Ryan Dzurko
Ex3
Dual Effects of Soil Creep and Hydraulic Erosion on Geomorphologic Evolution.
1. Simulate an evolution of geomorphology after an initial uplift.
Q1: What is the driving force for the geomorphologic evolution? How do the driving forces affect the geomorphologic evolution?
The driving forces are soil creep and hydraulic erosion. Hydraulic erosion creates concave slopes. Soil creep creates convex slopes. When the two transport processes work together, the soil creep will fill in the concavities creating a decrease in slope. 3/3
Compare geomorphologic evolution with different magnitudes of transport processes.
Kg=0.4 Kh=1.0 Kg=0.1 Kh=1.0
Spatial Profile at t=0.5 Temporal Profile at X= 0.5
Upper- Kg=0.1 Kh = 1.0 / Lower- Kg=0.4 Kh=1.0 Upper- Kg = 0.1 Kh = 1.0 / Lower- Kg= 0.4 Kh=1.0
Q2: Repeat this exercise for different combos of Kg and Kh. Why don't you plot profiles of elevation like what you did in Q3? By comparing the profiles in a graph, you can clearly see the effect of each coefficient.
Kg =0.3 Kh= 0.3 1/ Kg=0.3 Kh=3.0 2
/ Kg= 0.3 Kh=30 0 3
Kg=3.0 Kh=0.3 4
/ Kg=3.0 Kh=3.0 5
/ Kg=3.0 Kh=30 6
Kg=30 Kh=0.3 7
/ Kg=30 Kh=3.0 8
/ Kg=30 Kh=30 9
Describe the effect of the two coefficients on the geomorphologic evolution of the slope forms.
(Not sure how to word this, so I will describe what I see and what I know…)
After initial uplift, erosion rates appear to be gradual when low Kg (soil creep) and Kh (hydraulic transport) coefficients are present. As the Kh increases, (Kg remains low), the slope increases and concavities are great. (graphs 1-3)
As the Kg increases, concavities are still present but they are being “filled” in at a higher rate, so they are not as defined. (graphs 4-6) Erosion rates are still rapid and slopes are still steep.
A high Kg coefficient shows a decrease in slopes but very rapid erosion. As the Kh coefficient increases, slight concavities are formed, but the high Kg coefficient fills them in quickly.
~~I feel like something is wrong with these last few graphs as I thought that if the Kg was high and the Kh was low (or lower than Kg) slopes would not be nearly as high and I would see a less erosion. Look at the maximum height. When either Kg or Kh is very high, the elevation profile is very low, with which we can barely say about the shapes of hillslopes. The rates of graphs 7-9 seems very rapid, even though the slopes are not as high as in previous combinations. 2.5/3
Better graphs are:
What happens if we have persistent tectonic uplift?
At some point, the soil creep coefficient and the hydraulic transport coefficient will balance out, creating steady state forms or “time-independent” forms. This means that while both transport processes might still be active, neither one will be affecting the shape. The uplift is pushing material into the form, while the erosion processes carry some materials away.
Kg=0.3 Kh=1.0 Kg=0.3 Kh=10
Rapid uplift, with quiescence Persistent Uplift
Q3: Plot two temporal profiles at x = 0.5 2/2
Temporal profile x=0.5
Upper- Kg=0.3 Kh=10 Lower-Kg= 0.3 Kh=1.0
Q4: Repeat this ex. With diff. combos of the process coefficients.
Kg=3.0 Kh=10, Persistent Uplift Kg=30 Kh=.3, Persistent Uplift
Kg=3.0 Kh=1.0 Persistent Uplift Kg=30 Kh=.003 Persistent Uplift
With persistent uplift, steady state is achieved relatively fast. Nope. The impulse source does not make the height reach any steady state. Zero height is not a steady state we are interested in. The forms appear to be very similar although the heights vary. As material is being added to the form through uplift, material is being transported by hydraulic processes and soil creep. Because of the rates of these processes, they “balance” out.
Inputs = Outputs so change in storage is 0.
(the question asks to find a difference in the above forms. Aside from the heights, and slight difference –very small- in the time needed to achieve steady state, I don’t see a difference. What am I missing?)
How about these? With this kind of graphs, you can more clearly see the effects of soil creep and hydraulic erosion on hillslope shapes. 2/3
Total:
9.5/11= / 8.6