Final Project

These are sites along the main fork of the flathead river going back up to shafer meadows. I chose sites that I have been to, or I have not but could justify with really good aerial imagery and images from other people. I don't have photos of the high meandering section near the outlet into flathead lake, but those types of environments are easier to tell from aerial imagery anyway. I am very familiar with the other segments and have photos of them because my family has a timeshare along that stretch of river.

As far as where is it, and what it flows into, it is in Northwestern Montana. The middle fork meets with the south and north forks, then the stillwater, then empties into flathead lake. From there, the flathead river flows to the Pend Oreille and eventually into the Columbia.

Catchment patterns

Longitudinal profile of the Middle fork of the flathead to Flathead Lake

figure 1 There is ~3000 feet of river relief, ~139 miles long, and there are no noticeable knickpoints.

Flow regime

figure 2 (left)

The discharge at a currently discontinued site just south of Essex Mt shows the general flow regime

It is very clearly a snowmelt oriented system. Very very high spring flows followed by a slow decline bottoming out during the winter. Textbook snow based flow regime.

Landscape Units

A map (figure 3) of the landscape units for the Flathead river. We see that most of it falls within he canadian rockies and carbonate front however at the end dips into the flathead valley

I should note, All of the sites are shown here. From right to left (headwater to outlet) it is Shafer, Bear, Nyack, Lincoln (connected to Nyack, but noticeable style change), and Outlet.

Watershed patterns

Figure 4

We can see the nested watershed areas for the flathead. Note, the riverscapes consortium did not have the North fork of the Flathead, so that's why we get a watershed area from the outlet and the entirety without a hillshade. I will cover specific watershed stats in the respect site sections. For now it's just useful to see where they are and what their watersheds are.

I'll be honest, I don't see a significant use for many of the catchment morphometrics because this is a very strange geography and drainage network pattern that calculating a circularity ratio is likely not to change any interpretation. The big picture here is we have a highly irregular watershed that is very long overall which flows into a large open valley. That alone can tell you so much about how the system will generally be quite resistant to local precipitation. Just looking at the fact it is a mountain geography system in a temperate environment (see temp and precipitation graphs below), there is a very high drainage network density, but due to the high forest cover (evt map below) there is going to quite a lot of direct input into rivers, groundwater flows into rivers, but also delays due to infiltration and evapotranspiration. A form factor number isn't going to change the big picture, and I honestly don't feel comfortable applying a number to this watershed due to it's irregularity. The big picture pattern is far more insightful.

figure 5

This is a mean annual precipitation map throughout the flathead river area. The big picture here is there is high precipitation in the high mountains, and that ends up to around 40 cm in the lower portions, which is overall quite high rainfall and puts it more into a temperate forest range of rain.

figure 6

A mean temperature map of the flathead river extent. Overall, the mean temperature is quite moderate. It is a lot colder in the upper reaches (likely mostly due to elevation) but then warms up towards the flathead valley.

figure 7

A busy vegetation map of flathead river extent. The big picture is it is primarily conifer (mostly lodgepole) and riparian woodland until it reaches the flathead valley where its mostly agricultural land

figure 8

This just loosely shows the geologic units and fault lines. There are some noticeable things here. The portions above the south fork of the Flathead river are predominantly in carbonate rock (barring one mafic intrusion at the end of the Shafer site, likely why the river gets highly confined downstream of the Shafer site) and the river is running mostly along fault lines.. Downstream of the south fork watershed is almost all alluvium along limited fault lines. It should be noted, this entire area has been carved by glaciers in some capacity within the last 100k years. While the river shocking follows these fault lines very well, there is still the glacial aspect that forms these valley bottoms.

Shafer

Basic stats

~30% confinement

0.56% average slope

low-moderate valley sinuosity. High channel sinuosity.

Generally 1- 2 active channels. Up to 3 in spots but mostly 1-2.

Vegetation

Riparian woodland, spruce fir, lodgepole pine

Geomorphic Units

Predominant convex instream GU's are point and diagonal bars with some longitudinal bars. There are mostly instream planar features, likely a glide based on the imagery. There are occasionally some structurally forced pools and bars. There are quite a few backwaters and beaver ponds, some secondary channels and return channels

Floodplain GU's are mostly floodplain, backswamps, beaver channels/wetlands, flood channels, ridges, swales, and islands.

