Module 3: Catchment-Scale Controls on River Geomorphology

A series of morphometric analyses on the Logan River Watershed (HUC: 1601020303)

Interactive Map of the Logan river watershed

Click on the map to explore the Logan River Watershed boundary, the mainstem, and its perennial network.

Longitudinal profile

The Logan River travels roughly 86.4 km through Idaho and Utah, dropping over 1,100 meters in elevation before reaching the Little Bear River at an elevation of 1344 meters. The Little Bear River is the Logan River's modern base-level control. Today, the Bonneville Shoreline Trail intersects the Logan and reminds us that the Logan River's base-level was once much higher-- with an elevation of roughly 1,550 meters at the time the shoreline was created.

Above: Small rapid on the Logan River caused by an erosion-resistant section of bedrock.

Knickpoints identified in profile with red arrows
Controls hypothesis: The Logan has incised through the Bonneville shoreline sediment and up through the Canyon. The ability for the river to do work is limited by its flow and the gradient of the channel. The three hydroelectric dams present major controls on the river's base-level and prevent knickpoint propagation.

Longitudinal Profile: The Methods

I produced the longitudinal profile in ArcMap by interpolating the Logan River polyline and the 10 m DEM.
I used the identify tool on the DEM layer to pull the elevation from where the Logan River meets the Little Bear.
I knew that Lake Bonneville was present ~18,000 years ago. This is the age of the Bonneville shoreline. A quick google search said the elevation of the shoreline is ~1550 meters.
To get the length of the Logan River, I grabbed the sum of the polyline lengths from the attribute table in ArcMap.
Concavity = 2A/H ... Concavity = (2 * 190 m / 1050 m) ... Concavity = 0.36
I labeled possible knickpoints. Admittedly, my long profile could be better... With more time, I'd exaggerate the vertical to help make the knickpoints pop out.

Catchment Morphometrics

The Logan River catchment is about 50,000 meters long, with total area of 646,088,308 sq. meters, or roughly 646 sq. kilometers. The catchment perimeter length is 172,341 meters, or about 173 kilometers.

Circularity ratio: 0.3

Elongation ratio: 0.5

Form factor: 0.3

Maximum Catchment Relief: 1,699 meters

Relief Ratio: 0.03

Drainage Density = 0.5

Drainage Pattern: Dendritic (Youth)

Above: Dendritic pattern observed in Logan River and its tributaries.

Catchment Morphometrics: The Methods

I measured the HUC 10 length in ArcMap using the measure tool. I was up in the air about how to do this because the shape of the catchment is fairly irregular. I ended up trying to imagine the catchment within a rectangle and then "measured" the rectangle's length at its axis. I came up with 50,000 meters, or 50 kilometers. This seems like a high number, but it's still far below the channel length of 86 kilometers, so I decided it was a hair estimate for the purpose of this assignment.
I pulled catchment area from attribute table.
I measured the perimeter using the measure tool.
Circularity Ratio = (A/Ac) ... Circularity Ratio = (Catchment Area / Area of Circle with Catchment Circumference) ... Circularity Ratio = ( 646 sq km / 2,382 sq km) ... Circularity Ratio = 0.3
Elongation Ratio = (A^0.5 / L) ... Elongation Ratio = (Catchment Area ^ 0.5 / Catchment Length) ... = (26 /50) ... Elongation Ratio = 0.5
Form factor = (Catchment Area / Catchment Length ^ 2) ... (646 / 2500) ... Form Factor = 0.3
Maximum Catchment Relief = 3043 m - 1344 m ... = 1,699 m
Relief Ratio = 1699 m / 50,000 = 0.03
Drainage Density = (total km length of stream channels / catchment area km2) ... (217 + 86) / (646) ... = 0.5
It's young & dendritic.. seemed to be the best match to the various network patterns and stages of drainage network evolution shown in the textbook.

Stream ORder

The stream order of the Logan River at its mouth is 3rd.

Temple Fork (2) and many 1st order streams feed into the Logan.

The stream order of Temple Fork at its mouth is 2nd.

Spawn Creek (1) feeds into Temple Fork (1)

The stream order of Beaver Creek is 1st.

No other ephemeral channels feed into Beaver Creek.

*** I just used my judgement here-- I counted named perennial streams as 1st order for my count, and disregarded ones that didn't have names, for the sake of simplicity. It felt very subjective, so I just made that call at the beginning and used the same logic for all of the stream orders I "calculated".

The Logan appears to obey the Hortonian Laws of Stream Network Composition:

The law of stream numbers: as stream order increases, the number of streams of that order decrease
- - - (Yes, this has to be true by definition-- so yes, it's true for the Logan)
The law of stream lengths: as stream order increases, there is a direct increase in stream length for that order, such that first-order streams tend to be relatively short compared with streams of a higher order
- - - (Yes, this is true for the Logan.. many short 1-st order streams, the 2nd order streams are longer, The Logan is the longest, etc)
The law of catchment area: catchment area increases in a smooth progression with increasing stream order
- - - When you increase stream order, you're grabbing new catchment area.. so yes, increased stream order means increased catchment area. This is true for the Logan.

Fryirs, Kirstie A., et al. Geomorphic Analysis of River Systems : An Approach to Reading the Landscape, John Wiley & Sons, Incorporated, 2012. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/usu/detail.action?docID=1032536

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