Friday, April 18, 2014

Church Mountain and Sanford Pasture Landslides

LiDAR imagery does not extend all the way up to Glacier, Washington. As noted in my last post, the Church Mountain Landslide fills the valley floor of the North Fork Nooksack River near Glacier.
 
DEM (digital elevation model) of Church Mountain Landslide
Summit of Church Mountain is on the upper left
Lumpy area in lower center filling the valley is the thicker part of the slide deposit
The slide deposit extends nearly all the way to the left edge of the image
Note the change in image sharpness with LiDAR DEM on the left half

The Church Mountain slide is absolutely huge. Not to take anything away from the Church Mountain landslide, but the petty side of me has to point out that the Church Mountain landslide is not the largest landslide in the United States or even Washington State. The Sanford Pasture Landslide west of Naches, Washington is substantially larger. A very small secondary portion of this landslide collapsed a few years ago and blocked the Naches River. 
   
DEM of Sanford Pasture Landslide west of Naches

USGS topo map of Sanford Landslide

Aerial of Landslide



 
A final note: Sanford is not the Washington State champion; there is an even a bigger landslide south of Wenatchee.

Wednesday, April 16, 2014

A Few Deep-Seated Bedrock Landslides in Whatcom County

Shortly after the Oso/Hazel slide John Stark with the Bellingham Herald contacted me and asked if Whatcom County has any comparable landslide risks. In terms of likely imminent threat, there are no sites in Whatcom County that are directly comparable to the Hazel Slide in terms of size and pending risk. The Clay Banks (nooksack-river-temporarily-blocked-by-landslide, nooksack-river-blocking-landslide-notes, further-update-on-nooksack-river/clay-banks-via-DT, and more-on-clay-banksnooksack-landslide) has been the location of the largest slides along the Nooksack River, but its height is less than the Oso Slide and has more cohesion and is at least partially compacted.
 
That said, the steep mountain slopes of the more easterly part of Whatcom County hold plenty of potential smaller but still very hazardous landslide and debris flow risks. 
 
And then there is the fact that even bedrock mountain slopes do fail, and the Northwest Cascades of Whatcom County have had plenty of deep-seated bedrock landslides. While the risk of a large catastrophic bedrock failure event taking place anytime soon is low, the extent of the slide deposition area does warrant some long term planning considerations.
 
So a bit of LiDAR to illustrate a just a few.  

South end of Sumas Mountain

Sumas Mountain has very large deep seated bedrock failures on all sides. The one above is perched just above confluences of the three forks of the Nooksack River. Clearly there has been some major shifting and block movement, but thus far no valley filling collapse. The bedrock is Chuckanut Formation sandstone and siltstone.

Large slide west of Kendal

This slide has been well know as it shape is clear even without LiDAR on topographic maps with its spectacular lobe protruding out onto the former glacial river outwash plain clearing showing it is a post ice-age landslide. This slide is on the east side of Sumas Mountain within Chilliwack metasedimentary rocks.


There are numerous landslides on this particular Mountain. The deposit of landslide debris is clearly post glacial and covers the lowest youngest part of the North Fork Nooksack River valley. This slide in Chuckanut Formation rock is one over several that have come off of the aptly named Slide Mountain.

Slide west of Glacier, Washington

This slide is also within Chuckanut Formation. Unlike the previous shown landslides, this one does not show up on the geologic maps. Its lower end blends together with a much large landslide deposit from Church Mountain. The North Fork Nooksack flood plan is incised into the valley floor with a elevated terrace covering the southern half of the valley floor. That terrace is a huge landslide deposit from 2,000 year old Church Mountain (fieldtrips/the-church-mountain-landslide).

The above shown deep-seated bedrock failures are all pre historic. But there are few examples of deep-seated historic bedrock failures in recent years in Whatcom County.

One of the more pressing problem slides even stars in a movie: WWULandslide/landslideCamTimeLapse.

