Today's Peninsula Daily News ran a front page story on the most recent gravel nourishment project on Ediz Hook. Now let me first be clear that I love my local paper. I am a loyal subscriber to the PDN, and proudly read it every morning. But for this article I feel that I know too much. So let me ask the question, "Where do they get this stuff from?". It appears from the Army Corps of Engineers, who should know better.
The story that we are told is that the dams and the placement of rip rap have reduced sediment supply to Ediz Hook and that, as a result, Ediz Hook would go away without the engineering solutions provided by the ACOE. I want to examine an alternative hypothesis though - that Ediz Hook is, by its very nature, a mobile feature, a pile of sediment moving in response to a complex interaction between sediment supply, waves and sea level. The "erosion" observed on Ediz Hook MIGHT have less to do with these relatively small changes to sediment supply (I will discuss this assertion later) and more to do with the simple fact that Ediz Hook is heavily developed. It simply can't be allowed to move. Let me say in advance that this alternative hypothesis doesn't suggest that the engineering on Ediz Hook is the wrong approach. Regardless, Ediz Hook is important and there is a strong case to be made that it needs to be kept in place. I just think that the story backing it up should be right.
Let me start with the mythology that permeates this story: "Wave erosion and a lack of new sediment feeding the spit caused bank failure". In their 1971 "Report on Survey of Ediz Hook for Beach Erosion and Related Purposes" on page 13 the Army Corps forward the idea that, I think, persists to this day: "the system was able to maintain equilibrium". The idea is that the damming of the Elwha River combined with the placement of rip-rap to the west of Port Angeles under tall bluffs restricted the alongshore transport of sediment enough to create a severe deficit, "upsetting the balance" of sediment supply and loss on Ediz Hook. Erosion was the result. Interestingly, this story contradicts the geomorphic model of Ediz Hook published in Appendix B of the same report (and subsequently republished by John Downing in his 1983 book and again by Galster and schwartz in a 1990 Journal of Coastal Research manuscript, and shown here) which suggests that Ediz Hook has evolved and moved landward continuously since about 5000 years ago. The notion of equilibrium in such an extraordinarily dynamic environment - marked by changes in sea level, punctuated sediment supply and variable wave climate, is a difficult one for me to stomach.
The second question is, "How much has sediment supply been reduced?". The PDN quotes a figure suggesting that the removal of the dams will increase sediment supply by 35%. This figure comes from the National Parks Draft Environmental Impact Assessment for dam removal, published in 1996. This estimate was sourced to personal communication and was subsequently struck from the final EIS (though it appears in ACOE documents published as recently as June of 2011). Interestingly, this figure contradicts the Army Corps own estimates of how much sediment supply has been reduced by dam emplacement. In the same 1971 report mentioned above, a post-dam reduction of sediment delivery to the coastal zone exceeding 90% is stated. This would imply that after dams are removed that sediment delivery should increase 9-fold from its present delivery. What actually made it into the final environmental impact statement for the dam removal project (from 2005) was a nearly complete (98%) reduction in sediment delivery to the coastal zone, from an estimated 280,000 cy/yr to about 5000 cy/yr - figures that are cited to a 1993 Federal Energy Regulatory Commission Report. My own research suggests that the dams have probably reduced the supply of coarse sediment to the coastal zone by, on average, about 50 to 90%. But it is important to note that this supply is extraordinarily variable and seems to be related primarily to the magnitude of winter floods.
The key thing though, is to move away from percentages. A good estimate for the annual average historic (i.e pre-dam) coarse sediment supply is probably about 100,000 m3/year (based on what has accumulated in the reservoirs). Some of my work suggests that the river is delivering, on average, between 15,000 and 45,000 m3/yr. so the volumetric deficit would be on the order of 55,000 to 85,000 m3/yr. This then begs the question - how does this fit in to the whole sediment budget for the drift cell. And that question, well, nobody knows...my guess is that, relative to the budget for Ediz Hook, that that volume reduction is relatively insignificant.
