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Yesterday and last night California was hit by an atmospheric river bringing lots of rain and the flooding that comes along with it. Combined with a spring high tide, the storm surge gave us tremendous swells and surges along the shores of Monterey Bay. At this moment it isn't raining and the sky is lifting, so we are getting a brief break to dry out before the next storm comes through on Saturday. The National Weather Service's small craft advisory continues through tomorrow night. The NWS forecasts continued swells of 24-26 feet, with a period of 18 seconds, for the rest of today and tonight.

I wasn't the only person to brave the rain and see what was going on at Terrace Point. Several of the other marine lab folks were out there, and the common theme was "This is the biggest swell I've ever seen here!" I was grateful for my new boots and rain pants.

All of this action, combined with a high tide of +5.7 feet made for some cliff-bashing waves. When the big waves hit the cliffs, I could see large swaths of soil and ice plant falling away. Coastal erosion was happening in real time.

Here's a 1-2 sequence of a wave smashing against the little platform where we sometimes collect water samples. I like how the gull just rises above the most violent part of the splash.

Very large wave hitting a cliff
Wave hitting platform at Terrace Point in Santa Cruz, California
2023-01-05
© Allison J. Gong

and

Very large wave hitting a cliff
Wave hitting platform at Terrace Point in Santa Cruz, California
2023-01-05
© Allison J. Gong

To get a real sense of the energy in these waves, you need video.

This is the view from Terrace Point, almost right above that little platform, then looking down the coast towards Natural Bridges State Beach.

Big swell and high tide at Terrace Point in Santa Cruz, California
2023-01-05
© Allison J. Gong

Given that I've been keeping a watchful eye on Younger Lagoon for the past week or so, to monitor the behavior of the sand bar, my ultimate goal for the morning was to see what was happening there behind the gate. Turns out that much had changed in the past 24 hours or so!

Yesterday, the mouth of the lagoon looked like this:

Green bushes in foreground. Sandy beach in midground, with ocean to the left. Green plants on top of dark brown cliff in background. Cloudy and dark sky above.
Mouth of Younger Lagoon, before the big swell
2023-01-04
© Allison J. Gong

This is typical Younger Lagoon after it breaches the sand bar. Water is mostly flowing out, with the occasional splash of ocean trickling in. Note how extensive the beach sand berm is.

And here it was today, taken from the same location:

Green bushes in foreground. Sandy beach in midground, with ocean to the left. The ocean is pushing from the left towards the right. Green plants on top of dark brown cliff in background. Cloudy and dark sky above.
Mouth of Younger Lagoon, after the big swell
2023-01-05
© Allison J. Gong

It wasn't just a matter of breaching the sand bar. About half of the beach has been carved away. The ocean was pushing so far upstream that sea foam was deposited along the uppermost shores of the lagoon. All the white stuff that looks like sand? It's sea foam.

Narrow body of water from lower left towards upper right. Green and brown foliage on both banks. Whitish foam along shores of body of water.
Top of Younger Lagoon
2023-01-05
© Allison J. Gong

But the truly impressive action was at the mouth of the lagoon. Given the rain there must have been some fresh water draining out of the lagoon, but the vast majority of the water moving back and forth was sea water. For the time being, Younger Lagoon was merely another branch of the Pacific Ocean, rather than a body of water in its own right.

Watch this video to see the effects of the combined swell and high tide on the mouth of the lagoon. The second half shows the swell pushing up into the lagoon, all the way up to and beyond the overlook.

Pacific Ocean incursion into Younger Lagoon
2023-01-05
© Allison J. Gong

I had never seen anything like this before. A week ago I was wondering how quickly the regular sand bar would re-form. Now I'm going to see how long it takes to rebuild that entire beach!

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