal access parking, and recreation areas including tennis and basketball courts in these areas would also be exposed to both river and coastal flooding. The Fairgrounds west of I-5 will become highly exposed and vulnerable to flooding with 2 to 3 feet of channel deposition.
River flooding adaptation options: River channel dredging Reservoir management Levees Elevate structures
River flooding adaptation monitoring: River channel deposition Chance of extreme flooding
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7.1 Adaptation options
Del Mar’s Beach Preservation Initiative was drafted and adopted by voters in 1988 to remove private seawall encroachments from public property while providing protection for ocean front homes from wave attack. The seawalls provide protection from wave attack, to some extent, to the lower-lying landward properties, but the primary risk to these properties is river water flooding. The adaptation options in this section provide mechanisms to protect Del Mar’s low- lying homes from increased flood risk due to sea level rise.
7.1.1 Adaptation option: river channel dredging River channel dredging maintains the channel bed near its current elevation and maintains the river flood risk near the current risk level. This could be accomplished using marine-based floating dredges and barges and/or land-based equipment operated from the channel bank. Assuming the dredged material is primarily sand, the dredged material could be placed on the beach to provide nourishment as a beach adaptation measure. Material could also be placed to raise the elevation of wetlands as a wetland adaptation measure (e.g., using “spray” dredging), especially for finer-grained dredged material.
Southern California Edison has dredged the River channel as part of the San Dieguito Lagoon Wetland Restoration. Southern California Edison dredged approximately 40,000 cubic yards of sand from the channel in 2011, 16,800 cubic yards in 2015, and approximately 19,000 cubic yards in 2017 to maintain the tidal flow (tidal prism) required by mitigation permits. Southern California Edison is required to maintain a minimum tidal prism, which is achieved by maintaining a certain minimum channel cross-section; however, the permits and maintenance program do not account for future sea-level rise or require a certain channel bed elevation to be maintained. With sea-level rise, the tidal prism could be maintained for the restoration, while the channel bed elevation and flood risk increase. Modifying the channel dredging program to maintain the channel bed elevation as a river flood adaptation measure is therefore expected to be required.
As part of the Adaptation Plan, it is recommended that the City review ongoing channel survey data and deposition monitoring from the San Dieguito Lagoon Restoration and communicate with Southern California Edison on the channel dredging program to influence its benefit toward protecting City properties. It is encouraged that the City coordinate with Southern California Edison to identify optimal times and placements for dredging such that dredged material would remain in place for as long as possible based upon the findings and recommendations of the City’s Sediment Management Plan. Past dredging has not been designed to optimize benefit to the beach and protection from flooding.
7.1.2 Adaptation option: reservoir management The City of San Diego’s Lake Hodges Reservoir controls flows from approximately 87% of the San Dieguito River watershed. The primary purpose of the Lake Hodges Reservoir is water storage; however, the Reservoir can provide ancillary flood management benefits. In the past,
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extreme river flooding has occurred when the reservoir is full and extreme rainfall runoff events overtop the dam spillway and is conveyed downstream. The majority of the extreme river discharge at Del Mar has been contributed by the flow spilling over the dam spillway, as occurred in floods in 1978 and the early 1980’s.
In 2012, The San Diego County Water Authority (SDCWA) completed the Lake Hodges Projects that connected Lake Hodges to SDCWA’s new Olivenhain Reservoir for the purpose of improving water supply and storage (SDCWA 2016). The connection also allows water to be pumped back and forth between Hodges Reservoir and Olivenhain Reservoir (SDWCA 2016). While the primary purpose is water storage, the improved reservoir system and operations could provide improved flood management.
As part of the Adaptation Plan, the City can coordinate with the City of San Diego, the San Diego County Water Authority (SDCWA) and the Olivenhain Municipal Water District (OMWD) to explore Olivenhain and Lake Hodges reservoir management and operations options for improving river flood management at present and with climate change. Increasing reservoir storage has the potential to at least partially offset the projected increase in River flood risk with climate change and sea-level rise-induced channel deposition. Storage volume could be increased through management of the Lake Hodges Project via pump operation or by dredging sediment from the reservoir that has been delivered by the River and accumulated in the reservoir. Dredging reservoir sediment could potentially be compatible with beach nourishment and wetland sediment placement adaptation measures. This approach is logical in that it moves sediment trapped in the reservoir to the coast, where it is needed and would have naturally deposited without the reservoir; however, there are a range of constraints and feasibility issues that would need to be considered including transporting (e.g., trucking) sediment.
7.1.3 Adaptation option: levees Levees, such as engineered earth embankments, can be built along the river corridor up to elevations above flood levels to reduce the flood risk to areas behind the levees. The Adaptation Plan includes levees along the River flood corridor. Figure 7.1 illustrates how levees could be aligned with habitat restoration areas; specific locations of levees would require careful design, permitting and planning in conjunction with the Fairgrounds. The actual proposed levee alignments and wetland restoration areas would need to be planned in greater detail and would be different than shown in the example. The locations of the levees would also need to be assessed and planned in greater detail so that any levees tie into high ground.
The levees could be designed as “living levees” by creating gently-sloping upland, transition, and wetland habitats between the levee and the river (Figure 7.2). This approach is being adopted in wetland restoration practice to enhance habitat diveristy and provide wetland buffers and high tide refuge. Higher elevation transition and upland areas also provide space for wetland to migrate to with sea-level rise. Constructing living levees may be compatible with channel dredging if dredged materal can be placed to build the habitat slope adjacent to the levee. Soil for levee construction would need to meet specific engineering criteria and may need to be imported from off-site.
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Figure 7.1 Example to illustrate Living Levees along the San Dieguito River
[Revise Figure to remove the northern yellow line from the Fairgrounds property per STAC recommendation]
Figure 7.2 Living Levee Cross Section
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The levees would need to be planned and designed to avoid potential impacts to existing habitats, sediment transport, and flood levels upstream and downstream. By combining levees with habitat restoration, the intent would be to avoid construction in existing wetland areas and create new restored upland and wetland habitats that could mitigate for potential habitat impacts. The effects of levees and restored areas on river sediment transport, deposition, and scour during storm events would also need to be analyzed. For example, the effect of the San Dieguito Lagoon Restoration on sediment transport and the potential to reduce sand supply to the beach during storm events was an important consideration in the project evaluation and design. Constructing levees to protect portions of the City and Fairgrounds that would otherwise flood during storm events could potentially increase sand transport to the beach, however this would need to be fully evaluated. Confining river flows within a levee system also has the potential to increase flood levels upstream and downstream of the levee system, which would also need to be fully evaluated and addressed in planning and design. Within the levee system (i.e., between the levees), River flood levels would also likely increase and a plan and design to reduce any potential increase in flood risk to bridges crossing the river would need to be developed.
7.1.4 Adaptation option: elevate structures The ground floor elevation of homes and buildings or infrastructure such as roads can be raised to above river flood levels in the future, similar to the adaptation measure for raising structures to address North Beach coastal flooding, as described in Chapter 9. A key difference is that the area of potential river flooding is larger than the area of coastal flooding and a greater number of structures would be affected.
Raising roads and vulnerable utilities can be accomplished by placing fill to rebuild roads and replace utilities at higher elevations. Other options for raising roads and utilities may include replacing at-grade roads with pile-supported causeways. The Fairgrounds have proactively elevated structures they identified as vulnerable. Vulnerabilities to existing and planned railroad infrastructure will require coordination with NCTD and SANDAG.
As part of the City’s existing floodplain management program, the City already requires that new construction in the current river floodplain be elevated above the existing 100-year river flood elevation to meet Federal Emergency Management Agency (FEMA) National Flood Insurance Program (NFIP) requirements. FEMA is in the process of revising the effective Flood Insurance Rate Maps and accompanying flood levels; however, the NFIP does not currently consider sea- level rise and climate change. The City can consider modifying floodplain development policies and regulations to address sea-level rise and facilitate elevating structures over time through redevelopment.
7.1.5 Adaptation option: relocate public infrastructure The City can consider relocating public buildings, utilities, and other infrastructure as the river flood risk to public structures increases. For at-risk private property and structures, the City
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could consider incentives for facilitating relocation to allow for wetland restoration along the river. As noted above, a greater number of public structures are within the river flood risk area than the coastal flood risk area.
7.2 River adaptation monitoring The monitored criteria for river adaptation are channel deposition (e.g., driven by sea-level rise) and the flood risk due to sea-level rise, channel deposition, and potential for climate change to increase extreme precipitation and river discharge. Table 7.2.1 includes the projected increase in flood risk with sea-level rise/channel deposition and climate change from the Coastal Hazards, Vulnerability, and Risk Assessment (ESA 2016). These projections assume that deposition is not limited by sediment supply and that the river bed profile and flood profiles would increase in elevation with sea-level rise, with a rate and amount of deposition equal to the rate and amount of sea-level rise.
Table 7.2.1 Projected river flood risk with sea-level rise Sea-level rise and channel deposition 0 ft 1ft 2 ft 3 ft 5.5 ft
Annual chance of extreme 1% 5% 6% 6% 20% flooding (1% chance event)
Annual chance of significant flooding 5% 15% 25% 50% 100% (1980 event) Table 7.2.2 presents criteria to initiate planning for adaptation measures and anticipated extreme risk of flooding ranges over which measures will be effective. Based on the guiding principles, the flood risk criteria and thresholds are set to limit the risk of extreme river flooding and damage to less than 5% annual-chance of occurrence. Adaptation planning would be needed as river flooding and damage increases to 5%.The risk of more frequent, less severe, but still significant flooding such as the 1980 San Dieguito river flood event is estimated to currently be around 5% annual-chance. Adaptation to reduce extreme flood risk would reduce the risk of more frequent flooding. Table 7.2.3 provides estimated lead times to begin advance planning before adaptation measures could be in place to limit risk.
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Table 7.2.2 River flooding monitoring criteria to consider adaptation options Annual risk of Criteria & extreme 5% 15% 50% 100% Thresholds flooding*
Protect Channel dredging
Reservoir management Adaptation Options Levees Accommodate Elevate structures Retreat Relocate public infrastructure *Risk of flooding without adaptations
Table 7.2.3 Possible lead times for planning river flooding adaptation options Risk Actions Lead Times Adaptation Options River Protect 5-10 years Channel dredging flooding 5-15 years Reservoir management 15-20 years Levees Accommodate 5-10 years Elevate structures Retreat 15-20 years Relocate public infrastructure
7.3 River adaptation coastal permitting The Coastal Development Permit review and approval for river adaptation measures may be processed by the City of Del Mar through the Local Coastal Program (LCP) and/or by the California Coastal Commission, pursuant to the California Coastal Act. Additional approvals may be required from the U.S. or California Fish and Wildlife Service, the U.S. Army Corps of Engineers, the California State Lands Commission, the U.S. Coast Guard, the California Department of Boating and Waterways, and California Regional Water Quality Control Boards.
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CHAPTER 8
Bluff and Adjacent Beach Erosion Adaptation
This chapter includes a range of adaptation measures to address vulnerabilities from erosion of bluffs and their adjacent beaches. This is relevant to the South Bluffs, bluffs along South Beach including low bluffs fronting Powerhouse Park, and the North Bluffs. Permitting for some adaptation measures may be processed through federal, state or City entities, as summarized in Section 8.3
Vulnerability assessment: With 1 foot of sea-level rise, the current localized vulnerability of the LOSSAN railroad to bluff erosion will increase and extend along almost the entire southern bluffs. The railroad would need to be moved inland or other adaptation measures, for example with underpinnings, cassons, or soldier piles, would be required to reduce the risk of the railroad collapsing. If a seawall is constructed to protect the railroad, it will cause the beach to narrow and over time little to no beach will exist along the southern bluffs. If the railroad is moved inland and bluff erosion is allowed to continue, bluff-top property and sewer infrastructure in South Beach and along South Bluff would be vulnerable to erosion with 2 feet of sea-level rise. North Bluff properties and the low bluffs at Powerhouse Park would be similarly vulnerable to erosion.
Bluff adaptation options: Beach nourishment and retention Best management practices (BMPs) Railroad relocation Public infrastructure relocation
Bluff adaptation monitoring: Distance between coastal bluff edge and development Beach width adjacent to the bluffs
8.1 Bluff adaptation options
8.1.1. Adaptation option: beach nourishment and retention Nourishing and retaining the sand on the beach below the southern bluffs could provide short- to-medium term benefits of maintaining a beach for ecology and recreational use and reducing
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wave run-up onto and erosion of the bluff toe. In the long term, beach nourishment and retention may become more expensive if sand sources become limited or if the amount of sand required increases with sea-level rise. Current studies indictate dune restoration may not be an effective solution for reducing erosion of the bluff toe, as the beach is already squeezed in front of the bluff toe and sand placed for dune creation may not last. Additionally, beach nourishment and retention would not affect the erosion processes at the bluff top. Given the proximity of the southern bluffs to the Los Peñasquitos Lagoon inlet, the effects of beach nourishment and retention on the Lagoon inlet would need to be fully considered.
Beach nourishment for the North Bluff is not likely to be effective if limited to the City limit given the relatively short length of bluff shoreline and proximity to the San Dieguito Lagoon mouth; however, beach nourishment could be pursued in coordination with the City of Solana Beach. Table 8.1.1 summarizes benefits and constraints of beach nourishment adjacent to bluffs.
