Life’s a Beach

There has been an increasing amount of discussion lately about the loss of sand on the beaches due to powerful storm waves. Much of this focus has been on Southern California, but the same arguments could be made along the East Coast, as well as many other coastal areas around the globe.

From my wing of the asylum this is nothing new, and beach erosion is a topic that has always been discussed in both my college and high school geology/hydrosphere courses. I even have a multiple-choice test question for both groups of kids along the lines of:

11) Why is the beach losing sand?

I refer you to a recent New York Times article (25 September 2026) titled “Beaches Are Disappearing in Southern California as El Niño Bears Down” as just one example of the mounting angst about this particular concern. (Unless noted, the quotes included below are from this article. I encourage you to read it in its entirety.)

The fundamental points of this particular exposé are fairly simple:

As damaging as storms have already been this year, residents and local leaders are girding themselves for far worse in the months ahead, driven by what experts warn could be the strongest, wettest El Niño ever recorded.

(Feel free to review two recently published posts, including: the “The El Niño Southern Oscillation” for an introduction to the ENSO cycle in general; and “What’s in a Name?” for more on the Super Godzilla Monster El Niño that is planning to have us for lunch this season.)

Marker Bed, my novel and geology primer is now available on Amazon. With heroes and a villain — and Xoix of course — the story takes place 300,000,000 years from now and documents the recognition of humanity in the fossil record. It is a must read for anyone who loves the earth and hopes that it will survive our tender mercies. If you haven’t already obtained your copy, I encourage you to do so now. Click here to go to the Amazon website and lock in your copy.

But for now, back to the recent article in the Times:

For many, this summer’s damage is prompting a reckoning. Residents are fighting to protect their seafront property and calling for emergency armoring of the shore, typically by putting up walls of big boulders known as riprap or reinforcing sand berms.

Such efforts delay the inevitable, experts say. Without human development, beaches evolved with the sand ebbing and flowing, and the Coastal Commission wants to allow for more of that natural change. That might involve moving parking lots and roadways farther inland and replacing sidewalks with paths through sand dunes and native plants.

The beaches wouldn’t be at this point if it weren’t for human intervention. The only permanent answer is to get out of the way.

But none of this gets us any closer to understanding the science behind the reality, so I’d like to toss in my two cents (which should probably be worth a dime in these days of rampant inflation — I can’t be sure about you, but I’m not tired of winning yet).

I used to show a movie in my hydrosphere class at the high school called “The Beach, a River of Sand”. The message of the movie was simple: the sand on the beach, just like the sand along the bottom of a river, is constantly in motion.

It’s easy to understand this when you look at a river because the water is moving and picks up the sand and takes it along for the ride. Well, the same thing happens at the beach. We see the waves going in and out and say to ourselves “Yes, the water is moving all the time, so of course the sand is moving too”.

But the water is also flowing down the beach in what is called the “longshore current” (a.k.a. the “longshore drift”). The direction of the surface currents in the ocean (as well as the longshore currents) is in large measure controlled by a thing called the Coriolis Force, which I’ll try and cover in a separate post because the details are way too much to get into here.

But to get us past today, the short version is simple enough: the Earth is spinning on its axis, which causes everything moving across its surface to be deflected from a straight path. This includes the air in the atmosphere, which leads to the rotation of hurricanes and tornadoes.

The Coriolis Force also affects the movement of the water in the ocean, and contributes to the paths of its surface currents. This causes ocean currents to generally rotate in a clockwise direction north of the equator, with those currents south of the equator going counterclockwise.

What this means is that on the east coast of the United States the predominant current is warm water (the Gulf Stream), and is going from the south to the north. Therefore the sand — for the most part — is also moving from south to north. This is also why a hurricane will move northward and rain like crazy on the White House after nuking Mar-A-Lago. It’s opposite on the west coast, where the cold “California Current” — and the sand — is moving from north to south. (This relatively cold off-shore water also leads to the famous coastal redwood forests of northern California, as well as the infamous fog of London.)

And this is all fine and dandy. The earth has been relocating beach sand for over four billion years, and all without our permission (feel free to refer to a recent post titled “Older Than Dirt” for more about the age of the earth). But even after all those billions of years of sand being eroded from the beaches by the longshore currents, we still have sand on the beaches.

