Saturday, September 17, 2016

Rainy Field Work Returns

It has been a while since I got soaked in the rain. But my moisturizer was back today as I had a bit of field venture up the Skagit valley.
 

Getting wet was going to part of the field excursion anyway. The rain simply made it easier as I was already presoaked before reaching the first stream.

 
 
The brush including some thorny stuff preclude rain gear as I prefer keeping my rain pants and jacket in tact for those standing around in the rain projects. And this rain is a easy thing compared to what will come later in the late fall and winter.

Friday, September 16, 2016

Notes on Atmospheric River Research

Western Washington residents are familiar with the weather term "pineapple express". A pineapple express is a warm heavy rainstorm. The weather system that delivers these events is out of the tropics and hence temperatures will be mild with lots of rain.

Satellite images of water vapor over the oceans show atmospheric rivers hitting the U.S. West Coast in 2006 (top), 2009 (middle), and 2004 (bottom). (Images courtesy of NOAA.)

These events have been getting lots of attention by both meteorologists and climatologists. Because these storms can cause severe flooding and landslides, being able to predict them can improve the ability of communities and individuals to prepare and respond. Overall the prediction of these events has gotten pretty reliable. The harder part of the prediction has been some of the detail which can be very important. One prediction issue is just how much water is being carried out of the tropics and how much of it will be dumped as it makes landfall. Perhaps a bigger challenge is exactly where the landfall of the main section of atmospheric river will take place and Will the flow of the atmospheric river stay locked in one place or drift? The locked in one place scenario can mean a narrow band of the coast and inland will get huge rain fall with little to modest amounts to the north and south of the band. These locked in place events have proven to be major flood events and a cause of many landslides.

A few years ago I timed a filed project with the arrival of an atmospheric river in the northern Coast Range of Oregon. I am used to rain, but that experience was memorable. My crude rain gauge I left at the car (a bucket) measured nearly 7 inches of water in the 8 hours I was out in the field.  

The climate change question is Will these events increase in intensity and frequency? And Were there past natural variability in the pattern of these events? The more recent work seems to be pointing towards a modest increase in frequency for western Washington but heavier rainfall events when they take place.

From a hazard perspective considering landslides and flooding, this suggests more frequent floods and more landslides. But some consideration has to take into account the weather prior to the atmospheric river arrival. Cold wet weather with low land snow followed by a sudden warm rain with warm wind will greatly amplify the flooding and geohazards versus an isolated atmospheric river event.      

NCAR: atmospheric-rivers provides a press release on two recent papers by Shields and Kiehl Simulating the Pineapple Express and Atmospheric River Landfall. Both papers as well as others on the same subject are in the Journal Geophysical Research Letters - access to the full papers requires membership and subscription.

Tuesday, September 13, 2016

Port Orchard

I recently did a fair bit of research on geologic hazards in the Port Orchard area that mostly entailed research and remote sensing (LiDAR, aerial photographs and papers). Other previous work was always short site visits with little time in the city or simply passing through on the way to somewhere else. It was nice to get a chance to spend some time in the small city that serves as the Kitsap County seat.
 
The city is across Sinclair Inlet across from Bremerton. Port Orchard itself has a low key feel and look. But that said, the waterfront is not peaceful. There is a very steady hum and noise that readily crosses the water from the very busy Naval shipyard in Bremerton. The noise included the periodic revelry as well as a lot of barking sea lions. The noise reminded me of the signs around the Whidbey Naval Air Base that proclaim the jet noise as the "sound of freedom". The hum of the shipyard was steady though and I had no problem sleeping.
 
The west end of the naval ship yard with the Olympic Range in the distance

The east side of the ship yard

Washington State ferry making its morning passage up Sinclair inlet from Puget Sound and Seattle

One other aspect of this visit was the traffic around Bremerton. I got caught up in the evening commute. It was slow going. Listening to the radio as I slowly made my way around the west side of Bremerton I was struck by the lack of traffic reports for Bremerton. Our dominant radio stations are rather Seattle-centric. 

Monday, September 12, 2016

Squires Creek Rockslide, a Geology Opportunity

Doug alerted me to an exposure of white rock on Jumbo Mountain south of Darrington. his exposure is from a rock slide in Squires Creek.
 
2013 aerial

1989 aerial
 
The rock slide happens to be located within the Darrington-Devils Mountain Fault Zone. The fault is a major structure and is thought to be associated with a former tectonic boundary between accreted terrains.  
 
From Sauk Quadrangle Geology Map (Tabor and others, 2002)
TKegb: Eastern Melange Belt gabbro
TKhm: Helena-Haystack Melange peridotite and serpentine
Tbs: sandstone
TKeu: Eastern Melange Belt ultramafite

The slide may provide some excellent fresh exposures of some rocks that could use a bit more study.