Table 8.1.1 Bluff beach nourishment and retention benefits and constraints summary Benefits Constraints
Preserves beach • Limited sand resources
Reduces bluff toe risk • Less effective over time with increasing sea-level rise Transportation of sediment to receiver sites Short-term beach use and ecology impacts
8.1.2. Adaptation option: best management practices (BMPs) Best management practices (BMPs) for reducing bluff erosion include management of surface drainage as well as shallow subsurface groundwater drainage to the bluff edge and face to control local erosion and slope failure due to drainage. The goal of these practices should be to control surface runoff and avoid concentrated flow down the bluffs, reducing shallow groundwater flow that saturates upper soils and facilitates erosion, and management of groundwater daylighting at geologic layers. NCTD and SANDAG are already employing surface and subsurface drainage control measures to reduce erosion.
In addition to these surface water and groundwater BMPs, the City could investigate whether over-watering of landscaping within the South Beach and bluffs along South Bluff could be contributing to elevated groundwater flows to the southern bluffs and whether reducing this irrigation could potentially reduce bluff erosion.
It is possible that public access down the bluffs could be contributing to increased bluff erosion, as people frequently walking down bluff foot paths may be de-stabilizing soil, both directly and by preventing vegetation from establishing on the paths given that vegetated bluff is more erosion-resistant than bare soil. Access down the southern bluffs by crossing the LOSSAN railroad track or walking along the tracks is unauthorized; however, multiple paths down the bluffs are currently used. Public access and associated bluff erosion (if any) could be controlled by installing authorized pedestrian crossings of the railroad, with pedestrian under-passes (or
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over-passes), and constructing stairways down the bluffs to the beach. The Adaptation Plan recommends exploring one or more authorized railroad crossings and vertical access paths down the southern bluffs to reduce erosion. For example, two crossings and pathways could be installed at 7th and 11th Streets, where there is more space between the railroad tracks and the top of the bluff. Railroad crossings and beach access stairways are difficult to implement and feasibility may be challenging. Even so, the City should investigate these and/or other options together with NCTD and SANDAG as part of the Adaptation Plan.
Revegetating/restoring bluff vegetation on existing pathways may be effective in reducing erosion. New vertical crossings and pathways (e.g., stairways) could be installed to replace beach access via bluff-side pathways. A program to restore/revegetate large sections of the bluffs with more erosion-resistant vegetation could potentially de-stabilize the bluffs during installation and/or the period over which plants are establishing.
8.1.3 Adaptation option: railroad relocation The LOSSAN railroad track is currently at risk of bluff erosion, which is why NCTD and SANDAG have installed bluff stabilization projects. Removing the LOSSAN railroad track from the southern bluffs and relocating the track to an inland tunnel or other location would allow the natural processes of landward bluff erosion and beach migration to occur. While bluff erosion is not the only source of sand to the beach below, bluff erosion will continue to supply sand to the beach, in turn increasing the buffer the beach provides from wave action on the bluff toe.
The SANDAG 2050 Regional Transportation Plan (SANDAG, 2011) includes plans to remove and relocate the railroad; however, implementation of the planned project is not currently funded. The City supports railroad relocation as part of SANDAG plans and as a matter of City policy. The City Community General Plan (1976) includes zoning that designates the railroad property and right of way as a future open-space park area.
The City’s current zoning and Local Coastal Program (LCP) includes a Railroad land use designation for the railroad property and right-of-way. The Railroad designation allows railroad facilities and related structures provided a Conditional Use Permit is obtained from the City and is in full force and effect; however, this process is not currently followed by NCTD, SANDAG, and the City. The railroad right-of-way is complex. Rail operations engaged in interstate commerce are considered not subject to state or local permit jurisdiction. Even so, the right-of-way is located within the current LCP’s Shoreline Protection Area line and Beach Overlay Zone.
Railroad relocation would allow landward bluff erosion in order to maintain the beach below and the natural character of the Del Mar bluffs and beach. Currently, about 50 trains per day use the rail line, and SANDAG plans to increase this number to over 100 trains per day with double tracking of the corridor. On average, about 12 people per year are killed by trains in the San Diego corridor. Railroad relocation would further rail safety and operations, address an immediate safety problem, eliminate the need for reduced speeds due to bluff instability and service interruptions due to bluff inspections, and make increased traffic more feasible.
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8.1.4 Adaptation option: relocate public infrastructure After railroad relocation, the bluff will continue to erode landward through the current location of the railroad. With 1 ft of sea-level rise or more, the bluff is projected to erode and threaten buildings, roads, and the sewer line along the bluff landward of the railroad. The LCP as ammended by the BPI allows sea walls only as a last resort within the Shore Protection Area and Beach Overlay Zone. The City can consider relocation of public buildings, utilities and other infrastructure as the bluff erosion risk to public structures increases. Proactively, the City could consider options for facilitating public infrastructure removal where there is a public benefit, such as removing public structures to restore or preserve bluff trails or parks. As the low bluffs along Powerhouse Park erode due to sea level rise, an option would be to armor in the short run to preserve the park for public use, but the armoring will become expensive and less effective with extreme levels of SLR and could accelerate beach erosion.
8.2 Bluff adaptation monitoring The criteria to initiate consideration and planning for bluff adaptation is the distance between the the bluff top edge and the bluff top asset. A minimum buffer distance is based on an approximate structural buffer distance between the bluff top and a structure, which is required to provide enough bluff width to laterally support the structure. A structural buffer distance of approximately 10 ft is used based on a SANDAG study (Leighton & Associates 2010) of the distance within which bluff erosion presents a risk to railroad track stability (per the Coastal Hazards, Vulnerability, and Risk Assessment). The minimum buffer distance between the bluff top edge and a bluff top asset includes an additional safety buffer based on the approximate width of bluff that could collapse in a single erosion event. Adding this safety buffer to the structural buffer allows for the occurrence of an erosion event after monitoring criteria threshold has been reached and while the adaptation measure is being planned and implemented. A safety buffer of approximately 25 ft is used based roughly on the July 13, 2016, bluff collapse near 10th Street (Figure 8.1). Actual bluff top recession during this event is to be determined and may have been between 5 and 20 ft. To summarize, the minimum buffer distance is based on the following:
Structural buffer distance = 10 ft Safety buffer distance = 25 ft Minimum buffer distance = structural buffer distance + safety buffer distance = 35 ft
These projected distances provide an indication of the amount of sea-level rise at which minimum buffer distances would be insufficient for some portion or all of the railroad, rows of buildings, and the sewer line. With 1 ft of sea-level rise, additional adaptation (e.g., beach nourishment and retention and/or BMPs) is expected to be required to reduce the risk of erosion to the railroad. If and when the railroad is relocated and the bluff is allowed to erode, adaptation would be required to reduce the risk to some public infrastructure including sections of the sewer line (e.g., south of Seagrove Park and near 10th Street) with 1ft of sea-level rise. With 3 ft of sea- level rise, the following assets are expected to be at risk: portions of the sewer line; and the entire railroad along the bluffs. This indicates that the railroad may need to be relocated by
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or before this point (depending on the effectiveness of beach nourishment and BMPs). Table 8.2.1 shows the approximate projected distance between the bluff top and the railroad, the first and fourth rows of buildings, and the sewer line along the bluffs with sea-level rise (distances below the minimum of 35 ft shown in red indicate potential need for bluff erosion adaptation for some or all of asset class). The sewer line changes locations along the Del Mar bluff. It is located between the railroad and the first row of buildings in some areas and between or under first to fourth row buildings in other areas. Table 8.2.1 shows distances for areas where the sewer is located east of the first row of buildings.
Figure 8.1 Bluff Collapse near 10th St. in Del Mar on July 13, 2016
Projections in Table 8.2.1 are approximate and could be greater or less due to uncertainties. Actual distances will be monitored over time as part of the adaptation plan process. Table 8.2.2 presents monitoring criteria and adaptation measures with anticipated erosion ranges over which measures will be effective. Table 8.2.3 provides lead times to begin advance planning before adaptation measures could be in place to limit risk.
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Table 8.2.1 Projected distances from bluff top to railroad, sewer line, th 1st and 4 rows of buildings with sea-level rise (for areas with sewer between buildings) Sea-level rise: 0 ft 1 ft 2 ft 3 ft 5.5 ft RR 15 - 110 ft 0 - 70 ft 0 - 40 ft 0 - 10 ft 0 - 0 ft 1st row 40 - 170 ft 0 - 140 ft 0 - 120 ft 0 - 80 ft 0 - 0 ft Sewer 65 - 175 ft 10 - 190 ft 0 - 150 ft 0 - 100 ft 0 - 50 ft 4th row 270 - 450 ft 170 - 340 ft 140 - 300 ft 100 - 280 ft 10 - 210 ft
Table 8.2.2 Bluff erosion monitoring criteria to consider adaptation options Railroad setback from 15 - 110 ft 0 - 60 ft 0 - 35 ft 0 - 5 ft 0 ft bluff edge Sewer Criteria & setback from 40 - 170 ft 0 - 130 ft 0 - 110 ft 0 - 65 ft 0 ft Thresholds bluff edge 1st row setback from 65 - 175 ft 10 - 190 ft 0 - 150 ft 0 - 100 ft 0 - 50 ft bluff edge
Protec Beach and dune nourishment and retention t (soft
measures) Best management practices Adaptation Options Retreat Relocate Railroad (Phase 1) Remove sewer, storm drains, fiber Retreat optic cables (Phase 2) Table 8.2.3 Possible lead times for planning bluff erosion adaptation options Risk Actions Lead Times Adaptation Options Bluff Protect 5-10 years Beach and dune nourishment Relocate sewer, storm drains, fiber erosion Retreat 5-10 years optic cables Retreat Relocate railroad
As bluff erosion continues with sea-level rise, the beach below the bluffs could be nourished to reduce erosion at the bluff toe and improve beach access, aesthetics and habitat function. BMPs could also be implemented to reduce bluff erosion, such as installing vertical access paths (e.g., stairs) down the bluffs with authorized railroad under-pass (or over-pass) crossings and pursuing studies and measures to potentially reduce irrigation and groundwater flow-related erosion effects. With enough sea-level rise (e.g., 2 ft of sea-level rise), these adaptation
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strategies are not expected to be effective and the railroad would need to be relocated. Relocating the railroad would provide some buffer within which bluff erosion could occur without posing a risk to landward assets; however public infrastructure such as portions of the sewer line would also likely need to be relocated.
8.3 Bluff adaptation coastal permitting The Coastal Development Permit review and approval for bluff adaptation measures may be processed by the City of Del Mar through the Local Coastal Program (LCP) and/or by the California Coastal Commission, pursuant to the California Coastal Act. Additional approvals may be required from the U.S. or California Fish and Wildlife Service, the U.S. Army Corps of Engineers, the California State Lands Commission, the U.S. Coast Guard, the California Department of Boating and Waterways, and California Regional Water Quality Control Boards.
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CHAPTER 9
Beach Erosion and Flooding Adaptation This chapter includes a range of adaptation measures to address vulnerabilities from beach erosion and flooding in North Beach (north from 15th street to the San Dieguito river mouth). The beach level community in the City of Del Mar comprises a century-old beach front neighborhood that is fully developed with approximately 600 properties in a densely populated area, a major U.S. coastal route (101), and railroad tracks supporting commuter and interstate passenger and freight traffic. It serves visitors with direct public beach access at each street from 15th to 29th. Permanent lifeguard towers with public restrooms at 17th St, 20th St, & 25th St are supplemented with temporary towers during busy tourist seasons. This region has unique neighborhood features, topographies, and vulnerabilities. It is already subject to both coastal and river flooding. The homes and public infrastructure throughout the area benefit from sea- walls along almost the entire beachfront. The oceanfront homes have a higher elevation than homes to the east, where elevations decline from the oceanfront eastward toward the LOSSAN rail line. The beach in this area is an important part of Del Mar’s continuous, wide, walkable beach that stretches over two and a half miles from near Los Penasquitos Lagoon on the south to San Dieguito Lagoon to the north. Permitting for some adaptation measures lies within the jurisdiction of federal, state or City entities, as summarized in Section 9.3.
Vulnerability assessment: Public access along the beach (horizontal access) will be lost due to beach erosion with 1 to 2 feet of sea-level rise. Beach erosion and coastal storms will threaten sea wall integrity and increase flooding and storm damage. Low-lying roads and properties in North Beach will be highly vulnerable to coastal and river flooding, including the blocks between Ocean Front and Camino Del Mar/Coast Blvd and the blocks directly east of Camino Del Mar/Coast Blvd. The present low to moderate vulnerability to coastal flooding and wave damage will become a high vulnerability with 1 to 2 feet of sea-level rise, for low-lying roads and properties in North Beach, including the City’s 17th St Beach Safety Center.
Beach adaptation options: Beach and dune nourishment Sand retention Raise/improve sea walls and revetments Elevate structures Relocate public infrastructure
Beach adaptation monitoring: Beach width Flooding and storm damage frequency
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9.1 Beach adaptation options
9.1.1 Adaptation option: beach and dune nourishment Widening North Beach would reduce the risk of flooding and erosion of property along the beach. However, the width of the beach will diminish with time and sea-level rise, requiring an ongoing cycle of “re- nourishment” to maintain beach width. As sea-level rises, the frequency of required nourishment is likely to increase, because, in addition to widening the beach to offset erosion, additional sand will be needed to raise the elevation of the beach up to the increased sea level. For all these reasons, beach nourishment should be considered in conjunction with sand retention measures (Section 9.1.2).