Or, as the current clickbait would tell us, I should more accurately say that we used to have sand on the beaches — in these days of modern times, not so much.

So, what’s different now? Well, the grains of sand are being moved down the beach like always, but why don’t we have more coming in to replace it like we’ve had for the past four billion years? Well, if you swill the Kool-Aid and assume that humans are responsible, this time you’d be right.

The conventional culprits are all too obvious, and are being preached from all available pulpits: we’re trucking sand away for myriad reasons; sea levels are rising; El Niño is a recurring problem; and climate change is always ready to serve as everyone’s favorite go-to villain (except for those who think it’s all a hoax).

But there’s another reason which is possibly a bigger problem here: there’s not as much sand available to refill what’s being removed. “Well, that sucks,” I hear you wail. “What happened to the sand?”

Putting our heads together, I think we can answer that…

Let’s start by asking ourselves a simple question, “Where does the sand on the beach come from in the first place?” I think we can all agree that the sand comes from the erosion of the land, and is transported from the mountains to the beach by rivers and streams — another long-term earth process, and the one that for billions of years has been cleansing the continents of loose sediments and moving sand and gravel to the beaches… and in the process creating places like Kansas. (Refer to the 3rd Law of GeoFantasy for additional legal support for this.)

It turns out that the problem may not be so much at the beach — although that’s surely a part of it — but along the rivers that drain the land and transport the sediments.

There are several contributing factors here. Possibly the most obvious is that we are diverting so much water from the rivers — for drinking and toilets and sweet breath, agriculture, fracking, data centers, and many, many other uses — that there just isn’t enough flow anymore to transport the sand to where it needs to be.

But there is another factor that doesn’t get nearly as much public scrutiny, or respect — dams along the river systems themselves. Please refer to the post “All Lakes are Temporary” for more about this, including the math and science behind sediment transport and deposition.

Dams are definitely a complex and emotional topic on many levels but, as usual, the short version is simple. Every impoundment serves as a temporary base level, and forces the sediments that are being transported by the river to be deposited behind the dam (it works the same way in natural lakes as well).

A good example of this sedimentation — as detailed in the “All Lakes are Temporary” post — is along the Colorado River in the arid southwest of the United States; a source of water that is relied upon by seven states, as well as Mexico. I’ve read that, since the construction of the Glen Canyon dam in southwest Utah, as the Colorado River flows through the Grand Canyon there is so much of a decrease and change in the water levels that the sentiment load is being negatively affected, and even getting in the way of the rafters.

What to do? According to an AI summary by Google:

Federal agencies like the U.S. Bureau of Reclamation periodically release high volumes of water [from Lake Powell] to mimic natural spring snowmelt. These controlled floods move accumulated river sediment downstream to rebuild eroding sandbars, widen beaches, protect native riparian habitats, and preserve cultural archaeological sites along the Colorado River in the Grand Canyon.

Ah yes, the 6th Law of GeoFantasy saves us again.

Anyway, put it all together and it’s fairly obvious why there’s not as much sand making it to the beach to replenish that being lost to the longshore drift, and while that may answer our question and help explain the loss of sandy beaches, what’s a poor boy to do if he owns a house on the coast, and desperately needs a bit of sand so as to entice some sweet young thing to stop by and roll out a beach towel? (At the risk of being branded a woke liberal lunatic trying to be PC, this could just as easily be a “poor girl looking for a studly guy”.)

Well, one thing to do would be to build something that could work like a dam to block the longshore current and force it to drop its sand in front of his house. Many actually do this, and these small jetties even have a special name: a groin.

So, I live at the beach and build myself a groin to trap the sand that the nasty longshore current is so rudely eroding from my beach. Good news! My rockwork successfully grabs any sand coming from upstream — or up the beach, as the case may be — and I get all the pretty girls to stop and hang out on my beach because I have sand and that Bozo downstream doesn’t. Tough titty said the kitty, but I didn’t like him anyway.

But it’s still a drag for him. He wants sand and pretty girls too, so he’s forced to build himself a groin also. And then the guy next to him has to add one, and then the guy next to him, and then the guy next to him, and pretty soon we’ve got groin after groin after groin cluttering up the beach, trapping the sand, and once again, we’ve managed to interfere with nature… just to get a pretty, sun-bronzed, sunbathing beauty in front of the house (or a Chippendale beefcake pumping iron).