Kugururok Watershed

For my final project in Fluvial Geomorphology I evaluated five distinct reach types by their behavior in the Kugururok Watershed, located in the Noatak wilderness area.

Setting:

The Kuguruok drains to the Noatak River which acts at the base control point and eventually Kotzebue Sound in the Chukchi Sea , but for the purposes of the project I looked at sites that on contained within a pour point at the Trail Creek confluence
Physiographic and Geologic Setting: The area is split between the arctic foothills and The Brooks Range with the northern tree-line being located just south of the catchment and permafrost encapsulating much of the area. Thus, leading to vegetation like that of low-lying shrubs, grasses, and spruce trees. But much of the watershed lacks deep rooted plants (spruce trees) making for a highly sensitive riverscape, particularly notable in wide valley bottom settings

Site 1: Steep headwaters, confined valley setting

Site 2: Confined reach, planform controlled with occasional floodplain pockets

Site 3: Partly confined braided river with anastomosing sections, planform controlled

Site 4: Unconfined braided river with anastomosing sections, coarse gravel bed

Site 5: Partly Confined margin controlled meandering reach

Discussion: Catchment Scale

Fig 1.1 Watershed map of the Kug at confluence of Trail Creek

Fig 1.2 Elevation Profile of The Kugururok River, mapped on USGS national map (https://apps.nationalmap.gov/viewer/)

Average slope: 0.7%
Max Slope: 4.5%
2,807 ft of elevation loss
Main stem length: 40 miles

Site 1: Steep headwaters, confined valley setting

The headwaters of the Kugururok beings to form a gully when visible rills join to create a first order stream. At 3,300 ft above sea level and 68.445125 degrees North. The start of the channel has visible rills due to the high amount of sediment from glacial activity and lack of vegetation that is able to survive in the extreme environments.

Fig 1.3 Fan at beginning of reach, and blue polygon representing the channel

Fig 1.4 Topography highlighting the confinement of the headwaters

Refer to Site 1 for methods and formulas

Slope= 31 degrees
100% confinement - constricted , steep valley setting
Channel width= 1 m
Sinuosity= 1.05
Reach Length = 397 M

This is a typical headwater reach that is an ephemeral stream that has a short lived flow after spring runoff from its near by source. The lack of vegetation and loose sediment allow for water to converge and a channel to form at a higher elevation relative to the mountain peaks in the region. In stream units and bed material are unvaried throughout being composed of fine sand and a

Site 2: Confined reach, planform controlled with occasional floodplain pockets

Heading down in elevation I found a second site that more closely resembles a confined reach that is planar controlled, the narrow valley setting gives little room to room and adjusts through vertical accretion. There is no inactive floodplain and the channel frequently bumps up against the valley margin. There are several first order tributaries that are supplying sediment which is verified with the bank attached bars that are seen throughout the reach.

Similar to the other sites there doesn't appear to be inactive floodplain as areas that are not being regularly inundated with flow or runoff lack vegetation due. This coincides with the harsh landscape and short growing season, I believe truly inactive floodplain would lack vegetation in this climate.

Fig 2.1 Tier 1 units. Blue- Channel, Orange- active floodplain, yellow- tributary fans

Fig 2.2 Topographic map showing how the the reach with tier 1 units

Geometry and Calculations

To help better understand the river styling and behavior I preformed some calculations that help support my arguments for the river styling

Refer to site 4 for methods and formulas*

Elevation = 1427 ft
Reach Length =

% confined = 26%
% active floodplain = 54%
% active channel = 46%
Channel width
- Upper bound= 11.6 m ^2
- Lower bound = 10.3 m ^2
Sinuosity = 1.01
Slope = 7%

Fig 2.3 Red marks highlight areas where the channel and active floodplain match, this indicates to me there is a confinement.

Geomorphic Units and Bed Material

The high energy and first order stream tributaries lead me to believe the reach has a mixed load with fine sediment being supplied at the fans. The majority of the bed I hypothesize is made of cobble to coarse gravel.

As indicated by my sinuosity calculation and sleep slope the channel is fairly straight and boring. The floodplain pockets have indications of previous channels with the little room it has to move between hillslope. Much of the geomorphic units are runs, lateral bars, some ridge-swale patterning, and what appears to be island/compound bars.

Fig 2.4 Ridge and Swale/compound bar with blue= scour pool, yellow X's= ridges, and cut offs with the red arrows

Green diamond exemplifies a longitudinal bar, mid-channel

Fig 2.5 Lateral bar example, appearing to transfer to a diagonal mid-channel style bar

Site 3: Partly confined braided river with anastomosing sections, planform controlled

A wide valley setting placed between two separate mountains with equally as wide of valleys on river right and left, supplying a large budget of sediment. This would indicated the reach is transport limited and is prone to vertical accretion, these factors could also be attributed to the lack of cohesion. All these factors can circle back to the vegetation in the region and how the Kugururok River behaves when there are a lack of landform resisting factors. Much of the channel appears to be inundated on a yearly basis, but baseflow only supports one main channel, if the tributaries were to be omitted.

