GUT

North Fork Asotin Creek is a tributary of the Snake River in southeastern Washington. The watershed is roughly 35 acres with steep canyons. It transitions from sagebrush steppe at near 1800 ft to ponderosa pine forest at 6200 ft. We will be examining to geomorphic sites on North Asotin Creek today- F4, the downstream site and F6, the upstream site for their geomorphic variation.

2.1: Qualitatively describe the in-channel geomorphology of this reach.

The F4 reach is like a bowling alley. In other words, it's very uniform and mostly straight. F4 is one long continuous glide, with longitudinal features that go with the flow. The banks are convex, the majority of the channel is planar and the thalweg is concave.

2.2: Choose at least two survey years at this site to consider the temporal variability of morphology at this site. Which survey years are they and why did you choose them?

I am going to choose 2011 and 2017 to give myself the greatest chance of maximizing difference and more easily answering these questions.

2.3: What Tier 2 Forms are present in each year? Do they differ?

All tier 2 forms are present in each year. The walls mostly stay the same, however the location of some of the bowls/concave features shift. 

2.4: Do any of the Tier 2 Forms dominate the assemblage or is it fairly mixed? Is this true through time?

They are fairly mixed, although planar surfaces and flat bottom are the majority. Banks are convex/mounds, most of channel bottom stays flat and there are concavities at the thalweg. It seems that the concavities become more planar over time. There is a flattening to the channel bottom.

2.5: What Tier 3 Geomorphic Units are present in each year?

Both years have glide-runs, pools, pocket-pools, margin-attached bars and banks. 2011 has a rapid that by 2017 has expanded to a riffle. 2011 also has a rapid that has transitioned into a glide and 2017 has a riffle that has transitioned from a mid-channel bar.

2.6: Zoom in to 2 to 5 x bankfull width portion of the reach and look at the arrangement of geomorphic units. Is it coherent? Does it make sense based on what you have learned so far?

It is coherent. The arrangement is very clean, but it makes sense. There is room between pools and rapids, which are in the center of the channel. The bars are in the right location in the channel relative to their name. The only thing that leaves me doubting is where the bank is separated from the wetted boundary by a margin attached bar.

2.7: How well does GUT appear to be doing in each year at discriminating the in channel geomorphic units? Point out any weaknesses or concerns you might have.

The DEM and aerial imagery does not allude to much, so I don't see any weaknesses. That being said based on the question above I do have some concerns.

2.7: Identify in one of your surveys for this reach a distinctive pool, bar and planar feature. For all three identify all five attributes from the fluvial taxonomy (i.e., Table 6), then use those to identify the tier 3 name from Table 7 or 8 (this may differ than what GUT output is because it is not as resolved) and explain which attribute(s) were key for discriminating that unit from other units.

• • 2.7A : Pool

2.7 A1: GU Forcing- Not forced or forced by a geomorphic unit. The pool in question formed from a collection of pocket pools. A riffle formed upstream which may have increased flow and therefore size of the pools. The transition zones shrank and the flow width widened but this is an unlikely cause of forcing.

2.7 A2: GU Orientation- The pool is streamwise.

2.7 A3: GU Position- The pool is mid-channel.

2.7 A4: GU Low Flow WS Slope- It's a shallow convex bowl.

2.7 A5: GU Low Flow Relative Roughness- There is a low relative roughness.

2.7 A6: Tier 3 Name- Ramp

2.7 A7: Which attributes key for discriminating? It does not fall into any other categories. The riffle suggests a potential structural forcing or scour area, but there are not clear enough cues for me to assign it those tier names.

2.7 A8: Differences with GUT- GUT names it as a pool which I think is more accurate and reliable when there are few distinct attributes of this feature.

2.7B : Bar

2.7 B1: GU Forcing- It seems as the pool downstream filled in, so did the rapid (into a glide) and the transition became a location for aggradation with this mid-channel bar.

