Wednesday, November 26, 2014

Safe Travels and a Bit More Music

The Thanksgiving tradition blog post with Lisa Hannigan. Also some Angus and Julia Stone. Perhaps a bit of a melancholy theme to this selection.











Tuesday, November 25, 2014

Slope Fractures Before the Nile Landslide of 2009

DEM of Sanford Pasture Landslide
 
A landslide on the Naches River west of Yakima in 2009 diverted the Naches River and closed a State Highway. That slide was a very small part of a much older ancient massive landslide, the Sanford Pasture Landslide. The part that failed was a small section on the northwest end of the larger ancient landslide complex.

Sliding Thought Blog put up a nice post about the Sanford Pasture Landslide HERE. Alas, the posts at Sliding Thought have been discontinued - sensitive higher ups in the agency depriving us landslide wonks of some excellent insights.

When pulling some images together for a talk I decided to include a note on the Sanford Pasture Landslide simply because it was so large. It surpasses the huge Church Mountain Slide in Whatcom County and is much larger than the more famous Bridge of the Gods slide in the Columbia River Gorge. When pulling historic aerials together, I noted that the set of historic images captures the development of the fracture that began to form several years before the slide. The fracture was noticed by the Department of Natural Resources prior to the slope failure.

Pre facture image from 1998 with rock quarry in lower central part of image

Fracture can be seen on the steep slope on upper right in this 2009 image

2010 post slope failure with diverted river
 
WDOT has a lengthily post slide technical report that compiled lots of information and provides good figures and the geologic interpretations as well as assessment of the current stability of the slide area (NileValleyLandslidegeotechnicalreport.pdf).

Sunday, November 23, 2014

Wetlands, Farmland and Drainage on the Nooksack Flood Plain

Before our November sunny break I headed north to Lynden and noted the water logged Nooksack River flood plain south of town. 
 
Nooksack River flood plain south of river and south of Lynden
 
The river was not flooding. The source of water standing over acres of land was the result of lots of local rain and poor drainage. The silty soils, high ground water and subtle topography cause water to accumulate in the fields.
 
The DEM of the area shows the problem of drainage on the flood plain - it is essentially uphill to the river.
 
DEM of Nooksack flood plain

The river is flowing from east to west and is the dark olive green sinuous line in the image. The straight tan line on the west half is Guide Meridian Road. I took the watery picture from my car looking east south of the river. Note that there are broad olive green colored low areas well back from the river both north and south of the river. The two south of the river are linked to the river via narrow streams and ditches that are barely discernible in the image. Otherwise these two low areas are separated from the river by a subtle but definite uphill slope. Each color shade corresponds to 1 meter in elevation.

Without the ability to keep the narrow ditches and stream connections to the river these fields would turn into swamp land or wet lands depending on your word selection. Water on the fields is not a problem in the winter, but if the fields remain wet deep into late spring, the farm land will be of little value.

The Growth Management Act requires counties to protect wetlands; however, there is a recognition that agricultural land should be protected as well. Under the local GMA required regulations Whatcom County critical areas regulations for wetlands allow the maintenance of drainage channels on farm lands. But the work on these drainage channels still requires State permits from the Washington State Department of Wildlife and the work requires a farm conservation plan.

Saturday, November 22, 2014

Fault Y in the Kittitas Valley

Waitt (1979)  identified three faults cutting across the Kittatas Valley. While the faults do off set Pleistocene sediments of the Thorpe Gravel, no definitive off sets have been identified within younger (last 11,000 years) sediments. The off set of the Thorp Gravel alluvial plain north of Ellensburg can readily be seen in the DEM: 
Fault off set is an east-west fault cutting across the center of the DEM with up to the south 

This DEM has the fault marked in black

There are two other faults. One is closer to Ellensburg and the other towards the north.

The aerial view of the the fault shown above via Google earth:




Friday, November 21, 2014

Random bits of Whidbey Island History

I was digging a bit into the history of the water front area of Oak Harbor related to a project I was working on and came across a couple of unrelated but interesting bits on the history of Whidbey Island by David Wilma at http://www.historylink.org.

"The settlers learned to dose deer carcasses with strychnine and the wolves eventually became extinct on Whidbey Island."

A good reminder as to how wide spread wolves were and that returning to some natural condition ecosystem may not be so easy without a top predator keeping the deer population in check.

"Sea Captain Edward Barrington and Charlie Phillips opened a trading post at Oak Harbor in the early 1850s because he did not want to paddle a canoe two days to Olympia for supplies. Barrington became an important intermediary between whites and Indians when disputes arose. Local legend holds that Barrington, a large man with red hair and beard, confronted a group of raiding Northern Indians. Barrington showed the invaders his fear of no one by destroying a nearby Skagit burial canoe and placing a skull on a stick. He then began to dance and then rushed the raiders. They fled in panic and Barrington saved himself and local Skagits from death and enslavement. Northern Indians never again bothered Oak Harbor."

This legend does conjure an entertaining visual impression. What is definitely true is that northern Indians did routinely raid this area and had been for some time including in the 1850s. One of these raids near present day Port Gamble likely played a major role in the outcome of the Yakama War. The U.S. Navy fired on the invading Indians. North Puget Sound and Washington tribes were not receptive to the idea of joining the Yakama War in part due to appreciation of defense from the invading northern Indians. Barrington may have played some role in repelling an attack, but cannon fire from the U.S. Navy likely put an end to the northern Indian raids.   

