Beach Access, Coastal Preservation, Shoreline Armoring, Surf Protection
February 28 2017

A Perfect Time To Pursue the Best Solution: Managed Retreat at San Onofre

by Mandy Sackett

California’s ongoing winter storms have eroded the San Onofre State Park Beach's lower parking lot and access road over the past few months. As a result, the access road to San Onofre has undergone periodic closures because State Parks – which maintains the road and parking lot – is worried that vehicle traffic may collapse a 450-foot portion of the potentially unstable road.

This is a perfect time and place to implement managed retreat, the only real long-term solution.

Instead, in an effort to maintain immediate maximum access, State Parks was recently granted an emergency permit through the California Coastal Commission to install 900 linear feet (the length of three football fields) of riprap (rock armoring, as shown in photo below) to protect the road and a portion of the parking lot. The riprap would begin at the fence separating State Park and Military property at the north end of the "Church" parking area and extend south from there. This might sound like a logical solution, but it’s actually far from one – the riprap will hasten destruction of the beach and will quite likely impact what is one of California’s favorite waves.

Here’s why:

  • Passive erosion - Wherever a hard structure is placed along a constantly eroding shoreline, that shore will continue to erode landward to (and sometimes beyond) the structure, which means a gradual loss of beach in front of the seawall or revetment. While buildings and/or roads may be temporarily protected, the public beach is lost.
  • Active Erosion –Wave reflection, wave scouring, “end effects” and other coastal processes between the wall and ocean can actually increase the rate of loss of beach.
  • Loss of sand – Armored bluffs no longer contribute sand to the beach that they otherwise would through erosion. 

Here’s an Army Corps of Engineers diagram illustrating the above:

In short:

  • Excessive 'passive erosion' may impact the beach profile such that shallow areas required to create breaking waves for surfing are lost.
  • Due to the erosion and reverberation (backwash), surf spots can be severely degraded due to backwash that can also impede wave breaking, especially at higher tides.
  • A seawall, or other “hard” armoring devices’ impact will be exacerbated as sea level rise and storm events compound each other.

Why Armor?

State Parks is resorting to hard armoring as a first choice in hopes of maintaining maximum public access, but as noted, this seemingly quick and easy “solution” ignores the long-term implications. A better step would be develop a low impact short term solution to provide access and buy time to analyze future conditions at this location and explore alternative, more suitable designs. Typically this type of work would involve public input, but because the riprap is scheduled to be installed under an “emergency” permit, that part of the process is being bypassed. (In fact, emergency permitting is seen as an over-utilized loophole in the Coastal Act and there is currently legislation under consideration to close it.)

Emergency permits do not require thorough technical or alternatives analyses, and once the armoring or other “emergency” protection is in place, the structures tend to remain in place.

The Alternatives:

The most obvious way to avoid the negative armoring impacts described above is to implement proactive planning that requires landward retreat of structures from dynamic shorelines.  

For San Onofre, some options include:

  • Altering the bluff in order to shift the road further landward.
  • Relocating the parking lot to the top of the bluff.
  • Using sand and cobble or other “soft” armoring alternatives.

Planning for the long-term would likely yield significant cost savings over time while simultaneously sparing the beach and the waves. Studies at other locations have found significant cost savings associated with “soft” armoring when compared to “hard” armoring. Also see here.

Is it Worth the Risk?

One study showed that of the 30 surfing resources surveyed, 18 experienced a reduction in wave quality as a result of coastal armoring.

  • Best Case Scenario: Riprap 
    • The surf is only immediately impacted at high tide (by consistent backwash from the riprap).
    • The riprap will be submerged in 10 to 15 years, as predicted for this location by the latest COSMOS modeling.
    • The riprap will eventually be useless, wave destroyed and parking lot submerged.
  • ​Best Case Scenario - Soft armoring or landward retreat
    • No impact to surf
    • The parking lot is relocated or allowed to retreat from sea level rise over time, and there is little to no impact on the wave over the long term.
  • Worst Case Scenario - Riprap          
    • The surf quality is quickly degraded at all tides.
    • The riprap will be submerged and useless in 10 years, as predicted for this location by the latest COSMOS modeling.
    • The wave is destroyed and parking lot submerged.        
  • Worst Case Scenario - Soft Armoring or landward retreat
    • There is little to no impact on the surf.
    • The cost is higher initially but provides savings over the long term.
    • Soft armoring is insufficient and needs to be repeated over time.

The Surfrider Foundation is committed to protecting the ocean, beaches and waves, including those at San Onofre. In order to best protect public access and natural resources, more consideration should be given to riprap alternatives. The installation of 900 linear feet of riprap will cost an estimated $500,000 to $1 million, funds that could be used toward safer, friendlier options. And while the emergency permit is set to expire on Nov. 1, 2017, pulling out the riprap at that point may be deemed too expensive, which means the public will be stuck with a temporary solution made permanent problem.

As climate change and sea level rise threaten on the future of our coastline, California must stay ahead of the curve by proactively planning for changes at the local level. This is a perfect example of the type of reactive planning that will result in a severely degraded coast and yet, this is a perfect time and place to implement managed retreat: We can avoid the worst impacts by making smarter planning decisions at San Onofre today.

What You Can Do:

  • Stay tuned! Surfrider staff and partners are preparing to propose an alternative and will need your support.
  • Join the Surfrider Foundation today and support our work.
  • Volunteer and get involved with your local chapter!

Further Reading: