Monday, February 22, 2021

January 12th was a widespread and damaging event along Washington's shorelines

Various reports of flooding and erosion started rolling after an interesting coastal storm on or around January 12th, and what struck me most was how wide-scale those reports were...in terms of the number of different areas on Washington's Coast, in the Strait of Juan de Fuca and in Puget Sound that were affected in some way.  It really seemed to be a mix of processes (i.e. a high tide, storm surge, swell waves and locally-generated wind waves) expressed in various combinations around the state.   

On the coast and in the Strait of Juan de Fuca there were definitely waves that coincided with a reasonably high tide. - the shot at top is from the base of Ediz Hook right around high tide, illustrating the size of the waves beating on the upper beach of Ediz Hook.  However, around the inside of Ediz Hook waves weren't a factor, but the tide was high enough (the tide gauge in Port Angeles maxed out arund 2.8 ft above MHHW, which is indeed pretty high) to float most of the large wood on the upper beach:


Reports of erosion came in from a variety of places, including Kalaloch out on the coast:


and North Beach near Port Townsend:

Photo Credit:  Bob Simmons/WSU Jefferson County Extension

At Rialto on the coast it wasn't erosion so much as giant wood being thrown like matchsticks on to the National Park Service parking lot:

Photo credit:  Olympic National Park

and a subsequent analysis I did for Olympic National Park (see figure at bottom for the nerd stuff) suggested that the particular combination of tidal water level, storm surge and wave run-up combined to lead to one of the higher total water levels of the last ~13 years at this site.  

Reports from Westport were similar - overtopping of the sea-wall that protects the marina district, and extensive flooding.  This video by the owner of Stiches Quilt and Craft Shop provides a first hand view of the scene:

 

In Puget Sound its not clear to me how much waves played a role, but I did get at least a few reports of flooding, like this example from the Maple Grove neighborhood on Camano Island:

Photo credit:  Joan Schrammeck

The highest water level recorded in Friday Harbor (the nearest tide gauge to this site) was about 2.5 feet above Mean Higher High Water...a good high tide but certainly nowhere near a record breaker, suggesting that wind likely played some role in forcing this flooding in Puget Sound...

Modelled total water level for Rialto using still water levels recorded at the La Push tide gauge, coupled with run-up estimates modelled using equations from Stockdon et al 2006.  The "Parking Lot Berm Elevation Threshold" is an average estimate of the maximum elevation of the berm seaward of the parking lot at Rialto Beach derived from my own survey data.  This analysis suggests that total water level has only exceeded that berm elevation a handful of times since 2008.



No comments: