Managed or planned retreat allows the shoreline to advance inward unimpeded. As the shore erodes, buildings and other infrastructure are either demolished or relocated inland. Coastal managers realize that in many situations attempting to stop erosion through structural or non-structural solutions is a losing battle. Shoreline protection efforts and/or their repeated maintenance would be too costly and ultimately ineffective at preventing further erosion. A managed retreat approach typically involves establishing thresholds to trigger demolition or relocation of structures threatened by erosion. Therefore, this approach is frequently coupled with several other planning and regulatory techniques including: shoreline planning, to identify high-risk areas where this type of policy would be the only cost-effective, long-term solution; regulating the type of structure allowed near the shore to ensure that buildings are small enough and constructed in a way to facilitate relocation when needed; and instituting relocation assistance and/or buy-back programs to help with relocation costs or compensate property owners when their property becomes unusable. While the overall policy emphasizes retreat, a managed retreat approach may allow some erosion control measures using soft-stabilization techniques to prolong the life of shorefront buildings and other infrastructure for a little while. However, hard stabilization structures or repeated beach renourishment are generally not permitted.
Benefits: Usually less expensive then costly structural stabilization projects that may only be a temporary solution, especially in highly erosive areas. Maintains natural shoreline dynamics and enables shoreline habitats to migrate inland as the shoreline erodes to prevent loss of wetlands and other intertidal areas.
Drawbacks: Can be politically difficult to implement, especially where significant development has already occurred. May cause depreciation of shorefront property values.
In San Mateo County, California, the City of Pacifica had long battled chronic coastal flooding and beach erosion. For decades, the city had employed structural stabilization techniques to armor Pacifica State Beach and channelize San Pedro Creek. Despite these earlier stabilization activities, the City continued to face three main shoreline management issues: flooding of homes and businesses; erosion of Pacifica/Linda Mar State Beach; and maintaining habitat for the steelhead trout in San Pedro Creek.
In 1982, a major flood damaged more than 300 homes. One home was eventually lost, and two homes and a restaurant remained threatened by storm surges and erosion. Therefore, the U.S. Army Corps of Engineers and the City's Flood Control Committee supported proposals to further harden and channelize the creek to reduce the risk of flooding.
At the same time, community members were also concerned about on-going erosion at Pacifica/Linda Mar State Beach—a popular surfing location. The surfing community, led by Pacifica's mayor, favored shoreline restoration and argued that shoreline armoring was accelerating long-term erosion at the community's beach.
Further complicating the issue, San Pedro Creek supports a native population of steelhead trout. The California Coastal Conservancy and other partners therefore argued for restoration of the lower channel and creek mouth to improve habitat for steelhead and other species.
In the early 1990's the City of Pacifica, the California Coastal Conservancy, and the Pacifica Land Trust decided to collaborate to work toward a managed retreat strategy that combined "soft" stabilization techniques to enhance steelhead habitat, reduce flooding threats and preserve the sandy beach, with the removal of vulnerable structures along the beach.
During the 1990's, the City of Pacifica partnered with the California Coastal Conservancy, the California Department of Fish and Game, the Army Corps of Engineers, and the State Water Resources Control Board to expand and enhance the tidally influenced wetlands at the creek mouth and restore more than 1900 feet of eroding creek banks. This restoration both enhanced steelhead habitat and achieved 100-year flood protection for the nearby community. The wetland project also cost the community significantly less than other proposed flood control measures because it required less physical construction.
To address the remaining flood threat to homes and businesses, the City also removed the most vulnerable structures. In 2002, the City partnered with the Pacifica Land Trust and the California Coastal Conservancy to purchase two homes and their surrounding acreage for $2.2 million. They demolished and removed the homes and excavated concrete, rubble, asphalt, reinforcing steel, and tires. They also delivered 4,000 cubic yards of sand to rebuild dunes and restore four acres of beach and the nearby estuary. The city plans to relocate the one remaining shoreline structure—a Taco Bell restaurant—to the other side of Highway 1 as part of a planned retreat strategy.
Creative partnerships at the local and state level helped leverage the public support needed to implement a project that cost millions of dollars and took a decade to complete. Support of local government leaders, particularly the mayor, helped finance the up-front expenses for the ongoing project. Finally, a planned retreat strategy was made more politically viable because project partners had the capital necessary to purchase threatened structures outright.
The City of Ventura is facing on-going erosion at Surfer's Point, a popular surfing spot, adjacent to the mouth of the Ventura River. A California State Park bike path along the shoreline and an adjacent County Fairground parking lot, have also experienced frequent damage from erosion. Since the mid 1980s the Surfrider Foundation has been advocating for relocating the bike path inland, to prevent the future need of a seawall and destruction of a famous surf break. However, to protect the Point, the City decided to place boulders above the mean high tide line along its upper end. The project ended up exacerbating erosion further down the coast and the Fairground parking lot and bike path have continued to erode into the ocean; in some places more than 60 feet of land have been lost. When the City applied for a permanent permit for the rock revetment, the California Coastal Commission (the Commission) denied their request but recommended that the parties involved should work together to resolve the issue.
Nonetheless, Surfrider continued to advocate for a planned retreat strategy. A few years later, the former chairman of the Ventura Chapter of Surfrider was elected to the Ventura City Council providing further support for a "managed retreat" option, and discussions over what should be done with Surfer's Point resumed. Another working group was created. In 2001 the group reached a consensus for a "managed retreat" project that included:
As of Summer 2005, the initial planning and design process and environmental documentation for the project has been completed. The City of Ventura allocated one million dollars of U.S. Department of Transportation's TEA-21 funding for the design and relocation of the bike path. The total construction cost is estimated to be $3.8 million and the City is pursuing funding for the remaining costs. In addition, the California Coastal Commission approved a permit for a renourishment project that includes a five-year plan for opportunistic beach replenishment at Surfer's Point.
Often, the initial response to shoreline erosion is to build a seawall. Because managed retreat has not been a widely employed approach to shoreline management, it has been difficult to convince others that planned retreat might be the best economic and environmental solution for their erosion problems. Adopting a managed retreat policy at Surfer's Point has been successful because it began at a grassroots level. The Ventura County Chapter of the Surfrider Foundation continuously championed this approach for two decades and highlighted the benefits of the option to the City Council and general public. The project was also successful, because it involved all major players in the planning process. Although the process took time, and was aided by a change in leadership in one agency, a consensus was reached that managed retreat was the best alternative.