Catchment Scales Of River Geomorphology
Embedded Files
Map of the Logan River Watershed
Fig.1 and Fig.2: Figure one (left) shows where the Logan River is in relation to Utah. Figure two (right) shows the extent of the Logan River Watershed. I pulled the Logan River Watershed boundary polygon from Riverscapes to produce figure two.
Longitudinal Profile
To create a longitudinal profile of the logan river I used the Terrain Profile tool in QGIS. The y axis shows the elevation difference in meters while the x axis shows the distance downstream in km. Additionally I used the DEM provided by Riverscape viewer and drew a line and converted it to a polygon.
Base Level Controls
Base level control of the logan river today is Cutler Reservoir with an elevation of 1343 m. I found the elevation of Cutler Reservoir by using CalTopo. Base Level Control 18,000 years ago was Lake Bonneville at 1554 m that covered the valley.
Mainstem Length
Mainstem length is 86.4km I found the mainstem length by running the profile tool on the Logan River mainstem shapefile from the Riverscapes website in ArcGIS. This gave me the mainstem distance of the Logan River.
Concavity
To calculate concavity I used the concavity formula where concavity=2A/H where A is the elevation difference between the midpoint elevation from the profile and the midpoint of a straight line connecting the two elevations and where H is equal to the total difference in elevation
A=1935-1569.6= 366 m
H= 2465-1344= 1121 m
Concavity = 2(366)/1121=0.65
Knickpoints
Knick points on the logan river can be seen between 0.4 and 0.6. These knickpoints are First and Second Dam. The knickpoint before 0.1 is likley due to a difference in bedrock.
Catchment Morphometrics
Catchment Length, Area, Perimeter Length, Circularity Ratio, Elongation Ratio, Form Factor, Catchment Relief, Relief Ratio, Drainage Density and Drainage pattern
Catchment Length: I found the catchment length by finding the longest path that water could take. I then highlighted this polyline and ran the profile tool to find the distance of this polyline, I found that the catchment length=94.5 km.
Catchment Area: To find the catchment area I used QGIS and the watershed boundary layer from Riverscapes. I edited the attribute table and added a new field called area and in the expression box added $area. I found that the area was 646,562,177 m^2 or 646.6 km^2
Perimeter Length: I found the perimeter length using a similar method to catchment area but instead of adding $area I added $length to the expression box of the new field I created. I found the perimeter to be 172 km.
Circularity Ratio: Circularity ratio was calculated using the following formula: Rc=A/Ac where Rc is the circularity ratio A is the catchment area and Ac is the area of a circle with the same perimeter. Circularity ratio= 0.27
Elongation Ratio: A^0.5/L where A is the catchment area and L is catchment length. Elongation ratio=0.27. A value of 0.27 shows that the catchment is very elongated.
Form Factor: Rf=A/L^2 where Rf is the form factor A is catchment area and L is length. Form factor=0.07 this further supports that the catchment is very elongated.
Catchment Relief: H=E(max)-E(min) where H is the catchment relief E is the max elevation and Emin is the minimum at the mouth. I found the elevation values using the DEM provided by Riverscapes. Catchment relief= 1671.6 m
Relief Ratio:R=H/L where H is the catchment relief and L is the mainstem length. Relief Ratio= 0.019
Dranage Density=D/A where D is the total length of drainages and A is the area of the catchment. I found the length of the drainages by inspecting a drainage layer in QGIS and creating a new field using the field calculator for length. The drainage density= 1.249 km/km^2
Drainage Pattern: I believe that the drainage pattern for the Logan River Watershed is dendritic.
Stream Order
Stream order was found by inspecting the Hydrological Context For The Logan River dataset found from Riverscapes. Stream order was listed in the attribute table of the flood layer. The stream order at the mouth of Temple Fork is 4th order, at the mouth of beaver creek it is 4th order as well, and at the mouth of the Logan River is 6th order.
Hortons Laws Of Stream Composition: I belive that the Logan River follows Hortons Laws. The Logan follows the first law that states as a stream order increases there will be fewer streams of this order. This is shown by there being more first order streams than second and so on. Additionally, Hortons Laws states, while there are fewer number of these stream orders (1st and 2nd order) both mainstem length increase and catchment area decreases. This was shown in the Logan River as catchment area decreased as mainstem length increased. For these reasons I believe that the Logan follows Hortons Laws.
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