Tsunami surges

To document evidence of the tsunami yesterday, I took a few photos from the shoreline of Bodega Harbor.  Below I'll share a short time series, but before I do that I wanted to explain what you'll be seeing.  

I learned a lot from seeing the Tohoku tsunami in 2011.  It's easier to think about these effects not as one larger wave, but instead as a series of water level changes.  The water surges above the predicted tide height and then recedes below the predicted tide height, and this happens over and over and over again.  (In 2011 the effects were visible for at least 7 days.)  These changes in water level happen relatively quickly – e.g., rather than taking 6 hours to go from high tide to low tide, during the tsunami events we've experienced in 2011 and 2022 some of the water levels changed from the equivalent of high tide to low tide within 30 minutes!

So if the estimate for the Bodega Bay area was for the water level to change by 1.5 feet, then the water level would surge 1.5 feet above the predicted tide height and then recede 1.5 feet below the predicted tide height, and then the flow direction would change and the water would come in again and then go out again.  (In general, the water level deviations are greatest within the first day and then get smaller during the following days.)

Because waves in this area are large (often in the 5-8 foot range), it's actually harder to see the effects of a 1.5 foot water level change on the outer coast.  (Although there can be dangerous surges on sandy beaches.)  But the effects of the tsunami are much easier to see in Bodega Harbor during low tides because you can see the water flooding over the tidal flats and then receding and then flooding in again.  I'll admit, after spending most of my life around tides, it has felt somewhat surreal to me to see this happening!

So here's a time series of photos taken from the same site along Westshore Road.  There is a pink arrow pointing to a clump of algae for a visual landmark to judge the height of the water.  (Note that in these images the water flows in from the left and then recedes to the left.)

The first image was taken at 1:02 p.m. when the water level was relatively high:

 

Then the water receded and was very low within 15 minutes, the time of the second image at 1:17 p.m.:

 

Then suddenly the water started surging back in and it returned to the relatively high level within 7 minutes, by 1:24 p.m.:

After that the water receded again and stayed out for while (but it eventually came back in ~2:30 p.m. after I had left):

 

 

To make this a little easier to visualize, I've also annotated the water level graph from the tide gauge at Point Reyes.  The red line shows all of the water level changes above and below the predicted tide height associated with the tsunami.  I've put in pink arrows at the times that match the photos shown above:

 

 

Amazing to see the effects of the Tonga tsunami reaching Bodega Bay, ~5200 miles (8500 km) away.

P.S.  You can click on the images above and then move through the images faster to see the water level receding, flooding, and receding again.