Monday, May 16, 2016

Light and sediment in the coastal ocean

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Our dive site F1, roughly 1km east of the Elwha River mouth, before (top; summer 2011) and during (bottom; summer 2013) dam removal
Included among the many things that the Elwha dam removal project is teaching us is how sediment can interact with the community of living things in the coastal environment. In particular we are interested in the role that turbidity, due to fine sediment held in suspension, played during the height of the dam removal period (2012-2014) in driving changes to the marine algae community in the Elwha nearshore. The video set above shows, for example, what we saw at many of our sites scattered around the delta - places that had coarse substrate suitable for algae to attach to...but suppressed algae growth during dam removal. The answers to these sorts of questions go beyond the Elwha in regards to their importance. Globally, humans are changing the movement of sediment from the land into the coastal oceans, ergo we may also be altering coastal ecology on a grand scale via this sediment mechanism.

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What turbidity can do to light - a video shot in May 2012 at the same site as the videos at the top of this post. Dark!

To get a better handle on the movement of fine sediment from the Elwha River into the coastal zone Andrea Ogston (from UW's Sediment Dynamics Lab) and I proposed a project to Washington Sea Grant, which was funded (full disclosure: since I work for WSG I am not funded by the project, but do act as a co-PI). The project continues the Sediment Dynamics Group's long history of work in the Elwha nearshore tracking fine sediment dispersal, but builds on that by adding in to the mix better measurements of light in the shallow coastal area around the Elwha River mouth, and partnerships with the coastal ecologists working on the project (like Helen Berry and team from the Department of Natural Resources, and Steve Rubin, Melissa Foley and Nancy Elder from the US Geological Survey).


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Emily Eidam from the UW's sediment dynamics group collects a sediment sample from the sea floor with a Shipek sampler.

Last week was the first in a series of cruises on the UW's R/V Clifford A Barnes in order to collect bottom samples (i.e. see the video above), sample the water column for turbidity and other parameters, and also deploy a series of moorings specifically designed to measure sea-floor light:


Emily with a custom made mount and light measurement cluster


Looking down at the light measurement cluster - three HOBO light intensity sensors, and two Odyssey PAR sensors (provide by Washington Department of Natural Resources) 

A few more photos from the cruise are below:

A juvenile bivalve (probably Clinocardium?) in fresh mud deposits


Sediment samples!  Ready to go...


The spacious lab on the Barnes


UW undergraduate Morgan Mackay hauling the CTD.  Bachelor Rock is in the background


Barnes, side view


Cruise plan and station map













Friday, March 18, 2016

Bottle in the sand

Finding a bottle on the beach, or having someone else find one of my bottles, is straight-up exciting for me. The possibilities! So you can imagine my delight when I spotted a hint of glass poking up through the lower intertidal at a section of beach on the Elwha River delta. This particular location is one that I've been working at for almost 10 years, and has been rapidly eroding during that time. Here are some profiles and a time-series of beach position for this section of beach:

The time-series of beach position in this case goes back to February 2011 and suggests an average erosion rate of 2-3 meters/year...

I dug at the little hint of glass, which was sitting at the base of the active part of the beach, in the upper part of what we call the "low-tide terrace" here...in this case a sort of low-sloping feature that is in the lower intertidal and is covered with large clasts and old rip-rap:

The red arrow marks the location where I was digging. Here is another perspective, with the location of the bottle mapped on to one of Andy Ritchie's PlaneCam orthos from 1 August 2015:

and zoomed in a bit:

and I was amazed to dig up a completely clean and unbroken Clorox bottle:

I used Clorox's great heritage bottle guide to date the bottle to 1951-1954. The bottle was actually lodged under a small boulder, but was surrounded by what appeared to be old lagoon sediments. Looking back at some of the historic imagery its clear that the final resting place for this bottle was probably the edge of "Beach Lake", a once-upon-a-time river channel of the Elwha, that transitioned into a lagoon, and over time has shrunk as the delta has eroded. Here is a map at the same scale as the zoomed August 2015 map above, but using an image from 1939:

and two others at the exact same scale from 1965:

and 1977:

Is it possible that this bottle was somehow discarded into this lagoon/lake, and was lost in the lagoon-edge muds for some time? Eventually in that scenario, the barrier started to erode, burying the bottle. Here is the image from 2000:

This image suggests that the bottle was probably lying underneath a few meters of sand and gravel as the beach retreated. The process is continuing. This winter has led to rapid erosion of that section of shoreline, exposing the bottle but continuing the process of making Beach Lake smaller. Between mid-February and mid-March another storm event overwashed the berm, knocking the elevation down and pushing beach sediment almost fully across Beach Lake:

and here is the overwash deposit from that event (or events?) that occurred between mid-February and mid-March of this year, with an outline for clarity:

Wednesday, February 24, 2016

another giant passes...Doug Inman

Look at these guys studying beaches...in 1948! We are all just poorly-dressed copy-cats. Dr. Inman on the left, looking dapper. Photo from The San Diego Union Tribune

This article in the New York Times is a really nice summary of the massive contributions that Doug Inman made to coastal science, science diving, nearshore sediment transport and more.

I love this one..."this is not the approach recommended by Doug Inman". Photo from http://geology.uprm.edu/Morelock/coastref.htm

Friday, February 12, 2016

Kalaloch Beach

A few weeks ago while surveying Kalaloch Beach I was struck by the loss of wood from the upper beach. Below, for example, is a 12 March 2014 photo of a pile of large wood pressed up against an old wooden bulkhead that protects the trail running down from the lodge to the beach. In this photo Casey Nattinger, who I was working with alongside some students from the North Olympic Peninsula Skills Center, stands atop a pile of large wood, which is itself perched on a pile of accreted sand:

and below is a photo of the same feature (from a slightly different perspective), taken on 16 January 2016. Use the wooden fence for reference. The wood, and much of the sand, has been removed:

The loss of the wood from this beach is either a cause or a consequence (or perhaps a bit of both), of erosion of the beach and bluff. Here is a profile collected just south of the wooden bulkhead:

which suggests meters of erosion of both the beach and bluff in the two years since the photo above from 2014 was shot. Its hard to say how big a deal this is...its likely that this beach erodes and recovers each year, and I've never surveyed this beach in January before. But the loss of the wood likely is important. Here is why: The video at the very top of this post was shot yesterday, 11 February 2016 at 3:30 pm, when the tide gauge in La Push was reading a still water level of about 2.9 m above MLLW. The water, driven by set-up due to large waves, was easily working away at the base of the bluff, which sits somewhere around 4.0m above MLLW. Presumably, in past years, some wood would have remained along the base of the bluff to helped to dissipate some of the energy prior to it striking the base of the bluff. So where did the wood go? Here is the water level time-series from La Push for the last month:

which suggests that yesterday's high tide (the last high tide in the time-series) really wasn't all that high compared to those that have happened over the last month (and indeed the whole winter). In other words, it is likely that the ocean has been spending a good bit of time on the upper beach. Note in the video at top how easily those large pieces of wood are moved by the combination of water level (floating the log) and wave energy. The mass of large wood that had been loaded against the upper beach here was floated away. Probably as a result, here is what the base of the bluff looks like as of 11 February 2016:

That sort of cupping at the base of bluff will precede failure, and as happens in all too many cases on the coast, there is investment (the cabins at the iconic Kalaloch lodge) in the way:

how long this site has isn't clear, but bluff erosion doesn't grow back...

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).