Monday, December 16, 2013

Student research on Port Angeles Harbor

Students from my Introduction to Oceanography class deploy an oceanographic mooring off of the Port Angeles pier

My Peninsula College Introduction to Oceanography class just wrapped up for the quarter. This year, I tried a new thing (getting my students out on the water for a mini research cruise on the Olympic Coast National Marine Sanctuary's R/V Tatoosh), but also re-hashed an activity that was very successful last year: Building and deploying oceanographic moorings off of the Port Angeles pier. This year, though, I put more of an emphasis on analyzing the temperature and light data series that we collected between October and November.

The ingredients of a mooring

This is a tall order for students at the introductory level - I am asking them to create a hypothesis, plot these data and analyze them critically in order to try to ferret out patterns. But in the end I hope it is a valuable exercise and provides some insight into the process of science. Anyhow, I wanted to share one of this year's top papers, by Miranda Elsberry, who looked at the potential role that tides play in controlling the water temperature in the harbor. She does a nice job showing that in our data, there seems to be some relationship between the neap tide cycle and elevated water temperature in the harbo. Makes sense, right? We might assume that the residence time of water in the harbor goes up during the neap tide cycle, mixing is reduced, and temperature is thereby increased.

Introduction to Oceanography students building moorings

Anyhow,Here it is, in its entirety. Enjoy!

Tidal Water Levels and Bottom Water Temperature

For this final assignment I wanted to ask a question that I did not already know the answer to, I already knew the likely outcomes of questions like “Does Temperature vary with depth?” or “Does air temperature affect water temperature?” and so on. So I decided to explore the idea of tides. The question I had going into this assignment was: Does tidal water level affect the water temperature at the bottom of Station B? I chose to look at Station B because I thought that if the answer to my question was yes then it would be clearer at the medium depth of about 16 feet, rather than the deeper Station C or shallow station A. I did not choose to study Station A because of the possibility of the nearby creek changing the water temperature data.

Here are the stations referred to in her paper, for context

To see if there was a relation between water temperature and water level, I plotted the water temperature data collected by the Station B HOBO and the water level data that was provided in Canvas on the same chart. After plotting the data I looked for areas where the temperature and water level changed together.

Overall, I found that temperature did not clearly change with water level. However, even though the temperature line was clearly falling over time, there seemed to be a very slight change in the temperature plot where water level shows there was a neap tide cycle around the 16th and 28th of October. In my first plot (fig.1) I have circled the slight upwards bulges of the temperature line that occurred during the neap tide cycles.

Figure 1: Water Temperature at Bottom of Station B and Tidal Water Level Plot

I wondered if those slight changes were due to changes in air temperature instead of the tides. So I took the air temperature data that was provided in Canvas and plotted it on a chart with the bottom water temperature from Station B (fig. 2)

Figure 2: Air Temperature and Station B Bottom Water Temperature Plot

Other than the 5°F dip in air temperature and slight dip in bottom water temperature at the same time from around the 18th to the 23rd of October, the plot does not seem to show a very clear relationship between change in air and bottom water temperatures. So air temperature must not have caused the slight bulges in my first plot.

With plotting this data and examining it, I have found that there seems to be a connection between the water temperature at the bottom of Station B and the twice a month neap tide cycles. I do not know why neap tides would affect the temperature of water 16 feet below the surface, but there were very slight (by one degree) rise in temperature of the water when neap tides occurred. The change was very small, but it was visible on my chart, so it should be relevant. There are many other weather factors that I could explore that might have caused the temperature change, but air temperature did not seem to have caused it.

Friday, November 22, 2013

An On-the-water experience for Peninsula College Oceanography students

The Olympic Coast National Marine Sanctuary's R/V Tatoosh lands at Port Angeles harbor to offload a group of students from my Introduction to Oceanography course after a mini research cruise to a site on Port Angeles Harbor

I started teaching an Introduction to Oceanography class at Peninsula College last year, and have taken a keen interest in undergraduate education in STEM (science, technology, engineering and math). I've even gone so far as to get myself engaged with a nationwide project focused specifically on the question, "How do you go about doing ocean sciences education RIGHT at small community colleges?". Through that group I met Ardi Kveven, who runs the ORCA program at Everett Community College...and a few months back I went to visit her program in action. That experience motivated me to start talking to a variety of people who might help me provide my students with a true oceanographic field experience.

