The Pacific Northwest has weathered three bouts of high spring tides this King Tide season. King tides are the highest of the spring tides. On my home beaches, I’m talking about fall or winter spring tides. They occur during daylight, usually around noon, so they are easy to keep photographic track of. Combined with large waves and other contributing factors, high spring tides test the mettle of exposed coastal shorelines. I documented the test of the tide on an undeveloped sandy shore during the highest tides of November and December 2017, and January 2018. When you’re documenting tides, you need a landmark. In the photos below I use a trusty old stump and the backshore shelf to mark the reach of the highest swash.
November 4, 2017
The NOAA tide projection was for a 9.6′ high tide. NOAA’s National Weather Service’s morning forecast called for a 10 kt N wind, 2′ N wind waves, and a 6′-7′ NW swell. On the beach, I felt like the wind and wave forecasts were accurate. These are smaller than average winter waves on the northern Oregon coast. The setup was in place for an uneventful day, tidally speaking, and that’s what we got. the swash from the biggest waves didn’t even come close to wetting the stump, let alone the backshore.
December 3, 2017
The high tide projection was 10.3′, so a little higher than November 4. The morning forecast called for a 10-15 kt NW wind, 3′ NW wind waves, and an 11 NW swell. The wave forecast was more or less average for winter on the northern Oregon coast. Thus, I expected an average King Tide run up, which means my landmark is going to get inundated and the swash from the biggest waves will struggle to crest the backshore shelf.
January 3, 2018
The high tide projection was 10.4′ high tide. The morning forecast called for 5-10 kt E wind with 15-20 kt gusts near the gaps, 3′ E wind waves, and an 8′ NW swell. Surfers will tell you the east wind slows up waves and makes them break closer to shore. How might that influence the reach of tide? This time, even though the forecast was for a smaller swell, run up from the highest waves did dribble up onto the backshore shelf in places, and some large driftwood mobilized. This shows that you can’t rely solely on tide projections and wind and wave forecasts to accurately estimate King Tide, or any tide.
Factors like wave height (and there are others you might not expect too!) combine with tide height to dictate how king tide hits the beach. This season, their combined effects produced modest consequences. Modest or not, King Tide never disappoints when it comes to beachcombing.
This season’s high tides have nearly come and gone, but there is one more opportunity. Another round of high spring tides will test coastal shorelines January 29 – February 2, 2018.
Note: For comparison with the wave forecasts I reported above, the National Weather Service’s forecast for Thursday morning January 18, 2018 called for combined seas of 32-35′. That’s not unheard of, but it’s about as big as you are likely to see on the northern Oregon coast. I wasn’t there to see it but when those waves rolled in on the projected 8.9′ mid-day high tide, I’m guessing they got up on the backshore and ran all the way up onto the foredune shown in the photos above. That is enough to mobilize the sand and much of the big driftwood on the backshore shelf. I’m curious to see if my landmarks have a different look when I next visit them.