The dominant direction of sand transport along the Del Mar coast is from north to south. Beach nourishment could therefore contribute to closure of the Los Peñasquitos Lagoon inlet to the south, and could also affect the San Dieguito Lagoon inlet to the north (during south swells that transport sand from south to north). With sea-level rise, increased sediment supply may be a net benefit to the extent that it mitigates rapid shoreline and ecological changes. The Coastal Hazards, Vulnerability and Risk Assessment indicates beach nourishment will be effective up to 1 ft of sea-level rise. Thus, the Adaptation Plan prioritizes beach nourishment as the primary and immediate strategy for Del Mar’s North Beach area. Table 9.1.1 summarizes benefits and constraints of beach and dune nourishment.
Table 9.1.1 Beach and dune nourishment benefits and constraints summary Benefits Constraints
Preserves beach • Limited sand sources
"Living shoreline" provides beach and dune • Less effective over time with increasing habitat sea-level rise Reduces flood and erosion risks • Transportation of sediment to receiver sites Beach use and ecology impacts
Placement of sand typically provides a temporary benefit until the sand erodes and migrates away from the placement area. It is therefore important to consider the fate of the sand and implications of deposition in other areas. In general, increased sand supply is considered beneficial to most beach areas, but can be problematic at lagoon inlets and storm drain outlets. Sand deposition on rocky substrate may adversely affect habitat and recreation. The dominant direction of sand transport along the Del Mar coast is from north to south. Beach nourishment could therefore contribute to closure of the Los Peñasquitos Lagoon inlet to the south, and could also affect the San Dieguito Lagoon inlet to the north (during south swells that transport sand from south to north). However, with sea-level rise, increased sediment supply may be considered a net benefit in terms of mitigating rapid shoreline and ecological changes.
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9.1.2. Adaptation option: sand retention Sand retention measures include structures that prevent sand transport away from the beach and encourage sand deposition on the beach. Types of structures include the following:
Groins: These structures serve to maintain a wider beach but have the potential to diminish horizontal access along the beach. Constructing groins and other structures on the beach or in the ocean typically requires habitat mitigation (e.g., restoration of comparable habitat in another location) and could alter the character of Del Mar’s natural shoreline. New groin designs may become available in the future, so this option should be evaluated over time. Breakwaters: These structures maximize wave reduction and sand retention but can disrupt and alter wave patterns and interfere with surfing resources, which may negatively impact Del Mar. Current permitting and mitigation requirements ,and the degree of potential negative impacts, may restrict use of breakwaters as an adaptation measure. New breakwater designs may become available in the future, so this option should be evaluated over time. Artificial reefs: These structures create rocky reef habitat and have potential to enhance surfing resources; however, using artificial reefs to retain sand and enhance surfing is still in the experimental phase of development. They have been investigated, constructed, and tested in various locations including Orange County. Successful reef installation remains a work in progress to date. New reef designs may become available in the future to ensure that reef implementation will provide the intended benefits, so this option should be evaluated over time.
Table 9.1.2 summarizes benefits and constraints of sand retention measures.
Table 9.1.2 Sand retention measures benefits and constraints summary Type of sand retention structure Benefits Constraints All Retain sand Require mitigation Groins Maintains wider beach Affects horizontal access along beach Maximizes wave reduction and sand Breakwater Destroys surfing resources retention
Artificial reefs Creates rocky reef habitat Experimental / limited experience Potential to enhance surfing resources
9.1.3 Adaptation option: sea walls and revetments The existing sea walls and rip rap along North Beach provide flood and erosion protection for beachfront properties during typical storms and seasonal erosion. During severe storms, which can be coupled with severe seasonal erosion of the beach, waves can overtop the protective structures as in March 2016 (Figure 9.1) and cause damage as in the 1983 El Nino storm event
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(Figure 9.2). Improving North Beach sea walls and revetments provides an adaptation measure to offset the increase in flood risk with sea-level rise. This could be accomplished by adding a new section of sea wall or rock to the top of the existing walls/revetments; however, doing so may require significant modifications or a rebuilding of the existing walls/revetments. While beach access points along the City’s beaches from 15th Street north to the lagoon can be currently protected with seasonal berms, it may be important to consider improved sea wall protection for these locations.
Figure 9.1 Overtopping in Del Mar on March 8, 2016
While sea walls and rip rap provide protection to the existing property slopes, some studies show that these structures can contribute to erosion and accelerate beach loss when the beach width narrows and wave run-up frequently reaches the structure. As the beach narrows and sea-level rises, wave run-up and overtopping of the sea wall structures will also increase as the waves begin to break near or on the structures, and will require more frequent maintenance or reconstruction. With ongoing beach erosion and sea-level rise and without any other mitigating measures, fixing the shoreline location in one place with a sea wall or revetment will eventually lead to the loss of the beach seaward of the structure.
Sea wall and revetment construction is regulated by the CA Coastal Act and Del Mar LCP. The Coastal Act and LCP, which includes Del Mar’s Beach Preservation Initiative, allow for
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construction and maintenance of sea walls or revetments when necessary to protect existing structures or public beaches in danger from erosion, when designed to eliminate or mitigate adverse impacts on the local shoreline sand supply. New development may not rely upon protective devices (e.g., sea walls and revetments) that would substantially alter natural landforms. Table 9.1.3 summarizes benefits and constraints of raising/improving sea walls and revetments.
Figure 9.2 Coastal Damage Following 1983 Storm
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Table 9.1.3 Raise/improve sea walls and revetments benefits and constraints summary Benefits Constraints
Protects property and reduces flood and erosion Potential for loss of beach with sea-level rise risks for the design lifespan and conditions and without other measures
"Holds the line" and buys time to implement Potentially accelerates beach erosion with other adaptation measures sea-level rise In Del Mar, provides protection for properties May require more frequent maintenance or throughout North Beach reconstruction with sea-level rise Level of protection provided decreases with loss of beach
9.1.4. Adaptation option: elevate structures The ground floor elevation of homes and buildings or infrastructure such as roads can be raised to above sea-level rise flood levels (e.g., the 100-year flood level plus an allowance for sea-level rise) to reduce the risk of flooding with sea-level rise. Raising structures can include raising vulnerable buildings on pile foundations; however, there may be challenges with building height restriction, earthquake code compliance and other building codes. Further, while raising oceanfront structures could have potential to allow for some limited migration and persistence of a fronting beach, if it were done without accompanying beach and dune nourishment, shoreline migration would likely damage roads, infrastructure, and the many lower lying properties east of the shoreline.
Raising existing homes may not be feasible from an engineering and cost perspective, but is more feasible for new construction. However, this is likely an “all or nothing” plan, where the ocean ebb and flow and resulting shoreline migration would need to be enabled under all structures in the beach zone. If some structures are raised on pilings and others are not, the structures that are not raised are likely to be even more impacted and compromised by the lack of impediments to the ebb and flow of the ocean and migrating shoreline.
Building design and construction can be modified so that the second floor is above the target flood level and contains all flood-sensitive features, while the first (ground level) floor is used for parking and/or storage and is designed to be durable and resilient to flood damage. While this type of design is feasible for new construction, it may be unfeasible from a cost and engineering perspective as a retrofit to existing structures.
Raising roads can be accomplished by placing fill to rebuild roads at higher elevations. Utilities, that are vulnerable to flooding, erosion, or increased ground water levels with sea-level rise, such as sewer pipelines and storm drains, which are often buried along roads, can also be raised. Other options for raising roads and utilities may include replacing at-grade roads with pile-supported causeways. Table 9.1.4 summarizes the benefits and constraints of raising structures.
76 February66 13, 2018 Item 01 Chapter 9 Draft Adaptation Plan 2/2/2018
Table 9.1.4 Raising structures benefits and constraints summary Benefits Constraints
Beach erosion and flooding continues to migrate Protects vulnerable structures. inland, requiring additional adaptation
9.1.5 Adaptation option: relocate public infrastructure The City can consider relocation of public buildings, utilities and other infrastructure as the risk to public structures increases with sea-level rise. Proactively, the City could consider options for facilitating structure removal where there is a public benefit, such as removing structures to restore beach areas or parks. The roads and utilities in North Beach are located east of the oceanfront seawalls, so their more immediate vulnerability is flooding from the river.
9.2 Beach adaptation monitoring Criteria to be monitored for beach adaptation include changes in risk or chance of extreme coastal flooding and storm damage, and approximate beach widths. Projected flood and damage risks and beach widths with sea-level rise and without adaptation are based on the Coastal Hazards, Vulnerability, and Risk Assessment (ESA 2016). With greater than 1 ft of sea- level rise, winter/spring beach widths are anticipated to be great enough to eliminate a walkable beach and its storm protection, and the risk of flooding and damage are anticipated to exceed an acceptable level. Therefore, thresholds for initiating consideration and planning of beach adaptations are any of the following: Flood and damage risk approaching a moderate level (5% annual chance of extreme flooding and damage) Average or successive winter beach widths approaching 25 ft Average or successive summer beach widths approaching 80 ft Once adaptation measures are implemented to increase beach widths and/or reduce flood/damage risks, then the flood risk would be estimated for the adapted condition assuming future sea-level rise. Increasing flood/damage risks and decreasing beach widths would then continue to be monitored and compared against the beach width thresholds above. Table 9.2.1 shows projected beach widths with increasing chance of extreme flooding/damage.
Table 9.2.1 Projected beach width with increasing chance of extreme flooding/damage Annual chance of extreme flooding/damage (1983 event) 1% 5% 15% 50% 100% Summer/fall beach width 120 ft 80 ft 34 ft 0 ft 0 ft Winter/spring beach width 65 ft 25 ft 0 ft 0 ft 0 ft
Other beach adaptation criteria may be considered or added through further refinement, application, and re-evaluation of the Adaptation Plan, which could include the following: Beach elevation at the toe of the sea walls and revetments to serve as an indication of the exposure of the structure to wave action.
77 February67 13, 2018 Item 01 Chapter 9 Draft Adaptation Plan 2/2/2018
Risk of sea wall failure. As the beach narrows with sea-level rise, the beach and dunes could be nourished to improve beach access, aesthetics and habitat function, as well as limit future damages in areas that are eroded during storm events. Even so, it must be noted that with enough sea-level rise (e.g., 3 ft, corresponding to 50% chance of extreme flooding), the shoreline adaptation measures that would be required to maintain existing structures would be insufficient. The ground floor elevation of beachfront and adjacent homes and buildings could instead be raised. Table 9.2.2 presents the Beach Adaptation monitoring criteria and adaptation measures and anticipated beach width ranges for which each measure would be effective. Table 9.2.3 provides lead times to begin advance planning before adaptation measures could be in place to limit risk.
Table 9.2.2 Beach erosion monitoring criteria to consider adaptation options
Summer beach width 120 ft 80 ft 35 ft 0 ft
Criteria & Winter beach width 65 ft 25 ft 0 ft 0 ft Thresholds Annual risk of extreme 5% 15% 50% 100% flooding (without adaptation) Protect Beach and dune (soft measures) nourishment Protect Raise and improve sea walls (hard measures) Adaptation Protect Options Sand retention strategies (hard measures) Accommodate Elevate structures
Retreat Relocate public infrastructure
Table 9.2.3 Possible lead times for planning beach erosion adaptation options Risk Actions Lead Times Adaptation Options Beach Protect 5-10 years Beach and dune nourishment erosion Protect 10-15 years Raise and improve sea walls Protect 15-20 years Sand retention strategies Accommodate 5-10 years Elevate structures Retreat 15-20 years Relocate public infrastructure
9.3 Beach adaptation coastal permitting The Coastal Development Permit review and approval for beach adaptation measures may be processed by the City of Del Mar through the Local Coastal Program (LCP) and/or by the California Coastal Commission, pursuant to the California Coastal Act. Additional approvals may be required from the U.S. or California Fish and Wildlife Service, the U.S. Army Corps of Engineers, the California State Lands Commission, the U.S. Coast Guard, the California Department of Boating and Waterways, and California Regional Water Quality Control Boards.