Thursday, November 20, 2014

Notes on Tree Rings, and Old Forests and an Old Terrane on Orcas Island

I came across a couple of blow down trees that had been cut in order to reopen the road that they blocked. Both trees were Douglas fir and the site was on the dryer, western part of Orcas Island. Both trees were growing in very thin to almost non existent soil over Turtleback Complex bedrock. Knowing how old trees are can be helpful in evaluating slopes. In this case the trees were not really important for that purpose, but for other reasons I was curious about the age of the trees so I did tree ring counting.  



As can be seen the rings were very tightly spaced particularly that outer band shown above, but a mid section band was also very closely spaced. I ended up with a count of 220. The tree was much older than I had initially expected at first glance. The modest size by old age reflects the rather harsh growing conditions. The tree was growing out of bedrock with very little soil. Something to consider when trying to estimate the age of trees by girth alone. A few weeks ago I was in a forest of much larger Douglas fir and that stand of trees was less than 60 years old.

No much soil under those roots.

The forest where this tree was located is nearly all Douglas fir, but the trunk sizes varied suggesting a very mixed age. I did observe a few madrones which would suggest the forest canopy may have been more open in the past, but this forest was fairly open even now. Underbrush was very thin and it was easy to move through this forest with a moss dominated floor and very thin brush. All over very thin soils and fractured hard bedrock and solid bedrock - not much in the way of glacial related sediment at this location.

Take a close look at the tree lying on the floor of the forest. This is an old blow down, but it is still very much alive. Two of its limbs have become leaders growing as straight trees out of the trunk. This is a Douglas fir feature I have observed at several other locations on Orcas Island including some spectacular examples on Turtleback Mountain (selection-of-trees-on-orcas-island).

Elsewhere on Orcas I have observed very massive Douglas firs much bigger the 220 year old tree. Hence, I am now very curious about the age of those giants some of which are located on sites with very harsh growing conditions.

This blow down tree has a bit of a story to tell. One thing it shows is that at least at this site the area was not clear cut logged. Historically the San Juan Islands were known for not having particularly good timber relative to much of the rest of western Washington. This particular blow down tree seemed to be straight and not very limby. Perhaps its inland location and challenging site to move logs preempted this forest from being clear cut. The tree also had survived pre European/American land management - it had not been burned by fire. I did not observe any indication of past burn scars anywhere in this particular forest stand.

From a forest species perspective, the dominance of Douglas fir at this location dating back over 200 years is a bit different than nearby forest stands where lodge pole pine (locally called shore pine) are well represented as well as stands of junipers and oaks.

As for the bedrock of this forest. The rocks are part of the Turtleback Complex named for Turtleback Mountain on the west side of Orcas Island. Not supper exciting rocks to look at, but these rocks are very old and have a story to tell for those willing to extract the story out of them via microscopic mineral work and careful measurement of element isotopes.

A bit of Turtleback with the edge of a rock hammer on the right

Turtleback with faint mineral gneiss-like mineral alignment and green minerals (epidote?) with Douglas fir needle for scale.

The Turtleback Complex is one of several tectonic terranes in the Northwest Cascades System-San Juan mélange. Units within the mélange consist of a wide variety of low-grade to high-grade metamorphic rocks of various ages juxtaposed along now extinct tectonic fault lines. The terrains are slices of ocean floor, island arcs and possibly in some cases slices of terrane broken off of other continents and then accreted to the North American western margin via plate tectonic movements.

The Turtleback Complex is the oldest terrain in the San Juan mélange and has been correlated with similar very old rocks in the Northwest Cascades, the Yellow Aster Complex. Vance (1975) suggested the Turtleback was continental. The Turtleback contains a range of igneous rock types with intrusive cross cutting relationships, and I have found a fair bit of variety across the various locations I have encountered the Turtleback. Age of the intrusive rocks have been reported ages ranging from 554 Ma to 460 Ma (Whetten and others, 1978 and Brandon and others, 1988). This a very old terrane and plate tectonics does have some mind bending puzzles and correlating long traveled old terranes with their homeland will take considerable work. 

Sunday, November 16, 2014

BNSF Railroad and Unstable Bluffs near Bellingham

In late 2012 and early 2013 there were close to 100 shallow landslides that closed the rail line between Seattle and Everett, Washington due to wet weather and slopes above the railroad tracks becoming repeatedly saturated (railroad-landslide-closures). There was even a landslide that hit a moving train during that period.

The rail line just northwest of Bellingham has not been closed by landslides, but faces a significant risk of landslides in the future as the railroad track runs along the top of a steep eroding shoreline bluff.  

Its worth enlarging this picture to see the failure scarps at several places on the slope as well as a drain pipe installed to reduce water on the slope. 

Railroad without much space 

I routinely assess steep shoreline bluff slopes and recommend setbacks for homes from the top edge of steep shoreline bluffs - this section of railroad would not conform with recommended setbacks. But like homes close to the edge of a potentially unstable slope, the view is great. And I have enjoyed the view from the train while heading up to Vancouver, BC.
 The beach is very narrow at least along parts of the bluff and high water routinely reaches the toe of the slope causing erosion.
Shallow surface failure on bluff

The bluff is underlain by unconsolidated late ice age deposits of silt and clay and sand and gravel. The small slide shown above is the result of the toe of the slope being eroded by waves and then the slide area slowly working its way up the slope.

This reach of shore is exposed to south and west winds and has a large enough fetch and orientation such that large waves can be generated and combined with large storm surges.

A future challenge for the railroad.