The Elwha Delta gets hammered

A couple of days ago John Gussman sent out some beautiful pictures of the Elwha River delta, most shot from his drone.  One of the things that really struck me was how much the morphology had evolved from the sort of classic crescent shape that has characterized the delta since the dam removal period, which is nicely illustrated in this 2015 aerial photo:

An aerial image of the Elwha delta taken 23 September 2015 by Andy Ritchie's PlaneCam

By contrast, in John's photo the bar to the east side of the river mouth is set quite a bit landward relative to the west side bar, giving the delta a somewhat lop-sided look.

So given this odd morphology I was stoked to find that my old creaky time-lapse cameras looking down at the river mouth had managed to shoot photos through December, capturing in particular the series of storms that hammered the delta around Thanksgiving (which included some river flooding).  Indeed, those cameras revealed that the eastern bar had been pushed landward quite rapidly between roughly December 1st and December 4th (check out the video above, or here).

The video below (and also here) is a time-lapse of the raw 30 minute photos (not averaged for the day), and suggest a few days of elevated water level and waves:



which also suggests that there was some rapid landward movement of the bar to the east of the river mouth between roughly December 1 and 4.  I happened to get some profile data on 5 December as well, and have one profile line that cut through the section of bar visible in this video, Line 156:

You can really see the migration of that bar in my profile data from Line 156:

These data suggest roughly 50 meters of landward migration between September and December!

Interestingly though, the beach at Line 164 (which is outside the field of view in the video, to the east) is far more stable:

Its not abundantly clear to me what drove the bar migration in early December - it wasn't really a period of extreme wind, water level wasn't really all that high.  Flow was still a bit elevated by early December, but the big peaks had occurred earlier, around Thanksgiving.  And waves, at least as suggested by the buoy out towards Neah Bay, weren't all that big:

This plot is significant wave heights measured all the way out at the mouth of the Strait, and while those wave heights around the 29th of November are indeed sizable (5.5 meters!), by the 4th things had calmed down.  Indeed, it seems like the convergence of forcing was really between November 26 and 29, but by my eye the time-lapse suggests that the bar really moved between Dec 1 and Dec 4.  Very cool...it will take a bit more digging to figure out what really happened here.