Wednesday, January 29, 2014

Glines Canyon Dam now invisible

In case you didn't notice the latest happenings on the Elwha River - the Glines Canyon Dam, while still a bit there, is now invisible. A blast a few days back (see John Gussman's footage of the blast here) took out the last remaining section of the dam visible to the web cam.

Before: Glines Canyon Dam Site on 26 January 2014

After: Glines Canyon Dam Site on 27 January 2014

The blast also lowered the river at the dam site, increasing the gradient of the river, and thereby increasing its erosive capacity. As a result there was an almost immediate uptick in turbidity downstream:

turbidity at the MacDonald Bridge gage on the Elwha River, 26-28 January 2014

Typically turbidity is closely linked to river flow, but in this case there was no increase in river flow - this turbidity was generated by the dam blast.

River discharge, MacDonald Bridge, 26-18 January 2014

Monday, January 13, 2014

A Tale of Two Decembers

An image stolen from Cliff Mass's blog post about Seattle's December 17, 2012 high water event

Do you remember last December? Likely you do, but perhaps not for the reason that I am thinking of. Last December (2012) was notable for the high water and coastal flooding that wet the shoreline of most of the Puget Sound region. That high water event was due to a convergence of really two factors - high astronomical tides (also known as "king" tides around these parts) and big "non-tidal residuals", or the component of water level that is not due to predictable tidal forces. Its worth noting that the non-tidal residual is really made up of a bunch of processes (that Cliff Mass describes here, I have described here, and others have described a bunch of places)...but for simplicity's sake I'm just going to treat collectively.

Water level data from Seattle from the December 17, 2012 high water event, which matched the previous record high water event from 1983. This plot includes the predicted water level (the blue line), the actual water level (the green line), and the difference between the two, which I term the "non-tidal residual" (the red line).

This December has been pretty mellow from a coastal flooding what is the difference? Last December the highest predicted tide during December in Seattle (as an example) was 3.91 m above MLLW, which is just about identical to this year's highest predicted high of 3.907 m above MLLW on Decmeber 6. Furthermore, the average predicted water level for December 2012 was 2.11 m above MLLW, while for 2013 it was the same. In other words, there is not a huge amount of difference in the astronomical tidal water level.

Seattle water levels for December 2012 (top) and December 2013 (bottom). The red line in each plot is the predicted water level, and the blue line is the actual water level.

The big difference between the two years was in the non-tidal residual, or the part of water level that is not predicted by the astronomical tide. In Puget Sound the non-tidal residual is most closely linked to atmospheric pressure, though it can also be due to other processes. Just a few days ago, for example, La Push, WA on the outer coast experienced large non-tidal residuals that were likely due primarily to wind piling water up against the coast.

The plots above, which show the predicted and actual water level from December 2012 and 2013 are sort of hard to interpret, so the plot below should help to clarify the different between the two months - this shows the difference between the predicted and actual water level for the two months:

So what should be clear is that in 2012 December water levels were much higher than those in December 2013, not due to "tides" (at least in the way that we usually think of them as being driven by astronomical forces), but rather due to very high average non-tidal residuals that lasted pretty much all month. In fact, the average of all measured water levels in December 2012 was 2.28 m above MLLW, while in December 2013 it was only 1.92 m above MLLW, a difference of over 14 inches. And when it comes to coastal flooding, 14 inches of water level makes a big difference...

Monday, January 6, 2014

In Memoriam: Maury Schwartz, Coastal Geologist

Dr. Maury Schwartz teaching a class...on the beach. Photographed by Hugh Shipman in 1991 or 1992

Dr. Maury Schwartz, eminent coastal geologist and Emeritus Faculty at Western Washington University, passed on a few days ago in Bellingham. When I started research work on the Elwha I was always distinctly aware of standing on Maury's broad intellectual shoulders; Maury spearheaded much of the early observational and descriptive work on Ediz Hook and the Elwha river delta, and also made significant contributions to the body of work that informs our conceptual models of the coastal geomorphological system at Elwha.

When I accepted a job with Washington Sea Grant in 2010 and started preparations for returning to Washington one of my fists tasks was to reach out to Maury via email. I was honored that he responded quickly and enthusiastically, and that initial email conversation led to an extended discussion via email and in person. As a relatively young entrant working in the field of coastal geology in Puget Sound, it was a huge honor to converse with Maury and trade ideas and debate the formation and evolution of our complex beaches, coastal spits and bluffs. I recall in particular meeting with Maury at a coffee shop in Bellingham, and leaving with a series of papers that Maury had brought for me along with a collection of napkins full of scribbles and notes on spit formation and development.

The last time I saw Maury was in the late summer of 2013, when Jim Johannessen brought Maury out to the Olympic Peninsula on what would be their final pilgrimage together to the beaches of the Elwha River delta. Jim and Maury had worked together in the 1990s and published one of the earliest, if not the earliest, comprehensive set of quantitative shoreline change analyses for the beaches adjacent to the Elwha River mouth. Maury was visibly weakened, but with our help was able to make his way across the logs and cobbles to lay eyes on the first of the sediment to reach the coast after the removal of the lower dam on the Elwha River. Maury's contributions to our understanding of the coastal landforms of Puget Sound were huge, and even during that final trip his passion for understanding their workings was clearly evident. To stand on the beach with him was an honor and an inspiration to try, in some small way, to continue his legacy.