If you are just getting started using WILSIM-GC, it may be helpful to run a couple of example simulations, to familiarize yourself with the model and its capabilities. Here are a few options you might try.
Use Default Parameter Values and Change Your Viewing Perspective
Follow the instructions on the Start Using WILSIM-GC page; leave all of the parameters at the default values and click on the "Start" button. Watch the Grand Canyon develop. In particular, pay attention to the migration of the knickpoint: the point on the Colorado River where it begins to cut down into the stratigraphy of the canyon.
These default values were chosen because they will result in the development of a canyon that has a morphology, or form, similar to the Grand Canyon.
Experiment with these options:
- You can use the slider bars at the bottom and right sides of the main screen to change your viewing perspective.
- To pause the simulation, click on "Pause;" to continue the simulation, click on "Continue." (The button toggles between Pause and Continue upon clicking).
- To start a different simulation, or to begin this one again, you don't have to wait until this one ends and begin again. Just click on the "Reset" button. The "Pause/Continue" button will change to "Start," and you can start a new simulation.
Generate a Long Profile
At the end of the simulation, a window will pop up asking you to save the data to plot a "long profile." A long profile shows elevation changes along the length of the Colorado River, within the Grand Canyon.
- If you wish to plot a long profile, choose a location to save the data file on your computer, enter the file name of your choice, and click on save. The data is comma-delimited and has two columns: the first column is the horizontal distance, and the second column is elevation. The data can be brought into Excel to plot the long profile.
- The variable that controls how often data is stored is the "Storage Interval." Note that the default value for this variable is 1, meaning that data will only be stored once during a simulation (at the end of the simulation). Thus, the only profile that is available when the Storage Interval = 1 is the profile for canyon geometry at the end of the simulation. To compare profiles at additional time intervals, change the value of the Storage Interval. For example, if you set the value of the Storage Interval to 6, it will save profile data every million years (at 6 equal intervals over the 6 million year simulation).
Another way to look at canyon morphology is by selecting a cross section through the canyon as it develops. A cross section is a vertical slice. WILSIM-GC can show you cross sections through the canyon in any location. Here's how:
- Click on the "Cross Section" tab.
- The animation window will change to a bird's eye view. Use your mouse to click and drag a line where you want the cross section cut. The line of cross section is shown as an arrow, as in the image below, left.
- Click on the "Parameters" tab. The animation window will revert to your most recent perspective view, as shown below, right, with the location of your cross section shown as a semi-transparent plane.
- Click on Start (or Reset and then Start if you have run a previous simulation).
- At the end of the simulation, a window will pop up asking you to save the data for your cross section. Just as with long profiles, choose a location to save the cross section data file on your computer, enter the file name of your choice, and click on save. The data is comma-delimited and has multiple columns: the first column is the horizontal distance along your line of cross section, and each of the additional columns stores elevation data for a specific time interval. The data can be brought into Excel to plot the cross sections. If your Storage Interval = 6, you'll have data for 6 cross-sections, one every million years, as shown in the image to the right.
Use a Higher Erodibility Value
Suppose you would like to know what the Grand Canyon would look like, and how it would have developed, if the rocks that form the canyon walls were easily eroded (in essence, "softer"). In that case, you could adjust the "erodibility" of the rocks in WILSIM-GC and see how that affects the canyon.
- Drag the slider bar for "Rock Erodibility" down. For example, you might choose a value of 0.2 kyr-1. That's a rate of 0.2 per thousand years. A rock erodibility factor of 0.1 kyr-1 generates erosion at a rate equal to 0.1 meter per thousand years, for a fluvial channel of slope equal to 1 (45°) and drainage area equal to 1 square kilometer. A rock erodibility factor of 0.2 kyr-1 generates erosion twice as fast as that.
- Click the "Start" button (or "Reset" and then "Start," if you have already run another simulation).
- Notice how the canyon morphology differs from the one that develops with the default values.