West Sharp Park – Coast Latitude and Longitude for Coastal Record Project
N37 38.15 W122 29.87
West Sharp Park Coastal Infrastructure History
· Pacifica Pier, ¼ mile L Shaped Pier, Built 1973
· El Nino Storms 1982-1983
o Construction of Retaining Wall North of Pier – 1984
o Construction of Seawall South of Pier – 1987
City of Pacifica Sea Level Rise Adaptation Plan, Final Draft September 2018
Historical Coastal Hazard Response, Page 10 (Since the early 1980’s Pacifica and other coastal cities have used hardening of the shoreline/armoring to “protect” infrastructure and buildings sited by the coast.)
Land in the City of Pacifica has experienced damage from coastal flooding and erosion hazards that has required actions to protect existing development and people. Various approaches have been employed by the City and private property owners to adapt to coastal hazards, including protection (e.g., coastal armoring), accommodation (e.g., Beach Boulevard is frequently closed during large winter storm events to accommodate flooding due to wave action) and retreat (e.g., the Pacifica State Beach project at Linda Mar in 2005). Development along Esplanade that could no longer be protected from shoreline wave attack has also been removed.
Since the mid-20th century, the shore has entered an accelerated erosion phase of unknown genesis but potentially related to Pacific Decadal Oscillations and El-Niño Southern Oscillation2 conditions and potentially due to human activities including reduction of sand runoff from watersheds, and potentially a pulse and then decrease of sand associated with hydraulic mining in the mid-1800s (e.g. gold rush).
The 1982-83 El Niño caused major erosion events resulting in armoring efforts along Pacifica’s coast that have since continued. At the time, the Beach Boulevard seawall north of the pier was under construction to quickly prevent additional loss of land and improvements to erosion in West Sharp Park. Beach erosion is exacerbated in areas where the built environment meets the beach (Figure 1). Since 1983, coastal erosion has reached a greater density of built assets and property creating chronic shore management issues and resulting in much of the City’s shore being armored.
All shore protection structures require maintenance that can be costly, and even the most robust have been frequently augmented with new rock and other actions (e.g. Beach Boulevard and Land’s End [more recently known as Oceanaire Apartments] seawall repairs). The seawalls at Beach Boulevard and Rockaway are overtopped by waves and damage landward of these structures has occurred () and can be expected in the future. More recently, the Land’s End seawall failed (Figure 3) and the vertical public access is currently undergoing repair. Much of the armoring has been supported by the City of Pacifica and State and Federal agencies in order to protect public infrastructure. Armoring has also been constructed by private property owners. Following the 1983 El Niño and subsequent El Niño’s of 1997-98, 2009-10, and 2015-17, coastal armoring structures were constructed or repaired along Esplanade, Beach Boulevard, SF RV Resort, Rockaway and other locations. Recently, the City of Pacifica has supported the City of San Francisco in their request to permit after the fact the levee at the Sharp Park Golf Course in order to prevent flooding in the West Sharp Park neighborhood (CCC 2017).
The area south of the Pacifica Pier to Clarendon was renovated after the 1983 erosion damage by constructing a seawall and a park where private residential property had previously existed (Figure 5), a good example of a hybrid approach to shoreline adaptation. The project was funded by public sources and was initiated after storm damage to the private properties.
SLR Adaptation Plan, Sept 2018, Page 24 -
Sharp Park, West Fairway Park and Mori Point
Most of the area is armored. The northern section between the pier and Paloma is subject to frequent wave overtopping and damages to homes have occurred: Therefore, we believe this area is on the threshold of further damages and establish threshold of one foot of sea-level rise. Beaches are narrow and ephemeral, with armoring impeding lateral access from the degraded vertical access ways.
South of the pier, the beach tends to be more persistent and wider, and there is usually an accessible beach in the vicinity of the end of Clarendon, with reliable vertical and lateral beach access. The sea-level rise threshold for this area is estimated to be 1 to 2 feet. South of Clarendon to Mori Point, the beach persists although wave run-up can reach the levee and there is some armoring. The sea-level rise threshold for this area is estimated to be about 2 to 3 feet. This sub-area is exposed to flooding due to rainfall runoff which cannot flow directly to the ocean. The Clarendon area is exposed to flooding now, and the West Fairway development may be exposed to flooding if sea-level and ground water levels rise over 3 feet.
