Thursday, December 27, 2018

Big Western Red Cedars with Character

The coastal strip of Olympic National Park that coincides with U.S. Highway 101 has various pull outs and short trails to the shoreline. Near the north end of the strip just south of Ruby Beach (HERE) a sign indicates "Big Cedar". A short gravel road leads to a parking lot for a short hike through a grove of very large western red cedar trees that have a great deal of character. And they are big.

The multi crown branching canopy of the trees suggests past stresses. Most likely in my mind is intense storm events that have periodically broken off the tops of the trees. Periodic but very rare wildfire may have taken place as well that damaged but did not kill the trees. While high winds are common on the outer coast, there have been some some extreme wind events that would break the tree tops. A storm in the 1920s was reported to have had 120 mph winds. Given the 100s of years these trees have grown it is reasonable to assume that similar storms have impacted this grove of trees repeatedly.

The multi lead trees allowed them to survive the the logging events that swept over this landscape prior to protection of the forest as first a national monument and later as a national park.  

Sunday, December 23, 2018

Birch Bay Storm Surge Event Notes

Birch Bay in northwest Washington was the site of coastal flooding during the last storm system.

The flooding was in part the result of the initial low pressure system just off the west side of Vancouver Island. The low created pressure itself caused a sea level rise on the order of 1 foot above the astronomical tide levels. The location of the low off Vancouver Island also created winds that pushed water into the Strait of Juan de Fuca and Salish Sea. The local winds further enhanced the storm surge of tide levels. The local winds also were oriented to develop large waves in a bay that is otherwise rather calm.

The closest tide station with continuous measurements is just south of Birch Bay at Cherry Point. The storm surge at Cherry Point during the storm was 2.5 feet; a high surge for the Salish Sea.
The maximum storm surge coincided with the peak astronomical tide. I suspect that that the storm surge at Birch Bay was even higher due to local geometry of the shoreline and wind direction.

By comparison, the last big storm surge event at Cherry Point was in 2006.

The 2006 storm surge event also coincided with a high tide event and reached 12.5 feet. That event had essentially the same storm surge of 2.5 feet, but the astronomical tide level was 0.5 feet higher in 2006 versus 2018.

Birch Bay may have other issues that will drive erosion and flooding along the shore. The road along the bay is located on top of the upper berm of the beach. Sediment deposited on the road is removed and hence the berm remains at the same level. Sediment supply to the beach has also been disrupted by the cutting through the beach to build a marina on the north of the bay and by shoreline arming on the bluffs south of the beach. 

Thursday, December 20, 2018

Washington Outer Coast: Ruby Beach Notes

Ruby Beach is located in the coastal strip of Olympic National Park that is traversed by US 101. A short trail from the parking area leads to the beach with several rock stacks protruding from the beach and just off shore. 

Ruby Beach and Cedar Creek with Abbey Island in the distance

Stout Rock and Destruction Island in the distance

Arches within shoreline sea stack

The sea stacks and rocky islands along the coastal area are part of the Quillayute Needles National Wildlife Refuge. The Refuge is one of the earliest in America. It was set aside to protect birds and other wildlife by Theodore Roosevelt in 1907. At that time game hunters were decimating bird populations and the early refuges were critical in stopping the destruction of entire species of birds.

The Refuge is also included in the even larger Washington Islands Wilderness, a no public entry wilderness. The primary purpose of the wilderness area is to protect the bird and marine habitat around these critical islands. Destruction Island is not included in the wilderness but is included within the Wildlife Refuge.

The bedrock at Ruby Beach consists of ocean floor sediments that have been highly deformed in the process of accretion tectonics as ocean floor rocks were added onto the margin of North America. The rocks are Miocene in age. The highly disrupted bedrock layers can be best observed a short walk up Cedar Creek along the banks of the stream.

Tectonized ocean floor rocks on the banks of Cedar Creek upstream of Ruby Beach

Saturday, December 15, 2018

Scenic South Skagit Highway

Post my visit to the lower Sauk River, I returned home via the South Skagit Highway. The South Skagit Highway is on the South side of the Skagit. As such, it is on the shady side of the valley. This time of year, December, significant stretches of the road are in shade all day. It is a bit of an "off the beaten path" road with no towns and by far most travelers taking the main highway, State Route 20, on the north side of the valley. The main highway, being on the north side of the valley gets more sun, but the mountains on the north side block the views of Mount Baker. 

View of Baker with the Skagit River in the foreground

The South Skagit Highway route also provides some good road cuts revealing the ice age stratigraphy of the lower valley. The last ice age history in the lower Skagit Valley has some complexity with ice coming into the valley from the north (alpine glaciers) and from the west (continental ice) (Riedel, 2007).
Glacial age sediments upstream of the Baker River/Skagit River confluence

Success of farming operations does not have a lot to do with scenery, but this cattle operation along the South Skagit does add to the scenic drive. 