2.7 B2: GU Orientation- Transverse (GUT classifies it as diagonal)

2.7 B3: GU Position- Bank-attached/mid-channel

2.7 B4: GU Low Flow WS Slope- Shallow on one side, moderate on the other

2.7 B5: GU Low Flow Relative Roughness- Low

2.7 B6: Tier 3 Name- Diagonal Bar

2.7 B7: Which attributes key for discriminating? The flow widened, the orientation is diagonal and it's position is in mid-channel, with a smaller channel forming in between the bar and the left bank.

2.7 B8: Differences with GUT- No differences, this matches what GUT says.

2.7C : Planar

2.7 C1: GU Forcing- There appears to be no structural forcing

2.7 C2: GU Orientation- Longitudinal

2.7 C3: GU Position- Channel spanning

2.7 C4: GU Low Flow WS Slope- Flat

2.7 C5: GU Low Flow Relative Roughness- Low

2.7 C6: Tier 3 Name- Glide

2.7 C7: Which attributes key for discriminating? It's a low-gradient water surface and the flow is not deep

2.7 C8: Differences with GUT- GUT concurs

• 2.8: Turn off GUT and look just at the Topo DEM (e.g Detrended DEM and Contours) for one of the surveys. Manually map one geomorphic unit you think you can read in the topography.

  • 2.8A - What is the tier 2 Form and the tier 3 shape of the unit you manually identified?

There is a pool and bar for Tier 2. I would say a chute and a longitudinal bar for Tier 3.

• • 2.8B - How do the boundaries of the unit you mapped compare with what GUT derived?

They are pretty close.

• • 2.8C - How does the type you identified compare with what GUT identified? Explain the discrepancies if they exist.

It was a pool and a margin-attached bar. It looked like the anabranch was significant which is why I classified as longitudinal instead of margin-attached.

3 North Fork Asotin F6

• 3.1: Qualitatively describe the in-channel geomorphology of this reach.

This reach has a lot more geomorphologic diversity than the previous reach. There are a lot of pools, bars and riffles and the reach is not all glide. There are quite a few side-channel/backwaters as well as an island that form in 2017. The sinuosity is also greater.

• 3.2: Choose at least two survey years at this site to consider the temporal variability of morphology at this site. Which survey years are they and why did you choose them?

I am going to choose 2011 and 2017 to give myself the greatest chance of maximizing difference and more easily answering these questions.

• 3.3: What Tier 2 Forms are present in each year? Do they differ?

There are 3 types of Tier 2 forms present in both years: planar features, convexities and concavities. 2011 has hardly any planar features.  2017 has a glide, but the island formation and structural forcing has caused more channel space leaving the convexities and concavities to remain the same.

• 3.4: Do any of the Tier 2 Forms dominate the assemblage or is it fairly mixed? Is this true through time?

Convexities and concavities are dominant over time.

• 3.5: What Tier 3 Geomorphic Units are present in each year?

There are glide-runs, margin attached bars and pools in 2011.

In 2017, there are these features as well as the formation of a large riffle and a mid-channel bar.

• 3.6: Zoom in to 2 to 5 x bankfull width portion of the reach and look at the arrangement of geomorphic units. Is it coherent? Does it make sense based on what you have learned so far?

Yes, it makes sense. There is room between pools and riffle, which are in the center of the channel. The bars are in the right location in the channel relative to their name. I am slightly unsure that margin attached bars is correct for the deposition in the backwater.

• 3.7: How well does GUT appear to be doing in each year at discriminating the in channel geomorphic units? Point out any weaknesses or concerns you might have.

It does well except where the margin-attached bar is outside the bank.

• 3.7: Identify in one of your surveys for this reach a distinctive pool, bar and planar feature. For all three identify all five attributes from the fluvial taxonomy (i.e. Table 6), then use those to identify the tier 3 name from Table 7 or 8 (this may differ than what GUT output is because it is not as resolved) and explain which attribute(s) were key for discriminating that unit from other units.