The TKhm are odd slivers of serpentine and peridotite that are likely faulted slivers within much younger sandstone associated with the fault zone. These slivers have been deserpentinized.  Vance and Dungan (1977) describe deserpentinization taking lace during a preEocene or early Eocene event, prior to tectonic emplacement of the ultramafic rocks as faulted slivers within the sandstone. Just how these rocks were heated and deserpentinized is an interesting question and the answer has implications on the interpretation of the history of the formation of the Helena-Haystack Melange.

Sunday, September 11, 2016

Scrub-Steppe Fire Near Kennewick

A scrub-steppe fire burned just south of Kennewick yesterday morning. The abrupt appearance of a plume of smoke in otherwise very clear sky was a bit of a surprise.
 

Scrub-steppe fires are common as this is a land with a long stretch of dry season. However, the grasses in this ecosystem have changed such that it is thought that the fires burn with a greater frequency and greater intensity than in the past. This past summer has seen several very large scrub-steppe fires in eastern Washington including one west of Prosser and another large one controlled with a large back fire on the Hanford Reach. These fires can cover huge swaths of land in very short periods.

The fire was contained and burned a bit short of one square mile. The fire burned during the morning when temperatures were mild and there was little wind. I went up the ridge above the burned area in the late afternoon. If the fire had burned then, it would have been a different story as the wind was blowing about 40 mph and the temperature was in the mid 80s.
A mix of dust and smoke coming off the burned area


Roots of sage brush and rabbit brush were still smoldering and dust was kicking up from the disturbed dirt roads around the perimeter of the burn. The cause of the fire is not yet known.

Sharp edged lines around the burn area along dirt roads
The lack of wind during the fire made a big difference
 
If the wind had been blowing this slope would have burned and posed a threat to the homes on the ridge crest.
 

Tuesday, September 6, 2016

Vedder Wall

For a time Vedder Mountain acted as a divide between continental glacial ice on the northwest of the ridge and an ice free valley on the southeast side of the ridge. The ridge line raises over 1,500 feet above the Sumas Valley floor. The elevation from the picture below is only about 30 feet and the ridge line is 1,500. The trees growing out of the cliff face obscure the dramatic scale of the valley wall. The valley was formerly a lake bed and the Nooksack flowed into from the south before the Nooksack avulsion at Everson. The area still would be a swamp to lake if not for pumps operated in Canada that maintain the drainage of the valley. The Sumas valley in Canada is considered one of the richest tract of farmland in Canada.


There was very little flow at this waterfall given the dry weather.
I estimate that the falls is approximately 300 feet to 350 feet
 
Most of Vedder Mountain consists of Chilliwack Group metamorphic rocks. The formation is a former island arc perhaps as old as Devonian. The Chilliwack has been correlated with the East Sound Group. It is one of several accreted terranes in the Northwest Cascades/San Juans.  
 
The top part of the ridge on the southwest end is underlain by much younger and non metamorphic Huntingdon Formation. The Huntingdon was deposited on the Chilliwack roughly 50 million years ago. A deep weathered zone of ancient soil has been observed in some of the areas below the Huntingdon. This weathered zone of thick clay was mined for brick material in the early 1900s. 
 
DEM of Vedder Mountain area.
Sumas Valley is the dark green area in center
The valley southeast of Vedder Mountain has an elevation of 520 feet

The valley to the southeast was for a short time occupied by a very large river. The continental glacial ice flowing down the Fraser valley to the northeast flowed along the base of the mountains during the late stages of the last glacial period. The ice blocked the Chilliwack River which then flowed southwest to the Noooksack valley.4
Conceptual DEM of Fraser ice block Chilliwack  

Sunday, September 4, 2016

Forecast Water Demand Shifting

John Fleck at  http://www.inkstain.net/fleck/ alerted me to this: A-Community-Guide-for-Evaluating-Future-Urban-Water-Demand-1.pdf/. A good guide for water providers and those that are in a position to assess the infrastructure needs and costs in delivery of water.

The first figure in the report is history of water demand projections for the City of Seattle.

 
The graph shows how the water demand forecast has changed over time from assumed steady increase to nearly no increase projected in the latest forecast. The graph also shows that consumption of water by the City of Seattle has declined significantly since 1990. The big drop after 1990 was related to a drought year. But post 1992 drought demand never returned to the pre 1990 levels and has continued downward. The pattern shown by Seattle has been consistent in most U.S. cities. Changing attitudes and social norms, conservation efforts, regulations and pricing has pushed total demand downward despite increased population and economic activity.