Sunday, November 29, 2015

A Nice Weather Turn in Walla Walla

I had a project in Walla Walla prior to the Thanksgiving break. We arrived in freezing rain that switched over to light snow. The previous few days had been freezing fog. The morning was cold and dark, but I enjoyed a bit of a walk about the central part of the city.
Just a bit after finishing the site visit the fog and clouds were pushed to the south.
Weather station, grapes and the Blue Mountains

Rolling hills southeast of Walla Walla

Flocked elm on Mill Creek Road

Winter road scene with bare pavement as the clouds break apart

Friday, November 27, 2015

Mill Creek and Walla Walla

Walla Walla means place of many waters. A fit name for the multiple streams that flow off the west side of the Blue Mountains into east end of the valley.
Walla Walla valley with the Blue Mountains to the east.
The City of Walla Walla is within the northeast of the valley
The many waters concept has been enhanced by irrigation diversions. Mill Creek flows through the City of Walla Walla. Upstream of the city are diversions which route water into other streams such that there are numerous year-round creeks flowing through city. In addition to the engineered diversion works upstream of the city, the stream route through the city is very engineered.  
Mill Creek immediately east of downtown

Downstream of the above picture Mill Creek enters a tunnel and passed under portions of the downtown area. Down stream the creek remains heavily engineered and is contained with structures to reduce flooding and erosion. It may be the most engineered creek for its size of any stream in Washington State.

Early Walla Walla history made it clear that Mill Creek provided a huge benefit for the community, but the creek also periodically had very large floods that required significant flood control works.

Tuesday, November 24, 2015

A Turkey Day Blog Tradition - Safe Travels

A Turkey Day blog tradition. I had field travels today with safe roads mostly with only a bit of freezing rain.

Monday, November 23, 2015

Alluvial Fans and a Disappearing Creeks

Last week I headed out to check a few creeks that I have and am doing work on. A decade ago I assessed and mapped debris flow hazards associated with these creek. Debris flows are a major hazard on alluvial fans. A landslide or blockage in the creek can send a fluid mass of debris (and in western Washington lots of logs) down onto the upper part of the alluvial fan.

The hazards associated with alluvial fans are not limited to debris flows. Post debris flow streams on the fan can be very erosive. If the debris flow reroutes the stream, rapid down cutting may take place depending on the gradient of the new stream route. Erosion from the down cutting can then be deposited further down the fan causing flooding or stream movement at a new location. 

The purpose of my venture in the heavy rain event was to see how the streams on the fans in question were behaving during a large storm event as two of the creeks were flowing on new routes and one was flowing across an area where lots of previous deposition had taken place from storm events 5 and 7 years ago.

What follows is observations on one of the creeks. 

Old stream channel

The old channel no longer has any water flowing through it as the creek has been redirected. The channel shown above is one of several old abandoned channels on the fan surface. Water was flowing through this channel as recently as 2009. I had first observed this channel in 2004 when the stream was flowing here. From 2004 to 2009 the stream down cut 5 to 10 feet deep into the fan surface at this channel site.

The existing creek now follows a new channel route that angles across the alluvial fan towards another alluvial fan to the south. Above the new channel the creek can be seen to have dun cut a narrow channel that has a bottom lined with larger rocks such that the down cutting has been reduced.

Down stream the stream flows across a fairly gentle gradient such that despite the high flow the day of my site visit there did not appear to be any erosion as the flow velocity was not high.

Grasses and the soil under the grass was still in place at this location.

A bit further downstream the stream disappears. At this point the stream was flowing onto another alluvial fan with gravels from a stream located further south. Both fans have been deposited over a gravel filled ice age river valley that readily infiltrates lots of water.

Further downstream and looking upstream to the log shown above there is no water flow - at least on this wet day with local rivers at flood stage.

A few feet from where the picture above was taken is the channel and stream of the next creek to the south.

I followed this creek as well and its flow ended rapidly much like the first as it flowed onto the gravel and cobble river bars of the former ice age river plain.

Diminished stream as water rapidly infiltrates

Last bits of the stream soak into a meadow underlain by river deposits from an ice age river

Neither of these creeks are connected to another surface stream even during flood events and as such are not fish bearing and not potentially fish bearing.

Saturday, November 21, 2015

Remote Exploration of Santa Clarita Landslide

Susan alerted me to a landslide in southern California that has closed a road in Santa Clarita. Santa Clarita is in the mountains north of Los Angeles. Landslides should be expected if the weather pattern associated with the El Nino event soaks into the geology of this area.

I decided to explore this slide a bit. The fun of Google earth is tracking down sites like this and getting an idea what is going on. This is particularly good with the availability of newer higher resolution aerials. In the image above from this year one can see an incipient fracture at the top of the road cut where the failure took place. Additional breaks took place almost all the way back to the upper road. This is a deep-seated failure where the ground above the cut had has moved towards the cut as a mass pushing the pavement before it.