Rick Fletcher, OCNMS (with back to camera) and a student from Peninsula College prepare the Shipek sampler for deployment.

Those conversations yielded quick results: As a result of a very generous contribution of boat time on the Olympic Coast National Marine Sanctuary's R/V Tatoosh I was able to provide my Peninsula College Introduction to Oceanography class with an on-the-water experience. Yesterday, groups of students headed out to sites in Port Angeles Harbor to collect oceanographic data using a variety of tools and measurement techniques.

A group of students collects a water sample from a site near the Port Angeles wastewater outfall.

While the primary goal of this project was educational (in that it was intended to motivate students to pursue STEM fields), my hope is that we may be able to build a program that is able to sample sites in Port Angeles harbor repeatedly in the coming years. As a result sampling sites were set up in areas that may, in the years to come, change due to a variety of different environmental restorations either planned or in process. On Thursday, the class sampled sites that will be associated with the western harbor clean-up effort currently in the planning stages and a shoreline restoration on Ediz Hook, led by the Lower Elwha Klallam Tribe, that is currently underway.

Students process a sample and record data collected on a cruise on Port Angeles harbor.

In this way my hope is that, over time, the data collected by these students may start to contribute to our understanding of what successful environmental restoration in marine ecosystems looks like.

The R/V Tatoosh leaving the dock with a group of Peninsula College students on board

At each site we collected temperature, salinity and oxygen profiles using the OCNMS CTD. A sediment sample was collected using a Shipek grab, and then water samples were collected from the surface, and again at depth using a Niskin bottle. These samples were used to get independent measures of temperature and salinity (for the purposes of checking the data provided by the CTD), and we also measured pH in these samples with a hand-held electronic pH meter. Finally, a Secchi disk was used to estimate water clarity and light penetrations, and a plankton sample was collected.

A student processing the sediment sample from the Shipek grab.

Back at the dock we set up a sort of "lab":

Our lab...

...where, in addition to FREEZING (it was really cold) students tried to focus on sieving the sediment sample in order to collect and sort benthic invertebrates:

Students sieving a sediment sample

Benthic invertebrates from a site in the western harbor

A huge thank you to the Olympic Coast National Marine Sanctuary for making this happen, and particularly Rick Fletcher and Justin Ellis for operating R/V Tatoosh. Brad Stone from Peninsula College put in a huge effort on the boat to keep students on task. Also, Helle Andersen from the Feiro Marine Life Center worked on the dock, in the cold, to help students identify and understand their tiny invertebrates. Finally, numerous faculty at Peninsula College offered equipment, support and advice, but a particular thanks to Jack Ganzhorn, Brian Hague, and Barb Blackie.

Friday, November 15, 2013

Wandering HOBOs

I've said it before, and I will probably say it again: I am a fan of HOBOs. They are cheap and break-proof enough that I can use them with my Introduction to Oceanography Class, but also accurate and reliable enough that we use them routinely now in our efforts to understand the changing biological community around the mouth of the Elwha River. Most of these HOBOs have a pretty boring life - they get zip-tied to some fixed structure for days to months at a time, and sort of sit there doing their thing. In the video below, for example, you can see a few HOBOs attached to a "mooring" built and deployed by my Oceanography class in Port Angeles Harbor.

Occasionally, though, one goes rogue. And that was the case for the HOBO in the photo at top. This HOBO was found on August 7th, 2013 by Olympic Peninsula resident Vance Heydorn while beach-combing on the outside of Ediz Hook. Vance was kind enough to bring it to the Feiro Marine Life Center, which set off a round of serious head-scratching amongst a group of us that use these for research and education purposes. We all assumed that it was one of ours, lost from a mooring or mount somewhere in Port Angeles Harbor or the adjacent Strait of Juan de Fuca. We finally worked out that it definitely wasn't one of ours...which led me to contact the University of Washington's Friday Harbor Lab. It didn't take long to get word from one of their research teams that, indeed, this HOBO had been deployed in the intertidal zone at a site on the west side of San Juan Island on the 11th of July, and had gone missing at some point after that.