Finally, I want to consider another key argument made first by the Army Corps of Engineers in their 1971 report, that erosion from the bluffs to the west of Ediz Hook has been significantly arrested by rip-rap at their base. I am no fan of this rip-rap, lets be clear, but I have noted that the bluffs give every sign of being active (steep, unvegetated) and that the base of the bluffs is now, on average, about 70 feet from the rip-rap. Photos taken at the time of the placement of the rip rap (1929) suggest that the water line and protection structures were placed right at the base of the cliff. Bluff erosion is on-going. Doing the math in a rough fashion suggests that, at a linear erosion rate of about 1 foot/year the bluffs deliver on the order of 25,000 cy/yr of sediment to the coastal zone. This equates roughly with what the ACOE estimated in their 1971 report as the contemporary (i.e. post-rip-rap) supply rate. But has it decreased over time? Figures published by the ACOE in 1971 suggest that the answer is yes, but they provide none of their methodology and no estimation of uncertainty in their measurements. Based on my rough calculation using their erosion figures, the bluffs would have been eroding at a mean annual rate of about 2.5 meters, or about 8 feet, per year to deliver the estimated volumes. Given that the Dungeness bluffs seem to erode at a mean annual average rate of around 1 foot year I view the high estimate as suspect. This is an area that is well worth additional research - finding the old surveys used by the ACOE, revisiting them, working out their uncertainties, etc.
There is more to cover here. Notably I haven't even delved yet into observations published by the ACOE that they used to "show" that the hook was shrinking. Maybe my next post. In conclusion, though, it should be clear that I am not yet sold on the story of Ediz Hook's erosion. Its worth noting again, though, that this doesn't mean that I am, by default, opposed to the engineering done on the hook. Even if its not about a sediment deficit and more about migration, the fact of the matter is that a strong case can be made that Ediz Hook needs to be kept in place - I just want the story to be right.
Today's Peninsula Daily News (front page no less!) reported on an investigation that demonstrated that Carl Gustafson's conclusion in the 1970's, that a spear tip found lodged in a mastodon bone recovered in Sequim, WA, pre-dated the Clovis cultures that were previously thought to have populated North America. The investigation, published in Science, demonstrates once more that the stories we tell ourselves about how Homo sapiens populated North America are probably wrong.
The thing that it made me think of, though, is the phenomenal morphologic change that these pre-Clovis people must have been experiencing at the same time they were sending a spear into a mastodon 13,800 years ago near Sequim. Retreat of the continental glaciers happened just 1000 years previously, and the land was still actively rebounding after bring freed of the massive weight of ice. Between about 14,500 and 13,500 years ago, the sea level relative to the land in the Strait of Juan de Fuca dropped by ~150 m. In other words, EACH YEAR the sea was dropping by almost half a foot on average (see below a sea level curve for the Strait of Juan de Fuca, adapted from Mosher and Hewitt, 2004).
At the time that the mastodon was speared the sea was close to 200 feet lower than it is now, meaning that the shoreline would have extended far out beyond the modern-day Dungeness Spit, Ediz Hook and Protection Island, and that the mastodon's final resting spot would have been hundreds of feet in elevation and miles away from the coast. The Strait of Juan de Fuca would have been a much narrower water body, and Vancouver Island would have been almost within spitting distance of the Olympic Peninsula.
These observations may suggest something about the pre-Clovis people. Were the pre-Clovis people a coastal people in the same way that the Northwest natives are, reliant on marine resources? It is hard to imagine a very stable or productive intertidal ecosystem in an environment of such dramatic sea level change. Or were they inland hunters, relying on the big game that foraged on the post-glacial tundra? I would give a lot to go back and see that landscape...
