Thursday, July 12, 2018

Long Runout Landslide in Skagit Valley

Perkins, Reid and Schmidt (2017, Geology) compared landslides associated with glacial terraces in three valleys of the Cascade Range, the Cedar, North Fork Stillaguamish and Skagit valleys. Although the terraces have similar topographic appearances, the underlying glacial related sediments at each terrace differed and thus the mechanics and scale of the slides are differed. The terrace reviewed in the Skagit Valley is called Burpee Hill and is located west of Concrete.

Lidar derived figure from Perkins, Reid and Schmidt (2017) of the slides on the south side of Burpee Hill

Oates (2016) investigated the slides at Burpee Hill mapped the geology units and thicknesses of the units. She noted that the run out distances of these slides was truncated by the river. However, the deposit of one of the slides still remains on the opposite bank of the Skagit. 

The slide run out from the upper slopes of the slide area to the distal end of the deposit is over 6,000 feet. The slide deposit is a location of numerous homes in part because the slide deposit has created an elevated area above the flood levels of the Skagit River.

Regardless of the different mechanisms and style of slide initiation, all three terraces reviewed by Perkins, Reid and Schmidt (2017) are capable of generating long run out landslides. The hazard areas posed by these long run outs is a challenging policy issues at many government levels.  

Sunday, July 8, 2018

Trade War Notes

The trade wars have begun. Washington State does a great deal of international trade. In part, due to our northern ports facing the Pacific. But the State also produces a lot of products that are shipped overseas. The US Chamber of Commerce put together a state by state highlight of the value of exports that will face tariffs. For Washington State the value of goods facing tariffs is more $6 billion (

Mexico has been especially strategic and that nations's retaliation will hit Washington fruit hard as well as potatoes. The Canadian strategy is to avoid supply chain issues for Canada.

I am not convinced about the Trump administration strategy, particularly with regards to Canada, Mexico and the EU. And I suspect that China situation is not well understood and will lead to long term harm.

Krugman knows a bit about trade and suggests that Trump will be well remembered for his statement that "trade wars are good and easy to win": Krugman: how-to-lose-a-trade-war

It appears the European thinkers will be strategic as well

For Washington State - exports will remain important. It will be hard to consume all those apples.

Monday, July 2, 2018

Hole in the Clouds: Von Karman Vortex

Back in early February I observed spiral of low stratus clouds off the U.S. west coast. I put up a short note about it (swirling-hole-in-clouds).

Doing some random research on a favorite topic I came across this NASA image:

Holes in the stratus down wind of Tristan da Cunha

As a side note I have been fascinated by the South Atlantic island of Tristan da Cunha in part because I once had a map of the world completely covering on my wall and Tristan was right above the table I ate at - a remote island in the ocean demanding attention.

The hole in the clouds I observed is the same phenomenon and has a name - Von Karman vortex. And turns out that what I observed caught the attention of others and made the local news:

Sunday, July 1, 2018

Possible Wave Cut Slope on Marrowstone

Much of the shoreline bluffs on Marrowstone Island are very abrupt, with a steep vertical drop due to the hard glacial till that can stand for decades as vertical cliffs. 

Stepping off the bluff edge on this bluff would hurt
Bluff is 65 feet and mostly silty glacial till
Many of the shoreline bluff I have inspected on Marrowstone have this sharp edged drop at the top edge of the bluff. The bluff above is exposed to fairly frequent wave energy such that any material that calves or ravels off the bluff face is washed away. That said, the bluff retreat at this particular bluff can not be discerned comparing historic aerial photographs dating  back 70 years. 

A recent bluff I was inspecting was even higher than the bluff shown above; however, it was not as steep on its upper part due to the higher amounts of cobbles and gravel within the upper bluff. About 20 feet down the slope it became vertical similar to the bluff above.

Test pits for septic systems often save me a bit of time for looking at the surface geology of sites.   