Temperature data recorded by the HOBO

Its sort of hard to figure out exactly when this HOBO broke free from its mount on San Juan Island, but based on the temperature record, I would guess that it was sometime between July 27 and 6 August. The 27th is when the big daily spikes in temperature, which are characteristic of the intertidal zone (which undergoes wide temperature swings in the summer as it is alternately exposed to warm air and cold water) go away...and on the other end we know it made it over here by the 7th of August. Either way you slice it, it was a fairly quick journey from the San Juan Islands (a straight line distance of about 45 km).

Map of the journey

The light intensity data recorded by the HOBO doesn't tell us a whole lot more...except that Vance stored it in a fairly dark spot before he brought it back to the Feiro Marine Life Center:

Light intensity data recorded by the HOBO

Wednesday, November 6, 2013

Tsunamis in the Strait of Juan de Fuca

A photo of probable "tsunami sands" in the Salt Creek salt marsh, Strait of Juan de Fuca. Photo by Sarah Sterling.

Its well known that what are called "far field" tsunamis impact the Strait of Juan de Fuca...heck, one of my early posts to this blog was of a tsunami wave propagating into Port Angeles Harbor after the Tohoku earthquake and tsunami that hit Japan in March 2011. And within the academic and emergency management community it is also well known that we are at risk from very large "near field" tsunamis - one generated near to our coast. In particular a so-called "mega-thrust" earthquake on the Cascadia subduction zone could generate a large and potentially catastrophic earthquake and tsunami that could impact much of the Pacific Northwest coast. The Washington Emergency Management Department, for example, is very focused on tsunami outreach and risk reduction throughout the coastal areas of Washington State.

However, since there hasn't been a large earthquake or tsunami in this part of the world since the "historic" period started its hard to really accept that we have a risk, especially in the relatively protected waters of the Strait of Juan de Fuca. Communities on the outer coast of Washington State seem to have embraced their risk, and are taking various steps to reduce that riks, either by building vertical evacuation structures, practicing evacuation drills, or even

Increasingly, though, the traces of tsunamis that have impacted the shoreline of the Strait of Juan de Fuca are being uncovered. Today I learned of Ian Hutchinson, Curt Peterson and Sarah Sterling's latest paper, documenting their discovery of sand layers in the Salt Creek salt marsh, just west of Port Angeles. They detail the evidence that leads them to conclude that these sand layers were almost certainly deposited by tsunamis occurring 1000-2000 years ago (find the paper here, starting on page 12). This is added to some of the original work on the U.S. side of the Strait of Juan de Fuca that shows multiple tsunami sand beds in Discovery Bay, Curt Peterson's recently published work from Neah Bay, and tsunami sand beds documented on Whidbey Island. Taken together, it is clear that numerous sites on the Strait of Juan de Fuca appear to record repeated relatively large tsunamis.

What is at risk? Quite a bit, as documented here, and some communities are taking notice (see Clallam County's tsunami fact sheet and this story about the Lower Elwha Klallam Tribe's real evacuation after the Tohoku tsunami). Any time new information like Hutchinson et al, 2013 comes out, though, should be a moment that we reconsider our preparations, and redouble our efforts to plan and prepare.

Sunday, October 27, 2013

Building beaches in Puget Sound

Boulevard Park's new beach

The notion of putting beaches back together in circumstances where they have been lost (either due to erosion, armoring, or filling of intertidal habitat) is not a new one. There are countless case studies on-line describing some truly giant beach nourishment projects, and the Program for the Study of the Developed Shoreline at Western Caroline University maintains a nice interactive database of projects in the U.S. One thing that is notable from this database, though, is that beach nourishment on the west coast, and in Washington in particular, is still a relatively rare and small-scale thing...not absent, but not utilized here at the scale that it has been applied elsewhere - particularly on the east and Gulf coasts. As Hugh Shipman notes, though, we are seeing more and more of these sorts of "beach building" projects in our area...and with the increasing emphasis on coastal restoration, combined with the pressure that communities are going to face in the coming decades due to sea level rise, it is likely that we will see many more.