We have lots of wood around here, and some of it naturally makes it into the marine environment, delivered by flooding rivers and eroding banks. And then sometimes we help it along. Many harbors in the Puget Sound region are finding that they are "polluted" with wood waste. Decades of log rafting and storage in the quiet corners of the Salish Sea coated the bottom with logs, bark, twigs and wood fragments that can be meters thick.
Yesterday I had the opportunity to dive a site slated for a shoreline restoration by the Lower Elwha Klallam Tribe. Its an old log loading ramp - a place where trucks could drive over the water and dump their logs. Here is the site as it looked in 1990:
and here it is in 2009, after most of the over-water structure had been removed by the WA DNR:
Two things struck us as we descended to 60 feet under the surface that historically supported vasts rafts of logs. First, there wasn't a lot living in this environment. In particular, I was struck by the lack of shellfish. There were a few small Dungeness crab, a few monster Red Rock crab, and a Short-Spined sea stars (Pisaster brevispinus). Once we moved out of the major impact area I also spotted a large California cucumber (Parastichopus). In deeper water on some of the logs there were larger Metridium anenomes. But in the substrate itself - nothing that I could detect. No clams, no tube-worms, no amphipods.
Next, that there was an impressive amount of wood waste on the bottom. I could stick my entire arm into the bottom, up to my shoulder, and feel only bark and twigs. Even after being out of commission for 20+ years, there wasn't much sediment deposited on top of this waste. I suspect that the lack of shellfish and other life in the substrate is because there was no substrate - just wood.
We found many old log tags, some marked with the company name, "ITT Rayonier"
A giant Metridium. This one was almost almost a meter high.
One of those big Red Rocks, somehow getting big with nothing to eat? Look at the substrate - the pieces that look like big cornflakes? Those are big chunks of bark covering the bottom.
Today my facebook page was full of accounts, from friends living on Puget Sound proper, of high winds. Here in Port Angeles though it was quite calm, in stark contrast to the apparent wind tunnel effect that turned Admiralty Inlet, just 30 miles away as the crow flies, into a froth of foam and waves. I wasn't there, but I saw the video.
So this told me that this particular wind storm was probably from the south, and while Port Angeles was protected by the mass of the Olympics behind us, Puget Sound was hammered. So, on to the oceanography. The real indicator that this was a region-wide south wind event comes from the tidal gauge in Port Angeles:
Note the little green line at the bottom of the plot - this is the "tidal residual", or the difference between the predicted water level and the actual water level. This is also called "storm surge" - piles of water that move in response to changing atmospheric pressure. Today's residual was almost 50 cm, or over a foot, of extra water - quite a bit when you consider that our normal tidal range is around 8-9 feet.
Now on to the cool part. Where is this extra water coming from? Those strong south winds in Puget Sound were even stronger on the outer coast:
This plot from iWindsurf.com plots wind observations from Destruction Island offshore of the Washington coast. We see high winds - exceeding 50 knots in some cases - blowing w/o pause from the south.
That strong wind pushes water in front of it but the rotation of the earth causes an apparent diversion (the Coriolis "force") of that water mass to the right - into and up the Strait of Juan de Fuca. So, despite the fact that we didn't feel any of today's strong winds, we certainly experienced them as an extra high-tide.
The deeper I dig the more I find the history of my field (loosely defined as some mix of coastal oceanography, coastal geology and benthic ecology) fascinating. It turns out that a major turning point in our understanding of both waves and tides was motivated by World War II, and specifically the need to safely land a huge number of soldiers and equipment on the beach at Normandy.
Physics Today just published a really nice historical summary of tidal predictions, and their link to D-Day. It is a suggested read for the coast nerd. Find it here.