Bed composition

Primarily coarse grain bed. Bed load dominated. Finer sediments in the floodplain and beaver influenced features.

Structures

There are many structures, likely most from beaver and catch of large woody debris due to not being able to wash out large woody debris.

Channel Adjustment

Primarily lateral adjustment, may have some floodplain stripping in very high flow events for the fines in the floodplain. There is also some evidence of straightening during high flow events due to significant frequency of chutes in those point bars and high frequency of diagonal bars.

figure 9 image from 6/05/2016

Cross Section

Figure 10 Cross section of the Shafer site looking in the downstream direction. We can see that there is that low spot where the two channels and the bar are, separated by a slight mound, then followed by a little dip, likely a flood channel.

Bear Creek

Basic stats

100% confinement

0.74% average slope

High channel and valley sinuosity

Single threaded

Vegetation

Mixed conifer, deciduous shrubland, development

Geomorphic units

Instream GU's are mostly planar run. There are some bar forced pools, point pars, lateral bars. There are some riffles that then progress into rapids. There is a confluence bar at the very start of it.

There are very few out of channel units. The main ones are alluvial fans and talus slope (many anthropogenic influenced, however likely not anthropogenically created.). There are some sheets and cute cutoffs in relation to the bars, but no significant floodplain

Bed Composition

Very coarse grained, predominantly talus and alluvial outwash.

Structures

Minimal if any structures

Channel Adjustment.

Very little if any vertical adjustment due to the high confinement, competence limiting

Figure 11 image from 7/26/2014

Personal Images

Nyack Creek

Basic stats

~85% confinement. Note: confinement is calculated on either bank, this is high confinement but only on one bank, while the other high confinement sites are over both banks. The valley width metric (which I don't care to calculate because you can very clearly see in the image,) quite high relative to channel width. The confinement is more indicative of the geology and transient dynamics of river behavior here than a measure of it's actual ability to migrate.

0.32% average slope

Low valley sinuosity, moderate-high channel sinuosity.

3+ active channels

Vegetation

Riparian woodland, Pastureland, deciduous shrubland, wet meadow, grassland, mixed conifer, Emergent marsh

Geomorphic units

Instream units are point bars, diagonal bar,s longitudinal bars, scroll bars, lateral bars, reattachment bars, confluence bars, glide/run, structurally forced pools, bar forced pools, and chutes.

out of channel units are floodplain, chute cutoffs, islands, anabranch, flood channel, flood runners, paleo channels, and sheets. there are some alluvial fans and inactive floodplains (should be noted the inactive floodplain is due to the highway, drainage canals, and the railroad.)

Bed composition.

Very coarse and bedload dominated. I know from experience it's more in the gravel pebble boulder realm of size.

Structures

There is a decent amount of large woody debris, but most of it is not in the main channel. The main channel is quite large and can wash out LWD. However, the anabranch has many structures.

Channel adjustment.

A lot of lateral ability to adjust. It appears the main stream is a braiding adjusting system (with anthropogenic effects) due to the coarse grain, high transport, high frequency of many kinds of bar. The anabranch is likely more of a laterally adjusting system due to it being single threaded, a lower energy, and being fed from high stage and groundwater flows and having low confinement relative to the main stream.

Figure 12 image from 7/26/2014

Cross Section

Figure 13 Looking downstream. We can see that overall this valley is very flat. with little undulations throughout, then a noticeable low spot where the active channel is. This means there is quite a lot of floodplain that can be activated. I suspected that maybe the entire valley is dipping towards the north east since the river hugs those foothills and the fault quite tightly, and there might be a little bit of creedence to that, however it's not significant. That makes sense in hindsight because if there was a significant dip, there likely wouldn't be over a mile of floodplain.

Personal Images

Lincoln Creek

Basic stats

100% confinement

0.45% average slope

low-moderate valley and channel sinuosity.

single threaded

Vegetation

Foothill grassland, lodgepole, mixed conifer

Geomorphic units.

Runs, riffles, rapids, boulder bars, some lateral bars, and a couple potential small cascades.

