Final Project: Logan River Watershed
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Introduction:
The Logan River Watershed is located in the Bear River range in Northern Utah. The headwaters are located just over the Utah-Idaho border. The Logan River ends when it reaches it's confluence with the Little Bear River and eventually drains into Cutler Reservoir.
Data Source: USGS National Map Downloader
Catchment Morphometrics:
Catchment Area: 646,562,000 square meters (About 250 square miles)
Relief: 1,125 m
Dendritic Drainage Network
Steep watershed with a large drop in elevation along its profile
For a more detailed overview of the Logan River's Morphometrics take a look at:
Data Sources: USGS National Map Downloader, Elevation data
Main Stem Length: 82 km (82,000 meters)
Climate:
Since 1979, air temperatures have been increasing across Utah and snowpack has been decreasing. Peak snowpack has declined by about 16% (Hotaling & Becker, 2024). Decreases in snowpack and increases in temperature can result in lower water levels and warmer water. These factors combined with drought can negatively affect the Logan River by reducing biodiversity within the watershed and decreasing the amount of water available to all the users who rely on the river.
Flow Regime:
Logan River flows are measured at the mouth of Logan Canyon.
The majority of precipitation in the Logan River watershed is received in the form of snowmelt. This results in a snowmelt dominated hydrograph where peak flows usually coincide with spring runoff in June (Neilson, Strong, & Horsburgh, 2020).
Average Annual flow of the Logan River is 230 CFS.
Data Source: Utah Geological Survey
Geology:
The Logan River watershed is defined by karstic features that allow water to move through fractures and faults. This creates underground drainage systems throughout the watershed. Karst Springs; Ricks, Wood Camp and Dewitt Spring contribute significant flow to the Logan River
(Neilson et. al., 2020).
Physiographic Setting:
Wasatch and Uinta Mountains: [Ecoregion 19]
Composed of high mountains, dissected plateaus and intervening valleys
Central Basin and Range: [Ecoregion 13]
Composed of northerly trending, fault-block ranges with intervening drier basins
Semiarid Foothills: [19f]
5,000 to 8,000 feet elevation
Juniper and pinyon typically occur within a matrix of sagebrush, grama grass and Gambel oak
Wasatch Montane Zone: [19d]
Consists of forested mountains and plateaus underlain by sedimentary and metamorphic rocks
Douglas-fir and Aspen parkland are common. North-facing steep slopes often feature Engelmann Spruce and subalpine fir
Perennial stream provide water to low, arid regions
Malad and Cache Valley: [13i]
Contains wide terraces, alluvial fans and narrow floodplains
Water is provided to pastures and municipalities by mountain fed perennial streams
Cooler, shorter growing season
Data Source: EPA, Ecoregions
Site Locations:
Reach A: Partly Confined - Planform Controlled
Reach A:
41°55′08.73″ N, 111°33′50.51″ W
This reach is in a wide open valley bottom where the valley bottom margin is anthropogenically imposed by the road on the east side. The true valley bottom is located significantly further east of the road and this river would likely be more sinuous and feature a large active floodplain if it was not anthropogenically influenced. Anastomosing sections sit on either side of the river featuring active floodplains and a high likelihood of beaver activity. Inactive floodplains were determined by lack of vegetation as well as campgrounds, roads and other features that insinuate that the river is not overtopping its banks in those sections, at least not on a regular basis. The anastomosing sections also likely attenuate any high flows or flood that would occur in this section of the Logan River. This is likely a gravel bed section with some larger cobbles and boulders remnants of a past flow regime with higher competence than the Logan River has now.
Elevation: ~6500 ft
Reach Length: 878 meters
Slope: Relief of reach: 2003 m - 1980 m = 23 m
Rise/Run = 23 m / 878 m = .026 = 3% Slope
Confinement: Confinement was measured by dividing the length of the confining margins by the total length of the channel. 108 m (confining margins) / 904 m (channel length) = 0.11.