The above two pits were excavated into an area mapped as glacial till. At depth, the soil does become siltier and more typically of poorly sorted glacial drift observed elsewhere on the island bluffs as well as the steep cliff bluffs at Port Townsend. The round cobbles and slightly stratified nature of the upper units suggest some reworking of the sediments and forming a gravel/cobble lag. Glacial till can have some stratified layers due to water flowing at the base of the ice, and that was my working theory as to the high gravel and cobble  content in the test pits.

But on the drive over the mid section of the island, this slope is suggestive of a possible other explanation.

Maybe this higher portion of Marrowstone was reworked by wave action during seawater incursion during the late stages of the last glacial period.

The mass of glacial ice that filled the Puget lowlands caused the land surface to deform downward hundreds of feet. When the ice began to pull back, there was brief period when the sea invaded the lowlands and flooded the area at relatively higher levels than the current local sea level because the land surface was lower due to the ice loads. The water formed shorelines along the edges of areas inundated. After the land rebounded, theses former shorelines were uplifted to their current elevation.

These wave cut terraces are often rather subtle features. They are readily apparent in higher quality lidar (lidar-wave-cut-terraces-on-orcas-island).

Lidar imagery of southern San Juan Island
These wave cut terraces are pretty easy to see
The wave cut terraces on San Juan Island were recognized by geologists over 100 years ago (Bretz described them) as they are readily apparent. 

There is lidar coverage of Marrowstone; however, the quality is not as good as the more recent lidar coverage elsewhere and it is not clear if the slope above is a wave terrace.

But the slope is at the right elevation for having been a former shoreline. The hill slope is 170 feet. Across the water on Whidbey Island. Polenz, Schasse and Petersen (2006) mapping of the Freeland Quadrangle recognized former shoreline features at 125 to 130 feet at Double Bluff and 180 to 190 feet at Greenbank. Projecting across the water to Marrowstone the daisy covered slope shown above is midway between those two sites.

Friday, June 29, 2018

Deer Harbor Notes

I had a wet early morning stop on the upper end of Deer Harbor on Orcas Island. The view looking south from the upper bay down this protected inlet shows a few docks as well as the marina dock in the upper end of the bay.  

The upper part of Deer Harbor inlet

San Juan County used some grant money to replace the bridge across the upper part of the inlet a couple of years ago.

The first bridge across the inlet was built in 1915. This latest bridge replaced the span that had been built in 1970 (deer-harbor-bridge) and is a wider structure. The project was partially significantly supported by a Nearshore Ecosystem Restoration Project. By widening the estuary opening and removing a rocked bottom under the old bridge, the estuary is supposed to drain more freely and recover some of the original habitat features.

The harbor got its name from Hudson Bay Company hunters as the site was apparently a good deer hunting site. One of the early Hudson Bay hunters, Louis Cayou, stayed on and married a Lummi Indian. His name can be seen on an early survey and was later the name given to the estuary at the head of the inlet. 

Wednesday, June 20, 2018

San Juan Travels

I do feel very fortunate that my field work includes periodic trips out to the San Juan Islands. 
Before leaving the dock at Anacortes on the early morning boat

Mount Baker and the Twin Sisters and Obstruction Pass

Sunset off Lopez

Other passengers enjoying the trip and views

Willow Island

Friday, June 15, 2018

View and Notes on Racehorse Slide

I had a nice view of the Racehorse Slide (cool-oblique-lidar-image-of-racehorse) (first-description-of-racehorse-slide)on a recent trip up the Nooksack River valley. If the clouds and rain are not low, the slide area can readily be seen. 

2018 view of slide

2015 view of slide

I marked up the next picture with the arrow indicating the area of the block that detached and slid as down into the lower Racehorse Creek canyon in 2009. The headwall area of the older and much larger slide that spilled out across the Nooksack River valley is marked with a dashed line. Note that additional logging has taken place between 2015 and 2018 along the southwest side (right in the picture) of slide.