I've always been a believer in using photos to track change - in 2004, newly with the Surfrider Foundation, I kicked off a photo monitoring project focusing on the Elwha shoreline. I am also a natural cheap-skate and find that while I do love to play with expensive scientific equipment, I almost love it more when there are novel ways to measure natural systems with cheap, off-the-shelf kind of stuff. Time-lapse photography can be particularly valuable. Even if it doesn't yield quantitative data, it can help us to generate hypotheses or identify processes that are important over timescales that can be hard to observe directly. I experimented a bit with time lapse using CHDK on my Canon point and shoot, but realized that shooting long time-series would be problematic. Recently I was sent a few PlantCams to use to start collecting time-lapse at various points around the Elwha delta. At $80 each, these cameras are CHEAP and, because they are supposedly waterproof and built specifically for time-lapse outdoors, may be perfect for the sort of quick and dirty timelapse photography we have in mind to try to understand how the coast and delta changes over timescales of weeks to months to years. So just tonight I had the chance to pull the stored photos from the test camera that I put on our roof overlooking P.A. harbor:
Now I know what you may be thinking..."Nice timelapse of a tree". I will get better at aiming, I promise.
Jumped on an opportunity to visit the Lake Mills delta with Tim Randle of the Bureau of Reclamation and Gary Smillie and Brian Cluer of the National Park Service. Relative to the Lake Aldwell delta, the Lake Mills delta is huge - maybe 3-4 times the area, and seems to be composed of coarser sediment in general. Given that it is the primary trap for most of the sediment production in the watershed this makes sense. Overall it is an astonishing feature to visit. Tim, who had visited a month earlier, was shocked by the amount of change - a shifted river channel, new delta lobes, and a rapidly prograding delta front. It is a landscape in motion, with bigger changes coming over the next year...
The latest in a long list of steps to be taken in preparation for dam removal on the elwha river was taken a few weeks ago. the power-houses for both dams were turned off, and the water diverted out of the penstocks feeding the turbines, and through the spillways in the dams themselves. The spillways were also fully opened, lowering the levels of both reservoirs by 10-20 feet. These actions exposed even more of the impressive deltas that have built up at the up-stream ends of Lakes Aldwell and Mills, and, seeing as the sediment of the deltas is the beach building sediment of the coming decade I've taken a few opportunities over the last week or two to view those deltas.
The Lake Aldwell delta, 25 June 2011
The Lake Mills delta 25 June 2011
fine sediments (mostly mud) compressed onto the bedrock side of the reservoir. and check out the logs!
shear scarp at the former water level.
cool stratigraphy exposed by the lowered water level, Lake Aldwell delta
When we decided that I would be accompanying Christine to the National Conferhttp://www.blogger.com/img/blank.gifence on Volunteering and Service in New Orleans this year I immediately emailed random colleagues with Louisiana Sea Grant in the hopes I could meet some of them. It turned out that Melissa Trosclair Daigle, Jim Wilkins, Kevin Crow (all from the LA Sea Grant Law and Policy Program) and Julie Falgout from Marine Advisory Services did one better, putting together an awesome day of visits to a variety of very interesting sites. Since my whole purpose in coming was to take care of McHenry while Christine conferences, he went along for the ride.
The day started with a trip to the Bonnet Carre' spillway, which allows ACOE managershttp://www.blogger.com/img/blank.gif to divert some section of the flooding Mississippi River into Lake Pontchartrain, thereby protecting down-river communities, particularily New Orleans. The river is currently flooding, and the spillway was in full use, running a few days ago at 316,000 cfs, about 20% of the flow of the river. The diversion will likely last for months, and when the spillway is finally closed back down after the water recedes it will be full of deposited river sedimehttp://www.blogger.com/img/blank.gifnt.
After a lunch of seafood Gumbo and crawfish pistolettes we headed to the next stop, another ACOE project, a shockingly ambitious 1 billion dollar surge barrier designed to be closed down during hurricanes, preventing surge from forcing its way up the Mississipi River Gulf Outlet and inundating New Orleans and other communities on the river.
From there we headed to the Lower 9th Ward to look at what is still a devastated landscape, with swaths of lots stripped bare. Of interest, the shotgun houses that used to populate these neighborhoods are now replaced in areas with small, clearly innovative houses designed as part of the Make It Right program. Its an interesting juxtaposition - houses as modern and interesting as any in the country next door to ruined empty lots and still-damaged houses marked with the distinctive crosses that responders used in the immediate aftermath of Katrina.
