Jens Ammon
Catchment-Scale Controls on River Geomorphology
Logan River Watershed
Logan, UT
USA
Regional location of the Logan River Watershed (left) and detailed location of the watershed boundary (right). Watershed extent is denoted in red, channels in blue. Figures were made using Google Earth Pro.
Longitudinal Profile
Longitudinal Profile of the Logan River, the trunk stream of the Logan River Watershed. The present-day base level is controlled by the Great Salt Lake (1282 m). The base level at approximately 18000 BP was set by Lake Bonneville (1554 m). This historical base level corresponds to the major knickpoint present on the Logan River, indicating the knickpoint is due to a geological facies change.
​
The total length of the Logan River is 82.2 km. The concavity is 0.62 based on the following calculations:
Catchment Morphometrics
Catchment Length: 62.9 km
​
Catchment Area: 646.6 km (6.466x10 m )
​
Circulatory Ratio: 0.2
​
Elongation Ratio: 0.4
2
2
8
Form Factor: 0.16
​
Catchment Relief: 1699 m
​
Relief Ratio: 0.03
​
Drainage Density: 0.34 km/km
(Dendritic drainage pattern)
2
Note: catchment length was calculated with two straight line segments due to the curvature of the watershed.
​
Morphometric values were extracted from Google Earth or calculated as follows:
Stream Order
Beaver Creek Tributary
Temple Fork Tributary
Stream order of the Beaver Creek tributary (left) and the Temple Fork tributary (above). The dark blue line represents the Logan River trunk stream. Only perennial channels were included in the order classification.
​
Beaver Creek: Order 2
Temple Fork : Order 3
Using a similar coloring method as above, the Logan River trunk stream was classified as Order 4 at the mouth of the watershed.
​
Hortonian Laws as demonstrated by the Logan River Watershed:
1. As stream order increases, the amount of channels in that order decreases. There are numerous
Order 1 tributaries. The channels then consolidate with each Order increase, until only a single Order 4
channel remains.
2. As stream order increases, the stream length also increases. While there is the occasional long Order 1
tributary in the Logan Rive Watershed, the average length across all Order 1 channels is short (0.3 km).
3. Catchment area increases with increasing stream order. Higher Order downstream channels are fed
from all lower Order upstream channels.