Google earth also provides a very good before image in street view:

Google earth street view before landslide

Google earth street view of road cut at slide site

  The cut slope in the street view appears to be alternating silts and clays and maybe some fine sands consistent with lake sediments. A good recipe for landslides. The unit is the Mint Canyon Formation ( and consists of terrestrial lake sediments of mid Miocene age.

Finding the exact stretch of the landslide was greatly aided by these before and after pictures:
photos via laist.

This drone footage also gives a a very good perspective: drone via by dmitry

Putting geology hazard in perspective, Santa Clarita has a lot of hazardous ground:

Tuesday, November 17, 2015

Fields of Bracken

Once or twice a winter I do a site visit with the full intention of seeing a site while there is a big rain event. I took advantage of today's rain on top of the heavy rain the night before on already wet ground to assess the flow and conditions of a few creeks I am working on. The event did teach me a few things.

But a side observation was this opening in the forest.

The sharp contrast of the recently brown bracken with new green fall grass made for a nice path through the small prairie in the forest.

Old pastures in western Washington can become overtaken with bracken. Historic accounts of early farmers in the 1850s and 1860s (White, 1980) noted pastures and cultivated fields being plagued with bracken. Bracken covered old farm fields are a common feature in western Washington. Prairie lands and fields opened up within the forest land often did not turn out as hoped for by early pioneer farmers. Bracken sprouting from roots years after repeated plowing were an early recognized bane in some areas. Marginal farmland that has been given up on provides excellent bracken habitat.

Bracken was one a valued food source by area First Nations so a site like this would once have been viewed as valuable bit of farm land during a different era.


Land Use, Environment and Social Change by Richard White

Saturday, November 14, 2015

Forest Board Manual Update for Landslides

The Forest Practices Board met on Tuesday, November 10, 2015 (fpb_mtgpacket). One part of the meeting was to consider adopting an update to the Forest Board Manual Section 16 Guidelines for Evaluating Potentially Unstable Slopes and Landforms. The Manual is not a hard fast rule but the fact that it is official guidance suggests that deviating from the guidance may be challenged. Hence, timber industry wants to minimize specific language in the Manual while safety and conservation minded folks would like a stronger worded guidance to ensure forest practices that may impact potentially unstable slopes gets a thorough assessment. The conservation part of the guidance is that a significant motive of forest practice rules is to protect fish habitat. Landslide frequency and magnitude can have a harmful impact on fish habitat.  

The Board approved the new Manual Section 16. However, they indicated they wanted some areas reviewed that had been raised during public comment including comments by geologists. It is my understanding that the intent is to have DNR staff and technical experts review the issues over the next few months.

I did submit some comments regarding deep-seated landslides. One comment slightly modified to better fit this post is presented below:

Rule identified landforms (WAC 222-16-050) identifies 5 categories of unstable slopes A through E. With the exception of toe areas of deep-seated landslides (category B) and groundwater recharge to glacial deep-seated landslides (category C), deep-seated landslides will fall under the catch all category (category E).

Within Part 6 of the Manual, deep-seated landslides are only assessed in Part 6.1. Glacial deep-seated landslides are placed in another category, Part 6.2.  Part 6.2 references back to Part 6.1 so that glacial deep-seated landslides are evaluated in both Part 6.1 and Part 6.2.  

Part 6.2 should apply to all deep-seated landslides. Part 6.2 includes recommendations that should be applicable to all deep-seated landslides not just glacial deep-seated landslides. It is important that all deep-seated landslides be included in the evaluation procedures in Section 6.2.

It appears that the intent is to not include all deep-seated landslides in Section 6.2. The Board should ask if that is the intent and, if so, what is the justification of excluding deep-seated landslides from this level of review. Deep-seated non glacial landslides are very common and wide spread and are found in both non glaciated and glaciated areas throughout Washington State. Some of these landslides are potentially very dangerous and not considering the potential impacts from proposed forest practices would be a failure of the Board Manual.  

Presented below is an example of a deep-seated non glacial landslide location where a forest practice was proposed on Sumas Mountain in Whatcom County, the North Zender timber sale (#91633). This proposed timber harvest is clearly located on a deep-seated landslide per LiDAR imagery presented below as well as previous geologic mapping and expansion of the slide and further runout poses significant risk. 

The proposed Board Manual would have the landslide assessed under Part 6.1 but not under Part 6.2. The criteria and assessment of Part 6.2 would not apply to this obvious deep-seated landslide simply because it is not a glacial deep-seated landslide. There no reasonable basis that Part 6.2 should not apply to this landslide or similar deep-seated landslides.