This weekend I had the chance to check out the newly engineered beach in Boulevard Park in Bellingham Bay. This is a popular and heavily used park in Bellingham, with a shoreline that had been composed primarily of various sorts of rock, concrete, tires and piling to protect the shoreline. Designed by Coastal Geologic Services, the new beach is clearly designed to stay in place while providing new aesthetic, recreational and, possibly, ecological value to a highly altered shoreline. Anyhow, here is the site as it looks now:

I was definitely struck by how popular this little section of new beach was, despite being composed of a fairly coarse substrate. It has a small groin to the north to, I presume, trap sediment in transport due to the powerful south winds that sweep into Bellingham Bay in the winter. One process that was definitely in play when I visited - strong offshore transport of sediment due to numerous rock throwers...the grain size utilized is the perfect throwing size!

Friday, October 11, 2013

The Elwha season heats up again...

A juvenile Dungeness Crab utilizing the new sand accreting to the lower profile at Line 204...the first real indication from our surveys that this material is being used as habitat...

Fall is an exciting time for Pacific Northwest rivers, since this is the time period when we start to see opportunities for really high flows. For the Elwha River in particular many of us are pretty addicted to watching the flow of the river since, in general, the big morphologic changes in the river and coastal zone tend to correspond to these flow events. And this year it came early, on September 28th, with the flow gauge at MacDonald Bridge recording what was likely the largest flow since dam removal started:

Based on previous work it seems likely that this flow delivered a substantial volume of new sediment to the coastal zone, but much of it is probably below the water's surface. I started getting questions almost immediately, though, regarding whether we were seeing any changes on the beach due to this river flow. The answer...possibly? In the time lapse video below, for example, you can see some large wood moving on to the river mouth during the high flow period (28-30 September or so). Its not totally clear to me from the time lapse that the morphology of the river mouth changed substantially during that flow, though...

Beach surveys on 4 October and 7 October do show some interesting changes to the beach...but whether these are linked directly to the Sept 28th high flow isn't clear. In the figure below I present data from the four transects that I monitor once or twice a month, collecting a profile and grain size photos at each site. Across the top are the profiles from my last three surveys at each site, and I've circle some of the interesting developments at each site. At lower right in the figure is a time-series of the position of the beach on the if the line is pointing downward that suggests erosion, whereas a move into the positive scale on the y-axis suggests beach growth.

Interestingly enough, the beach at line 132 has seen some of the most obvious change over the last few months of summer, at least in terms of changes high up on the beach face (#1 in the figure above). In this case I've circled accretion of a storm berm over the last month, composed of sand. This part of the profile at this site is typically very coarse - this grain size photo from 3.50 m elevation at Line 132 from 6 August 2013 photo is representative:

but can be compared to the photo from the same profile and elevation collected on 4 October 2013:

At Line 164 I've circled an area of new accretion (#2 in the figure above). This is a place where the high flow in September may have made a difference, since the river channel now runs along and truncates that profile. So that accretion that I've circled appears to be, effectively, a bank of the river. During our survey on 7 October we were unable to cross the channel at this point, and could not extend the profile.

At Line 190 the big story is what appears to be a very slight inflation of the profile on the high intertidal beach. If you track Line 190 in the time series of beach position at lower right you can see that this beach has eroded dramatically over the last two to see even a hint of profile accretion is something. Interestingly enough, though, the grain size photos suggest that the beach at this elevation is still very coarse:

so its not totally clear what is going on here.

Finally, the news from my most eastward profile is continued accretion of sand in the low intertidal (#4 in the figure above). This is all medium sand that appears to be transporting on-shore from a deposit in shallow water just off-shore. This brings me, though, to the most exciting observation from my shoreline survey week...the first observed utilization of sand on the lower profile as habitat. We found a Dungeness Crab snuggled up in the sand waiting out the low tide at about the 0.5 m elevation on Line 204 (see photo at top of this post). This is a site that, one year ago would have looked like this:

and probably wouldn't have been viewed as attractive by Dungeness Crab. Now, though, it appears to fit the bill.

Thank you to Karsten Turrey for assisting with the 7 October 2013 beach survey...

