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Figure 1: Geographic location of the study catchment (HUC 1601010107).
Geography
Geography
The Big Creek-Bear River (HUC 1601010107) is locate in Northeastern Utah and drains into the upper section of the greater Bear River which runs into the Great Salt Lake. The basin is occupied by several rural ranching communities such as Randolph, Utah. I chose to study this catchment because I am already conducting research on the impact of regenerative grazing rotations on stream health. The streams are considered to be largely degraded, and I'm curious as to the larger scale geomorphic factors that would contribute to the widespread channel incision.
Catchment Characteristics
Catchment Characteristics
Figure 2: Visualizations of climate metrics in the Western United States. (1) Instantaneous discharge data from the USGS gage (10023000) for Big Creek near Randolph, UT (2) Average annual precipitation (3) Average winter temperatures (4) Average spring temperatures (5) Average summer temperatures (6) Average wind velocities (7) Average annual snowfall.
Climate & Hydrology
Climate & Hydrology
The Big Creek catchment is located at a high elevation in a semi-arid climate. As shown in Figure 2.1, its hydrograph is characteristic of a snowmelt-driven watershed (average snowfall is shown in Figure 2.7) with several monsoon floods in the late summer and fall. The region experiences very low winter temperatures (Figure 2.3) with moderately warm springs and summers (Figures 2.4 & 2.5) and moderate average annual wind speeds (Figure 2.6).
According to my research contacts at the Utah Geologic Survey (UGS), the Big Creek watershed has a very complex shallow groundwater system that drives baseflow in many of the streams.
Vegetation
Vegetation
The catchment is mostly occupied by several varieties of sagebrush due to the arid climate. The dominant riparian species are willow, cinquefoils, forbs, and sedges. In the higher elevations, the uplands consist of conifer forests and aspen stands. The alluvial valley surrounding the mainstem Bear River is primarily grass and agricultural cover (Figure 3).
Figure 3: Existing vegetation landcover classes from the LANDFIRE national dataset and curated by the Riverscapes Data Exchange.
Figure 4: Geologic materials underlying the Big Creek watershed. Curated by the Riverscapes Data Exchange.
Geology
Geology
The Big Creek watershed is located in the Basin and Range physiographic province, so we see North-South oriented Horst fault block mountains surrounding large Graben alluvial valleys with the same orientation. As far as bedrock composition, the dark tan areas shown in Figure 4 are Cretaceous conglomerates. Light tan areas are Tertiary alluvial and colluvial deposits. The blues are carbonates like limestones and dolomites that were deposited by shallow oceans during the Paleozoic era.
Figure 5: description
Figure 6: description
Study Sites
Study Sites
The study sites' valley bottoms are delineated with dashed yellow lines (Figure 5).
Figure 7: description
I don't think this watershed gets enough water or experiences enough tectonic activity to generate bedrock confined streams. The primary confining landform seems to be alluvial fans since the rocks and hills are so old and and weathered, and there is limited precipitation that can flush the fans far enough into valleys to truly confine the streams. Additionally, the majority of the stream network is flowing through either a conglomerate in the upper reaches or Tertiary alluvial/colluvial deposits in the lower reaches, so the general meandering planform makes sense to me because of the ease of lateral erosion through these weaker rocks and deposits. The meandering is also explained by a combination of weak floods and dense riparian plant communities such as willow and sedges that would hold banks together during high flows.
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