There is almost no floodplain. The occasional pocket on the bars exist, but overall its surrounded by talus and vegetated slopes. There might be one terrace, but it's hard to say because it may just be built up anthropogenic area (which I think is more likely)

Bed composition

Boulders, bedrock

Channel adjustment.

There's almost no room to adjust. Its adjustment is likely on the geologic scale since it's lying on boulders and bedrock, so there will be very limited erosion and transport

Figure 14 image from 7/26/2014

Personal Images

Outlet

Basic Stats

0% confinement

0.10% average slope

low valley sinuosity. High into very high channel sinuosity

3+ channels into single threaded channel

Vegetation

Wet meadow, Riparian woodland, pasture and wheat, Deciduous Shrub, Orchards

Geomorphic units

Instream units in the upper portion are predominantly point bars, diagonal bars, lateral bars, longitudinal bars, structurally forced bars, chutes, glides, secondary channels, return channels, backwater bars. The lower portion is primarily scroll bars, point bars, eddy bars, and glide. There may be some shallow thalweg but not entirely sure if that or bar forced pool.

Out of channel units in the upper portion are predominantly islands, meander cutoffs, backswamps, anabranches, levees, chute cutoffs, ridges, swales, paleochannels, sheets, fans, terraces, inactive floodplain (due to human modification), floodplain, flood runners and flood channels. The lower portion has significant meander cutoffs, floodplain, inactive floodplain (human influenced due to roads, canals, agriculture, etc) ridges, swales, levees, paleo channels, and flood channels,

Bed composition.

Upper portion seems to be coarser grained material while in the lower portion it is predominantly fine cohesive sediment.

Structures

Minimal large woody debris. There are some in the side channels in the upper portion, but the lower portion doesn't have anything.

Channel adjustment

Both portions appear to be laterally migrating, however the upper portion is more of a braided migration while the lower portion is single thread meandering migration.

Figure 15 image from 7/26/2014

Figure 16

The longitudinal profile (barring digitization mistakes) from the upper to lower portion shows that the single threaded meandering portion is basically flatwater while the anastomosing section is clearly not flatwater. This could be a combination of there being multiple confluences into the flathead river in that upper portion, bed composition, vegetation (upper portion is more riparian than lower portion) and the Seli'š Ksanka Qlispe' Dam at the foot of Flathead Lake which artificially raises the level of the lake. It was constructed in 1938 and likely is the source of the debate whether Lake Tahoe or Flathead Lake is the largest freshwater lake in the US west of the Mississippi river.

This leads to the internal debate of "why is there this major change in the river style"?. I've already sort of covered them, but I believe it is one part the sediment transport load coupled with the confluence of the stillwater basin in the upper portion. This would bring a lot of coarser, more stage dependent, less cohesive sediment into the mix. Add in the extremely fertile alluvium that sponsors high plant growth, you can get this anastomosing system, I believe. There is also the major caveat of anthropogenic effects. There is the Hungry Horse dam of the South fork, Highway 2 paralleling the Middle fork for a long way, and development across a large portion of all of these rivers. Is the anastomosing section actually from a river change due to anthropogenic effects? I am not confident in saying whether it is or not, to be honest.

Once you get into the Flathead Lake backwater, you're also lower in the catchment, it's extremely low energy. You can get this gravel sand transition zone which is now highly cohesive and vegetated due to agriculture and historical riparia. That is the textbook "how we get meandering streams". Cohesive sediments and vegetation. Now, the big conundrum is... what is the historical look of this reach? we do see paleo channels in the imagery, which helps show that it likely still was single thread meandering. However, there has been so much floodplain reworking since the dam construction, it's hard to know the dates and preservation of those paleo channels without sediment surveys. How low and steep was the floodplain? What did the sediment conveyance look like without upstream modifications? What river changes, if any, occurred due to the base level rise? We can make general predictions about the big large scale patterns, but from what the Imagery gives, I can't say that my bear creek site was a wonderful stage 0 anastomosing stream. All I can say is the anthropogenics undoubtedly had an effect on sources, sinks, connectivity to the hillslope and floodplain, and likely changed the overall river profile to some extent.