Monday, September 9, 2013

The ups and downs of the Elwha restoration

Dams have two big consequences in rivers, and I usually focus on just one of them - the blocked DOWNstream flow of sediment. But yesterday I had the opportunity to go out to the river and observe the UPstream flow of fish in the newly opened middle reach of the Elwha River. This is the reach between the two dams:

This isn't a new thing - fish spawned in the middle reach last summer, but the river is flowing clear again in the middle reach, which makes for some very nice bank-side viewing conditions:

Okay, enough of the UPstream flow...but lets stay away from dirt for at least one more post. How about the downstream flow of paddlers through the newly opened Aldwell dam site (video by John Gussman):

Altair to the Sea from John Gussman on Vimeo.

And since we are on the topic of John Gussman, he sent along this nice perspective on change in the river itself, looking downstream from the Altair Bridge:

photos and layout by John Gussman

Tuesday, September 3, 2013

Ampelisca...easily my favorite amphipod

A close up of Ampelisca sp. collected from the sea floor off of Green Point

What is your favorite amphipod? Everyone should have one. In 2011 I co-authored a short piece on the potential role of benthic amphipods (and Ampelisca in particular) in nearshore ecosystems of the Strait of Juan de Fuca, which appeared as a sidebar (p 170-171) in Chapter 6 of "Coastal Habitats of the Elwha River, Washington - Biological and Physical Patterns and Processes Prior to Dam Removal". That piece was prompted by observations of the amphipod Ampelisca at two sites we use as reference for our Elwha sub-tidal surveys: Green Point at the mouth of Siebert Creek and Low Point at the mouth of the Lyre River.

Site 7SS1 off of Green Point in the Strait of Juan de Fuca

As part of this year's effort we re-surveyed a variety of sites that we hadn't visited since 2009, including a site called 7SS1 just to the east of Green Point. This site was one of the locations that first led me to sit up and take notice of these benthic amphipods because they absolutely cover the seafloor

A shot of the seafloor at site 7SS1...each of those things is an Ampelisca tube

This time around I decided to do a quick and dirty estimate of the density of these amphipods at this site by collecting a single sample (in this case using a 6 inch diameter tube pressed into the seafloor). I then sieved and hand sampled the amphipods out of that bulk sample, counted the individuals then dried the entire sample (in my home oven...much to my family's chagrin) and weighed the dried sample.

the mass of amphipods pulled out of the sediment sample from 7SS1, a total of 613 individuals

When all was said and done the numbers were astonishing...613 amphipods (and I think I did pretty well here, plus or minus maybe 10% on the count) in the sample, which equates to ~36,000 amphipods per square meter. The dry mass of the sample came out to 5.8 g, which equates to ~340 grams per square meter - or the equivalent of about two or three quarter-pounders with cheese. In 2009 we observed bite scars at this site that we attributed to gray whale feeding:

A divot in the seafloor, observed in 2009, that we attributed to Grey Whale feeding

in part because we observed whales feeding at this site in 2008 (see below) - no wonder when there is so many available calories, and a literature on gray whale feeding on Ampelisca, both off Vancouver Island and at summer feeding grounds in the Arctic.

A Grey Whale observed on the surface near site 7SS1 in 2008

Ampelisca seem to require particular grain sizes to build their tubes, and the hypothesis we presented in the report call-out wondered if the dam removal may make particular grain sizes more available to these amphipods and promote their recruitment in the Elwha coastal zone (where they are relatively infrequent)...still watching on that one.

Friday, August 16, 2013

Tracking community change in the nearshore zone

A red sea urchin (Stronglyocentrotus franciscanus) with a transect survey tape draped over it, at a site off of the Elwha River mouth)

Coastal resilience is not just about the physical interactions (erosion, flooding, tsunami) between the ocean and coastal communities. The concept also includes ecosystems, and the ability of coastal ecosystems (which support coastal communities) to respond to changes. In that vein, I've continued with a project I helped to initiate while a graduate student at UCSC designed to assess how the Elwha dam removal will change or affect the marine biological community that lives in the coastal zone adjacent to the Elwha River delta. Originally a USGS project, our team is now a nice example of multi-agency collaboration, with contributions from USGS, the Lower Elwha Klallam Tribe, WA Sea Grant, EPA and the US Coast Guard. We've just wrapped up our second of three sessions this summer, working to collect data on the fish, invertebrate and algae community at >20 sites at the Elwha and two reference areas (Green Point and Low Point). We also deploy and recover sensors logging temperature and light data, and measure information on the substrate.

