1950 Jackson Creek, Skagit County Debris Flow

The Highway 9 corridor from Sedro-Wooley to Kendal follows the Samish River Valley and then after crossing a very subtle divide follows the South Fork Nooksack River Valley. I previously noted the alluvial fans associated with steams that flow into the Sanish River Valley (alluvial-fans-altering-samish-river).

Doing some review of the valley I came across this 1950 aerial of Jackson Creek with a recent debris flow scar path and deposit on the alluvial fan that extends out onto the Samish Valley floor.  

Jackman Creek 1950 with debris flow scar and debris flow deposit

Timber harvests have started up again in the Jackson Creek watershed, but the creek and the steep slopes near the creek have been partially buffered versus the previous log everything approach. The other substantive change is road construction across stream subject to debris flows have generally improved to reduce the risk of the road causing a debris flow. That said the creek is lined with steep unstable slopes and future slope failures and accumulation of debris  

Jackson Creek (2023, Skagit County) 

The Jackson Creek alluvial fan has resulted in a lake upstream from the fan and there is a lake down stream that is influenced by another alluvial fan at Mill Creek. Both of these lakes may also be influenced by beaver activity. Mill Creek had a debris flow in 1983 that resulted in a fatality.  

Lidar bare earth (via Skagit County)

It appears that a fairly large berm was built post the debris flow. There is a gap in the berm where a natural gas pipline was constructed. The dredge spoils are on the distill end of the fan and this spot may need periodic dredging to keep the creek passing under the railroad.

Highway 397 Road Cut West of Nine Mile Canyon, Part I

 

Highway 397 is a spur highway off of Interstate 84 south of Kennewick that accesses the Finley area to the east of Kennewick. The route by-passes Kennewick, angling across the northern slopes of the Horse Heaven Hills south of Kennewick. A road cut just west of South Nine Canyon Road (46.07'47", 119.04'38") got my attention with a variety of geology units. This post is Part I and is focused on the west end of the cut slope where a sedimentary unit is exposed between Columbia River Basalt Group lava flows.

West end of the cut slope

Lake sediments from between lava flows. The sediment appears tuffaceous.

A mix of basalt rubble and sediment

Basalt rubble within sediment with some very 'cooked' sediment

Sediment at base of lava flow

Closer view of sediment at base of lava flow

Reidel and Fecht (1994) geology map covers this area at a 1:100,000 scale. The scale precludes some detail and the sediment interbeds are not shown. Furthermore the road cut post dates the geology mapping of the area. They note that these interbeds of sediment are generally best exposed in road cuts. Where the interbeds are mapped they are referred to as continental sedimentary deposits. In places where gravel is present, the gravel appears to be sourced from ancestral Columbia River or Salmon/Clearwater River flow paths as the grvael contains rocks with a continental affinity.

The map does indicate that the lower basalt below the sediment is the Umatilla Member and the upper basalt is the Pamona Member. Both of these members are part of the Saddle Mountains Formation of the Columbia River Basalt Group. 

The delineation of these basalt flows was accomplished via a combination of geochemistry, magnetic polarity and isotopic ages.  

The lava flows in the chart above between the Umatilla and Pamona are generally more localized lava flows or smaller flows restricted to ancestral river valleys. The lack of flows between the Umatilla and Pamona as well as the thinness of Continental deposits at this site suggests this site was elevated relative to the broader Columbia Basin similar to today.

 

My Forest Enemy: Ilex aquifofium

While doing field work I come across what I have decided is a personal enemy on regular basis.

Eglish Holly (Ilex aquifolium)

I was able to pull this one out by the roots.

I at times visuzlize the Pacific Northwest forests in 10,000 years being a forest of holly. The holly shown above was in an old growth forest. I have come across holly in old forest areas ranging in elevation from the inland coastal areas to as much as 3500 feet in the Cascade Range. I have been digging it out of my own forest stand on regular basis, and when I can, I yank it out of the ground and stick it into a spot above the ground while traversing through the forest during a field ventures.  .

KUOW covered recent efforts to get this plant listed as a noxiuos weed (kuow.org/have-a-holly-noxious-christmas). The issue strikes me as a state government and ethics failure.  

Windfall and Dog Hair

I plotted out a route to a steep slope at the headwaters of a creek in the Northwest Cascades. While approaching the site I noted windfall trees on the edge of a clearcut.

While walking the road and a section of trail took about 2 hours to cover 6 miles with a fair bit of elevation gain and hiking out took about 1.5 hours as it was downhill, the last quarter mile to the steep slopes I wanted to reach took nearly an hour each way. 

Windfall trees and dog hair young trees

Dog hair western hemlock obscuring downed trees

It is a slow process navigating over fallen logs and brancheds that tend to break. It did not help that portions of the area were also steep. 

I did reach my goal of getting to the steep headwater slope - that presented its own challenge as there were cliffs in the forest.

Very steep forested slope

Made for a bit of a long day and light got a bit dim before getting back to my starting point, but I did get some nice views as the clouds broke up. 

Whitechuck and Glacier Peak

Whitehorse and Three Fingers