Model Sensitivity Exercise

To run this exercise, you must be able to run ARC/INFO with the GRID module. It is best (but not essential) to have a white background. This can be enabled by setting the CANVASCOLOR variable to white. Under the unix cshell, the command is "setenv CANVASCOLOR white". Under NT, click settings/control_panel/system/environment.

Download It unzips into a directory named "mod", containing a partially digested DEM, a menu, and amls.

Under unix, cd to the mod directory and start arc. Under NT, launch arc (which is called "arc worksatation" under version 8). At the "Arc:" prompt, change to the mod workspace, .e.g. "w d:\classes\riv2000\mod".

At the "Arc:" prompt, type "&run model". You will see a large canvas and a menu. The menu shows the default values for soil transmissivity, bulk density, soil depth in meters, friction angle phi, and cohesion in kilopascals.

Click the "RUN MODEL" button. It will take a few seconds before the message "Model 1 is complete" appears in the bottom of your text window. You still don't see the result.

Enter "1" in the little "Run:" box on the menu, and click "plot left".

Now try changing one of the parameters, either by typing new values or using the sliders. Note that a soil depth of -1 is allowed. This is not negative soil, but is a special flag denoting measured soil depth. The areal coverage for soil depth is a bit less than the entire catchment as shown.

To show your second model run, enter "2" in the little box, and click on "plot right".

You can continue to make more model runs, and to display any pair of models side by side.

If you start to lose track of your runs, click the "show runs" button, and the model parameter values will appear in the text window. If you hit the zoom button, you can click twice in the image to enter a zoom box. You will not see an immediate result, but the zoom box will be in effect for all subsequent plots on either side, until you click on the "full window" button. You can plot contours over any plot by clicking the "plot contours" button. If you click the "plot to file" button, you will be prompted in the text window for the root name of an ARC/INFO metagraphics file, which will receive the results of the next plot button. You can also enter any ARC/INFO command you can think of in the little window on the menu.

When you are through, click "Clean and Quit". This should delete all the file you have created. At he "Arc:" prompt, type "q".

If you are in the Drainage Basins Dynamics class, answer these questions.

Direct questions to Harvey Greenberg and Dave Montgomery

Main Mountain Drainage Research Group Page