Geometry/ Calculations

*refer to site 4 for methods and formulas

Elevation = 1,101 ft
Reach Length =2,904 m

% confined = 48 %
% active floodplain = 31 %
% active channel = 68 %
Channel width, main channel**
- Upper bound= 111 m
- Lower bound = 165 m
Sinuosity = 1.3
Slope = 2.8 %

Fig 3.1 Polygons mapping of reach 3, blue-active channel, orange- active -floodplain, yellow-imposing tributary fans. Black polygons represent areas that appear active due to the exposed gravel but act like anastomosing sections where discontinuous vegetation has formed. Purple polygons is an area of hillslope that is not a part of the valley bottom, refer to Fig 3.2 for topography

Fig 3.2 Topographic map, Change in elevation seen mid channel where there is hillslope/rock outcrop

Fig 3.3 Blue areas showing points of confinement, either from hillslope or tributary fans

Geomorphic Units, Bed Material , and Behavior

The evidence we have to understand the behavior of the channel is imagery that is taken from a period of baseflow, but using some of the reach geometry and characteristics we can begin to under the processes. This reach has main channels, ones source zone comes from the namesake of the river, while the other is supplied from the tributary on river left. Upstream of the tributary where the rivers main channel splits, the anabranches that follow river left appear to be infilled and this could be caused by the change in slope as the tributary delivers sediment downstream.

At higher flow I could suspect the the main channel on river right widens and inundates some of the mid-channel bars, but that flow ultimately opens up the other smaller channels and in to some extent acts as sheet flow leading to vertical accretion.

The bed material is made of a mix load that varies from coarse gravel to fine silt/sand, with evidence of sediment sorting(Fig 3.4) from the imagery where a darker material is perched mid bar and becomes lighter in color as you get closer to the channel.

Geomorphic units:

Planar: Glide, potential runs at chute cut-offs

Concave: bar forced pools, shallow thalwag

Convex: compound bars, lateral bars, diagonal bars

Fig 3.4 Showing evidence of sediment sorting and a mix bed load. The darkest material would indicate the heaviest(i.e. coarse gravel) at the highest point of the bar, the lighter blue marks indicates material that is smaller and finer, and the lightest blue markings would be the finest sediment (i.e. sand)

Fig 3.5 Compound bar. Green- Island, Red X - pools, Orange- shallow thalwag, purple x - diagonal bar

Fig 3.6 Bar forced pool, green arrows indicating where flow is be shunted from high points(magenta X) towards pools (purple Xs)

Site 4: Unconfined braided river with anastomosing sections, coarse gravel bed

Fig 4.1, fig 4.2 , and fig 4.3 (on right) show tier 1 geomorphic units with plain imagery for justification. As well as topography to help distinguish between main channel valley and elevated surfaces that could be labeled hillslope

Discussion:

I based my decisions off of some imagery with the assistance of USGS topography maps to help in the argument.

-Active floodplain was determined with imagery by looking at where there was active bar vs. where vegetation had developed(indicating inactive)

-The black polygons indicate areas of inactive floodplain where the river has anabranched and developed an island.

-Fans acted as an imposing boundary on the main channel and developed where tributaries joined the main stem. I looked at topography( fig 2.3) to help justify where the the boundary of the valley floor is, and what vegetation could be attributed to the tributary

I argue that this site is unconfined due to the proportion confined and lack of constriction on the reach, determined through Arc pro(fig 4.5) and some simple math.

The reach has a reach perimeter length of 18,220.7 m, with 870 m being restricted along both sides of the channel(fig 4.5), refer to methods below
- 5% is confined
Riverscape width, manual measurement taken off Arc
- Upper reach, 1012 m
- Downstream, 331 m
Site Length, 8386 m
Proportion of active, table 2.
- Area of active channel: 538,7278 m^2, 48%
- Active floodplain: 560,7447 m^2, 48%
- No proportion of the valley bottom appears inactive The imagery shows no paleo landforms that are infilled or not being impacted by the modern channel
- Sinuosity= river length/ straight line
  - Sinuosity =89991 m /8386 m = 1.1, fig 2.4 showing channel length both birds flight and floating path measurements
- Slope, calculated by look at elevation loss from the upper point of the reach in comparison to the lower
  - elevation loss/reach length= 717-623/8386= 1.12 %
Given the lack of confinement on the channel and lack of main channel distinction, with a combination of both active bars and vegetated bars(islands),I would classify this riverscape as wandering river with both anastomosing and braiding characteristics.