78 February68 13, 2018 Item 01 Exhibit C
SEA LEVEL RISE TECHNICAL ADVISORY COMMITTEE MEMBERSHIP AND RECOMMENDATIONS (12/7/17 & 1/25/18)
Terry Gaasterland, STAC Chair Start: Jun 01, 2015 End: N/A Category: Bluff resident/property owner; Design Review Board member; Former Finance Committee member
John Imperato, STAC Vice Chair Start: October 2, 2017 End: N/A Category: Beach area resident/property owner in the low-lying floodplain area
Kristin Brinner Start: Jun 01, 2015 End: N/A Category: Surfrider Foundation, Beach Preservation Committee member; Organic Chemistry PHD
Gabriel Buhr Start: Jun 01, 2015 End: N/A Category: Coastal Program Manager, Coastal Commission San Diego Office (non-voting)
Robin Crabtree Start: Jun 01, 2015 End: N/A Category: Beach area resident/property owner; Traffic and Parking Advisory Committee member
Charles Fletcher Start: Jun 01, 2015 End: N/A Category: Beachfront resident/property owner
Dustin Fuller Start: Jun 01, 2015 End: N/A Category: Environmental Planner, 22nd District Agricultural Association
Sarah Giddings Start: Jul 06, 2015 End: N/A Category: Scripps Institute of Oceanography, Assistant Professor (SLR technical expert)
Mark Handzel Start: Jun 01, 2015 End: N/A Category: Bluff resident/property owner
Nancy Stoke Start: October 2, 2017 End: N/A Category: Beach area resident/property owner in the low-lying floodplain area
Vacant Start: February 5, 2018 End: N/A Category: Bluff resident
79 February 13, 2018 Item 01 MINUTES SEA-LEVEL RISE STAKEHOLDER-TECHNICAL ADVISORY COMMITTEE (STAC) CITY OF DEL MAR
DEL MAR (TEMPORARY) CITY HALL, COUNCIL CHAMBERS 2010 JIMMY DURANTE BOULEVARD, SUITE 100, DEL MAR 92014 THURSDAY, DECEMBER 7, 2017 – 4:00 PM City Council Liaisons: David Druker, Dwight Worden
COMMITTEE’S STATEMENT OF MISSION/PURPOSE: Oversee the Sea-Level Rise Local Coastal Program Amendment process to make sure that the process is open, inclusive and develops consensus amongst the many stakeholders; to assist City staff and the consultant with the sea-level rise planning process; to assist in the review of technical studies and sea-level rise planning scenarios; to assist the community in prioritizing vulnerable coastal resources; to discuss and provide advice and policy recommendations to the Del Mar City Council; and to provide input to the Del Mar City Council on the Local Coastal Program Amendment process. (Ref. City Council Resolution 2015-10)
1. CALL TO ORDER
2. ROLL CALL Meeting start time 4:09 p.m.
STAC Attending: Chair Terry Gaasterland, Charles Fletcher, John Imperato, Mark Handzel, Robin Crabtree, Nancy Stoke, Kristin Brinner, Bruce Bekkar and Gabriel Buhr STAC Absent: Sarah Giddings and Dustin Fuller City Council Liaisons Attending: Dwight Worden; Dave Druker Staff: Kathy Garcia, Amanda Lee, Tanner Barclay, Shaun McMahon
3. APPROVAL OF MINUTES
Minutes for October 26, 2017 approved- (Motion by Brinner, second by Handzel vote 7-0- 2 with Bekkar and Buhr recusing as absent from 10/26/17 STAC meeting)
4. STAC RECOMMENDATIONS FOR ADAPTATION PLAN
Presentation by Chair Gaasterland on behalf of Subcommittee identifying the changes made to the draft since the October 26, 2017 STAC meeting. Overview by Principal Planner Amanda Lee and review of the November 30, 2017 memo provided in advance of the meeting to help STAC consider the Adaptation Plan and provide input to the Council.
The following speakers provided comments: Alice McNally Don Mosier Jerry Jacobs Udo Wahn Mark Wyland Randal Stoke
80 February 13, 2018 Item 01
STAC Minutes December 7, 2017 Page 2 of 4 Julia Chun-Heer Jon Corn (Time donation from Lucille Lindsay, Heather Lindsay, Joy Simon, Larry Hayward, Paul Rhodes) Jim Jaffee Stefanie Lee Walt Crampton Laura DeMarco Joe Sullivan
After STAC member questions and discussion on Item 4, STAC took the following actions:
1) Motion Kristen, second Bruce. Managed retreat should be in the Adaptation Plan document as an adaptation option. Vote failed 2-5-2 with Bruce and Kristen voting yes; Nancy, Jon, Robin, Mark, and Kim voting no; Terry and Gabe (conflict as CCC rep) abstained
2) Motion Mark, second Kristen. Establish a summary of the perspectives and different issues that STAC grappled with regarding managed retreat. Vote passed 8-0-1 unanimous with Mark, Kristen, Nancy, Jon, Robin, Bruce, Kim, and Terry voting yes; Gabe abstained.
3) Motion Kristen, second Bruce. Summary of STAC’s struggle with managed retreat should go in AP Chapter 10. Vote failed 4-4-1 with Kristen, Bruce, Terry, and Jon voting yes; and Kim, Mark, Robin, and Nancy voting no; Gabe abstained.
4) Motion Mark, second Robin. Summary of STAC’s struggle with managed retreat should go in a memo or letter. Vote passed 7-1-1 with Mark, Robin, Nancy, Jon, Bruce, Kim, and Terry voting yes; Kristen voting no; Gabe abstained.
5) Motion Robin, second Mark. Action by the City is required to remain viable. Vote passed 8-0-1 unanimous with Mark, Kristen, Nancy, Jon, Robin, Bruce, Kim, and Terry voting yes; Gabe abstained.
6) Motion Robin, second Mark. Do not add a reference to the DMMC Nonconformities regulations in the Adaptation Plan. Vote passed 8-0-1 unanimous with Mark, Kristen, Nancy, Jon, Robin, Bruce, Kim, and Terry voting yes; Gabe abstained.
7) Motion Robin, second Jon. The Adaptation Plan should clarify that the BPI voter initiative allows seawalls in North Beach as highlighted in the subcommittee draft. Vote passed 8-0-1 unanimous with Mark, Kristen, Nancy, Jon, Robin, Bruce, Kim, and Terry voting yes; Gabe abstained.
8) Motion Mark, second Jon. Prioritize beach nourishment and sand retention in the Adaptation Plan per the subcommittee draft. Vote passed 8-0-1 unanimous with Mark, Kristen, Nancy, Jon, Robin, Bruce, Kim, and Terry voting yes; Gabe abstained.
9) Motion Bruce, second Kristen. Artificial headlands should not be included as an option in the Adaptation Plan. Vote passed 4-3-2 with Bruce, Kristen, Terry, and Mark voting yes; Nancy, Robin, and Kim voting no; and Jon and Gabe abstained.
81 February 13, 2018 Item 01 2
STAC Minutes December 7, 2017 Page 3 of 4
10) Motion Robin, second Mark. Prioritize protection of beach street ends and beach access as a high priority adaptation measure per the current subcommittee draft. Vote passed 8-0-1 with Mark, Kristen, Nancy, Jon, Robin, Bruce, Kim, and Terry voting yes; Gabe abstained.
11) Motion Bruce, second Kristen. Include in the Adaptation Plan Executive Summary per the current Subcommittee draft that “At this time retreat is intentionally not included as an adaptation option for private property.” Vote 5-3-1 passed with Bruce, Kristen, Mark, Jon, and Terry voting yes; and Kim, Robin, and Nancy voting no; Gabe abstained.
12) Motion Robin, second Nancy. To delete the phrase “At this time” from the statement: “At this time retreat is intentionally not included as an adaptation option for private property.” Vote failed 3-5-1 with Robin, Nancy, and Kim voting yes; Bruce, Kristen, Mark, Jon, and Terry voting no; Gabe abstained.
13) Motion Mark, second Jon. STAC acknowledges it is intended that under the Adaptation Plan owners may choose adaptation strategies for their own property. Voted passed 8-0-1 unanimous with Mark, Kristen, Nancy, Jon, Robin, Bruce, Kim, and Terry voting yes; Gabe abstained.
14) Motion Robin, second Bruce. Include in the Adaptation Plan Executive Summary per the current Subcommittee draft that “Analyses of the financial and legal impacts of adaptation measures will be performed when any future project is initiated.” Voted passed 8-0-1 unanimous with Mark, Kristen, Nancy, Jon, Robin, Bruce, Kim, and Terry voting yes; Gabe abstained.
15) Motion Kim. To recommend option to create a Geologic Hazard Abatement District. Motion failed due to no second.
16) Motion Mark, second Kim. STAC recommends the City Council explore and pursue all options to finance strategies for adaptation. Vote failed 3-3-3 with Mark, Kim, and Nancy voting yes; Terry, Kristen, Bruce voting no; Jon, Robin, and Gabe abstained.
17) Motion Jon, second Mark. The Adaptation Plan should identify adaptation preferences for the Fairgrounds, Railroad, and Lake Hodges per the current Subcommittee draft, including the modification to Figure 7.1 (Living Levees along the San Dieguito River) as requested by STAC member Dustin Fuller on behalf of the Fairgrounds. Vote passed 7-0-2 with Mark, Kristen, Nancy, Jon, Robin, Kim, and Terry voting yes; and Bruce and Gabe abstained.
18) Motion Mark, second Jon. The Subcommittee should meet to put together a preliminary recommendation on the qualities of a walkable beach. Voted passed 8-0-1 unanimous with Mark, Kristen, Nancy, Jon, Robin, Bruce, Kim, and Terry voting yes; Gabe abstained.
19) Motion Mark, second Robin. The Subcommittee should revisit the corrections, cautions, suggestions, and requests collected by the Subcommittee for incorporation into the current draft. Vote passed 8-0-1 unanimous with Mark, Kristen, Nancy, Jon, Robin, Bruce, Kim, and Terry voting yes; Gabe abstained.
82 February 13, 2018 Item 01 3
STAC Minutes December 7, 2017 Page 4 of 4
20) Motion Mark, second Robin. City should conduct a survey of residents through an independent survey company before the City Council makes a decision on the Adaptation Plan. Vote failed 1-6-2 with Mark voting yes; Kristen, Nancy, Jon, Bruce, Kim, and Terry voting no; Robin and Gabe abstained.
Subcommittee will meet December 14, 2017 (to incorporate final non-substantive edits, draft memo/letter describing the perspectives and different issues that STAC grappled with regarding managed retreat, and draft a description of the qualities of a walkable beach) and will report back to STAC on January 25, 2018 for additional STAC action as needed to provide a recommendation on the Adaptation Plan as a whole.
5. CITY COUNCIL LIAISON COMMENTS
Mayor Worden and Deputy Mayor Druker thanked STAC for their hard work.
6. COMMITTEE MEMBER UPDATES None
7. STAFF UPDATES None
8. ORAL COMMUNICATIONS FROM THE PUBLIC (NON-ACTION ITEMS)
Dave Grubb (did not speak; had to leave meeting early) Laura DeMarco
9. ITEMS FOR FUTURE AGENDA
Adaptation Plan follow up; ESA Update on Sediment Management Plan & Wetland Habitat Migration Studies
10. ADJOURNMENT 7:41 pm motion to adjourn Fletcher, second Crabtree. Unanimous support.
83 February 13, 2018 Item 01 4 DRAFT MINUTES SEA-LEVEL RISE STAKEHOLDER-TECHNICAL ADVISORY COMMITTEE (STAC) CITY OF DEL MAR
DEL MAR (TEMPORARY) CITY HALL, COUNCIL CHAMBERS 2010 JIMMY DURANTE BOULEVARD, SUITE 100, DEL MAR 92014 THURSDAY, JANUARY 25, 2018 – 4:00 PM City Council Liaisons: David Druker, Dwight Worden
COMMITTEE’S STATEMENT OF MISSION/PURPOSE: Oversee the Sea-Level Rise Local Coastal Program Amendment process to make sure that the process is open, inclusive and develops consensus amongst the many stakeholders; to assist City staff and the consultant with the sea-level rise planning process; to assist in the review of technical studies and sea-level rise planning scenarios; to assist the community in prioritizing vulnerable coastal resources; to discuss and provide advice and policy recommendations to the Del Mar City Council; and to provide input to the Del Mar City Council on the Local Coastal Program Amendment process. (Ref. City Council Resolution 2015-10)
1. CALL TO ORDER
2. ROLL CALL Meeting start time 4:04 p.m.
STAC Attending: Chair Terry Gaasterland, John Imperato, Charles Fletcher, Mark Handzel, Robin Crabtree, Nancy Stoke, Dustin Fuller, and Kristin Brinner STAC Absent: Sarah Giddings and Gabriel Buhr City Council Liaisons Attending: Dwight Worden; Dave Druker Staff: Kathy Garcia, Amanda Lee, Adriana Jaramishian
3. APPROVAL OF MINUTES
Prior to the vote approving the minutes, Brinner raised a concern about votes taken by the advisory committee on December 7, 2017, and stated she believes several STAC members have a conflict of interest that should disqualify them from participating on certain votes due to financial interest. The Meeting Minutes for December 7, 2017 were subsequently approved by STAC with the understanding that the potential “conflict of interest” concern would be raised to the attention of the City Attorney. Motion Gaasterland, second Imperato. Motion passed by vote 7-1 with Handzel voting no. [City Attorney will advise.]
4. RECOMMENDATION TO CITY COUNCIL ON DRAFT ADAPTATION PLAN
Presentation by Chair Gaasterland on behalf of Subcommittee identifying changes made to the draft per STAC’s action at the December 7 meeting and additional minor corrections for STAC to weigh in on. Red dot correspondence from the Beach Preservation Coalition (cover letter, strikeout underline of STAC subcommittee’s draft memo on managed retreat, and Walt Crampton white paper) is posted on the web page.
The following speakers provided comments: Sheree Wade (speaking for Diana Lynch, Ocean Front) Walt Crampton (received time donation from Joy Buca, Sherri Hayward)
84 February 13, 2018 Item 01 STAC Minutes January 25, 2018 Page 2 of 5 Jon Corn (received time donation from Heather Lindsey, Lucille Lindsey) Tina Thomas
After STAC member questions and discussion on Item 4, STAC took the following actions:
1) Motion Handzel, second Crabtree. Keep option for armoring bluffs at Powerhouse Park in Adaptation Plan (AP) Section 8.1.4. Vote passed 7-1 (Brinner voting no).
2) Motion Crabtree, second Handzel. Keep the statement in AP Section 4.6 second paragraph: “After much discussion, STAC determined that it is too early in the process to include managed retreat as an adaptation option for Del Mar.” Vote passed 7-0-1 (Imperato abstained).
Consideration of whether to include a definition of walkable beach will be deferred to future sediment management plan discussions. No vote was taken. Text will be left as is.
