Ediz Hook getting a new dose of gravel

Just wanted to add a few views of the most recent gravel nourishment on Ediz Hook. The Army Corps contracted with Bruch & Bruch construction (a local P.A. based construction firm), agreeing to pay them $626,000 to dump and spread 50,000 tons (about 40,000 cubic meters - probably somewhere, in a sorta kinda way- around what the Elwha spits out during a big flood) of mostly gravel (with some sand mixed in) in the intertidal zone. For the two short (~500') hook segments over which the gravel is spread the hook gets about 20' wider. But its obvious that this material is quickly transported along shore (and, I am guessing a lot of it is transported off-shore), spreading out along the hook, due to the oblique wave angle. It would be pretty cool to tag some of these...

Its amazing to see the slopes maintained by the seaward edge of this gravel pile. Unlike most of our beaches, which are mixed, the "beach" formed by this temporary sediment pile is a true gravel beach, of the sort studied in the UK. Waves interacting with this beach crash impressively on the steep beach face, and standing on top of the pile you feel like you are going to get washed away by the run-up. But then, the whole wave just dies as the energy is dissipated into the void in the rocks. As a result, even though the beach is so steep, there is very little apparent reflection.

Where do they get this stuff from?

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.

Before the Clovis

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...

Consumed by Wood

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.



Big raft chain

Facebook as an oceanographic tool

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.

Tides at D-Day

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.

time lapse: accelearated learning

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.