  • 3.7A : Pool

• • • 3.7 A1: GU Forcing- the converging of 2 channels

    • 3.7 A2: GU Orientation- streamwise

    • 3.7 A3: GU Position- mid-channel (it's classified as margin-detached

    • 3.7 A4: GU Low Flow WS Slope- shallow

    • 3.7 A5: GU Low Flow Relative Roughness- low

    • 3.7 A6: Tier 3 Name- Pool

    • 3.7 A7: Which attributes key for discriminating? the size and uniformity and structural forcing

    • 3.7 A8: Differences with GUT- none

  • 3.7B : Bar

• • • 3.7 B1: GU Forcing-  riffle pushing through channel bend

    • 3.7 B2: GU Orientation- streamwise (diagonal)

    • 3.7 B3: GU Position- margin-attached

    • 3.7 B4: GU Low Flow WS Slope- shallow to moderate

    • 3.7 B5: GU Low Flow Relative Roughness-low

    • 3.7 B6: Tier 3 Name- margin-attached bar

    • 3.7 B7: Which attributes key for discriminating? It's structural forcing and it's position in the channel

    • 3.7 B8: Differences with GUT- orientation

• • • 3.7C : Planar

• • • 3.7 C1: GU Forcing- none

    • 3.7 C2: GU Orientation- streamwise (listed as diagonal)

    • 3.7 C3: GU Position- mid-channel (listed as margin-attached)

    • 3.7 C4: GU Low Flow WS Slope- flat

    • 3.7 C5: GU Low Flow Relative Roughness- low

    • 3.7 C6: Tier 3 Name- glide/run

    • 3.7 C7: Which attributes key for discriminating? slope/forcing

    • 3.7 C8: Differences with GUT- position and orientation

• 3.8: Turn off GUT and look just at the Topo DEM (e.g Detrended DEM and Contours) for one of the surveys. Manually map one geomorphic unit you think you can read in the topography.

  • 3.8A - What is the tier 2 Form and the tier 3 shape of the unit you manually identified?

I identified a pool and a margin-attached bar.

• • 3.8B - How do the boundaries of the unit you mapped compare with what GUT derived?

The boundaries are the same.

• • 3.8C - How does the type you identified compare with what GUT identified? Explain the discrepancies if they exist.

The bar is not mapped because it's outside the active floodplain. The pool was actually a glide- which could be incorrect. The feature was at the edge of the DEM so it's hard to say if the glide has a steep slope or if it is actually a pool, but you just can't tell because you are missing the rest of feature.

3 Differences between F4 & F6

• 3. 1 : What are the primary differences from exploring GUT between these two sites that you noticed between the in channel geomorphic units of these two sites?

F4 was very channelized which led to a uniform planar surface. F6 had more structural forcing and therefore more concavities and convexities.

• 3. 2 : What inferences can you make about geomorphic processes and behavior when contrasting GUT outputs between these two sites?

There is more structural forcing and wood in F6 leading to a much more messy channel.

• 3.3 : If you only had one GUT output from each of these two sites (i.e. one snap shot) how representative would be your inferences about geomorphic processes? If you did not have the luxury of six or seven surveys, but just one, would your conclusions above be different?

They would be less confident, because the rate of channel change is unknown. So they would be representative, but you would have to take them at face value.

4 Synthesis

• 4. 1 : How are the Tier 2 Forms from GUT different than what we discussed in field?

They are the same.

• 4. 2 : How are the Tier 3 GUs GUT exports different then the ones we discussed? Why do you think GUT does not output the same things?

I though GUT produced similar features to ones we saw in the field, but also I don't really remember.

• 4.3 : How would you apply Tier 4? Do you have enough information here to do that?

You could look at the aerial imagery to determine vegetation. It is more difficult to determine substrate and grain size so you couldn't apply that portion of Tier 4.

• 4.4 : Does exploring these GUT outputs give you more or less confidence in applying the fluvial taxonomy through manual mapping off of topography versus identification in the field?

I'm impressed at how well GUT worked, but it still had flaws. I don't think my confidence level changed from this project. I would use GUT when conducting mass mapping of geomorphic units and field mapping on smaller projects of higher importance. It depends...