Logging had taken place on and adjacent to the 2009 slide shortly before the failure took place. As can be seen in the photograph above additional logging has been taking place along the older large slide headscarp and along a block that has remained attached on to the right of the slide. That block is located on the south side of the slide. 

lidar showing large slide area and deposit

The impacts of logging on large deep-seated landslides is uncertain. It certainly is not positive, but a direct connection between logging and reactivation of deep-seated bedrock landslides has not been firmly established. The 2009 slide was certainly coincidental with the logging that had taken place, but it also took place during a very intense rain on snow event that was likely on the order of a 25 to 50 year event. Estimating the water input difference between the slope harvested and not harvested  might be an informative exercise. I am not aware if anyone has tried this. The land in question is managed by the State DNR.   

Wednesday, June 13, 2018

Notes on the Culvert Case Being Upheld

The Supreme Court split 4-4 with Kennedy sitting out. Hence, Washington State will need to proceed with fixing fish blocking culverts as previously ordered by the the US District Court.

Not much to read as with a split opinion there is no decision to be written and no dissent.   no

The story here is a good summary of the result.

Various parties had press releases. Bob Ferguson has perplexed some with his position and taking this case to the Supreme Court in direct conflict with the position of the governor and the Washington State Lands Commissioner of Public Lands.  I add a bit of commentary at the end and will do a future post with a bit more. In any event, the lower court ruling standing is a big deal.

Washington State Attorney General Bob Ferguson issued the following statement:

"Today’s ruling brings a resolution to a case that has gone on for nearly 20 years, defended by multiple attorneys general. It is unfortunate that Washington state taxpayers will be shouldering all the responsibility for the federal government’s faulty culvert design. The Legislature has a big responsibility in front of it to ensure the state meets its obligation under the court’s ruling. It’s also time for others to step up in order to make this a positive, meaningful ruling for salmon. Salmon cannot reach many state culverts because they are blocked by culverts owned by others. For example, King County alone owns several thousand more culverts than are contained in the entire state highway system. The federal government owns even more than that in Washington state. These culverts will continue to block salmon from reaching the state’s culverts, regardless of the condition of the state’s culverts, unless those owners begin the work the state started in 1990 to replace barriers to fish. 

I look forward to working with tribal governments to advocate for the funding necessary to comply with this court order, and to ensure other culvert owners do their part to remove barriers to salmon passage."

The cost impacts are relatively modest in the scheme of the entire state transportation budget. At issue was the State's obligation. That is not the same as the Federal government; Mr. Ferguson knows that, but wants to complain about the different treatment. Some have expressed concern that counties and cities may have to follow a similar path; however, that was not before the court and Mr. Ferguson is over simplifying the problem with other blocking culverts - the lower court already determined that issue and the State's position was vague.   

Hilary Franz, commissioner of public lands, issued this statement:

"Today’s decision affirms that it is our collective responsibility to ensure the survival of Pacific salmon. This decision is fair under the letter of the law, but it is also just. Protecting salmon is an issue not just of importance to Washington’s tribes, but to all of us.

The time is now to think boldly about how we move forward on many fronts, including culverts.

My agency, the Department of Natural Resources, stands ready to work with tribes, state agencies, counties, private landowners and federal partners to restore and protect our treasured salmon. 

It is time to stop fighting over who should do what. Instead, let us roll up our sleeves, stand shoulder to shoulder, and get to work saving our Pacific salmon for future generations. It’s time to do the right thing."

Based on previous statements by Ms. Franz, she gets that this issue is bigger than just the tribal fishing rights - expanding fish populations will benefit both tribal and non tribal fishers.

Friday, June 8, 2018

Palm Beach on the Key Peninsula, Wasshington

Palms in gardens in the Pacific northwest are always a bit of a surprise. They just seem so out of place. This stand of palms is on the coast of Key Peninsula, part of the complex of inlets that make up of the southern end of the Salish Sea/Puget Sound.