Cross Sections

Upper

Figure 17

Lower

Figure 18

When comparing the two, the lower portion is noticeably flatter over the active floodplain. We see the western paleo channel is actually lower than the contemporary active channel, and we see a gentle dip to the east. Meanwhile the upper portion has a bit more floodplain topography. There is also some evidence of terraces here with flat but still low elevation areas on both sides couple with still looking like somewhat floodplain deposits (due to the agriculture and city landscaping). Overall these aren't saying a whole lot about the system, other than there is more floodplain in the lower portion than upper portion, and that there is a paleochannel that is lower than the current base level control of flathead lake, which makes sense considering the dam at the foot is in place.

Intercomparisons

Of course, none of this categorization matters without comparing these sites to each other, then placing them in their watershed context.

Pairwise Comparisons Fluvial

I just want to draw attention to a few of these. Obviously outlet's that are low slope and have lots of sediment are going to be sandy and have lateral unconfinement etc.

What makes Nyack transition into Lincoln? That is an interesting question considering there is a marked difference so quickly. I believe it is a few factors. The valley width of Nyack is quite wide, but then pinches into the Flathead range as an antecedent or superposed stream system, so there is a significant geologic condition. The other factor is slope and bed composition. It is clear that for whatever reason (be it glaciers, lakes, etc) the valley of the Nyack reach is built up evenly while the Lincoln reach is not built up in the contemporary flow regime because the bed material is boulder and bedrock, which are highly resistant to transport. This also results in a significant slope change when moving from that deposited segment of Nyack into the incised segment of Lincoln.

Why is Shafer partially unconfined in spite of it's relatively high slope? This I believe is primarily due to the escarpment and valley width. It has quite high valley width with low relief hillslopes while other similarly steep segments are very narrow and have high relief.

I cover above why Upper and Lower Outlet are so strange, but I'll summarize here it is likely a result of anthropogenic effects (constriction, agriculture, loss of upstream sediments, diversion, base level changes), backwater, nearby confluences, and pattern of upstream accumulation zones.

Big Picture

So, what's the big picture of this watershed? what are the drivers for river diversity in this system? It appears the primary drivers are geology, past glacial activity, slope, sediment fluxes, and in the lower portions, anthropogenics. . We see in this selection of sites those to be the best metrics. Nyack to Lincoln is clearly due to past glaciers and the geology. Upper to Lower Outlet are specifically a result of anthropogenics and sediment flux (debateably past glacial due to flathead valley formation). The rest of the sites are all differentiated based on the slope, valley width, and geology.

Aspects of Interpretation that can use Development

This thread on these sites and this watershed could be developed a bit more. Of course going out in the field and doing systematic surveys can get really good data for what is happening. There can also be repeat surveys to get temporal data. As far as interpretations based on the evidence here, I draw sediment budget inferences about the sites based on process form relationships, but these systems are complex enough that I could end up being wrong on my inferences if we went in and actually surveyed the budget. There also can be a bit more development in the quantitative and figure realm. I didn't make specific maps of GU's, I just summarized the observed GU's. More accurate conclusions can be drawn by going in and mapping out the GU's. I also chose not to be very specific on hydrology and morphometrics in the sites. I just gave a general flow regime coupled with a short description of what can be seen as far as morphometrics are concerned. However, quantifying and comparing either between sites or across watersheds can be quite useful, however I would only want more specific data to be able to put those into a better context. Big picture improvements can be made on sediment budgeting, detail in observations, sub water surface mapping, and in general, deeper analysis of the sedimentological history in order to start to parse out a bit more of river behavior and change.

Quick summary of Flux Controls

Overall, the things controlling the flux conditions seem to be valley width, elevation above active channel, climate (notably snowmelt), the Hungry Horse Dam, and human adjustments.

Summary of River Behavior

along the sites, the most variable and subject to avulsions and the like were the Nyack, Shafer, and Outlet sites, however Nyack and Outlet have anthropogenic effects that might resist the regular behavior of the river. Bear and Lincoln are so highly confined and bedrock ladden that river behavior is relatively one note.

Loose credits for data and software used

mapping was done in Google maps, Google earth Pro, Caltopo, ArcGIS Pro and Arcmap

Data came from the Riverscapes Consortium, USGS, ESRI, and the EPA.

Page updated

Google Sites

Report abuse