Friday, April 19, 2019

Snow Geese on Samish and Skagit Flats Have Not Left Yet

After being on eastern and central Washington ventures, I wondered in the snow Geese had left the Skagit and Samish flats for their breeding grounds on Wrangel Island in the Russian Arctic. The question was readily answered as the main flock flew over me while I traversed the flats.    

Apparently the leave date varies for these birds (Stevick, 2017). A later leave date may present problems as the flock may do a heavy graze on fields that have been planted. In this case the field has not yet been planted and the field that the flock was leaving is a Fish and Wildlife holding.   

Monday, April 15, 2019

Rock Fall Momentum: An Example at Highway 397

The construction of Highway 397 was completed to provide a bypass around Kennewick to the east side of the city and to Finley. The route through the Horse Heaven Hills involved a number of cut and fills to achieve acceptable grades on the highway. One spot where there was excess cut material at the grade down to Zintel Canyon made for a nice illustration of momentum and rock fall run out. 

2004 image of cut and fill work on a portion of 397. 
Cut material was used to fill the side canyon the road was crossing.

2006 image of excess cut material deposited on the slope below the cut area
On the ground view looking up at slope

A boulder that traveled well beyond where most of the other rocks stopped

Several rocks traversed the entire slope to the valley bottom

Not a particularly complex concept, but a nice illustration of how the larger boulders with greater mass and thus initial momentum had enough energy to travel well beyond the distance of most of the smaller rocks that had been disposed of at the top of the slope. 

Sunday, April 14, 2019

Post Fire Ridge South of Kennewick Notes

In the summer of 2017, a fire burned through grass land south of Kennewick (scrub-steppe-fire-near-kennewick). The fire was contained by previous existing roads and fast action by local fire fighters. Another fire started in the same area in the summer of 2018. Both days were hot, but the 2018 fire coincided with high winds and the result was a larger fire that jumped across roads including a state highway (with an assist fro burning paper from an illegal dump). The fire burned up onto the ridge on the south edge of Kennewick.

I noted that risk in 2017.

If the wind had been blowing this slope would have burned and posed a threat to the homes on the ridge crest.

Burned over area from the 2018 fire

This fire was primarily a grass fire, but still destroyed 5 homes as well as several other buildings. 

I took a walk along the ridge crest to assess what the ground looks like 8 months later.

View of Zintel Canyon

Kennewick is a rapidly growing city and has been growing rapidly for many years. The commercial centers have shifted well away from the downtown and has pushed south past the initial line of hills south of Kennewick.
The plastic screening on the fence around the water reservoir was melted. 

Somehow the perimeter of the this small ant mound makes for better grass growth.

The south side of the ridge has bedrock just below the surface. This primarily the result of high wind exposure that strips off soil. But there is a hint of periodic water erosion as well. 

Rocky ground

Alignment of basalt rocks on slope

These stringers of rocky ground are more prevalent on longer and steeper slopes throughout eastern and central Washington. This south slope has barely developed these features. The features form from rather rare heavy summer down pours.

There is also an interesting anthropogenic feature on the south slope.

Metal buckets partially filled with rocks and attached to barbed wire

The buckets were formerly attached to wood fence posts to help keep them anchored in place on the rocky ground that was also subject to high winds. The fence posts and cattle are no more.

The burned over area took out the patches of sage brush that were beginning to reestablish on the ridge

Replacement power pole. Within the former sage area, the fire burned hotter and longer and took down power poles 

Not a fire related phenomenon, but erosion along dirt roads is an issue. These road follow a natural gas transmission line route and a high voltage electric transmission line. The roads are just north of the crest of the ridge and underlain by thick silt related to the ice age floods that covered portions of the ridge when flood waters briefly formed a huge lake above Wallula Gap (ice-age-floods-dem-and-lake-lewis)

The actions of gophers beneath the snow that covered this area over the winter could be seen.

These ridges of soil are a common feature in snowy areas, but it is the first time I have seen them here. Typically this area gets very little snow - its warmer than most other areas east of the Cascades, but also has very low precipitation. But this winter the snow accumulation was well over a foot and stayed on the ground for a long time.

I was curious if the snow melt caused any erosion on the steep north side of the ridge above the homes that have tucked up directly below.

Despite the complete burn off of vegetation and record snow I did not observe any surface water erosion on the steep slopes. These silt soils can hold a lot of water.

Life is coming back in the burn area. These silty soils and north aspect have all sorts of plants that go past my limited botanical knowledge base.

I did recognize lupine

An early bloomer

While water erosion is not present, wheels and wind erode deeply in these silt soils

I used to know the specific species of beetle, but it leaked out of my head. 
This beetle was on a mission

As noted above, the ridge was briefly covered by water during the larger ice age floods. Those floods carried blocks of ice from the north and rocks were embedded in the ice. Hence, ice age glacial erratics are present on the ridge.

The frequency and intensity of wildfires has increased in the scrub steppe of this area. So much so that the sage brush habitat has declined. The presence of cheat grass has increased the recurrence of fires and how burned areas recover.

Just outside the burn area, there is an intact sage covered landscape. It is surrounded by roads and development and thus the large fire was not able to get into this sage stand. 

Tuesday, April 9, 2019

Ouch: Tribulus terrastris

I had project on the east side of the Cascade Range that involved some soil sampling to assess fill soils and underlying native soils on a site. The green grass on a sunny spring day looked like a soft easy project.

After a bit of digging I knelt on the grass to gather up some soil samples and label the sampling containers. I felt a few pokes through my pants that I initially assumed to be Russian thistles (tumble weeds) which are prevalent in areas with disturbed ground. However, when I reached the pavement with samples and equipment in hand, I found I had a coating of woody thorns on my shoe bottoms.

The hard woody thorns are from Tribulus terrastris. 
The common name for this plant varies, but on this day the name puncturevine seemed applicable.

Sat on the curb and pulled the thorns out of my shoes. I gathered the seeds and put them in a bag for later burning. I did not want to spread this non native plant anymore than it already has. 


Tuesday, April 2, 2019

Tala Point Boulders and Either a Large Erratic or Outcrop

Tala Point is at the north end of a large drumlin ridge that divides entrances to Port Ludlow and Hood Canal. The topographic map indicates boulders at the point.

Indeed, the tip of Tala Point is covered with boulders.

Tala Point. Foulweather Bluff is on the right across the Hood Canal entrance. On the left is Double Bluff on Whidbey Island. The water between Foulwather Bluff and Double Bluff is the entrance to Puget Sound. 

I assumed the boulders at Tala Point were derived from glacial erratics from the eroding glacial drift  of the bluff. However, a closer look shows that this boulders are simply blocks of hard drift.

East and south of the point, erosion is much slower and the bluff slope is tree covered and the beach is a broad sandy beach.

However, just off shore is a very large glacial erratic boulder or Is it an isolated bedrock outcrop?  

If this isolated rock is an erratic it is truly immense. It is hard to gauge in the picture above without any scale, but using a GIS tool in an aerial view, the rock is 45 feet long. 

The other possibility is it is an isolated bedrock outcrop. That idea is supported by the geology map of the area combined with the bathymetry on the map.

Geologic Map of the Port Ludlow and Southern Half of the Hansville 7.5-minute Quadrangles, Kitsap and Jefferson Counties, Washington (Polenz, Favia, Hubert, Paulín, and Cakir, 2015)

The question of erratic versus boulder may or may not be readily solvable. If the rock is not Crescent Formation, then it would be an erratic. However, if it is Crescent it could be an outcrop or an erratic that was not transported very far.