11% Confinement -
This fits into the category of Partly Confined - Planform Controlled with 10-50% confinement
Sinuosity: Sinuosity was measured by dividing the length of the channel centerline by the valley bottom centerline. 918.74 m / 878 m = 1.04 Sinuosity. This reflects a relatively straight channel with little meandering
Proportion Calculations:
Total area of valley bottom: 168,318.32 square meters
Proportion of Valley Bottom Channel:
Area of active channel / area of valley bottom = 11,760 sq meters / 168,318 sq meters = 0.07
7% of the valley bottom is active channel
Proportion of Valley Bottom in Active Floodplain:
Area of active floodplain / area of valley bottom = 55,071.84 sq meters / 168,318.32 sq meters = 0.327
33% of the valley is active floodplain
Proportion of Valley Bottom Inactive:
Area of inactive floodplain / area of valley bottom = 101,486.48 sq meters / 168,318.32 = 0.60
60% of the valley bottom is inactive floodplain
[These calculations were done by hand using Google earth measure tool, therefore these values are a rough estimate.]
This elevation profile is taken at the lower end of this reach where there is an active confining margin (hillslope) on river right. The active floodplain is confined by the road. This elevation profile reflects the low slope of the valley bottom throughout this stretch, and how this changes when the river comes into contact with the hillslope as a confining margin.
Geomorphic Units
The primary geomorphic units that can be found in this section of river are pools, runs and some small rapids. There are also some chute cutoffs as well as secondary and anastomosing channels. While there may be some riffle crests in this section they are difficult to determine at the level of imagery I was able to find for this project. This section is located closer to the headwaters of the Logan River where the river is likely supply-limited and has less sediment to deposit for instream geomorphic units. Due to the low level of sinuosity as well, there is less capacity for the river to deposit units such as bars.
Reach B: Confined
Reach B:
41°47′59.35″ N, 111°38′17.47″ W
This reach is a low slope, confined reach of the Logan River. The river is confined on either side by bedrock and hillslope, and features some small floodplain pockets along the main channel. Due to the low slope the channel features geomorphic units such as a diagonal bar and some in channel rapids that appear to be caused by rocks likely deposited by hillslope processes. This section of the Logan River features steep bedrock canyon walls restricting the sinuosity of the river. The bed of the river is gravel with large cobbles and boulders in some sections. There is some fine grained sediment due to the low slope of this section, which is reflectled in the presence of a diagonal bar.
The pins mark the site of this confined reach looking upstream, reflecting the steep canyon setting.
Elevation: ~5,540 feet
Reach Length: 597 meters
Slope: Relief of reach: 1640 m - 1633 m = 7m
Rise/Run = 7m / 597 m = 0.012 = 1% Slope
Confinement: Confinement was measured by dividing the length of the confining margins by the total length of the channel. 571m (confining margins) / 624.21 m(channel length) = 0.91.
91% Confinement -
This fits into the category of Confined with occasional floodplain pockets.
Sinuosity: Sinuosity was measured by dividing the length of the channel centerline by the valley bottom centerline. 624.21 m / 597 m = 1.04 Sinuosity. This reflects a relatively straight channel with little meandering likely due to the confinement of the river in this location.
This elevation profile is from the upper end of this reach, reflecting the steep bedrock confining margin located on river left. The road coincides with the hillslope confining margin. While this section does contain some flood plain pockets they are not reflected in this elevation profile.
Geomorphic Units
This reach is low slope which is reflected by long stretches of runs and some rapids where the river is constricted or affected by large boulders likely input to the river from hillslope processes. One diagonal bar can be found in this section, likely due only to the low slope of the river.
Reach C: Laterally Unconfined
Reach C:
41°44′3.96″ N,
111°54′30.70″ W
This reach is located near the end of the Logan River where it joins with Cutler Reservoir. The reach is confined mostly by anthropogenic margins, such as agriculture but still has significant space to meander within it's floodplain. This is a very low slope reach of the river and likely has a sand bed. This area is defined by it's slow moving, torturous meandering pattern. Geomorphic units include ridge and swale topography, oxbow lakes and flood runners. It is difficult to determine how much the Logan river actually floods here due to the controlled nature of flows of the river as it flows through Logan and heavily populated areas. Irrigated agriculture also likely affects the river here and could result in canals or other structure that alter the flow and movment of the river in this section.