Wednesday, June 6, 2018

Twin Dogs and Twin Sisters and Good Lighting

A few weeks ago we had a stretch of weather where the rain came not out of the west but from a low pressure system in Oregon which wrapped the atmospheric flow around to flow into western Washington from the southeast. The result in northwest Washington was some turbulent clouds coming over the North Cascades. 

The result was a brief moment of remarkable lighting. The western sun lighting the twin dogs with the Twin Sisters rising above a low cloud bank.

View of the Twin Sisters from the Nooksack River valley

Wednesday, May 30, 2018

A Hazard of the Job

Health and safety meetings and plans are part of a lot of work places. The idea is to reduce the unexpected - that is anticipate the things that can cause a safety issue. The picture below shows a safety issue that has caught me and recently gave an associate a problem. 

The cobble beach makes for tricky footing as the cobbles shift while walking and can also be slippery. Hence, one gets preoccupied with watching carefully where to place a step. Hence, it can be easy to loose site of a large sharp log sticking at out at 5 feet 8 inches above the ground.

It is sort of a funny thing to receive a hard joust from a stationary spear or log. Its even funny when it happens to you, but it sure can hurt while at the same time making one feel very silly.

Friday, May 25, 2018

Mink Encounter on Orcas

I see Lontra canadenis (river otter) on my coastal ventures. On rarer occasions I will see Neovison vision (American mink). We spotted this mink passing below us on the beach on the north shore of Orcas Island. I was struck by its comfort of being so much out in the open.

The same day and not very far away we heard screeching that I initially assumed was a hawk. Instead it was two minks rolling down the bluff slope and biting at each other.

My take was that this was not a fight but was mating - but I am no expert on the ways of mink courtship or dueling and found the encounter confusing. I will say that the minks in question seemed rather oblivious to my presence with their full attention on each other. 

Wednesday, May 23, 2018

Amazing Video of Fox vs Eagle with a Rabbit Inbetween

My observations of foxes at American Camp (HERE) were not much compared to posted coincidentally on the same day as my post. Besides the great imagery, the vent was captured on video. Pretty amazing event, but also good filming and photography work.

Monday, May 21, 2018

American Camp Foxes

Red Fox on San Juan Island

Before starting a short hike to observe the dune field and wave cut terraces at American Camp, I noted the warnings at the end of the road about not feeding the foxes and keeping a 75-foot buffer from them. The fox above seemed to understand that rule as the fox maintained about a 75-foot distance from me as it went about its business.

The foxes are clearly habituated to humans, and have thus become a park attraction. The fox in the San Juans is a part of the complex dynamics of shifting ecology as a result of the introduction of non native species (the fox is only one of many), land use change, and cultural change. The non native fox is a part of that mix. Many of the foxes on the island are not red. 

Adventures Northwest (the-foxes-of-san-juan-island) has a good write up on the foxes at the park. 

While heading out on Pickett Road, this fox ignored the car as I passed by.

Fox at pull out on the prairie. Note the warning sign about foxes on the fence.

Saturday, May 19, 2018

Euchloe ausonides insulanus - Island Marble butterfly at American Camp, San Juan Island

I had a bit of time to visit American Camp in San Juan Island National Historic Park. The park is on the southern end of the island where the American military set up camp during the joint occupation of the San Juan Islands from 1859 through 1874. The American Camp section of the park has extensive prairie land. This prairie supports a rare butterfly, Euchloe ausonides insulanus - Island Marble butterfly.  

This butterfly has gotten some recent news coverage regarding the efforts to protect the species. The Island Marble butterfly was rediscovered in 1998 after being last observed in 1908. The rediscovery occurred at American Camp (wdfw). One threat to the butterfly is deer (see sign above). The deer like to eat off the tops of mustard plants and inadvertently consume the eggs of the butterfly or the places the butterfly would like to lay eggs. Hence, solar powered electric fences have been installed to protect the butterfly food source.   