Monday, April 14, 2014

Perspective on Rain and Oso/Hazel Landslide

Rain gets a bum wrap when it comes to landslides. Heavy rain caused the landslide is a common statement. Record breaking rain caused landslide or landslides. Yes, there is a correlation of when landslides happen and rain events, but you can not blame the rain for making steep mountain slopes, steep shoreline bluffs or steep river valley bluffs. The blame the rain gets added to by forestry types as well. Any suggestion that a landslide was caused by logging leads to finger pointing at rain.

Rain has taken a fair bit of blame for the Oso/Hazel Landslide. And much as been made of record breaking rain. So it was time to check those rain fall records.

The two stations with long term records are Arlington and Darrington. Oso is located roughly half way between these two stations. Darrington has records going back to 1911 and Arlington's goes back to 1922. Finney Creek is a remote station with too short of a record to be much use for comparison. Darrington being more deeply in the mountains is far wetter - roughly twice as wet as Arlington.

Darrington:

The 19.30 inches of rain for March 2014 was the wettest March ever. The mean for March is 8.61. So headlines are record rain causes landslide. Twice normal rainfall triggers landslide. However, slow down and look at some other months. Like January 1953 when 31.22 inches fell. Or the infamous winter of 1933 when 30.42 inches fell in December. All in all the March record has been exceeded in other months at Darrington 17 times. 

Arlington:

The March 2014 rainfall of 8.70 inches at Arlington fell short of the March record of 9.23 inches. The March 2014 rainfall amount has been exceeded 20 times in other months.  

Saturday, April 12, 2014

A Last Gasp for Coal Mining In Washington

  
John Henry 1 coal mine and processing in Black Diamond

Coal mining came to an end in Washington State with the closure of the Centralia Coal Mine in 2006. The John Henry 1 Mine in aptly named Black Diamond has not operated since 1997 but has recently applied to reopen and in the process finish some reclamation. The Environmental Assessment (JHM_EA.pdf) is currently in the public comment period. The John Henry 1 Mine has a contract to supply coal for cement production to a Richmond BC concrete company and hopes to perhaps sell coal for cement production in Seattle. In addition to the coal seam that the mine intends to exploit, the formation also contains a seam of clay that is also used in concrete formulations.

Monday, April 7, 2014

Canyon Creek Another Path to Reducing a Gelogic Hazard

The Whatcom County Council acting as the Whatcom County Flood District Board of Supervisors will be voting this evening on accepting a grant agreement with the Washington State Department of Ecology for Flood Plain Restoration Provsio funds whatcom.council/agendabills/ab2014-139.pdf. The $2 million grant will be used to widen the flood plain area on the lower reaches of Canyon Creek. The project serves two purposes: 1) improves salmon habitat on a degraded reach of the stream, and 2) reduces the risk from flooding, erosion or debris flows at the site. 
 
Lower Canyon Creek 2006 USDA image via Google earth

The grant will fund additional work that has already been done to reduce the geologic risk at the site. The Google earth image below from 2013 shows active work on the west bank of the creek as the levee was pulled back last summer.


The lower reach of Canyon Creek flows across the eastern side of a broad alluvial fan before entering the Nooksack River. The creek channel and flood plain of the creek were well incised down into the older fan surface leaving the impression that most of the fan was an old feature and not subject to flooding. The creek location had been stable for many decades. A large subdivision was platted on the older fan surface with roads laid out and homes were built. The apparent peaceful situation all changed in 1989.


LiDAR image of the fan with the Nooksack River just to the west of and eroding the distal portion of the fan. Deep-seated landslides are apparent on both side of the canyon upstream of the alluvial fan.

A large flood impacted the Nooksack River basin in 1989. Extensive major flooding took place on the Nooksack. Canyon Creek also flooded, but more importantly the creek eroded is west bank on the lower reach chewing hundreds of feet westward and into the platted lots of the subdivision. After the flood the eroded bank was lined with boulders to impede further erosion. Within days of completion of the project another major flood event took place and boulders were stripped away. These events destroyed 4 homes and damaged a resort property near the mouth of the creek.