Elevation: ~4,420 feet
Reach Length: 1617.68 m
Slope: Relief of reach: 1348 m - 1346 m = 2m
Rise/Run = 2m / 1617.68 m = 0.0012 = <1% Slope
Confinement: Confinement was measured by dividing the length of the confining margins by the total length of the channel. 498 m (confining margins) / 7,336.53 m (channel length) = 0.067.
6% Confinement - This fits into the category of Laterally Unconfined with less than 10% confinement.
Sinuosity: Sinuosity was measured by dividing the length of the channel centerline by the valley bottom centerline. 7,336.53 m / 1617.68 m = 4.5 Sinuosity. This can be considered torturous meandering with substantial bending and turning in the river channel.
Geomorphic Units:
This reach features geomorphic units that are characteristic of a highly sinuous riverscape. These include ridge and swale topography and oxbow lakes, which reflect the historical movements and positions of the river in this location. Paleochannels can also be seen reflecting where the river has been far enough in the past that they do not have water in them, like oxbow lakes. Flood runners reflect where water is likely to flow in high flows and also where avulsions may occur in the future and further oxbows form.
Conclusion
Each reach studied in this analysis reflected it's unique position within the Logan River Watershed which in turn, affects its form and processes. Reach A, the site located most closely to the headwaters, reflected a wide valley bottom river. The river had large floodplains located on either side and had anastomsing channels. This area is likely affected by beaver activity and can act to attenuate large floods. The valley setting is an important control on this site and reflects the rivers ability to meander. This section of the river reflects a gravel bed and large cobbles within the river that are often the source of rapids or other in channel features. Located further downstream, Reach B is in a highly confined section of the watershed where the canyon is defined by bedrock and hillslope on either side. Due to this confinement, the river at reach B was very straight and only featured occasional floodplain pockets. Geology is a key factor in the controls on reach B. While confined sites usually have more slope, this was a low slope site, as well as the other sites analyzed. The final site I chose is at the very end of the Logan River near it's outlet to Cutler Reservoir. This section is located in the deposition zone of the watershed. Reach C features torturous meandering, which is often caused by low slope and slower moving waters as well as significant amounts of sediment deposition. This site is highly anthropogenically influenced due to agriculture and other imposed margins. All three sites featured similar anthropogenic confinement by the road, although the sites in the canyon featured this more. The Logan River is an important resource for Cache Valley but often has issues with water quality and is facing an uncertain future as climate change alters the amount of water the river receives. Analyzing different reaches within a river and understanding the catchment scale controls such as geology, hydrology and ecology are important aspects of understanding river behavior. This project provided me with valuable experience for how to analyze and read different riverscapes as well as how to put them into context within the rest of their catchment.
One limitation to this project was the imagery I was able to find in order to analyze each reach. I struggled to find good imagery of the Logan River to look closely at features such as instream geomorphic units. This reflects the important of having good, high resolution data to utilize in watershed analysis.
References:
Cybercastor. (2023). Riverscapes Context for HUC 1601020303 for WATS 5150. A Riverscapes Project data set of type: Riverscapes Context. Owned by: USU RAM. Available from: https://data.riverscapes.net/p/d033fd87-b155-4a72-a272-29fa701fff78/
Hotaling, S., & Becker, K. (2024). Recent Climate Change in Utah, 1870–2023. Climate Resiliency.
Neilson, B. T., Strong, P., & Horsburgh, J. S. (2020). State of the Logan River Watershed. Utah Water Research Laboratory, Utah State University.
U.S. Geological Survey. (2000). Ecoregions of Utah [Map]. U.S. Geological Survey. https://store.usgs.gov/assets/MOD/StoreFiles/Ecoregion/112579_ut_front.pdf
U.S. Geological Survey. (2024, January 30). USGS 1/3 Arc Second n42w112 20240130 [GeoTIFF]. The National Map. https://www.usgs.gov/the-national-map-data-delivery
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