Wednesday, February 3, 2016

A real flood season at Elwha

The plot above of river flow from the McDonald Bridge gage on the Elwha River looks so very different then that from previous winters. We've had multiple flows above 10K cfs, three that have exceeded 20K, and one that went above 30K cfs. The river has spent a good bit of time above the median flow based on records dating back >100 years.

I've got a camera up at Fox Point watching the river mouth, and its been a fun ride this winter will all of this water pushing through. The mouth has been making a lot of changes...check it out below. What you see here are the average of individual photos taken every 30 minutes during daylight hours. This helps to adjust for variations in lighting and water level associated with tides, and better visualize the actual morphology change at the river mouth:

The timeline of this video aligns with the plot above - 90 days. I've also added notations to the slides on days when flow falls into one of three bins: >10K cfs (but less than 20K), >20K cfs (but less than 30K), and >30K cfs.

In particular what I think is cool is that the video suggests that the river is building new bars (visible by the end of the video emerging above the waterline) at locations seaward of the mouth position in early November...probably due to the at the mouth building on top of sediment that was pushed off of the delta during the large floods of mid-November. To better control for water level here is a photo taken at the the lowest part of the daylight tide on 6 November 2015..the water level was about 0.8 m MLLW according to the P.A. gauge:

and here is a photo taken at the same water level (+/- 10cm according to the P.A. gauge) on 1 February 2016:

Monday, January 25, 2016

Pacific Anamolies

Had the chance to attend the Pacific Anamolies Workshop at the University of Washington last week. I went with two goals:

1) get the latest on the progression of this year's positive ENSO event, and particularly anything relevant to its coastal impacts on the west coast of the U.S. Turns out that most of the ENSO stuff presented was mostly focused on temperature, not so much on coastal impacts...but it was interesting none-the-less. The full proceedings of the workshop can be viewed here: http://uwtv.org/pacificanomaliesworkshoptwo/

2) Try to connect some very warm temperature observations we've made at Elwha to other datasets from around the Pacific. That is the topic of the poster I presented (see above), and was somewhat fruitful.

In the poster above I label three "events" measured at depths of ~30 to 60 feet in the central Strait of Juan de Fuca. Event "C", and the winter that proceeded, was the one that everyone had in their data, and everyone was talking about. This was associated with the on-shore movement of the infamous "Blob" in the fall of 2014. The on-shore movement of this warm water elevated temperatures in the Strait of Juan de Fuca (and in Puget Sound, and BC for that matter) for the whole winter...by a lot.

Events "A" and "B" in that record remain somewhat of a mystery, even though they were pretty darn warm events that each lasted about a week. And again, this is at depth, not at the surface. Still trying to figure out those two.

Tuesday, January 5, 2016

Delta evolution in fast forward

Time lapse is a great tool, and one of my goals for the Elwha project has been to develop a time-lapse video of the development of the Elwha River delta over the course of the project. To this end I, along with partners from the US Geological Survey, Olympic National Park, and the Lower Elwha Klallam Tribe, have tried out a variety of approaches and camera locations. Of those that I've tried two have stuck - one on either side of the river mouth looking down at the mouth. Turns out that keeping a camera stable and operating for years at a time is no easy feat, but the outcome is still interesting I think. Check out this example, which runs from early 2012 to December 2015 (though with significant gaps). Let me know what you think:

Why bother with this? A lot of my continued interest in the Elwha is explained in this article I recently published in AEG News (starting on p. 20).

Wednesday, November 25, 2015

Poking around at FW Bay

Every year for my Peninsula College Oceanography Class I offer an optional field trip in which we head out to FW Bay during a winter low tide, and poke around for an hour or two. This year's trip happened during last night's beautiful low tide, with cold but crystal clear conditions and a bright moon. This year's trip happened just 6 days after Tuesday's storm, which featured high tides and substantial wind...it must have really rocked the intertidal. We seemed to see it - many crabs missing legs, everything coated with a layer of silt...

As with last year's trip, there were two groups of animals that really seem to dominate the FW Bay intertidal:

The porcelain crabs, and the:

the gunnels

Both occurred, often in large numbers, under nearly every rock we looked under.

As with last year, we also came across a brooding female Red Rock crab, but unlike last year this one was alive and well:

Perhaps most unlike last year, we stumbled across a nice size Sunflower Star (photo at top), and a full-size Pisaster ochraceus:

in addition to many Leptasterias hexactis (which we typically see there), and a blood star.

Wednesday, October 14, 2015

Moorings away!

Step 1: Start with a table full of line, tape, zip ties, buoys and weights...

Back at teaching my Peninsula College oceanography class again, and earlier this week the class designed and built their temperature and light moorings. This continues to be one of my favorite activities with my class - getting to throw stuff in the ocean for science just never seems to get old. Next year I am hoping to take the next step, and build at least some of the sensors we deploy.

Step 2: Pay careful attention to the mount for the sensors...this is the crux of the assignment

Step 3: Make sure all knots are good, sensors are turned on, and the water depth and tides are properly accounted for

Step 4: Over the side

Friday, September 25, 2015

Vegetating the old beach at Elwha

I was struck this morning, during my monthly shoreline survey on the Elwha River delta, by the profusion of what I presume is Beach Pea (Lathyrus japonicus) growing directly on top of what was, just a few years ago, the active beach face east of the Elwha River mouth. Check out this before/after series from a site just a few hundred meters east of the Elwha River mouth:

There is also some alder and American Dunegrass (Leymus mollis) in there. Its a phenomenal transition to witness...from a coarse high(ish) energy beach to a stable backshore lagoon type system.