Submerged reefs was not added as a specific type of adaptation option. Text will be left as is.
3) Motion Handzel, second Crabtree. Add introductory text to AP Chapter 3 (as read in record by Chair Gaasterland) to explain why the information was included in the AP. Vote passed 8-0.
STAC Member Stoke wants the AP document to identify the STAC membership. No vote taken.
Motion Gaasterland, second Imperato. Keep the managed retreat summary as a memo, return it to the Subcommittee to refine and polish, and incorporate red dot correspondence input. Motion withdrawn to allow STAC to continue with discussion to address and finalize the memo.
4) Motion Gaasterland, second Imperato. Delete notes listed at the end of Memo Section 10.6. Vote passed 8-0.
5) Motion Handzel, second Crabtree. List in alphabetical order the individual STAC member written statements on managed retreat in the memo. Ask the City Attorney if a descriptor (i.e. beach resident, bluff resident, Fairgrounds rep, or Surfrider Foundation rep) should be included for each STAC member. Allow each STAC member to opt in or out. Vote passed 8-0.
Motion Brinner that STAC member statements be the only thing in the memo. No second.
6) Unanimous consensus to delete a statement from the managed retreat memo introduction: “Ensuring the future of both natural resources and public infrastructure through accommodation or relocation was well accepted throughout the STAC process.” Vote passed 8-0.
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85 February 13, 2018 Item 01 STAC Minutes January 25, 2018 Page 3 of 5
7) Motion Gaasterland, second Handzel. Delete portion of the last statement in the second paragraph of the managed retreat memo introduction “- protect, accommodate, retreat-”. Vote passed 7-1 (Brinner voting no).
8) Motion Gaasterland, second Brinner. Delete statement (third sentence in second paragraph of memo section 10.1) relating to landward migration of the shoreline and what it could mean in North Beach. Motion fails by vote of 2-5-1 with Gaasterland and Brinner voting yes; Fletcher, Crabtree, Imperato, Stoke, Fuller voting no; and Handzel abstaining. Sentence stays in.
9) Motion Crabtree, second Handzel. To reconsider the highlighted statement (third sentence in second paragraph of memo section 10.1 considered in vote #8) in order to change “would” to “could”. Vote passed 6-1-1 with Gaasterland voting no; Brinner abstaining.
10) Motion Crabtree, second Handzel. Add “There is concern that” at the start of the last sentence in the second paragraph of memo section 10.1 and change the existing reference from “would” to “could”. Vote passed 7-0-1 (Brinner abstained).
11) Motion Crabtree, second Imperato. Anytime the managed retreat memo refers to “state guidance” it will be replaced with “Coastal Commission guidance”. Vote passed 7-0-1 (Brinner abstained).
12) Motion Gaasterland, second Handzel. Unanimous consensus to remove the reference “nearly equally” from managed retreat memo section 10.2. Vote passed 8-0.
13) Motion Gaasterland, second Imperato. Unanimous consensus to delete the parenthetical phrase “(both before and after the addition of two additional members from beach level neighborhoods)” from managed retreat memo section 10.2. Vote passed 8-0.
14) Motion Crabtree, second Imperato. Unanimous consensus to delete the statement in memo section 10.2 (following the parenthetical phrase that was deleted by vote #13: “Over a two and a half year period, the committee established its position on managed retreat with reliance on tools including the ESA report and much input from regional stakeholders, but with limited input from beach-level residents”. Vote passed 8-0.
15) Motion Gaasterland, second Handzel. Delete the last sentence from managed retreat memo section 10.2 “Further, STAC requested the City Council add two additional STAC members from the beach level neighborhoods.” Vote passed 8-0
16) Motion Gaasterland, second Imperato. Delete the last sentence from #3 in the managed retreat memo section 10.3. Vote passed 6-1-1 with Brinner voting no and Fuller abstaining.
17) Motion Crabtree, second Imperato. Replace “general majority consensus” with “discussion” under memo section 10.3 #7. Vote passed 8-0.
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86 February 13, 2018 Item 01 STAC Minutes January 25, 2018 Page 4 of 5
[STAC member Handzel clarified that Memo section 10.3 refers to the Adaptation Plan Section 2.1 discussion of Coastal Act goals. STAC member Brinner noted per California Public Resources Code section 30007.5, the legislature recognizes conflicts may occur between policies in the Coastal Act and they should be resolved in a manner which on balance is the most protective of significant coastal resources.]
18) Motion Crabtree, second Handzel. Unanimous consent to delete the highlighted/struck out sentence in memo section 10.4 “They must understand the perspective and decision making criteria that property owners employ to make sense of proposed SLR risk mitigation policies. For a managed retreat policy not to further heighten social, economic, legal and political conflicts,”. Vote passed 8-0.
STAC member Crabtree confirmed that the reference to 800 parking spaces in her statement in the memo was confirmed as correct by City parking enforcement staff.
19) Motion Gaasterland, second Crabtree. That the STAC recommend adoption of the Del Mar Adaptation Plan as a result of the revisions incorporated by STAC. Vote passed 8-0.
20) Motion Gaasterland, second Crabtree. To adopt the STAC memo on managed retreat as edited to accompany the Adaptation Plan. Vote passed 8-0.
[STAC member Fuller left the meeting after conclusion of Item 4.]
5. ESA PRESENTATION TO STAC ON PROPOSED APPROACH FOR THE SEDIMENT MANAGEMENT PLAN AND WETLAND HABITAT ASSESSMENT
Lindsey Sheehan, Hydrologist, Environmental Science Associates presented a power point with the proposed methods and approach for the Sediment Management Plan and Lagoon Habitat Evolution Assessment, which are the planning level technical analyses currently in process. [The power point is posted on the City’s web page with the January STAC agenda.]
The Sediment Management Plan will identify how sediment moves through Del Mar (from the river and along the coast) and how sediment transport may change with sea level rise in Del Mar. ESA is collecting the history of beach nourishment and dredging in Del Mar and relying on existing technical studies that are available relating to the littoral cell as a whole. A data gap identified is how sediment that moves in and out of the lagoon could change with sea level rise based on coastal wave forces, the inlet and beach morphology, and lagoon dynamics. The analysis will consider sediment transport along shore and across shore and will take into account existing shoreline protection and the differences sediment transport along areas with bluffs and within the lagoon inlet. They are using geomorphic models for their analysis. The work product will be a report with a long term sediment budget assessment (rates and patterns of deposition and erosion quantities of sand); and recommendations for a channel dredging plan and beach nourishment plan specific to Del Mar’s needs. A report draft should be available in March.
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87 February 13, 2018 Item 01 STAC Minutes January 25, 2018 Page 5 of 5 STAC member Stoke requested that ESA factor the City of Carlsbad project in progress to remove a pipeline that runs perpendicular to the beach. Lindsey confirmed that ESA is accounting for all factors that may affect sediment transport in the littoral cell.
At the request of STAC member Handzel, Walt Crampton agreed to provide the City/ESA with his artificial headlands concept as something that could be plugged into the model as a hypothetical.
The Lagoon Habitat Evolution Assessment will identify the habitats in Del Mar that are vulnerable to sea level rise and the potential patterns and locations for habitat to migrate into upstream and upland areas adjacent to the San Dieguito Lagoon. The analysis will look to understand the migration pattern for different habitat types and where the habitats are most likely to establish. ESA will use the SLAMM (Sea Level Affecting Marshes Model) model, which will consider variations in tides.
On February 22, ESA will return to STAC to present their initial findings on these studies.
STAC member Handzel requested the City add to the “wish list” the ability to have ESA test the viability of a living levee as an adaptation strategy.
6. CITY COUNCIL LIAISON COMMENTS
Mayor Worden and Deputy Mayor Druker congratulated STAC on reaching this milestone on the Adaptation Plan and thanked the STAC members for their hard work. If new comments come up as the Adaptation Plan process continues along, they are still welcome. STAC 2.0 is the next role for STAC to provide input on sediment management and STAC’s vision for the beach.
7. COMMITTEE MEMBER UPDATES
STAC member Crabtree requested a presentation on the City’s Beach Preservation Initiative. Mayor Worden volunteered to provide this as an information item on a future agenda. [See Del Mar Municipal Code 30.50 (Beach Overlay Zone) and City Council adopted BPI guidelines.]
8. STAFF UPDATES None
9. ORAL COMMUNICATIONS FROM THE PUBLIC (NON-ACTION ITEMS)
Dave Grubb
10. ITEMS FOR FUTURE AGENDA
Next meeting will include ESA’s Initial Findings for the Sediment Management Plan & Lagoon Habitat Migration Studies. Chair Gaasterland requested the information item from Mayor Worden on the Beach Preservation Initiative (BPI) be added to the next STAC agenda.
11. ADJOURNMENT
6:50 pm Motion Crabtree, second Imperato to adjourn to 2/22 meeting. Vote 7-0.
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88 February 13, 2018 Item 01 Exhibit B
Outreach Summary for the Del Mar Sea Level Rise Adaptation Plan
Over 20 public meetings were held to discuss the coastal resiliency planning in process and the proposed draft Adaptation Plan. This included 17 STAC meetings/workshops since September 2015. In addition, the STAC subcommittee met over 10 times and neighborhood specific meetings were held to help bring similarly situated stakeholders together. Three neighborhood-specific public forums focused on affected neighborhoods within North Beach and along the Coastal Bluffs were held by the City Council liaisons in the spring-summer of 2017.
Sea Level Rise Technical Advisory Committee (STAC) Council Advisory Committee Meetings (17 public meetings/workshops): 4 STAC meetings in 2015: September 24, October 15, November 5, and December 3, 2015 7 STAC meetings in 2016: January 14, February 25, April 14, May 5, June 9, July 21, and September 29, 2016 5 STAC meetings in 2017: June 22, August 24, September 21 (DMTV), October 26 (DMTV) and December 7, 2017 plus additional meetings of the STAC Subcommittee 1 STAC meeting to date in 2018: January 25, 2018 (DMTV) plus additional meetings of the STAC Subcommittee
Other Del Mar Coastal Resiliency Planning Forums in 2017 (3 public meetings): North Beach Public Forum 4/12/17 North Beach Public Forum 4/26/17 Coastal Bluff Neighborhood Public Forum 8/14/17
Press Releases and Newspaper Ads May 2016- notification of public availability of the draft Vulnerability and Risk Assessment October 2016- notification of public availability of the draft Adaptation Plan January 2018- published notice of public availability of the draft Adaptation Plan/Notice of public hearing of the Planning Commission on February 13, 2018
Mailed Public Notice April 2015- announcing vacancy opportunities for STAC March 2017- Notice hand delivered to all addresses and Mailed notice sent to all owners and residents in North beach announcing April public forums hosted by Council liaisons July 2017- Mailed notice sent to all owners and residents in coastal bluff neighborhoods announcing August public forum hosted by Council liaisons August 2017-January 2018- Mailed notice sent to all owners and residents in coastal resiliency planning area for STAC meetings in August, September, October, and December 2017, and January 2018
89 February 13, 2018 Item 01 Exhibit B
January 2018- Mailed notice of public availability of the draft Adaptation Plan/Notice of public hearing of the Planning Commission on February 13, 2018
Email/Text blasts via Notify Me Database: “Notify me” is a City database for individuals to voluntarily sign up for email or text notifications. Regular updates have been sent since April 2015 to interested persons in the database. In June 2017 the database was greatly expanded to reflect increased participation by residents and owners in the coastal resiliency planning area. All attendees who signed in at a STAC meeting (June 22, 2017 to present) were added to the “notify me” database. Prior to June 22, 2017 interested persons were added only if they signed up for “notify me” online themselves or requested staff to sign them up. In all cases, email confirmation is required in order for the individual to receive notifications- this is an automated feature of the “notify me” technology
City Managers Weekly Updates:
Since 2015, the City Managers weekly updates have included notice of upcoming STAC meetings, grant funding awarded to the City to help fund the planning project, and other items of interest relating to project milestones and opportunities for public participation.
Climate Kids Art Exhibit:
The City of Del Mar hosted the Climate Kids Art Exhibit (sponsored by the Climate Science Alliance) at the Del Mar Library and City Hall in September-October 2017. The art exhibit and activities at the library helped to bring public attention to the coastal resiliency planning occurring within Del Mar and at the regional level.
90 February 13, 2018 Item 01 Exhibit E
Additional Adaptation Plan Revisions for Consideration The following additional minor corrections are proposed to address technical inconsistencies and minor clean- up edits from the STAC working draft (1/11/18) Adaptation Plan version:
Description Proposed change/rationale 1 AP Section 1.3 – Amending Delete “schools” and “hazardous materials” from list of determined the LCP vulnerabilities. Explain that the low sea level rise scenario is based on dramatic reduction of fossil fuel use, which has not yet occurred.
2 AP Section 1.6 – Purpose of Clarify the AP is a “tool box” that will provide the basis for developing Adaptation Plan new policies in the Local Coastal program and that the AP strategies included are based on the technical analysis from the Coastal Hazards, Vulnerability and Risk Assessment (ESA 2016) that used flood risk and shoreline change modeling.
3 AP Chapter 2 – Defined From the list of definitions in the prior working draft, only “adaptation”, Terms “coastal erosion”, “coastal flooding”, and “tidal inundation” were actually used within the AP document to help explain terms where the common dictionary meaning of the term is not intended and/or where clarification of intent cannot be readily explained in each context where the term is used. Delete terms that are not referenced within the AP.