Electric fencing in dune and prairie area

Being alerted to the possible presence of the Island Marble via the electric fencing, I spotted a few of the butterflies. And even managed to get a picture of one. It was a thrill to see such a rare species.

Efforts are being made to protect the butterfly and possibly expand its range ( Prairie areas in the San Juans have been greatly diminished and even where still present have altered from the original ecologic make up via invasive plants and grazing by domestic animals and now a high deer population.

The prairie at American Camp is on a south facing wind swept area underlain by glacial sediments that were reworked by wave action as the island emerged from below sea level during the late stages of the last glacial period. The prairie has numerous wave cut terraces and large kettles where blocks of buried ice melted out along the ice margin. The south exposure, rain shadow from the Olympic Range, and well drained soils as well as historic fire setting by First Nations peoples has resulted in one of the larger prairies in western Washington.

Lidar bare earth of American Camp
Note wave cut terraces, kettle depressions and dune field

Wednesday, May 16, 2018

Balsamorhiza sagittata Season in Central Washington

I was fortunate to have some central Washington ventures at a fairly optimum time for wild flowers. The Balsamorhiza sagittata was in peak condition on the east slopes of the Cascade Range - at least I think these are Balsamorhiza sagittata. There are multiple Balsamorhiza, but I am guessing sagittata based on my amateur plant skills and the fact that it is the most common of the balsamroots.

This particular hill side was lightly burned about 10 years ago and grazing has been limited to wild life only, so the crop of balsamroots was enough to cause me to pause and admire the slope before heading uphill.    

Monday, May 7, 2018

New Ecosystem Along the Columbia

Highway 243 spurs off Highway 26 just south of the Interstate 90 bridge over the Columbia River. 243 follows the Columbia River south to Highway 24 just north of the Highway 24 bridge across the Columbia. The scenic highlight is Sentinel Gap where the river passes through the Saddle Mountain ridge.   

1,600-foot cliffs and talus slopes in the gap

The foreground feature of trees along the river is a relatively new development. 


The dams on the Columbia River, particular the Canadian dams, prevent the Columbia from the past wild seasonal swings in river flow. The tamed river no longer has huge late spring and early summer floods as the Canadian dams hold water back. The loss of these large flood events has allowed trees to become established along portions of the river bank where previously the floods would have removed them. The river reach at Sentinel Gap has become progressively more wooded over the decades since the dam building era. The trees are a mix of willow, cottonwood and juniper as well as other brush,and this growth has formed a new ecosystem along the river. 

Saturday, May 5, 2018

Wiyakuktpa - The Gathering Place, Clover Island, Kennewick

Kennewick is located along the Columbia River in southeastern Washington. Clover Island is an island owned by the Port of Kennewick. The island today is a small remnant of the original island which has been covered by water backed up by McNary Dam. However, even before the dam the island would have been subject to inundation from the large floods associated with the late spring snow melt from the mountains to the north. Dams in Canada have largely minimized flooding on the Columbia.

The island has been going through a slow but steady development including a fair number of sculptures including this min park that recognizes the early use of the island as a gathering place and a place ceded to the United States by the Cayuse, Umatilla, and Walla Walla Tribes.

Bronze sculpture of Indians gathering tule
Tule was a major component for home construction

Sunday, April 29, 2018

Impressive Lidar Resolution Aids Field Work

Regular readers of this blog know that lidar imagery and elevation models are a regular feature of posts on the Washington Landscape. That is in part because utilizing lidar is a routine part of my work. Lidar has been a bit of a revolution for geology as well as land use planning.

New high resolution lidar was released earlier this year by the Washington State Department of Natural Resources. The lidar coverage is part of a program to obtain high quality lidar coverage for much of the state. The new lidar covers areas that previously had no lidar and also covers areas where lidar was available, but was of lesser quality. 

The newer lidar data sets have amazing resolution that allows for spotting land features on the order of a foot or two in scale. I utilized the new high resolution lidar recently on a couple of small-scale projects.  