The beginning of this week was dedicated to grain size surveys on the beach at the Elwha delta. What that means is that I got up early each day and spent hours taking photos of the ground. To spice things up a bit I decided to try something that I've been thinking about for some time - creating a time lapse of the rising tide. I've got some kinks to work out (need a bigger SD card, for example, since mine filled within 6 hours taking a shot a minute) but the result is very cool. More importantly, it may help me to get at some things I've wondered about, like how wave height and breaking characteristics change as the tide rises over the low tide terrace. We've also talked about using a similar technique to monitor changing grain size and shoreline position. Probably more of this to come.
Today I head the opportunity to visit Discovery Bay with Dr. Brian Atwater from the USGS, Carrie Garrison-Lanery, a PhD student at the UW, Lee Whitford from the PT Marine Science Center, and a reporter from the Seattle Times. Carrie was investigating the site as a potential addition to her investigation of earthquake-related subsidence in Puget Sound. I went along to watch the proceedings and figure out if and how we can work with Carrie and Brian to do some education on the tsunami history in this area.
The sand layers that mark numerous tsunamis are clearly visible just inches below the surface of the marsh, and extend to about 8 feet depth, where we ran into what may be the bottom of the shallow bay from thousands of years ago. In total we counted maybe 8-10 sand layers, each perhaps marking an individual tsunami occurring sometime in the past 3000-4000 years.
We started by watching Brian dig a pit, about 3 feet deep, in which you could see two sand layers. Brian then used a corer to pull sediment from beneath the bottom of the pit, revealing further layers. The top three layers were also visible in the side cut of the creek channel draining the uplands. Very cool. Hopefully you can make out the lighter colored sand layers in the photos above...
Yesterday we dove to set up a pressure sensor for recovery. This is the fourth time that this instrument has been recovered and each of the previous three times the instrument has been recovered by divers, leaving the cage on the bottom. This time was the last, and se we had a boat to pull up the entire thing: cage, instrument and weights. And thank goodness for that because we found the cage chock full of sand and gravel. I've had to dig sand and gravel out of there before, but typically just a little. This time it was filled to the brim and probably would have taken me a full tank of air just to dig the instrument out of there. Interesting, since there was not appreciable accretion on the sea-floor around the cage. Sign of a wave of sediment passing this location?
Using CHDK on my bottom of the line Canon PowerShot I shot about 60 photos on a time lapse setting (one every 30 seconds) of Port Angeles Harbor between about 2:30 and 3:00 PM local time. I got lucky - the periods of the tsunami waves propagating through the Strait of Juan de Fuca are about 30 minutes - so I captured a full wave before my POS camera failed. The currents generated within the harbor associated with these waves are fairly minimal, though there is a noticeable current at the entrance - maybe 2-3 knots. NOAA CO-OPS data suggests a wave amplitude at this time of about 50-60 cm. You sort of have to look close - focus first on the dock piling in the near field.
My son is 13 months old. Just after he was born the Chilean tsunami generated a wave that was visible on the shores of Santa Cruz, where we lived at the time. I dragged the family down to a building above the beach and we watched as the waves hit. It was visible, but damage was minimal, and it provided more of an ooh-ahh moment. I posted to this blog the day of that event.
Today's tsunami was much more significant for the west coast. Santa Cruz harbor has experienced damage in its harbor. Initial reports from Crescent City suggest significant damage. Here in Port Angeles I am getting reports of well over a meter (54 inches) of water level fluctuation, though thankfully without enough current to do any damage yet.