Yes, there had been extensive flooding, but the flows and violence of the floods on Canyon Creek were far in excess of what would be expected by flooding. By one estimate the flood levels on Canyon Creek were estimated to have been a 1 in 10,000 year event. The problem was in the canyon above, deep-seated landslides had shifted and dammed the creek triggering huge surges of water as the dams failed.

LiDAR image of landslides impinging on both sides of the creek

In addition to the huge flow of water a huge sediment input from the slides was being deposited on the lower flood plain of the creek pushing the creek to the west. In the early mid 1990s a large rock levee was constructed in the flood plain to stop the erosion and to narrow the stream flow area such that sediment would be transported down the creek. 

LiDAR of fan and levee
Heavy blue arrows indicate the Nooksack River
Thin blue lines denote potential avulsion paths of Canyon Creek

The project worked as intended during its first flood event. However, three big problems became apparent right away and a fourth even bigger problem began to be recognized.

One problem was that the flow forces were greater than the largest rocks that could be moved with construction equipment and portions of the structure were damaged in the first winter. Another problem was that funding to build the levee was not enough to extend it the entire length of the lower creek and hence the lower end of the levee was built with even smaller rocks. This levee section was breeched subjecting part of the resort buildings to flood and thick gravel deposits. The lower levee breach was a good thing because another problem was high flow surged water across the Nooksack River where the opposite bank was eroded by the water surging out of Canyon Creek.

Yet another problem was the new structure destroyed all of the salmon habitat on the lower reach of the creek and had created a fish barrier for up stream fish migration. And not just any salmon, but an endangered species of salmon. Hence, any repair work on the levee was going to require significant mitigation. 

But the biggest problem may have been the conclusions of numerous geologists that the levee was not providing adequate protection to allow building on significant portions of the upper alluvial fan and furthermore that the levee actually was increasing the risk for some properties beyond the risk if nothing had been done. The biggest problem was that the even a modest flood event had damaged the levee, and if the levee was breached where that damage had taken place, the creek would then be stuck on the wrong side of the levee and flow with all its force through a wide swath of the subdivision as shown with the thin blue arrows in the above LiDAR. The potential levee failure seemed rather likely as there was no funding source to repair the levee and the repairs would be exceedingly expensive.

So instead of a repair job a new  path was forged. Buying out properties on the fan including the existing resort and removing the buildings and ultimately moving the levee back. In all the resort was removed and 28 building lots were purchased. This effort was in part helped by the fact that the County regulations made it very difficult to obtain a building permit as there were not very many geologists that would challenge the County's view that the properties in question were with a severe geologic hazard area. (I do know of one lot with a new home that I deemed unsafe, but another geologist concluded otherwise and the County accepted the report. I ten to be fairly conservative regarding geology hazards and utilize a higher standard than what was at that time used by Whatcom County). 

The moving back of the levee and the purchase of properties in the highest risk zone including the resort with its log cabins has been a big step in reducing the future risks at this site. There are still homes that in the event of a very big landslide and dam burst will be at risk, but the efforts are a big step in the right direction.

A bit on the geology. The two deep-seated large landslides are associated with a fault contact within metamorphic rocks and like involved highly sheared and altered bedrock.

Mount Baker 1:100,000 Quad (USGS)
Ql= landslide,
note the extension fault trace the length of the landslides on both sides of the creek
 
Area where slides are impacting creek.
The forest road on the east side slope of the canyon has dropped several feet as the slide continues to move

While the hazard has been reduced, ongoing monitoring of the landslides in the steep narrow canyon is warranted as this pinch point could become a really big problem if the slides have significant rapid movement.

LiDAR: Wave Cut Terraces on Orcas Island

LiDAR images heavily featured in articles on the Oso/Hazel Landslide and is a very powerful tool for identifying large landslide features http://seattletimes.com_mudslidelidar. With  little ground work and experience in an area LiDAR images also greatly assist in geologic interpretation. I was doing some pre site visit work for a couple geology hazard assessments on Orcas Island and noted a couple of linear features in the LiDAR (along with a few other features).    