2006 lidar

2017 lidar

There is an obvious difference in the sharpness of the lidar images between 2006 and 2017. The arrow in the second image from 2017 points to a feature completely obscured in the 2006 image. The feature appears to be an erosion feature. 

Erosion feature
A small ravine eroded into slope from water discharged on to the slope from an uphill road ditch

The erosion feature was not the site I was looking at. But seeing it in the lidar before going out in the field suggested that I might get a good exposure of the underlying geology units on the hill slope, Indeed, I did get a good view of the underling glacial related sediments exposed in the small ravine.

What is impressive is how small this ravine is. The feature is only a couple of feet across and five feet deep at its deepest and yet very apparent in the new lidar.   

Friday, April 20, 2018

Culvert Case Notes: a Few Highlights

Washington State appealed a 9th Circuit Court ruling on culverts to the US Supreme Court (Washington State v United States 17-269. Oral arguments were earlier this week. The short story is State roads stream crossings in many places have blocked salmon fish passage. This blockage led to a 9th District Court ruling that the State of Washington needed to accelerate culvert replacements on State Road stream crossings due to the violation of Indian treaties.

I can't say I understand the State's position other than it is keeping with a long time Washington State tradition of not being very supportive of "usual and customary" treaty fishing rights for treaty tribes.

The Supreme Court oral argument transcripts are HERE for those that try to decipher where the Supremes might be heading. 

I noted a few highlights:
JUSTICE SOTOMAYOR (to Noah Purcel arguing for Washington State): In the courts below during the argument in the Ninth Circuit, you said the Stevens Treaty would not prohibit Washington from blocking completely every salmon stream into Puget Sound.

MR. PURCELL: I remember that answer well, Your Honor, and that was a mistake at oral argument about how our theory....

JUSTICE GORSUCH: -- the treaty, which guarantees the right to all usual and customary fishing grounds, really means half of them?

  The point of a treaty I would have thought would have been to -- to freeze in time certain rights and -- and to ensure their existence in perpetuity, regardless of what other social benefits a later municipality might be able to claim.

I don't see anything in the treaty -- maybe you can point it to me, maybe I'm just missing it textually -- anything in the treaty that says: Ah, and your rights to those usual and customary grounds and stations is limited by, and may be completely eliminated, if necessary, to meet other domestic interests that a municipality might have, which is, I think, the position you're taking, I think, before this Court.

 MR. PURCELL: Not exactly, Your Honor.

JUSTICE KAGAN: And like Justice Gorsuch, I'm wondering where that is in the treaty? 

Much of the Washington State argument and back and forth with the Justices at oral revolved around vague standards about that applied prioritization of culverts. Given a recent opinion by Gorsuch on another case, being vague may not be a good idea. I did not fine the 9th Circuit ruling on prioritization vague:

"The court ordered correction of high-priority culverts — those blocking 200 linear meters or more of upstream habitat — within seventeen years. For low-priority culverts — those blocking less than 200 linear meters of upstream habitat — the court ordered correction only at the end of the useful life of the existing culvert, or when an independently undertaken highway project would require replacement of the culvert. Further, recognizing the likelihood that accelerated replacement of some high-priority culverts will not be costeffective, the court allowed the State to defer correction of high-priority culverts accounting for up to ten percent of the total blocked upstream habitat, and to correct those culverts on the more lenient schedule of the low-priority culverts."

Allon Keden arguing for the United States of America against the Washington State appeal had this quote: "The state takes about a half dozen quotations out of context from more than 1,000 pages of record and briefing."

Keden's quote matches how things went during the first appeal to the Court of Appeals for the 9th Circuit. The Court of Appeals panel stated "Washington misrepresents the evidence and mischaracterizes the district court’s order.