Table 2. Showing excel calculations for proportion of active channel

Fig 4.4 and table 4.1 Sinuosity evidence

Calculations

Percent Confined

After drawing polygons in Arc I converted the active channel to lines in order to determine a perimeter length( table 2.2)
Next I took length measurements of area where the floodplain and channel aligned, showing a valley extent and valley margin as the same point. This would indicate a point of confinement
Took the total length of confinement from step 2 and calculated this as a percentage

Table 2.2 Site 1 channel perimeter length in meters, total length= 18,220.7 meters

Instream Geomorphic Units and bed characteristics

Geomorphic units are useful is defining a rivers morphology in order help understand the processes and control factors on a reach scale.

Bed Material

Pictured on a downstream section(fig 2.) of the Kug the riffles and bar material exemplify a coarse bed and mix load
A suspended load is seen where the tributaries meet the main stem and in those areas there appears to be more fine grain sediment, but from areal imagery the suspended and fine grain sediment is minimal as it is most likely getting carried downstream fairly quickly once supplied.
Conclusively, given the coarse evidence of imagery there is mix load at this reach

Geomorphic Units

Given the imagery and what appears to be base flow I will describe the units present

Planar Units
- runs and small rapids
Concave features
- pools, secondary channels
Convexities
- Diagonal bar, island, compound bars, longitudinal bar, point bar, ridge and chute channels, riffle-pool sequences

Fig 4.8 Example of coarse gravel present at a lower reach site

Fig 4.9 Example of an island at higher flow

Fig 4.10 Showing a compound bar. Yellow-ridge, magenta- channels/cutoffs, green-scour pool, orange-pools

Fig 4.11 example of a ridge and chute sequence. Red lines/arrows show channels at higher flows. Yellow X's show ridges where vegetation has developed

Site 5: Partly Confined margin controlled meandering reach

The last reach I selected is at the lowest point in the catchment in contrast to the other reaches, and comes in from the Trail Creek whose base control is the Kugururok River. At this point on the Trail Creek the river cuts through a valley setting, whose present day setting is a narrow valley flood with bed hillslope generating confinement, and creating a supply limited reach

Fig 5.1 Polygons showing active channel, floodplain, and fans

Fig 5.2 Topographic map with polygons

Calculations and Geometry

Refer to site 4 for methods and calculations***

Elevation = 669 ft
Reach Length =8,656 m

% confined = 51%
% active floodplain = 64%
% active channel = 35%
Channel width, main channel**
- Upper bound= 247 m
- Lower bound = 153 m
Sinuosity = 1.2
Slope = 1.2%

Fig 5.3 Light blue polygon is active channel, dark blue lines indicate areas of of confinement

Geomorphic Units, Bed Material , and Behavior

This reach on the trail creek has little capacity to change but adjust laterally between the valley margins. The bed material is comprised of coarse gravel with a light suspended load, and given the shallow slope of the reach the bed material is only entrained during high spring run-off. There are areas that have began to anastomose where vegetated islands have form, but no area of the valley bottom is inactive as bars are regularly inundated.

Geomorphic Units

Planar Units
- runs and small rapids
Concave features
- pools, shallow thalwag, secondary channel,
Convexities
- Diagonal bar, island, compound bars, longitudinal bar, point bar, ridge and chute channels, expansion bar

Fig 5.4 An example of a mid-channel bar where sediment has fallen out of entrainment due to flow divergence

Fig 5.5 Riffle-pool sequence, red lines are riffle crests and X are pools

Discussion: Catchment Scale

There are a few dominating processes that are apparent in all fives reaches but more so when the channel has room to both vertically and laterally adjust, and these indicative of the climatic region. Lying north of the Northern tree-line impacts the amount of cohesions that is found in this system, as well the sediment that is being supplied to the system. Glacier systems that occupied the region in the past lead to the amount of fine sediment that is supplied in the system and carried throughout. The steeper reaches and more confined setting act like stores but are more quickly able to move it throughout given the concentrated flow, while reaches like 3 and 4 are prone to vertical accretion and act like sinks to some extent. Because of the nature of the region and the watershed being a intermittent due to freezing during much of the year, most geomorphic work is done around peak runoff in the spring to early summer when there is snowmelt. Additionally, the system is very flashy and responsive due to the permafrost as groundwater quickly fills and generates runoff. Due to the lack of anthropogenic constraints lack of cohesion I found that inactive floodplain wasn't present in this system and the channel or channels are frequency changing and interacting with the valley margins, and as climate change continues to take dramatic effect in the Arctic as more water will be supplied to these system through melting permafrost and changing precipitation patterns.

Kugururok

Confluence with the Noatak

Kugururok

Kuguruok

Confluence with the Noatak

Kugururok

Confluence with the Noatak

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