Thursday, September 17, 2015

El Nino and the Washington Coast

Coastal erosion along the California coast associated with the 1997-1998 El Nino winter

We are experiencing El Nino conditions now, which are very likely to continue...with forecasts pointing towards a strong peak in late fall or early winter. What does a strong El Nino mean for the Washington coast?

The scientific literature exploring the coastal impacts of El Ninos on the west coast of the US suggest that we should expect above-average erosion and property damage. BUT, most of this literature focuses on impacts in California...and in California there is no doubt that El Nino winters are a big deal. In California the cost of coastal damage from both the 1982-1983 El Nino and the 1997-1998 El Nino was measured in the millions of dollars. There is quite a bit less available regarding how previous El Nino winters have played out on Washington's Pacific coast. The one analysis that I could find (which includes as a co-author Washington State Department of Ecology's own George Kaminsky) looking at erosion along the west coast during El Nino winters that INCLUDED shorelines in SW Washington was unclear. El Nino years WERE erosive on the SW Washington coast...but so were lots of other years not associated with El Nino conditions.

This paper, though, shows how multiple mechanisms exist that can conspire to create potentially erosive conditions on Washington's Pacific coast during El Nino winters. At play are three primary factors: Elevated average winter sea level, above-average wave size, and a change in the average wave direction over the winter season.

Average sea level is definitely elevated during strong El Nino winters on Washington's coast. Here are monthly average sea level data from Toke Point, Washington (on the coast in the mouth of Willapa Bay):

Note in particular the "spikes" in the plot above, marking months in which average water level measured at this tide gauge was >0.3 m (~ 1 foot) above the long-term average for that month. The first is centered on Feb 1983, and the other on February 1998.

But its not just about water level. On the open ocean coast above-average waves and changes in mean wave direction play a major role in driving patterns of erosion and damage to infrastructure during El Nino winters (see references here and also this paper). What to expect in the inland waters of Washington where ocean waves aren't much of a factor? Here there is virtually no documentation that I could find regarding any unusual coastal impacts associated with the 1997-1998 winter. In fact, I spoke to Hugh Shipman, Coastal Geologist with the Washington Department of Ecology regarding his recollections from 1997-1998...and mostly he talked about other years, especially 1996-1997 when heavy precipitation drove coastal bluff erosion and failure around Puget Sound:

A home in Seattle after heavy precipitation in the winter of 1996-1997.

All that being said, El Nino years definitely do drive elevated average sea level in Puget Sound. Here is the monthly average sea level for Seattle:

again, with those large "spikes" in average water level during the winter of 1982-1983 and 1997-1998, identical to those observed in Tokeland. In fact, the highest water level ever recorded in Seattle happened on January 27, 1983 - during a strong El Nino winter.

But unless those elevated water levels are associated with some heavy winds/waves, or maybe some heavy precipitation, they may not lead to much in the way of damage. Instead, it can lead to some coastal "nuisance" flooding - definitely a problem, but typically not extraordinary in terms of damage. But should we expect stormier conditions this winter in the inland waters of Washington associated with a strong El Nino, that could couple up with elevated water level and really cause some damage?

There is an apparent relationship between El Nino winters and a reduced frequency of storms specifically associated with north wind and colder than average temperatures (Nick Bond, personal communication). This is perhaps consistent with the observation from past El Nino winters of higher than average winter temperature:

Temperature anomalies during El Nino winters versus a long-term average. Courtesy of Nick Bond.

But what about general storminess? Based on a very preliminary analysis I am going to go out on a limb and say that there likely isn't much connection between El Ninos and heavier-than-usual wind or lower pressure (associated with storms) in the inland waters of Washington State. To arrive at this conclusion I collated hourly observations from the Seattle tide gauge from 1991-2001, and looked at patterns for the winter months (October - March). Here are those data for wind speed expressed as a box plot for each winter, where the red line is the median value, the edges of the box represent the 25th and 75th percentiles, and the "whiskers" cover approximately between the 1st and 99th percentiles of the distributed data. I didn't include outliers here, since my interest was in average winter condition:

So as you can see the winter of 97-98 really doesn't look too different than the 3 or 4 winters that preceded it (though it looks like those winters were windier, on average, than those at the beginning and end of the decade).

Wind direction tells a similar story:

with the winter of 97-98 really not looking all that different as compared to the 3 or 4 winters before, as well as the winter of 98-99...though all of those winters collectively look to have had a bit more south wind than the winters at the beginning of the decade (and the beginning of the 00's).

and finally, pressure is generally a good indicator of storminess, with lower pressure equating to a stormier winter. In seattle, there isn't much distinction, on average, across the winters I looked at:

And what about precipitation? Generally for our area El Nino winters are associated with less precipitation than normal. Here, for example, is a look (courtesy of Nick Bond) at how precipitation has varied nationally during El Nino winters since 1957 (strong and weak), as compared to the long-term average:

Indeed, that is the forecast for this winter (20 August 2015 update).

So all in all, what to expect? There seem to be two stories - one for the Pacific Ocean coast favoring an increased chance for erosion and damage due to the combination of higher-than-average water level, higher-than-average wave heights, and a shift in the average wave direction. And another for the inland waters, favoring some elevated water level and perhaps enhanced nuisance flooding...but possibly not much else, at least that would be unusual as compared to any other winter.