There are a few interesting observations from the summer. We've been astonished by the recruitment of juvenile Dungeness Crab (Metacarcinus magister) at many of our sites. Check this video from a site near the base of Ediz Hook:

Our data set really isn't effective at detecting changes in these sorts of mobile and patchy species over time, but we can say that we've never seen anything like this before at our sites. Does it somehow have something to do with the removal? With ocean conditions? Pretty intriguing...

Next, we've hypothesized that the seafloor along parts of the shallow nearshore of the Elwha coastal zone would see substrate transitions as sediment from the Elwha River mouth enters the coastal environment. Furthermore, we expect that new habitats and biological communities would develop in these areas. At most sites, though, (outside of those sites that are more or less right in the river mouth) we haven't yet detected a dramatic shift in the substrate (from gravel to sand, for example)...but there is now at least one notable exception. At a site in shallow water (~25 feet) about 500 yards to the east of the river mouth we've tracked the arrival of sand from the river, which now entirely covers the seafloor. This video, for example, was shot in September of 2009:

That seem piece of sea-floor now looks like this:

We've been able to constrain the timing of the arrival of this sand to the last two months. Now, in the years ahead, our goal will be to assess if this material sticks around, and if and how a different biological community takes shape in these areas.

Thursday, August 8, 2013

On the water with ORCAs

The way in...literally and metaphorically for many students!

No, not Orcinus orca...the Ocean Research College Academy, an Everett Community College-based program and creation of director (and biologist, mentor, educator, USCG certified captain, grant-writer, development specialist...the list goes on and on) Ardi Kveven. I met Ardi at the ASLO conference in New Orleans in 2013, and was stunned that I hadn't heard of her program before. They use a cohort approach, serving running start students at Everett Community college with ocean sciences as the unifying concept behind core learning in English, Math, Science, History, etc. The students take part in monthly (give or take) cruises in Possession Sound and, at this point (~10 years in) have an astonishing long term data set, not to mention a track record of student success.

I joined cruise #64, with the Hat Island ferry as our research platform. My goal in going was to: 1) try to understand more about how to do STEM education and ocean sciences education right (Ocean Literacy and Workforce Development is one of WA Sea Grant's Critical Program Areas) and also 2) try to steal as many ideas as I could for my own Oceanography class at Peninsula College.

I definitely got what I came for - I'm impressed. I had a great day talking to students, watching them deploy instruments, manage data and samples, and describe their processes to me. A few more photos of the day:

pre-cruise prep in the lab

ORCA's location in the Everett Marina makes the trip to the research vessel a breeze - a 5 minute walk

pre-cruise briefing

Students from ORCA prepare to deploy instruments off of the bow of the Hat Island ferry

An ORCA student handles a sediment sample

Just a taste of ORCA's beautiful new shore facility

Wednesday, July 17, 2013

The Changing Elwha River pictures

Many of us have marveled at some of the photography coming out of the Elwha, from people like Tom Roorda and John Gussman (amongst others). Their imagery tells the story of the removal and restoration better than the science in most cases.

But on the science side of the project, photography is being used more and more as a measurement tool, from which all sorts of relevant information can be extracted. On the beach we use images to measure beach grain size. And Andy Ritchie, at Olympic National Park, has worked out a nice method, known as the "PlaneCam", to collect very inexpensive orthoimages, which allow for very precise measurements of landscape features. These images are being used to measure how the river and reservoirs are changing during dam removal, and are also used to assess how the shoreline is changing over time.

Towards that end I compiled a time series of aerial orthimages, both from Andy's set and also anything collected before the dam removal started (these came from a variety of sources, credited in the film), to provide yet another perspective on how the Elwha dam removals are influencing the coastal zone, and specifically the mouth of the river...

