I'm sitting in Friday Harbor at the moment, teaching at Friday Harbor Labs for the quarter. Yesterday we were hit by a little storm, characterized mostly by rain and some strong-ish south winds - the video above was shot at South Beach on San Juan Island in the afternoon), but what made this storm notable from a coastal stand-point is its co-occurrence with a higher-than-usual astronomical tide. This led to higher-than-average water levels, something with an average annual return frequency of approximately 3 years on the coast, and maybe 1-2 years in Puget Sound. However, in some places water levels on the shoreline were exacerbated further by run-up associated with waves.
Some visuals of the event: here on San Juan Island the ocean was interacting with large wood on the very upper part of the shoreline for most of the day. Here is a time-lapse of the shoreline on South Beach covering most of the day, in which you can make out large wood getting pulled into the swash zone and moved rapidly alongshore:
On the more protected shores on the other side of Cattle Point, where wood tends to accumulate lower on the shoreline, large wood was afloat, but not moving anywhere as rapidly:
|Peak still water level measured at tide gauges in coastal Washington on 17 November 2020. The time of the peak is given on top of each bar.|
|Peak non-tidal residual (NTR) measured at tide gauges in coastal Washington on 17 November 2020. The time of the peak is given on top of each bar.|
So again, the NTRs varied between the coast and Puget Sound, and were relatively large - approaching 1 meter on the coast, and 0.6 meters in Puget Sound. The timing of the peaks was also quite interesting...generally the largest NTRs occurred on the coast in the morning, and in the early afternoon in Puget Sound. This turned out to be really important, as the peak NTRs were out of phase with the highest tides in each location. This is good, as it helped to reduce the peak water levels for the day. If they had been in phase we would have definitely seen some water level records broken in Washington State yesterday.