Under the threat of sea level rise, a number of coastal communities around the world will have to decide between protecting coastal homes and structures or giving way to the persistent impacts of coastal erosion by retreating from the coastline.
A recent FEMA-funded study warned that each year, on average 1500 homes and the land on which they are built could erode into the ocean due to rising sea levels and extreme weather events. The upcoming Intergovernmental Panel on Climate Change’s next Assessment Report (due to be released next year) is expected to include increased sea level rise estimates, as it will be its first to account for melting ice sheets. Continued research is making it increasingly apparent that many of the coastal management and development strategies employed thus far must evolve.
Until quite recently, the overwhelming response to coastal erosion—especially in developed areas—has been to armor the coastlines through hard engineering strategies, such as seawalls and piles of rock referred to as riprap or revetments. However, coastal armoring interrupts sediment patterns and intensifies erosion elsewhere. As a result, a number of coastal areas in the state have begun to consider managed retreat, an approach that involves giving space for natural processes.
Among the key benefits of managed retreat are the restoration of native processes and sediment patterns. Managed retreat can also be used in conjunction with soft engineering strategies, allowing for customizable solutions to meet the needs of different coastal land uses and characteristics. This article highlights a few instances in the state in which managed retreat has been considered as an alternative to coastal armoring.
Goleta Beach, Goleta, CA
Goleta Beach, as seen from behind rock revetments. Image courtesy of Flickr user Damian Gadal
Managed retreat can be a contentious coastal management strategy because it requires the removal or relocation of man-made structures or amenities away from the coast. This has been highlighted in Santa Barbara County, where a plan to remove parking spaces and rock revetments at Goleta Beach Park has been contested by a local community group and the Chamber of Commerce. At the center of the issue is Goleta Beach Park, a stretch of lawn and parkland currently protected by revetments.
Friends of Goleta Beach Park, the opponents of the County Planning Department’s proposed plan—dubbed “Goleta Beach 2.0”—claim that the loss of recreational opportunities and approximately one-fifth of the parking availability will dramatically hamper coastal access at Goleta Beach, which draws an estimated 1.5 million visitors per year.
Proponents of the plan, including the Surfrider Foundation and Environmental Defense Center, are calling for managed retreat in order to ensure the long-term stability of the beach. Under current conditions, the revetments protecting the park and parking lots exacerbate beach erosion during storm events. Should the County go forth with the plan, a number of “at-risk” utility lines and a bike path would be moved inland for protection.
Surfer's Point, Ventura, CA
After partially eroding, a bike path at Surfer's Point had to be removed and relocated inland. Image courtesy of venturariver.org
Just 40 miles to the south of Goleta Beach, Ventura’s popular Surfer’s Point serves as a model for what could soon take place at Goleta. After attempting to bolster the shoreline with boulders to protect a bike path and parking lot that were being eaten away by waves, erosion intensified down the coast. Proposals of an underground seawall, which would have ruined the breakpoint—and thus, the namesake—at Surfer’s Point were briefly considered as an alternative, but managed retreat was decided upon as the ideal way to maintain natural sediment patterns and restore the beach.
The project, which was led in part by Louis White, PE, and Bob Battalio, PE, of ESA PWA—who are working closely with SPUR on the Ocean Beach Master Plan—included relocation of the existing bike path and parking lot 60 feet inland, then the removal of riprap and its replacement with thousands of tons of sand and cobble stone. The beach is currently being returned to native dune ecology.
Ocean Beach Master Plan
The Ocean Beach Master Plan (OBMP) recommends managed retreat south of Sloat Boulevard, a long-term process that would involve the removal of the Great Highway and the creation of a multi-use recreational trail connecting to Fort Funston. Most importantly, it would allow for the restoration of native dunes, increasing the recreational and ecological function of the area. The OBMP also recommends narrowing the Great Highway between Lincoln and Sloat in order to create a multimodal promenade and allow for a natural dunescape.
Weighing the Costs and Benefits of Relocation
As a state that has long devoted premiere shoreline to expensive homes and businesses, managed retreat represents a paradigm shift. However, as more research goes into sea level rise and the impacts of sediment pattern interruption caused by hard engineering strategies, it is likely that coastal management strategies will more frequently involve managed retreat. Relocation assistance and buy-back programs help make managed retreat a more politically friendly option, especially for coastal property owners.
As always, solutions should be explored on a case-by-case basis. Last month’s blog post about New York City highlighted the city’s inability to retreat in developed areas due to infrastructure needs and population density along many of the shorelines. As more and more areas of the coastline fall under the threat of erosion, it will be important to figure out costs and benefits associated with protecting or relocating structures. How will coastal jurisdictions decide what to protect, and at what financial and ecological costs?
One of the most noteworthy examples of managed retreat comes from North Carolina, where the Cape Hatteras Lighthouse was moved 2900 feet from its original location at a cost of $9.8 million in 1999. Image courtesy of the National Park Service
The National Oceanic and Atmospheric Administration (NOAA) has encouraged coastal states to utilize “No Build Zones” through Coastal Management Programs, which are required by the Coastal Zone Management Act (CZMA) of 1972. The CZMA requires states to manage coastal development in order to minimize losses due to flooding, storm surges, or erosion, as well as to protect natural coastal features. Other means used to prevent and limit coastal development include setbacks, which require development to be a specified distance from the water’s edge, and rolling easements, which allow development, but without any erosion control methods.
While new coastal development will undoubtedly take a far more precautionary approach in the coming years, existing communities will have a big decision to make: armor or retreat?