Monday, July 1, 2013

Coastal Sediment Distribution from the Ledgewood Slide

Much of the toe of the Ledgewood slide has eroded back dramatically, consistent with time lapse photography from the site. The scarp is now quite steep and tall (3-5m throughout most of the slide - the survey pole in the photo is 2m high). In this photos, at the very base of the scarp, you can make out the darker uplifted clays that were so prominent on the toe immediately after the slide.

I've posted a few times now about the large Ledgewood slide on Whidbey Island, which happened early this year. I've had the opportunity to visit the slide three times now to both do some very small-scale surveying of the shoreline, as well as collect time lapse photos of the toe of the slide as it erodes. My overall goal is to generally contribute to the efforts to understand the slide as a whole, but specifically look at the coastal consequences of large bluff failures like this one. In particular I wanted to try to document where, how and how much sediment from the slide recruited to adjacent beaches.

My approach was to do repeat surveys on a small number of transects both on and adjacent to the slide toe. The first set was collected just a few days after the slide...and I finally made it out last week with a small group of Island County residents to repeat those surveys. In general, we found erosion of the sub-aerial portion of the slide - the toe material that was in or above the intertidal, and some indication of deposition of some sediment below MLLW (though this is scanty since we couldn't really work below about MLLW). We also found deposition on the intertidal beach both north and south of the slide. Here are some example profiles from on the bluff toe itself:

Beach profiles from three sources: 2001 aerial LIDAR (courtesy of the Puget Sound Lidar Consortium), which I use here as a suggestion of the pre-slide beach position, a 2 April 2013 profile (immediately post-slide), and the data we collected on 26 June 2013. On these transects in the middle of the slide the scarp became very steep and tall (>3 m; see photo above), and I wasn't able to collect data on the scarp itself, or on the upper surface due to both safety concerns and vegetation on the upper surface that would have blocked the GPS signal.

At either end of the slide I was able to survey to the same surface I surveyed on 2 April...more or less "connecting the dots"

The profile from the other end of the slide

Profiles from the beach adjacent to the slide suggest some deposition of that eroded material on the intertidal beach, but probably not too far north. Here are the profiles from two transects north of the slide:

This transect was the furthest north one that I collected on 2 April 2013, and there is limited, if any, deposition at this site 139 meters north of the toe of the slide.

By contrast the transect immediately north of the slide shows uniform deposition across the entire profile...about 1 m vertically.

The grain size data I've collected isn't ready for prime time yet, but you can get a sense for the grain size transition on the beach by looking at these photos, suggesting that the material accreted to the intertidal beach is a mix of lots of sand, and a good bit of gravel. These photos are on the profile line above, immediately north of the slide. Check out the first one, collected 2 April 2013:

and compare it to this one from 26 June, taken at approximately the same elevation on the beach (just above MLLW) and more or less the same perspective (note the shoreline protection in the far field to orient yourself.

Based on the very limited number of profiles that I measured, it does appear that more sediment from the slide has migrated south

Here are the profile data from the transect immediately south of the slide. Here too there is a fairly uniform deposition of 1 m of sediment across the intertidal profile. If you watch closely, this deposition, as well as some of the dynamics associated with the transport of sediment on to the beach, is visible in the time lapse video.

To the south, as we moved away from the toe of the slide, we were still seeing measurable accretion on the profile. This is the furthest south repeat profile that I have, but based on grain size variation we estimated that sediment from the toe of the slide had deposited on the intertidal beach at least 375 m south of the slide.

Back of the envelope estimates of sediment volumes, based on these very limited data, suggest on the order of 18,000 m3 eroded from the toe of the slide (that is probably a low estimate)...and ~2000 m3 deposited on the intertidal beach to the north, and maybe 6000 m3 deposited on the beach to the south. Again, VERY loose estimates...and based on the observations of a variety of people, if I had to guess, I would say that the remainder (>10,000 m3) has moved into the sub-tidal zone (below MLLW) or was finer material (mud, silt and clay) that was stripped off of the toe and moved away from the site by currents.

A special thank you to Paul Morris, Jan Wright, Mark Kennedy and Jan Kennedy for their help with this re-survey! Also, John Erlick for hosting my time lapse camera...