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.   

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."

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.     

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.

Cool Oblique Lidar Image of Racehorse Slide by Washington DNR

The Washington State Department of Natural Resources has a set of new images derived from utilizing lidar (new-lidar-screensavers-of-washington). One of the images is the Racehorse Slide in Whatcom County which I very recently coincidentally posted on recently (first-description-of-racehorse-slide).   

The steepness of the upper part of the slide appears a bit exaggerated, but the imagery overlain on the lidar and aerial oblique views does provides a compelling image.

Within the news post associated with some other great images, there is a series of changing images of the Racehorse slide. I screen saved on that has labels added.

The slide is a complex slide associated with large scale dip slope failures and appears to consist of multiple failures. There are a number of these large scale dip slope failures in the Chuckanut Formation in Whatcom County and the scale and potential consequence is a bit disconcerting. The marked up image shows the Racehorse Creek landslide of 2009 that appears to have failed on the same bedding plain.

Images like this are a good wake up call to the potential hazards in our mountain valleys. This slide could use a bit more study and understanding.     

First Description of Racehorse Slide

I visited the Racehorse Slide in Whhatcom County this week. The Racehorse Slide is a big slide that extended across the valley floor of the Nooksack River.

Lidar of racehorse slide

The first description of the slide may be attributed to the government land survey crews. I took a look through the field notes from the original government land survey that traversed this slide. Galbraith noted the piles of rocks and none of his survey witness tress were large. 

   

Pringle, Schuster, and Logan (1998) took a crack at dating the slide via a log exposed in the Nooksack River bank below the slide. They got a date of 3,780 radiocarbon years ago. Given the location of the log this date can be viewed as a maximum date; the slide may be younger, and based on the appearance of the boulder field I suspect it is substantially younger.

Note lack of weathering rind on this coarse sandstone

Besides the rather unweathered appearance of the sandstone boulders, there are no large old stumps within the boulder field. Perhaps there are some elsewhere on the the slide. The lack of large stumps is by no means definitive regarding the slide age - it may simply mean that fire recurrence may have been frequent enough to prevent large tress from growing in this area. Early accounts of the area summarized by Cashman and Brunengo (2006) suggest that the area had been burned over in the late 1800s.

    

Whatcom-Labounty Wild Land Northwest of Bellingham

Just to the northwest of the Bellingham city limits is a swath of land between Interstate 5 and Northwest Road. From a map perspective, I have long been familiar with this area. The city designated it as an urban growth area back in the early days of the Growth Management Act in the mid 1990s. The land is underlain by Bellingham Glacial Marine Drift consisting mostly of silt and clay. Glaciomarine drift consists of silty clay soils that were deposited by melting glacial ice floating on the sea at a time near the end of the last glacial period when the local relative sea level was higher than the present (the mass of thick glacial ice that had covered the area had depressed the land surface hundreds of feet in the region).

Northwest of Bellingham, the glacial marine drift topography is a relatively hummocky landscape. I suspect the hummocky landscape was the result of underwater currents during the late stages of glacial marine deposition. Soils maps indicate the soils are Whatcom-Labounty soils. The Whatcom soils are well drained at shallow levels and wet at depth and the Labounty soils are poorly drained and tend to be wet. The poor drainage and hummocky nature of the area is such that it was poor farm land and poor forest land. The wetlands as well as very soft soils also have made it rather poor land for urban development; I estimate the area is on the order of 60 percent or more wetlands. 

The result is a swath of land at the city's edge that is wild land. While other wild lands at the city edge attract recreation, the brush, wet ground and lack of trails means a venture into this area is a brief wilderness experience even if one can hear the freeway and air planes at the nearby airport.

Start of my venture was a classic bush wack only on level ground.  

The wetlands rewarded me with an early bloomer - Lysichiton americanus (skunk cabbage).

The biggest challenging was navigating across or in some cases through areas of standing water.

Water coverage of this landscape has been increasing. Beavers in this area can go about their works relatively free of disruption. They do not bother with permits to cut trees down in forested wetlands or get hydraulic permits or dam permits.

A forested hummock raising above the wetlands as an island provided a brief spell of easy walking.

A partially blown over Douglas fir redirected the lead to a limb.

Sometime in the past fire had visited this island in the wetlands.

I did manage to get to my sample site along a particular branch of wetland drainage. Under the black organic layer the soil is stained by iron precipitate.