The constant shad stretches provided some nice winter scenery.

The trees enclose the road on many stretches, in part die to lack of power lines and the need to trim.

Thursday, December 13, 2018

Sauk River Dynamic Channel Migration

The Sauk River is a tributary River to the Skagit. It is in part fed by waters from Glacier Peak and in late summer is cloudy from glacial sediment. After a dry stretch of winter weather, the rive was clear when I recently visited the Sauk a bit up stream from its confluence with the Skagit. 

The Sauk is a dynamic river that moves about on its valley floor. I have made a few geology assessments considering channel migration and subsequent erosion hazards on the Sauk. Others have as well ( My recent trip up the Sauk allowed me to take a look at a river reach I had evaluated 15 years ago.

Well casing has survived the erosion so far

Concrete and piping at former home site

Foundation and septic tank lid

Ongoing bank erosion

For modest homes along the river, stopping channel migration on the Sauk is prohibitively expensive. Besides the permitting issues, the Sauk is a big river with very high flood flows, and thus bank protection would require large scale engineered structural solutions beyond the reach of small rural home owners. Channel movement on some reaches of the Sauk has been as much or more than quarter mile. The lower end right before the confluence is especially dynamic and can readily be seen along the Concrete-Sauk Road.

Lower end of Sauk with broad areas stripped of trees by recent channel movement

That movement has found its way to the valley edge and took a bite out of the Concrete-Sauk Road.

Overflow channel aimed at the Concrete-Sauk Road

Friday, December 7, 2018

Foreset Lava Flow South of Moses Coulee

Much of eastern Washington is underline by the Columbia River Basalt Group. The eruptions took place primarily in northeast Oregon between 17 and 14 million years ago. In central Washington the large lava flows encountered rivers flowing from the north and possible the west. The flows would have dammed the rivers forming lakes. Subsequent lava flows flowed into those lakes. The Columbia River's subsequent carving a deep valley into the basalt flows with some enhancement with the large ice age floods provides exposures to the lava/lake interactions. The interaction of lava flows with water and lake sediments can readily be seen along numerous road cuts and outcrops (columns-and-palagonite) including Interstate 90 west of Vantage. A basalt flow invading lake sediments like an intrusion can be seen at the top of McNeil Canyon north of Chelan (invasive-basalt-at-top-of-mcneil-canyon).   

Along Highway 28 south of Wenatchee there are great exposures of multiple large lava flows. South of Moses Coulee there is a palagonite rich layer that shows foreset bedding structure.        

Angled units within the yellow palagonite and basalt. Younger lava flows on the cliff top did not interact with water and  developed columnar joints upon cooling.

Sunday, December 2, 2018

Lake Crescent and Landlsides

A trip around the Olympic Peninsula typically entails a drive along the shore of Lake Crescent on the northwest of the Peninsula. The lake is one Washington State's largest. By area it is number 6, but by volume it is number 2 behind Lake Chelan.

Lake Crescent 

The lake is within a glacially eroded valley on the northwest flank of the Olympic Mountains. The valley was not carved by ice coming out of the Olympics, but by the massive Juan de Fuca ice lobe that covered much of the area well up the flank of the Olympics.

The depth of the lake has taken awhile to get a handle on because it is so deep. Dartnell, Warrick, and Wegmann (2017) completed a bathnmetry study and came up with a result similar to a depth of a previous effort by Eian Ray and Jeff Enge. These more recent efforts have found a maximum depth of about 600 feet.

The more recent bathymetry shows what appears to be a landslide on the lake floor. The over steep mountain slopes in this glaciated area have failed in the past with several large scale landslides recognized in the area of the lake.

Portion of Schasse (2003) compilation geology map
Blue hatcher line shows estimated elevation of glacial ice
Note several large landslides in yellow

The landslide at the east end of the lake has been interpreted to have dammed the lake, splitting the lake into two lakes, Lake Sutherland and Lake Crescent. This deepened Lake Crescent by about 50 feet and the lake began draining to the northwest via the Lyre River. This new drainage arrangement allowed a new species of fish to develop associated with the lake. 

If one looks carefully while driving Highway 101, the ground between the two lakes is hummocky typical of large landslide deposits. Other slide deposits are evident as well. 

Slide deposit above east shore of lake

The highway crosses a large slide complex to the west of the lake as well.

Lidar bare earth image of slide complex west of Lake Crescent via DNR Lidar Portal

The lake is located in the transition zone between the very wet west side of the Olympic Peninsula a dn the drier north and northeast rain shadow side of the Olympic Mountains.

Lake Crescent and with Storm King Mountain in the distance

Cloud bank on the west ridge of Pyramid Mountain