For those of us on this side of the Pacific this event will do some damage, but, on the scale of what we may experience in the future, this is a small event. Our thoughts must be first for those killed or missing in Japan, Russian and other parts of Asia most impacted by this earthquake and tsunami. Some of the video coming from Japan and Russia is astounding. Unlike most of the video that emerged from the Indonesian tsunami, much of what we are seeing is hi-def and taken from the air. It provides some insight regarding what we could experience from a Cascadia Subduction zone earthquake generated off of the shores of Oregon and Washington.
NOAA has generated a propagation model for this tsunami, the results of which suggest that Chile will see some of the most damaging wave heights from this event on this side of the Pacific:
The scale that they provide here, I assume (I haven't yet looked into the details of this model) tries to predict the wave height in deeper water. Tsunami waves are hugely long, many kilometers, but in the open ocean their heights can be just tens of centimeters. However, as they approach the continental shelf interactions between the energy propagated in the wave and the bottom causes the wave to slow and the wavelength to shorten. The wave responds by growing in height. My point in providing this brief explanation is to suggest that the scale on this model output shouldn't be taken as suggestive of the wave height at the shoreline.
What comes next are a series of plots taken from the NOAA tides and currents web site, generated by NOAA Center for Operational Oceanographic Products and Services. Each plot has three tracers: In blue is the predicted tidal water level, in red is the observed water level, and in green is the difference between the two. The green one is the one to pay attention to.
On this side of the Pacific it appears as of right now that Crescent City, CA is seeing the largest waves associated with the tsunami
Data from the North Olympic Peninsula illustrates how complex the propagation of these waves are. It appears that Port Angeles is seeing the biggest wave heights (though not by much), suggesting that the Strait of Juan de Fuca may be somehow funneling energy propagating from the Pacific. In Westport amplitudes are smallest:
Moving up the coast La Push saw some slightly larger waves:
but in Neah Bay they initial waves were a bit smaller:
The hydrograph from Port Angeles suggests that we are in the middle of the wave train:
and finally the most recent data from Port Townsend suggests that the wave is just reaching there, and has attenuated since reaching Port Angeles:
An increasing probability of coastal flooding due to extreme high tides is one of the impacts of climate change in the Pac NW that we should consider. Here is a brief from today's Seattle Times regarding Edmonds preparations for expected high tides this weekend.
They mention in the paper that these "king" tides occur once or twice a year. The astronomical components of water level, controlled primarily by the relative position of the sun and the moon, do indeed combine a few times a year in such a way to produce extremely high (and low) water levels. Usually communities are relatively well prepared for the astronomical component of king tides, since they are regularly occurring and predictable.
The trouble for coastal communities occurs when some climatic or oceanographic event adds more water on top of the already high water levels. In this article the additional water is attributed to precipitation. Sea level rise will also add elevation to the peak water levels. In Puget Sound strong winds in the Pacific Ocean can also push water into the inland sea, raising the overall water level. Finally, we must consider that waves (even the wind waves generated in Puget Sound) can increase the destructive force of high water.
Much of our region is still in a pattern of post-glacial rebound, which ameliorates to a degree the influence of pure or "eustatic" sea level rise. Relative sea level in some parts of the Salish Sea is, in fact, dropping rather than rising (Neah Bay, for example) because of high rates of tectonic uplift. We also have a tendency to think of sea level rise in rather simple terms, as a bit more water filling the tub. The real question for our region is a bit more complex: "How will the probability of occurrence of "king" tides increase over the next 10 to 100 years as sea-level increases and storm and precipitation patterns change?". In other words, will we see more articles like this one, in more places, over the coming years?
As the Coastal Hazards Specialist for Washington Sea Grant I spend my time on research, education and outreach on topics like chronic erosion, climate change, tsunami and other coastal hazards. Current projects include:
1) monitoring the shoreline of the Elwha River delta to detect changes due to the Elwha Dam Removal
2) Assessing the influence of climate change on the resources of the Olympic Coast National Marine Sanctuary
3) Evaluating the impact of debris from the Tohoku tsunami on the shorelines of the Olympic Peninsula