LiDAR southeast Orcas Island

The terraces on the lower right appear to be wave-cut terraces. Similar wave cut terraces have been noted in previous posts (wave-cut-terraces-in-san-juans and isostatic-rebound-on-northwest-blakely).

There are some faint linear features in the upper middle of the image as well. The area where these features are located is generally bedrock, but it turns out these features are not bedrock, but instead are underlain by loose glacial deposits. I interpreted the units to be ice wasting deposits as they were non compact suggesting very late stages of glacial recession. Possibly they mark an upper area of glacial margin at a time when the ice sheet was partially grounded on the upper slopes of the island and floating on sea water.

The north end of Orcas Island near the town of Eastsound is where the wave cut terraces are more distinctive. Enough so that if you know what your looking for in areas of cleared of trees you might be able to see them without the aid of LiDAR.  

Wave cut terraces around the Eastsound area
Note as well the deep-seated landslide on the west shore

The Lappen (2000) geology map that covers the area has these areas as either undifferentiated glacial deposits or glacial marine drift. The drift is thick here with one area of at least 60 feet to the east of Eastsound. Elsewhere, on the mainland, Lappen called out previously identified wave cut terrace areas as emergent drift in the Birch Bay, Point Whitehorn, and uplands near Lake Terrell in Whatcom County and part of the uplands above Padilla Bay in Skagit County. LiDAR images of the area were not available in 2000, and as far as I know the wave cut terraces on Orcas had not yet been identified in the literature. Although I should note that Bretz (yes, the same guy that figured out the ice age floods of eastern Washington) described the wave cut terraces on the south end of San Juan Island. I had identified wave terraces on Orcas without LiDAR after Lappen completed the map compilation; otherwise, Lappen would have included them on the map. But identification of the terraces was over a very limited area until the LiDAR images became available. 
 
During the last glacial period northwest Washington was covered by a thick layer of glacial ice that advanced down into the low lands out of the coast range of British Columbia to the north. In the San Juans the ice was on the order of 5,000 feet thick. The mass of ice pushed the surface of the earth downward hundreds of feet. Towards the end of the ice age the ice began to retreat and sea levels began to rise. In the San Juan Islands the sea flooded the lower slopes of the islands before the glacial ice had fully retreated. A large area of mostly floating glacial ice covered the area. As the ice melted silts and clays as well as sand gravel and boulders would melt out of the ice and fall to the sea floor leaving a glacial unit called glacial marine drift.

But with the load of ice removed the land surface rebounded with local uplifts of hundreds of feet. Part of this uplift is recorded in the shoreline terraces cut into glacial drift as seen above and elsewhere in the San Juans. The highest terraces I have seen are approximately 330 feet above sea level. Hence, a minimum of 330 feet of uplift has taken place. However, sea levels continued to rise as ice around the world continued to melt as the ice age ended and hence the total uplift has been even greater. Most of the rebound in the northern Puget Sound has been completed, we apparently have a bouncy crust beneath us. In other parts of the world such as Hudson Bay and Scandinavia the rebound is continuing and readily measurable even over historic times with former coastal communities now well inland.

Sunday, April 6, 2014

Spring, Baseball and Memories of Seasons Past: Macklemore and Ryan Lewis - My Oh My

Macklemore and Ryan Lewis capture a landscape shaping moment in Seattle history. A very good argument could be made that the Edgar Martinez triple and Griffey scoring the winning run in the bottom of the 11th and that 1995 season set in motion changes to the area south of downtown Seattle that would not have happened if not for that particular season. And just maybe, the Mariners will play this season at a level fitting of those changes. Some good old landscape views and lots of Seattle pride in the video.



Wednesday night I camped for the first time versus the motel routine. The weather was not particularly Spring-like and it seems early for baseball, but then it takes awhile to warm up in northern western Washington with all that cold northern Pacific water. I listened to the Mariners v Angels. The Mariners are off to a good start, maybe we will have some my-oh-my moments this year.