4 AP Chapter 3 – Coastal To maintain the strong scientific basis in the Adaptation Plan (as Processes and Human prepared by Environmental Science Associates), transfer STAC’s Adaptations recommended Chapter 3 to be an Appendix of the AP (together with the City’s Sediment Management Plan) and renumber the AP Chapters.
Chapter 3 was drafted by STAC as a collection of references to various documents prepared by a variety of sources non-specific to Del Mar (2001-2016). This was helpful to facilitate public discussion in the interim on the dynamics of sediment transport while the Del Mar-specific Sediment Management Plan is finalized by City consultant, Environmental Science Associates. The analysis in Chapter 3 was not peer reviewed for technical accuracy. Instead, the Sediment Management Plan is what will serve as the City’s supporting technical document to describe how sediment moves through Del Mar from the river and along the coast, and the City’s long term plans for river channel dredging and beach nourishment.
5 AP Chapters 5-9 – Sediment Update the document to defer to the findings and conclusions of the Del Management References Mar Sediment Management Plan in order to minimize or avoid the potential for statements in conflict within the AP.
6 AP Chapter 6- San Dieguito Clarify that the purpose of Chapter 6 is to include adaptation measures Lagoon Wetland Adaptation to address wetland habitat resiliency for the Lagoon.
91 February 13, 2018 Item 01 STAC Memo to City Council Revised January 25, 2018
From: The Sea Level Rise Technical Advisory Committee To: City of Del Mar Council Members Date: January 25, 2018
Managed Retreat in Del Mar
The Sea Level Rise Adaptation Plan aims to keep risks related to sea-level-rise within acceptable limits. The planning process identified vulnerabilities in the City of Del Mar, considered strategies to limit risks, and evaluated the feasibility and application of those strategies within the context of Del Mar. Following Coastal Commission guidance, adaptation options fall into three categories. They can protect property, for example, through improved sea walls, levees, beach replenishment, or river channel dredging. They can accommodate changes due to sea level rise, for example, by raising structures or adding sediment to wetlands to maintain vegetation elevations. The third category of adaptation options involves managed retreat and became the focus of much debate, discussion, and deliberation. Adaptation through managed retreat allows wetlands to migrate and expand; relocates public infrastructure, including, for example, roads, utilities, sewers, storm drains, fiber optic cables, and railroad equipment; and creates incentives to remove or relocate private property when extreme risks arise.
As STAC deliberated and received communications from the citizens of Del Mar, managed retreat through wetland migration and expansion never raised issues. Del Mar values the San Dieguito River and river-mouth, its associated wetlands, its beaches, and its bluffs as important natural resources. Protecting these resources and ensuring access emerged as a high priority. Likewise, managed retreat through relocation of public infrastructure was accepted. Public buildings at risk include the fire station, public works, the sewer lift station and park facilities. Other vulnerable public infrastructure provides essential services to citizens and access to beaches, bluffs, and lagoon for public benefit and enjoyment. They include sewage management, internet access, storm drainage, transportation and parking, lifeguard stations, and public safety equipment. The Adaptation Plan includes options at all levels for Del Mar’s shared vulnerable resources.
In contrast, managed retreat as an adaptation strategy for private property emerged as contentious and fraught with economic, legal, societal, and multi-faceted financial impacts, as well as physical constraints. This Memo aims to review and summarize two and a half years of structured discussion among STAC members and citizens of Del Mar regarding managed retreat as applied to private property.
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California Coastal Commission guidance is lacking on retreat in urbanized beachfront Sea level rise adaptation strategies aim to manage risks to Del Mar’s public and private property, natural resources, infrastructure and assets. Consideration of managed retreat as an adaptation strategy involved a wide range of perspectives, a high level of emotional response, and fundamental disagreement over whether and how to include “managed retreat” in the Adaptation Plan as an adaptation strategy.
The California Coastal Commission guidance on managed retreat discusses retreat as an approach to allow shorelines to migrate inland. In Del Mar, this view of managed retreat is insufficient as guidance for planning for amending the LCP, especially in light of Del Mar’s topography. Landward migration could eliminate rather than relocate the sandy beach and the public access to it (which is in direct conflict with the policy of enhancing public beach access). The City of Del Mar includes over two miles of high density, urbanized beachfront, both at beach level and atop ocean bluff. Residents and visitors have unfettered access to broad beaches. Del Mar’s beaches, beachgoers, and over 600 beach-level homes would be negatively impacted by managed retreat. There is concern that landward migration of the shoreline could mean that wetlands and river- mouth will replace the public benefit of a well-used and walkable beach, a residential community, an urban environment with businesses, restaurants, a motel, parks, and a community center, and associated roads and public infrastructure.
While the California Coastal Commission guidance emphasizes “prioritizing natural infrastructure”, it lacks discussion and analysis on retreat in an urbanized context. Expanded guidance is needed to consider how managed retreat may or may not be a viable adaptation strategy in Del Mar specifically, and more generally, in urbanized shorelines or in areas where there is no contiguous open space for the shoreline to migrate inland and connect to. Without balanced and informed guidance on retreat in urbanized, medium-density beachfront areas, local groups must apply common sense and values when considering retreat. In short, existing guidance prioritizes natural infrastructure without addressing the economic and legal impacts of replacing private property with wetlands and beaches and introducing substantial new risk of flooding to adjacent private properties and public infrastructure. The guidance documents lack adaptation examples applicable to Del Mar’s established beachfront neighborhoods. The documents defer to a jurisdiction’s risk tolerance and lack discussion of how to apply managed retreat to urbanized beachfront via the Local Coastal Program Amendment process.
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STAC consideration of managed retreat in Del Mar In Del Mar’s sea level rise policy planning process, managed retreat for private property was the most controversial issue that the STAC committee evaluated and debated. The committee has been and continues to be divided on this issue In the first year of deliberations, managed retreat was included in the STAC’s draft Sea Level Rise Adaptation Plan as an option for all regions (wetlands, river, bluffs and beaches). In the second year, STAC evaluated the impacts and implications of managed retreat to each area and realized that for Del Mar, managed retreat of private property had profound economic, societal, and legal implications, and could, in fact, increase risks rather than limit them. STAC decided to exclude private property managed retreat completely in its final version of the document.
Foundations of STAC’s position on managed retreat STAC’s position on managed retreat for private property resulted from discussion, debate, and evaluation of the following factors:
1. The voter approved Beach Protection Initiative (BPI) and certified City of Del Mar Local Coastal Program allow seawalls in the beachfront region from 15th St. north to the river-mouth.
2. Vocal and committed community engagement on private property managed retreat clarified that it will impose significant costs to Del Mar. For example, the inclusion now of private property managed retreat strategies will increase market uncertainty and potentially reduce land values at a time when much remains unknown regarding how SLR will evolve over the short and long term.
3. Approaches to managing coastal erosion have different distributions of benefits and costs to community at local and regional levels. Hard engineering options (e.g., sea walls) may protect community or private assets but the beach in front of the structure has potential to erode and result in loss of beach. In such a case, beach amenity and use for locals and visitors are lost in favor of protecting homes and or infrastructure; and significant downstream impacts (e.g., loss of tourism industry) may also occur.
4. The committee determined that the City of Del Mar would benefit from a better understanding of the future implications of seawalls in North Beach. Further, the City would benefit from investigating all possible adaptation options that have potential both to maintain the beach and to protect property before starting to consider private property managed retreat strategies.
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5. Success of hard and soft engineering options is highly dependent on the nature of the physical environment, the affordability of the mitigation measures and successfully negotiating an outcome that reconciles different contending interests. Some managed retreat actions may well emerge as a component of other adaptations as balanced, well-considered projects are planned.
6. There was discussion within the committee that managed retreat should be considered only as a last resort after all other adaptation strategies have been fully evaluated and determined not to be viable, and is not an appropriate adaptation strategy for Del Mar.
7. The third goal in the California Coastal Act needs to be more fully understood. It specifies that decisions impacting the California Coast must be made to: "Maximize public access to and along the coast and maximize public recreational opportunities in the coastal zone consistent with sound resource conservation principles and constitutionally protected rights of private owners."
Next steps The challenge for the Planning Commission and the City Council in developing coastal policy over the next decade will be to design and implement institutional arrangements that prevent and/or resolve legal, financial, engineering and social conflicts in coastal locations threatened by accelerated Sea Level Rise. Many government agencies and key stakeholders argue that there is a need to mitigate the risks of SLR by modifying the coastal urban planning framework. However, strong evidence indicates that risk mitigation policies that are unpopular and socially divisive in the shorter term will not be accepted over the long term. In general, policies designed to manage long term risks tend to be controversial. Therefore, community involvement will continue to be central to the success of strategies for gaining public acceptance of schemes designed to reduce long-term risks.
Finally, the public should be engaged in deciding how to manage the long-term risks of SLR and in determining the actions to be undertaken under various SLR scenarios. While public engagement is time consuming and expensive, it is important for policy makers to understand and respond to community concerns, match policy to community needs wherever possible, and give the community a greater sense of ownership over the design and implementation of new policy. It is critically important that the Planning Commission and the City Council make the best possible decisions for the Del Mar community they serve while not negatively impacting public access to the beach. Both the Planning Commission and the City Council must define a process to understand the concerns of various constituents and engage in dialogue with the community.
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Range of positions on managed retreat
STAC MEMBER, Surfrider Foundation Representative – K. Brinner Address managed retreat now. We need to face the issue of Sea Level Rise head on, now, proactively. By removing managed retreat as an adaptation option from the Adaptation Study, we have removed what might be our only option once seas have risen above a certain level. When this will occur, no one knows. Originally we tied the managed retreat option to the amount of sea level rise, frequency of coastal flooding, and the loss of a walkable beach. By coupling retreat to these triggers, we were not saying when retreat might be necessary. We were simply reinforcing two of the STAC’s guiding principles: maintaining a walkable beach and reducing flood risk. Without retreat as an option, we have abandoned these guiding principle. Under the high SLR scenario, beaches in Del Mar will be lost if the back of the beach is fixed by sea walls. Low-lying areas in North Beach will be continually flooded by storm and high-wave events. No amount of sand replenishment, sand retention devices, or even the complete restoration of natural sand supply through returning rivers to their undammed state will be able to prevent beach loss and flooding if the beaches are not allowed to move inland in face of rising tides. How to compensate private property owners and how to manage the process of retreat are important questions that will take years, possibly decades to work out. We need to start that conversation now. By removing retreat as an option, we are deciding against starting this difficult conversation. By removing retreat as an option, we will be forced to react quickly, without as much time to examine the financial, legal, and social issues associated with managed retreat. Decisions are better made with time and information; by removing retreat as an option, we may be forced to make decisions quickly, without all of the needed information, and our options will be more limited. The entire STAC voted overwhelmingly in support of these guiding principles. These guiding principles were not made in isolation - they are supported by the California Coastal Act and the Del Mar Community Plan. The public has an inherent right of access to and along all beaches and shorelines. We have not acted in the beach-going public’s or the community of Del Mar’s best interests by removing retreat as an adaptation option. The beaches are a public trust, and belong to every Californian. Without retreat as an option, we are abandoning our beaches in interest of the protection of private property, contrary to the laws and guidelines of Del Mar and the state of California.
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STAC MEMBER, Beach Resident – Robin Crabtree Public beach access depends on protection and accommodation. Sea Level Rise is an environmental change that all beach goers and Del Mar residents will need to adapt to any changes that occur. We do not know exactly how much sea level will rise and when it will occur or how soon. With this Adaptation Plan, Del Mar will now gather monthly and yearly data in order to identify any changes. As changes occur, it will be important that adaptation options are thoroughly reviewed including any new options being used nationally and internationally. One example to monitor is the research of the effectiveness of different shapes of seawalls in Japan. STAC has acted in the interest of both the beach-going public and the Del Mar residents. A walkable beach is a high priority with our residents and visitors! STAC with Del Mar resident input reviewed the option of managed retreat of private property and together most believe it is not appropriate at this time. There are so many options to be reviewed and utilized before any discussion ever needs to take place regarding managed retreat of private property. There are over 600 homes in the Del Mar beach community with the homes along the beach behind sea walls at about 13 feet above sea level. East of the beach, the homes and properties decrease to eventually 3 feet above sea level before reaching the railroad tracks. In addition, within the beach community, over 800 public parking spaces allow public access to the beach. If the homes are gone, the parking is gone, beach access is gone and now the visitors and residents are gone! Where is the walkable beach? Before any discussion of managed retreat of private property begins, an engineering evaluation of the beach community and managed retreat needs to be completed. I direct you to the technical paper titled “The Practicality of Managed Retreat” written by expert Walter Crampton. Therefore, managed retreat of private property is not an appropriate adaptation option to be included in this Del Mar plan.
STAC MEMBER, Beach Resident – Kim Fletcher Managed retreat is not suitable for Del Mar’s North Beach. I am more convinced now than when I first attended a STAC meeting, that Managed Retreat is not suitable for the Del Mar North Beach - 600 residents could be victimized by waves and flooding. The economic loss to the City of Del Mar and private homeowners would be disastrous. We should exhaust all possible alternatives first; such as Sand Retention and Replenishment, as well as Groins, proper regulating the tide flow of the San Dieguito River. I have been on the Del Mar Beach my enter life and permanently for 28 years. We lost most of our sand in the period from the late 70's to early 80's. Since then the loss has been much less. Let's not rush into Managed Retreat until we have more facts.
