What If We Stop the Wave Before It Reaches the Beach?
A Conceptual Coastal Resilience Assessment for Southern California
A wave hits a seawall hard enough to throw water twenty feet into the air.
Our response is often to build a stronger wall, or to try and add some jetty to redirect the wave energy.
But watching the different coastal-defense systems around Southern California fail to protect properties worth millions led me to a different question:
Why are we waiting until all that wave energy reaches the shoreline?
Southern California's beaches are not merely scenery. They are protective infrastructure between the Pacific Ocean and homes, businesses, roads, railways, parks, utilities, and entire coastal communities.
The Proposal in One Sentence
I see the potential to select one highly vulnerable Southern California shoreline and fund a comparative coastal-resilience study testing whether a submerged offshore berm can measurably reduce wave energy, erosion, overtopping, and long-term public costs without creating unacceptable ecological, recreational, or downdrift impacts, and in-fact perhaps even lead to significant benefits beyond preexisting conditions.
California's own climate assessment estimated roughly $18 billion in residential and commercial property in Los Angeles, Orange, and San Diego counties could be exposed to permanent inundation under a 50-cm sea-level-rise scenario, with substantially greater exposure when major storms are added. (California Energy Commission).
This isn't climate change fearmongering or scientific fabrication as many people often think. This is about observed real patterns and the lived experience of millions of people along the coast.
We are going to spend enormous amounts of money adapting to this problem. We already do.
I think we should seriously investigate whether some of that infrastructure repair money belongs underwater.
The Problem Isn't Just the Wall or the Sand or Erosion. It's the Wave.
Look at what happens with the common approaches we see around SoCal.
On an ordinary beach, the wave reaches shore, crashes and sends water in a thin layer flying up the beach. We love to stand and put our feet there and feel the sand and water flow over our feet and ankles. But those who have done that know that the longer you stand there, the deeper you sink. Sand moves, a-lot! In the images below, we can see an example of typical beach topography.
On some beaches, there are vertical seawalls facing the open water, or with a 'hard armoring' or large boulders at the base of the wall. The wave crashes against the wall and the water gets thrown high and hard into the air. Some lands back in the ocean, some on the boardwalk.
Slope the concrete and water can rush upward and impact the seawall or boardwalk even harder!
In some innovative cases, we have curved the wall and redirect some of that water seaward. This can still be a forceful event.
Pile large rocks, build a jetty, import sand, add a wall... anything. Some people even have to resort to sandbags to keep a structured wall and prevent overtopped seawater from flowing into their homes.
The images above identify a few of the existing methods to control waves with destructive power when they reach the shoreline.
These approaches can all be useful. But they share one fundamental characteristic:
The wave still reaches the shoreline before our major intervention begins.
The Proposal: Build the Breakwater Underwater
Instead of placing the primary defense directly against the coastline, like walls, jetties, rocky shorelines, and breakwaters, imagine constructing a broad submerged berm or artificial reef running parallel to shore that interferes with wave energy long before it reaches the shoreline.
It remains below the water.
The beach can still look like a beach, and we can still manage the environment safely.
But an incoming wave encounters an underwater, artificially raised section of seafloor before reaching land. In the image below, we can see an approaching wave.
As the water becomes shallower over the berm, the wave transforms. It can shoal, steepen, refract, break, and create turbulence. Those processes dissipate and redistribute energy.
When the wave passes over the submerged feature, the energy is shifted and absorbed before the main body of water in the wave reaches the shoreline.
By the time the remaining wave reaches shore, the objective is for the shoreline to face a substantially less destructive wave environment.
That distinction is the entire idea:
Don't just build a stronger wall. Reduce the force reaching it.
This isn't invented physics. Natural reefs, sandbars, shoals, and changing seafloor elevations already transform waves. Artificial reefs are also recognized in California Coastal Commission guidance as a potential hybrid strategy for beach erosion and for wave run-up and overtopping. (Coastal Documents)
The proposal is to intentionally engineer that effect where the economics and physical conditions justify it.
Why This Could Matter for Erosion
Waves don't only threaten buildings. They move sand.
A healthy beach is itself a remarkably effective coastal defense. Its sand, slope, dunes, and nearshore bathymetry provide space across which ocean energy can dissipate.
Lose enough beach and waves begin interacting with things we don't want them interacting with: cliffs, foundations, seawalls, roads, railways, and homes.
So the potential benefit of an offshore berm isn't simply preventing one spectacular wave from overtopping a wall.
If designed correctly, changing the nearshore wave environment could potentially:
reduce destructive wave energy reaching vulnerable shorelines;
reduce wave run-up and overtopping;
reduce some forms of storm-driven erosion;
protect the toe of vulnerable coastal bluffs from wave attack;
help beaches and nourishment projects remain functional longer; and
reduce reliance on increasingly extensive hard armoring at the water's edge.
That last point matters environmentally, too. California's Coastal Commission recognizes that conventional seawalls, revetments, breakwaters, and groins can interfere with sediment transport, redirect wave action, affect adjacent shorelines, reduce habitat, and contribute to the long-term squeezing of beaches between rising seas and fixed development. (Coastal Documents)
A submerged berm doesn't magically eliminate those concerns. It changes where and how we attempt to solve them.
Consider What We're Already Spending
San Clemente provides an excellent example, and could stand to save millions, or even billions by implementing this type of infrastructure.