It should be noted that much of the 9th's ruling was based on Washington State's own studies:

"WDFW and WSDOT, stated, “Fish passage at human made barriers such as road culverts is one of the most recurrent and correctable obstacles to healthy salmonid stocks in Washington.” The report concluded: A total potential spawning and rearing area of 1,619,839 m 2 (249 linear miles) is currently blocked by WSDOT culverts on the 177 surveyed streams requiring barrier resolution; this is enough wetted stream area to produce 200,000 adult salmonid annually. These estimates would all increase when considering the additional 186 barriers that did not have full habitat assessments."

In sum, we disagree with Washington’s contention that the Tribes “presented no evidence,” and that there was a “complete failure of proof,” that state-owned barrier culverts have a substantial adverse effect on salmon. The record contains extensive evidence, much of it from the State itself, that the State’s barrier culverts have such an effect. We also disagree with Washington’s contention that the court ordered correction of “nearly every state-owned barrier culvert” without “any specific showing” that such correction will “meaningfully improve runs.” The State’s own evidence shows that hundreds of thousands of adult salmon will be produced by opening up the salmon habitat that is currently blocked by the State’s barrier culverts. Finally, we disagree with Washington’s contention that the court’s injunction indiscriminately orders correction of “nearly every state owned barrier culvert” in the Case Area. The court’s order carefully distinguishes between high- and low-priority culverts based on the amount of upstream habitat culvert correction will open up. The order then allows for a further distinction, to be drawn by WSDOT in consultation with the United States and the Tribes, between those high-priority culverts that must be corrected within seventeen years and those that may be corrected on the more lenient schedule applicable to the low-priority culverts."

Wednesday, April 18, 2018

Self Armored River Bluff

We recently traversed along the base of a late-Pleistocene terrace consisting of glacial till and ice proximal meltwater. The terrace formed by incision and erosion by the Nooksack River to create a river bank bluff. The bluff is about 25 feet high. There are numerous large cobbles and boulders at the base of the bluff along the river edge derived from cobbles and boulders that have fallen from the terrace slope forming a lag of very course sediment along the edge of the river. Many of the boulders are much larger that the cobble sediment within the gravel and cobble bars within the river area. 

Cobbles and boulders in the river bluff slope 

The large cobbles and boulders accumulated at the base of the slope along the river appeared to be limiting the erosion along the terrace. The bare slope above shows that some erosion has taken place, but the size of the rock large on the lower slopes was considerably larger than that within the river gravel and cobble bars.

Post our traverse, a review of aerial photographs dating back to the 1930s found no discernible change in the position of the terrace edge over a period of 80 plus years. The historic aerials also showed the river was frequently flowing right at the base of the terrace. Hence, the rocks armoring the lower terrace were effectively reducing erosion for most river flow events.     

Saturday, April 14, 2018

Dungeness Spit Notes

I had a brief venture to the Dungeness River delta. Standing on the saltwater mash flats of the delta I had a view across the marsh and the water of Dungeness Bay.

The Dungeness Lighthouse was a speck on the horizon and only a bit more visible with the telephoto view.

Dungeness Bay looking towards the tip of the spit

Lighthouse viewed via telephoto view

The Dungeness Spit is a remarkable thin stretch of sand and gravel beach extending out into the Strait of Juan de Fuca over 6 miles from the main coast.

A big chunk of sediment comes from the high eroding bluffs to the southwest of the spite. These bluffs are exposed to fairly large waves coming into the open water of the Strait of Juan de Fuca. Ian Miller has put together a scheme for getting a better understanding of this remarkable spit (surveying-dungeness-spit). And it is remarkable - its the longest spit in the United States. Schwatz, Fabbri and Wallace (1987) provide a map of the sediment (drift) movement on this complex spit.

Drift map (Schwartz, Fabbri and Wallace, 1987)

The spit is complicated by the presence of another source of sediment from the southeast from sediment inputs from the Dungeness River as well as periodic waves generated by south winds blowing onto the backside of the spit.

Light House on distal lobe of the spit

Beyond the lighthouse, the spit is a no-entry wild life preserve as critical habitat for many bird species.