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STAC MEMBER, Bluff Resident, Committee Chair – Terry Gaasterland Managed retreat applies differently across Del Mar’s diverse regions. Protecting our natural resources in Del Mar – our beaches, our wetlands, our bluffs – is a top priority and drove much of STAC’s deliberation. Del Mar’s natural resources include a wide sandy beach ranging from urbanized oceanfront to high bluffs fronted by broad sand and reefs that make waves ideal for surfing. Del Mar residents and visitors enjoy running and walking on the beach, spending hours on a sunny day near the surf with towels, picnics, and happy children at play. Surfers from far and wide join the local surf crowds at 8th St, 11th St, and 15th St and on down to the river-mouth. Beach enjoyment happens year-round, in all months. On nearly every day of the year, runners and walkers can continue for nearly 3 miles from lagoon to lagoon – albeit at low tide only when winter storms have washed the beach sand into the offshore reefs. This beach resource, complemented by Del Mar’s canyon paths and wetland overlooks, comprises Del Mar’s most important asset. It draws newcomers and visitors and adds great value to homes and businesses. It must be protected, nourished, and cared for with highest priority as sea level rise planning moves forward. Del Mar’s STAC studied the many adaptation options identified throughout California as the state and other localities evaluated vulnerabilities and how to minimize them. STAC has drafted this Adaptation Plan to minimize risks in all areas of Del Mar. Protection and accommodation options will be the most important while sea level rise remains steady and slow. STAC regarded managed retreat as wise for some areas, including the lagoon wetlands and the bluff tops. However, STAC recognized, with much community input, that managed retreat in the oceanfront area of North Beach has complexities and implications that go far beyond the guidance received from the State. Specifically, STAC came to understand that managed retreat in the beach-level communities means losing beach access, putting sea-level (or below) homes to the east at greater risk, and loss of property, infrastructure, and resources. In short, STAC could see clearly how managed retreat options can be applied in wetlands and bluffs, but could not come to census or develop a clear view of how managed retreat options could apply in the urbanized oceanfront areas without introducing new vulnerabilities, loss, and risk. Many other options to protect and accommodate have yet to be explored in detail. Many are promising and have potential to maintain Del Mar’s natural resources in much their current state for many decades to come. Thus, STAC decided – in a vote that involved all members, after much community input – it is premature to include managed retreat for private property in the current STAC draft Adaptation Plan.
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STAC MEMBER, Bluff Resident, Committee Secretary – Mark Handzel Private property managed retreat is a complicated issue that the voters of California should decide. Classic Free Rider Problem of Sea level Rise: Sea-level rise is by definition a phenomenon that affects every California coastal community as a result of CO2 emissions. When it comes to reducing carbon emissions there is a classic free rider problem. The free rider problem is a market failure that occurs when people take advantage of being able to use a common resource, or collective good, without paying for it, as is the case when citizens of a country utilize public goods without paying their fair share in taxes. Coastal communities would benefit from lower emissions by relying on the public to make sacrifices and reduce their pollution levels. Sea-level rise is to a large extent caused by externalities. When you drive an SUV, the contribution to climate change and sea-level rise is an external cost which you don't experience personally. Free markets are notoriously bad at including external costs in prices. The consequence is that there is over-consumption of goods which pollute and cause sea level rise. In theory, economics has a solution to the problem of externalities. If you can work out the external cost of driving an SUV, you can place a suitable tax to make people pay the social cost and reduce demand to the socially efficient level. The difficulty is working out and then agreeing on a suitable external cost. If the real cost of climate change and sea level rise is as high as current science indicates, it would suggest carbon emitting vehicles are seriously undertaxed and the social cost of carbon emissions is much higher than current legislation suggests. The difficulty then also becomes convincing the general public that due to the external costs of pollution there is a need to establish a carbon tax to acquire private property via managed retreat. Consideration of private property managed retreat is premature and requires additional local and state guidance: As a result of the free rider problem, it is clear that a private property managed retreat policy will impose the most significant and unfair costs on affected coastal communities. Another problem with sea-level rise is that there is tremendous uncertainty about the future costs of sea-level rise. The imposition of private property managed retreat strategies for pre-existing communities will certainly increase market uncertainty and reduce land values. Local communities should adopt voter-approved initiatives similar to New Zealand, where the Queensland Sustainable Planning Act requires local councils to compensate owners when a planning decision reduces property values (section 704). Thus, local communities need to resist private property managed retreat strategies until a dedicated statewide funding source is created. It is recommended that a dedicated State of California funding source, such as a carbon tax, for fair market land acquisition be established before private property managed retreat is required in any community plan. A voter proposition on the California ballot would be the best way for California to determine if the public values
8 99 February 13, 2018 Item 01 STAC Memo to City Council Revised January 25, 2018 their beaches enough to impose a carbon tax. If the California people do value their beaches, then they should be more than willing to impose a state-wide carbon tax to implement private property managed retreat. In summary, private property managed retreat is a complicated issue that the voters of California should decide.
STAC MEMBER, Beach Resident, Committee Vice Chair– John Imperato Managed Retreat is a “Last Resort” Option Managed Retreat results in loss of public beach access: Consequences of designating Del Mar’s North Beach as a Managed Retreat (“MR”) zone are immediate and significant and should be weighed against any possible benefits of MR. North Beach residents have been vocal in their opposition to the inclusion of Managed Retreat in Del Mar’s Sea Level Rise Adaptation Plan. Proponents of Managed Retreat see this option as “essential to securing beach access” in view of predicted sea level rise. Furthering the dialog between these opposing viewpoints requires questioning the presumed nexus between managed retreat and beach access. This was done in the untelevised STAC meeting in November 2017 and the answer was that due to topology of North Beach, Managed Retreat would revert the beach into a wetland with no remaining beach access. Experts posit that removing the sea walls, or not repairing breached sea walls under the MR scenario, would cause the shoreline to meander and ultimately move inland in an easterly direction. This would merge the shoreline with the river wetlands, turning the North Beach area into a low-lying wetland. There would be no accessible beach with this dynamic migrating shoreline. Accordingly, the mantra “Managed Retreat must be included in the toolkit because it will provide public beach access” repeated by proponents of Managed Retreat is neither accurate nor productive. In fact, no examples or explanations illustrating how Managed Retreat would improve beach access have been presented proponents of Managed Retreat. Under a Managed Retreat scenario, beach access is forfeited to the wetlands. Stated another way, once the beach walls are compromised under Managed Retreat, beach access will ultimately be eliminated. In distinct contrast, Del Mar’s North Beach currently provides public access and free parking at every street end, which makes Del Mar a shining star for beach access among all of California’s beach towns. This beach access can be preserved through the other adaptation options presented. Designating North Beach for Managed Retreat would have an immediate impact on Del Mar. Property values would drop and property owners in North Beach would likely petition for property tax reductions. Increased disclosure requirements of the Managed Retreat designation would encumber real estate transactions, and reluctance of
9 100 February 13, 2018 Item 01 STAC Memo to City Council Revised January 25, 2018 commercial lenders to lend into North Beach under current lending practices would bias North Beach into a “cash only” economy. This would destroy the economic diversity of the North Beach and make North Beach only available to cash buyers. North Beach would have a hard time absorbing the negative impact of a Managed Retreat zone designation. Because Managed Retreat results in lost beach access and losses to private property, this adaptation option, if included in the proposal by Del Mar’s City Council, should be presented as the last resort it really is. Managed Retreat is an “all lose” scenario. Managed Retreat Cannot be Justified as a Preferred “Natural’ Option: Del Mar currently has a serious problem that exists independent of sea level rise - the upland San Dieguito watershed above and below the Lake Hodges Dam, which provided over seventy percent of the natural sand replenishment for Del Mar has been severely compromised by development. The jetty construction at Oceanside Harbor has further starved the nature beach replenishment mechanism. The California Coastal Commission preference of Managed Retreat as a “ more natural option” at this point in the development cycle cannot be justified in view of the past wholesale destruction of the natural replenishment mechanisms that will only be amplified by sea level rise. The Coastal Commission cannot justify rejecting Del Mar’s modified LCP on the grounds that it fails to include a Managed Retreat option solely because it Managed Retreat a “more natural approach”. Managed Retreat must be considered in the face of the lost beach access and negatively impacted private property values that would result.
STAC MEMBER – Beach Resident, Nancy Stoke, 40 year resident of Coast Blvd.\ Retreat strategies are not appropriate for Del Mar In the North Beach area of Del Mar there are just under 600 residences that would be directly and immediately impacted by the inclusion of a retreat strategy. Due to the topography of the North Beach area, the highest part of the neighborhood is the line of homes on the sand that are protected by individually financed sea walls. Removal of those sea walls will impact the beach-visiting public and every home in the North Beach area, as those behind the front row are all at lower elevation and the entire neighborhood will become a wetlands and will not remain a walkable beach. It is impossible to find a public benefit in the removal of homes that are in the most densely populated area of the city and provide housing for those of the lowest economic level. The North Beach area is also the most visitor-serving area of Del Mar; it has over 800 public parking spaces and is one of few places in the region that has public access to the beach at every block between 15th St and 29th St and public restrooms/showers at the lifeguard towers in multiple locations. From an economic standpoint, the homes on the sand generate the most property tax revenue for the city; the city would have a difficult time replacing that revenue and still providing required services. And if designated and zoned for retreat now the homes in
10 101 February 13, 2018 Item 01 STAC Memo to City Council Revised January 25, 2018 the neighborhood will be unable to obtain financing, home sales will have to be cash- only transactions, and property values and resulting property tax revenues will be negatively impacted. CA Hwy 1 and the major railway run through the middle of the North Beach area. It could be re-built to be elevated above the wetlands that would exist if the homes were removed. That would do nothing to serve public access to a walkable beach, as there would be no walkable beach. The Fairgrounds is an important public asset that generates significant revenue for the State and the region; it provides a wide variety of cultural and recreational activities and is the home of one of the most highly recognized and awarded County Fairs. Again during the recent firestorms the Fairgrounds has proven to be an invaluable treasure as an evacuation site during times of regional emergency. A managed retreat strategy is not appropriate for the Fairgrounds; its many public uses must be protected and maintained. We live among the most renowned climate and oceanographic scientists in the world. Surely there will be new ways to combine a walkable beach with sea level rise without resorting to retreat and total loss of the public beach that so many love and use on a regular basis. It was only 30 years ago that cellular phones had to be hard-wired into vehicles. Surely there will be something new that doesn’t exist today that will allow Del Mar to manage sea level rise with tools other than retreat. Retreat may be an acceptable strategy for other areas of the CA coast that are not highly populated and are of a different topography. Retreat is not an appropriate strategy for Del Mar.
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The Infeasibility of Managed Retreat for the City of Del Mar: A White Paper
Geotechnical Engineering The California Coastal Commission Sea Level Rise Policy Guidance Document provides a Coastal Engineering chapter on adaptation strategies to effectively address coastal hazard risks and to protect Maritime Engineering coastal resources, accounting for the uncertainties surrounding projections of sea level rise over the next century and beyond. The Commission document notes that adaptation strategies should be chosen based on the specific risks and vulnerabilities of a region or project site, and the applicable Coastal Act and Local Coastal Plan (LCP) requirements, with due consideration of local priorities and goals. Adaptation strategies may involve modifications to land use plans, regulatory changes, project modifications, or permit conditions that focus on avoidance or minimization of risks and the protection of coastal resources. The adaptation options described in Chapter 7 of the Commission’s Sea Level Rise Policy Guidance Document are intended to provide guidance for potential LCP and permitting strategies. It is important to recognize that not all strategies listed in Chapter 7 are or will be appropriate for every jurisdiction, as each represents unique geographies and geomorphologies.
Chapter 9 of the Sea Level Rise Stakeholder Technical Advisory Committee (STAC) Report dated January 11, 2018, summarizes the viable beach erosion and flooding adaptation strategies considered appropriate for Del Mar. Notably absent from Del Mar’s beach erosion and flooding adaptation strategies is the concept of managed retreat. Coastal Commission Staff argue that this adaptation strategy must be included in the City of Del Mar’s Adaptation Plan. The Coastal Commission’s Sea Level Rise Policy Guidance Document provides significant discussion and recommendations for incorporating managed retreat into future LCPs to help property owners (public and private) plan for and address future sea level rise, storm surge, coastal flooding, and erosion. Given the available technical data, it would appear that managed retreat is not a viable adaptation strategy for the City’s North Beach and Valley Districts and has not been included in the City of Del Mar’s Sea Level Rise Adaptation Plan. The basis for this conclusion follows.
The City of Del Mar’s Unique Geology and Geomorphology
Given the Coastal Commission’s current stance against shoreline protection devices, it is conceivable how certain agencies, along with environmental groups, could possibly embrace
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managed retreat as a viable adaptation strategy for preserving the City of Del Mar’s unique coastal beach experience. However, one of the features that makes the City of Del Mar’s, and particularly Del Mar’s North Beach, so unique is its coastal geology or, more specifically, its geomorphology or the evolution of this very unique coastal city. Del Mar’s North Beach is truly unique and along the state’s 1,100-mile coastline, is one of only nine small coastal segments having similar geomorphology. Del Mar’s unique geomorphic character lies in its location at the mouth of the San Dieguito River, with the San Diego Lagoon creating a truly unique coastal experience along Del Mar’s approximately 4,400-foot- long North Beach.
In the recent geologic past, the San Dieguito River mouth, as it empties into the ocean, would migrate from the City’s northerly headlands adjacent Dog Beach southerly down to Power House Park, with the actual active width of the river mouth only several hundred feet wide to maintain the necessary ebb flow tidal velocities to keep the river mouth open.