The U.S. Army Corps of Engineers' authorized shoreline project calls for approximately 251,000 cubic yards of sand along about 3,400 feet of coastline, followed by nourishment roughly every six years over a 50-year federal project period. The initial placement alone was estimated at approximately $16.3 million.
The project protects not only recreational beach but infrastructure including the LOSSAN rail corridor. (U.S. Army Corps of Engineers). All said and done, this represents a double digit million-dollar expenditures every few years for the foreseeable future.
And that is the key economic realization. We are spending over $15 million dollars every 5 years just to replace sand. No erosion control. No resiliency. No problem solving. Just letting the problem happen over and over again.
When we compare this strategy to the underwater berm suggested herein, we should compare:
50 years of erosion + nourishment + emergency repairs + storm damage + infrastructure protection
against:
the lifecycle cost of reducing the damaging forces causing some of those losses.
What Might It Cost?
This is where a conceptual assessment needs to remain a conceptual assessment.
There is no responsible way to say, "A Southern California submerged berm costs $X per mile" without knowing water depth, geology, material source, dimensions, construction method, wave climate, environmental mitigation, access, and required performance.
But we can establish a useful order-of-magnitude hypothesis.
If a relatively short, high-risk section of coastline already justifies a ~$16 million initial nourishment project—and repeated nourishment for decades—then spending tens of millions of dollars on a long-lived offshore intervention is not automatically unreasonable. (U.S. Army Corps of Engineers)
For conceptual screening, I would investigate pilot-scale systems in the several-million-dollar range and larger permanent installations in the tens-of-millions range, rather than pretending we presently know a precise construction price.
Suppose, purely as an economic scenario, a $30 million system protected a coastal area facing $300 million in cumulative property, infrastructure, nourishment, and storm-related exposure over its useful life.
It would need to prevent or defer only 10% of those losses to equal its initial capital cost.
At $500 million of relevant lifecycle exposure, the threshold falls to 6%.
Those are not predicted savings. They demonstrate why the concept deserves a proper benefit-cost analysis.
In other words, this concept only needs to make a small impact to have big savings.
There Are Serious Questions to Answer
This cannot become "dump rocks offshore and hope." This is NOT what I am suggesting here.
Changing waves changes currents and shoreline structures, habitat, and beachfront exposure and more.
Changing currents changes sediment movement.
A structure that protects one community while accelerating erosion somewhere else is not a successful resilience project. This concept requires intense modeling and investigative study to remain feasible.
There are also legitimate questions involving surfing and recreation, marine habitat, fisheries, navigation, water quality, construction impacts, public access, sand supply, sea-level rise, and maintenance. Though, some of these areas may experience benefits as well!
California law specifically requires shoreline-altering structures protecting existing development or public beaches to address adverse impacts on local shoreline sand supply. (California Coastal Commission)
Those aren't reasons to dismiss the concept, but in fact reinforce the potential positive impacts to the coastline.
They're the design requirements AND features.
So Let's Test It
I am not proposing that California construct hundreds of miles of underwater walls tomorrow.
I'm proposing something much less radical:
Find one highly vulnerable section of Southern California coastline and seriously model the idea.
I want to-
Map its bathymetry.
Model its waves.
Model its sediment.
Simulate different berm heights, slopes, widths, materials, distances offshore, and storm conditions.
Model neighboring beaches and impacts to sediment transport mechanisms.
Evaluate habitat and recreational effects.
Then compare the 30- or 50-year economics against nourishment, conventional armoring, repeated repairs, and doing nothing.
If the model fails, we've learned something about more than just this idea.
If it looks promising, build a limited, monitored pilot where some specific areas of shoreline are protected by these berms, studied during storm surge and king tide events, and then, if that works, scale carefully to implement in the most vulnerable communities.
A REST Approach to a Multibillion-Dollar Problem
This is also an example of the kind of thinking I developed the REST Framework to encourage:
Recognize the problem: We are losing beaches and exposing increasingly valuable coastal infrastructure.
Explore the whole system: waves, sediment, beaches, walls, cliffs, ecology, infrastructure, property, public access, construction, and economics.
Systemize what connects them: one major driver is the amount and character of wave energy reaching vulnerable shorelines.
Translate that understanding into an actionable question:
Can engineered underwater topography reduce destructive wave energy enough to make a vulnerable coastline safer, more stable, and less expensive to maintain over decades?
This is really just a scientific hypothesis worth testing. But the stakes are HUGE. People, their homes, property, livelihoods, and the beach communities we all know and love depend on viable solutions to mitigate storm surge related impacts to our coastline.
And given the amount of money, infrastructure, natural coastline, and public space Southern California stands to lose, I think it's a question worth asking before the next wall gets taller or sea levels get higher.
What If Coastal Infrastructure Did More Than One Job?
Coastal protection is the primary purpose of this concept, but an interdisciplinary approach raises a larger question. If Southern California were to invest millions of dollars constructing permanent infrastructure offshore, could that infrastructure provide additional public value?
Depending on location and design, a submerged coastal-resilience system could potentially be studied not only for wave attenuation, but for marine habitat creation, environmental monitoring, oceanographic research, renewable-energy integration, water infrastructure, and other compatible uses.
These possibilities should not be assumed to work, nor should they compromise the structure's primary coastal-resilience function. But they should be investigated.
If we are going to build infrastructure in the ocean, we should at least ask how many problems it can responsibly help solve.
Want to learn more?
Contact Kevin@greenisms.com
Thanks for reading!
Special Thank you to JBA Trust and this video demonstrating these conditions and the study of wave impact energy.
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