Existing property and infrastructure is at risk to coastal erosion so actions should be taken soon. San Francisco will maintain the SPGC berm and armoring in accordance with Coastal Development Permit (CDP 2-17-0702) to prevent ocean-driven flooding in the sub-area. Adaptation planning undertaken for the SPGC, which is under the authority of San Francisco, should be coordinated with the City of Pacifica to ensure the consistency with Pacifica’s adopted policies and community values. A public access improvement plan should be included as part of any erosion-specific adaptation strategy.
· 2020-2030 (immediately) – Maintain and expand armoring structures to protect public infrastructure. Includes expanding the south Beach Boulevard seawall to the SPGC berm. The City is currently planning to update the Beach Boulevard retaining wall north of the pier to a seawall. Wave overtopping of both north and south Beach Boulevard structures is currently an issue.
· 2030-2040 (~1 ft SLR) – Armor upgrades to limit wave overtopping will be needed without beach nourishment.
· 2050 (~2 feet SLR) – Wave overtopping may become unmanageable with 2-3 feet of SLR and further actions such as elevating structures may be needed. If seawalls are not raised and/or SLR exceeds 2-3 feet, further actions may be needed such as utility relocation and further reducing the usage of Beach Boulevard and closing it during storm events.
Due to the potential lead time of establishing a sand source, beach nourishment planning should begin immediately. Coarse sand and/or gravel sources are also preferable and would be more cost effective than finer sands due to sediment transport regimes in this sub-area. By constructing sand retention structures along north Pacifica, the efficacy of beach nourishments can be increased.
· 2020-2050 (immediately) – Nourish beach to reduce armoring maintenance requirements and provide recreation and ecology benefits. Sand retention structures will increase the efficacy of beach nourishment (at an additional cost). · Ongoing – San Francisco should nourish the beach in front of the SPGC berm as needed to maintain the current beach width.
Flood protection is already needed for homes and businesses along Clarendon Avenue during rain events and will need to be improved around the SPGC to manage flooding of Laguna Salada regardless of the condition of the SPGC berm. San Francisco is expected to maintain the SPGC berm which protects the Sharp Park neighborhood from the coastal flooding source, but existing pumping facilities in SPGC are not designed to mitigate flooding in and around the course during significant rainfall events (i.e., a portable pump station is currently used to manage rainfall-runoff flooding along Clarendon Avenue). The priority recommendations for flood protection surrounding SPGC are therefore based on the rainfall (fluvial) flood source, but would also be effective during a major coastal storm if the SPGC berm is overtopped or breached. Flooding due to wave run-up landward of Beach Boulevard seawalls is already an issue. If the seawalls are not properly maintained and upgraded in the future to accommodate higher sea-levels, private landowners will need other mechanisms to adapt to flood risks such as raising homes.
· 2020-2030 (immediately) – Construct Clarendon Ave stormwater basin, pump station, and interior SPGC levee to protect homes and businesses from existing fluvial storm flood hazard zone.
· 2060-2070 (~3 ft SLR) – Construct West Fairway Park stormwater basin, pump station, and interior SPGC levee to protect western homes from future coastal/fluvial flood hazard zone.
In absence of any armoring or beach nourishment, managed relocation of private property by private property owners (optional) and realignment of public infrastructure will be needed by 2050.
· Timing is dependent on presence and condition of coastal armoring structures, location of built assets relative to the bluff edge and or flood hazard zone, willingness of property owners to engage in managed retreat, and availability of public funding for relocation of public infrastructure. A managed retreat alternative will require significant lead time for both public and private property, so planning and feasibility should be pursued as soon as possible.
SLR Adaptation Plan Pages 50-51
Sharp Park, West Fairway Park and Mori Point The backshore along the Sharp Park, West Fairway Park and Mori Point sub-area (shown in Figure 12) is low enough such that assets and property are subject to wave run-up and overtopping under existing conditions. Sea level rise adaptation strategies thus must address coastal flooding as well as erosion. Current management at Clarendon includes beach berm building between the Beach Blvd seawall and SFGC levee, which leads to storm water ponding on the landward side and requires a portable pump station. Aside from coastal flooding from wave run-up and overtopping, flooding hazards at Sharp Park include rainfall-runoff entering Laguna Salada during storm events which cannot drain directly to the ocean due to the presence of the levee and limited capacity pump station. To address the coastal erosion and flooding hazards with SLR while addressing the above values and concerns, the proposed adaptation strategies include protection measures such as revetments and beach nourishment as well as flood management measures for Laguna Salada. The adaptation strategy of retreat is also included at the direction of the CA Coastal Commission (Appendix B). Details on the alternative adaptation strategies analyzed for this plan are presented in Table 9 below.