During the last ice age about 18,000 years ago when sea level was about 400 feet lower and the shoreline at the time about 2½ miles further seaward, North Del Mar was a coastal valley not unlike San Diego’s Mission Valley, with a relatively level valley floor with its elevation about 120 feet below the sea level of today; albeit still about 280 feet above the ancestral shoreline at the time. This ancestral shoreline represents the edge of the very gently sloping continental shelf through which all of the major ancestral rivers have incised as all of the coastal rivers flowed westward. As sea level again rose after the last ice age, these ancestral rivers became drowned out, with river sediments then deposited within these incised submarine and now-buried ancestral rivers. Interestingly, the ancestral San Dieguito River, in 60 feet of water (or about 4,000 feet offshore), is where SANDAG mined substantial quantities of sand for its regional beach nourishment projects in both 2001 and 2012, with this ancestral sand source off of Del Mar representing a very good quality coarse alluvial sediment, and used it on several of San Diego’s North County beaches in 2001, and again in 2012.
As sea level continued to rise up to contemporary times, the coastal lagoons – including the San Dieguito Lagoon – were eventually filled in with alluvial sediments, with the surface of the San Dieguito Lagoon today, although somewhat variable in elevation, typically at no more than elevation +3 feet NGVD 29. It is on this contemporary lagoonal surface that man extended both roadway embankments and a railroad embankment, the Del Mar Fairgrounds,
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and of course at least the eastern portion of the urban area we now refer to as Del Mar’s North Beach.
The seaward face of this lagoonal deposition was then further affected by longshore sand transport within the 52-mile-long Oceanside Littoral Cell. Alongshore sand transport is driven by waves breaking at an angle to the shoreline. It is generally southward in winter and northward in summer. Estimates of long-term transport potential for the Oceanside Littoral Cell average about 750,000 cubic yards per year to the south, and 550,000 cubic yards per year to the north (USACOE, 1991). This means that a total of about 1.3 million cubic yards of gross sand transport per year are capable of being mobilized, with a net southward rate of about 200,000 cubic yards per year.
It is this longshore sand transport that further alters the seaward edge of the lagoon, with the foreshore (in the presence of sufficient sand) created and built up as normal waves passing through the surf zone place material in suspension, thus loading the uprush water with sand. The broken wave swashes up the beach face, with its water percolating through it, eventually to be returned back to sea. The down rush is smaller than the uprush due to this percolation, and therefore cannot carry much of the sediment load back down the beach face, with the process causing the beach to accrete. The backshore, and ultimately the beach berm itself, is a result of the landward accretion from waves during more severe storms.
Within the recent geologic past in Del Mar, this beach berm formed along the seaward edge of the San Dieguito Lagoon, with the crest of the beach berm being relatively uniform at about elevation +13 feet NGVD 29, and it was on this back beach that the first row of houses were constructed in Del Mar running from Power House Park to the river mouth. The width of the beach berm across the river mouth was also relatively uniform, with its seaward edge since being eroded away. However, its landward edge more or less coaligns with Ocean Front, which exists throughout Del Mar North at around elevation +10 feet. The back of the beach berm continues to descend at a relatively uniform slope down to Camino Del Mar, which is typically around elevation +7 feet. Easterly of Camino Del Mar extending to the railroad embankment, the ground surface drops to a relatively uniform topographic low of around +6 feet, creating a relatively large basin between Camino Del Mar and the railroad tracks that, at times, has experienced flooding when waters exceed the capacity to drain northerly back to the San Dieguito River. An illustrative cross section is provided (Figure 1) through Del Mar’s North Beach, easterly to the railroad tracks and then continuing easterly
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into the San Dieguito Lagoon. While the cross section shown on Figure 1A was drawn with no vertical exaggeration and shows the relatively flat Del Mar North Beach area, Figure 1B, with a 10 to 1 vertical exaggeration, clearly shows this very unique geomorphic condition that only exists along eight other river/lagoon mouths along the 1,100-mile-long California coastline; namely, San Diego’s Mission Beach, Newport’s Harbor Island, Sunset Beach, Alamitos Bay Peninsula, Channel Islands Harbor Beach, Ventura, Carpinteria-Sand Point, and Moss Landing just south of San Francisco.
Figure 1 also includes a typical seawall protecting the seaward-most row of North Beach homes, with a top-of-wall elevation of +15 feet. Upon reflection, it should be obvious that if the seaward row of homes along Del Mar’s North Beach were removed to accommodate planned retreat, the next row of houses on the east side of Ocean Front are typically about 3 feet lower in elevation and presumably would need even a higher seawall elevation, say at +16 to+18 feet, or 6 to 8 feet above the first-floor of the next row of residences.
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Figure 1: Typical seawall protecting the seaward-most row of North Beach homes, with a top-of-wall elevation of +15 feet
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As reach progressive row of residences is removed, the coastal erosion problem becomes more acute, with each easterly seawall required to become taller in elevation, completely at odds with the guiding land use goals and principles outlined in Chapter 2 of the STAC Report.
The adaptation strategies outlined in Chapters 8 and 9 of the STAC Report work well for the City of Del Mar, while in contrast, managed retreat, at least in this very unique geomorphic environment, cannot work and still provide the goals espoused by the citizens of Del Mar and the City’s elected officials.
The economic value of this state’s beaches is undisputed, particularly in Del Mar, and given the specter of a potential one, to worst case two meter rise in sea level by the end of the 21st century, beach nourishment remains a viable adaptation strategy, particularly when incorporating sand retention structures, with the annualized cost of beach nourishment incredibly small compared to the wholesale loss of the 600+ residences in North Beach.
An ongoing beach nourishment program meets the objectives of the Public Policy Institute’s Program for California Coastal Management with the changing climate, and similarly achieves the objectives of saving the beach by James Titus.
The Fallacy of Utilizing the Worst-Case Sea Level Rise Scenario
In recognition of the Coastal Commission’s interest in addressing worst-case scenarios, there is an amount of sea level rise beyond which additional stabilization no longer makes sense. For example, under a worst-case scenario, if there were 10 feet of sea level rise, none of the proposed adaptation strategies described in Chapters 8 or 9 would likely be sufficient to resist this worst-case scenario, and at that point in time, we anticipate that there would be general agreement that retreat would remain the only viable option. In lieu of managed retreat, under this scenario, we would anticipate a consensus agreement for what we would refer to as “wholesale retreat” under a worst-case scenario. This, of course, is very different from managed retreat in that wholesale retreat would require the abandonment and removal of essentially all low-lying improvements northerly of Power House Park, returning this area to an environment not unlike San Elijo Lagoon today. Under that worst-case scenario, and depending upon the continued commitment from Caltrans, the railroad, and other interested agencies, transportation and utility corridors across the restored San Dieguito Lagoon could
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be similar to the infrastructure that crosses San Elijo Lagoon today.
To put this worst-care SLR scenario into perspective, which we will arbitrarily define as more than 2 meters of sea level rise over the next century, researchers at Scripps Institution of Oceanography currently estimate that the probability of 2 meters of sea level rise by the year 2100 is at 1/2 percent. As a practical matter, 2 meters of sea level rise can be accommodated by the year 2100 through beach nourishment protecting Del Mar North’s approximately 1.4-km-long beach (assuming the use of sand retention structures) at a total cost of less than $1 million per year (Flick and Ewing, 20091).
Using the above example, we conclude that the beach erosion adaptation strategies described in Chapter 9 remain both viable and economical through the year 2100, with an exceedingly low probability of a more severe SLR scenario beyond which Del Mar’s North Beach community might consider wholesale retreat.
Concern has also been raised regarding the availability of an economical sand source for future beach nourishment projects. As described previously, sand sources for SANDAG’s 2001 and 2012 Regional Beach Sand Projects were mined from San Diego County’s ancestral offshore rivers below 60 feet of water depth on the continental shelf. Current estimates for the still-available offshore sand volume within the ancestral San Dieguito River Valley exceed 2 million cubic yards, with a still available sand supply within the ancestral San Diego River likely exceeding several billion cubic yards of relatively clean coarse alluvial sediments suitable for beach nourishment well into the next century. In short, significant quantities of excellent quality coarse granular alluvial sediments exist in San Diego’s nearshore environment, exceeding any anticipated San Diego County beach nourishment needs over the next century.
Jurisdictions with Similar Geography and Geomorphology to Del Mar
There are several jurisdictions across the California coast that share similar geomorphology to that at Del Mar's North Beach. Namely, a beach berm, in all instances with a descending back beach sloping down to a lagoonal back bay. They include the following:
1 Reinhard E. Flick and Lesley C. Ewing, 2009, Sand volume needs of southern California beaches as a function of future sea level rise rates, in Shore & Beach, Vol. 77, No. 4, Fall 2009.
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Area Comments Mission Beach Locally as narrow as 550 feet in width. Beach berm elevation is around +13 feet. Back beach steps down initially to about +10 feet, and then further down to about +6 feet. Newport-Harbor Island Harbor Island, where it fronts the Pacific, ranges from 300 to 700 feet in width, with the bike trail around elevation +12 feet, and Balboa Blvd stepping down to about +7 feet. Newport- Balboa Island This island is within Newport Harbor as much as 1,500 feet in width and drops in elevation from about +10 feet to +7 feet, extending from south to north. Sunset Beach This is about 500 feet in width. Beach berm is at +13 feet, with South Pacific Ave stepping down to about +8 feet. Alamitos Bay Peninsula This is 350 to about 700 feet in width. Beach berm is around elevation +12 feet, with East Ocean Blvd at +7 feet. Marina Del Rey Although somewhat similar in geology to the other areas, this elevation consistently is around +16 feet and does not step down to the east, so I’ve not included Marina Del Rey in our list of back bays. Channel Islands Harbor Beach berm elevation around +13 feet. Ocean Drive around +12 feet. Sunset Lane around +9 feet. South Harbor Blvd around +6 feet. Ventura This area is interesting in that, while similar to Del Mar, there is also a series of groins at about 1,300 feet on center, with each groin about 400 feet in length. Carpinteria-Sand Point Sand Point is at about 250 to 350 feet wide. Sand Point has only one row of houses, so managed retreat would simply remove the entire row of houses and may not be appropriate. However, the geology remains similar. Moss Landing Back beach elevation is around +10 feet, and as with Carpinteria-Sand Point, has only a single row of buildings, so planned retreat would be simply removing all of the improvements in the area.
The fact that there are other similar locations that share Del Mar’s unique geology and geomorphology only bolters the case that “managed retreat” cannot be treated as a “one-size- fits-all” adaptation strategy that can be applied across the California coast.
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For example, the City of San Diego certified Local Coastal Program for the Mission Bay Planning Area does not address managed retreat. Currently, only the Ocean Beach Community Plan and Local Coastal Program mentions, “The anticipated Citywide Adaptation Plan should include in its scope of work an assessment of potential measures to address the managed retreat or relocation of existing development at risk from bluff erosion or failure, and the degree to which property owners should assume risks associated with their properties in hazardous areas.” Given this, it will be telling if the proposed Adaptation Plan (currently the City has not pursued such a Plan) will differentiate the unique geographies within the City’s coastline (i.e. the difference between Ocean Beach versus Mission Bay). The remaining jurisdictions’ Local Coastal Programs listed in the previous table make no mention of managed retreat and/or as a strategy specific to the unique geography of their beaches, bays, and harbors. That being said, all the jurisdictions are at very stages of development of the sea level rise adaptation policy development and will most likely come to the same conclusion as Del Mar in that managed retreat is not a practical adaptation strategy for certain geographies located within their coast line.
As of the writing of this Chapter, the only communities actively looking at managed retreat within their communities are the Cities of San Francisco, Pacifica, and Ventura. However, managed retreat is only being suggested for open space areas, public infrastructure, and not specifically residential. Additionally, the areas under consideration do not share the same geography and geomorphology as Del Mar.
Conclusion
In addition to the unfavorable geomorphic conditions, managed retreat is incompatible with Del Mar's voter-approved Beach Preservation Initiative (BPI) (Refer to Section 6 – Authorized Protection Structures and Section 8 – Issuance Shoreline Protection Permit). Furthermore, the implementation of managed retreat could endanger over $1.5 billion of Del Mar's tax base and potentially the demographic diversity of Del Mar, as much of the majority of housing in the impacted lower-lying areas are apartments and multi-family housing. Lastly, managed retreat threatens public access as the arterial coast highway linking the City of Del Mar with surrounding beach communities, as much of the Pacific Coast Highway and the associated provision of free publically-available parking spaces would be negatively impacted by flooding.
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In summary, one of the features that make the City of Del Mar’s, and particularly Del Mar’s North Beach, so unique is its coastal geology or, more specifically, its geomorphology or the evolution of this very unique coastal city. Del Mar’s North Beach is truly unique and along the state’s 1,100-mile coastline, is one of only nine small coastal segments having similar geomorphology. Del Mar’s unique geomorphic character lies in its location at the mouth of the San Dieguito River, with the San Diego Lagoon creating a truly unique coastal experience along Del Mar’s approximately 4,400-foot-long North Beach. For the reasons explained above, so-called “managed retreat” is not a viable adaptation strategy for potential sea level rise in Del Mar, and it would not result in any tangible public benefits. At the same time, it would likely have detrimental economic and societal impacts.
Walter F. Crampton, R.C.E. 23792, R.G.E. 245
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