Figure 1. Dover, etal. 2007, Mork, etal. 1990
Figure 3. Site Map
Left-Hand Fork is a small offshoot of the Blacksmith Fork River, it flows east to west through the Bear River mountains. The climate of the Bear River Range is semi-arid with seasonal variation in precipitation and runoff. The flow during the observation at these sites was low before the spring runoff. This river system is in a fault-block mountain region with the predominate rock type being carbonates and intermixed sand and mudstones (Figure 1.). Vegetation along this river catchment is forest and riparian systems with dogwood, big tooth maples, and grasses. This catchment has an approximate length of 23 km with an elevation range from 1555m to 1990m (Figure 2.). Three sites were evaluated in the Left-Hand Fork (Figure 3.).
Figure 2. Elevation Profile
Figure 4. Site 1 Map
Figure 5. Site 1 cross-section
1720m elevation
Latterly confined narrow canyon, straight flow
Steep vegetated banks, no floodplain (yellow)
Flow with 2m , flow depth 50cm
Characteristic units: rapids, cascades, pools and runs
Sediment consist of gravels to boulders 1cm - 40cm
This site is in a narrow V shaped canyon 3-5m below the road (Figure 4.). It is 100% confined by the steep vegetated banks of large alluvial bolder fall. The flow is a narrow straight run approximately 500m long between to bends in the canyon. No flood plain is found within this site. Maximum flow height no grater than 50cm above current state (Figure 5.). Geomorphic units include a series of rapids an pools Figures 6 - 8).
Figure 6. Rapids and runs
Figure 7. Rapid and pool
Figure 8. Steep banks with dogwood
Figure 9. Site 2 Map
Figure 10. Site 2 cross-section
1690m elevation
Partly confined canyon, with structural forcing from cliff face
No south bank, flow forced against cliff (purple)
No floodplain
Flow travels around large point bar (red)
Flow divergence around mid channel bar and large boulders (red)
Flow width 4m-5m, flow depth 50-60cm
Sediment consists of large gravel to boulders 5cm- 60cm
This site is a riverbend with partial confinement by a cliff forming rock unit in place of the south bank (Figure 9.). The north side of the channel has a large point bar approximately 30cm above current flow level, and shallow tree covered bank rising 2-3m to the road (Figure 10.). Between the beginning of the cliff face and slightly down stream of the point bar is a mid channel bar 3-5m long and 3m wide. The bend acts as a transition between relatively smooth flow upstream and a series of rapids and pools in the narrow section structurally forced by the cliff (Figure 11.). Large boulders are found in the downstream direction but it is unclear if they are moved by the flow or have fallen from the rocks above (Figure 12.).
Figure 11. structural forcing by cliff face
Figure 12. mid channel bar, large bolder fallen from cliff
Figure 13. Site 3 Map
Figure 14. Site 3 cross-section
1660m elevation
Partly confined - unconfined
Flow curves around flood plain pockets (green)
Through ground flow visible in north center of flood plain pocket(blue)
Point and lateral bars along the margins of flood plain pockets (red)
Eddy pool structurally forced by road (purple)
Flow width 4m, flow depth 30 cm
Sediment consists of course sand to large gravel, 1 mm-10 cm
This site is the low end of my study area, it is unconfined or slightly confined (Figure 13). Flood plain pockets 50cm above current flow level are identifiable and differentiated from bars and banks (Figure 14 - Figure 17.). At the north west of the site the flow runs up against the road forcing an abrupt change in direction and creating an eddy pool (Figure 18.). Although the eddy pool is primarily fed by the main channel there is also evidence that subsurface through flow also feeds this pool. Down stream of the site the flow undergoes an increases in velocity and a decrees in sinuosity with a steeper elevation gradient suggesting this is a knickpoint for this catchment.
Figure 15. point bar and eroding bank
Figure 16. lateral bar, point bar and floodplain
Figure 17. eroding bank
Figure 18. flood plain and eddy pool