NetLogo User Community Models
by James Steiner (Submitted: 03/05/2004 )
WHAT IS IT?
A terrain generator demo and watershed simulator, with a nifty 3-d terrain visualizer thrown in as a bonus.
HOW IT WORKS
The patch "elev" is the hard surface of the terrain. Level is the measure of the current surface level. If the patch is dry, level is the same as elev. If the patch is wet, then level is greater than elev by the depth of the water.
To simulate the flow of water, each "wet" patch compares it's own "level" with the level of it's neighbors. If any neighbor has a lower level, the patch finds one of the neighbors with the very lowest level, figures the difference between the two levels, and shares half of that difference with the low neighbor. In other words, water pours from the patch to it's lowest neighbor to make both patches level. All the water on the high patch could pour into the low patch, if needed.
HOW TO USE IT
To get started, click one of the terrain generator buttons. The model comes with river valley and volcano (atoll) generators.
To add water to the river, click the river? switch on.
Click on Drain? to contantly remove water from the bottom row.
To make the volcano "erupt" click the erupt? switch on.
To add water to the entire surface of the terrain (to turn the volcano into an atoll, for example) click the rain, rain-hard, or quick-fill buttons. Rain-hard is 100 X the normal rain-rate. Rain and rain-hard add to the already present water, if any. Quick-fill sets the water depth to be even with the mean elevation of the entire terrain.
To create a flash-flood, click the flood button. The top row gets flooded.
The dry-all button removes all the water from the terrain.
MAKE IT FLOW:
Click the Flow button. The water on the terrain will seek it's own level. Rivers flow, lakes form, dams fill, lava flows, islands emerge from the sea!
After that, if you make changes in the terrain, or to see the effects of water flow, click the "render-3d" button to update the display.
To clear the 3-d display, click the clear-3d button.
The animate button continuously refreshes the 3-d display, useful when adjusting the tilt and spin sliders.
The auto-spin switch causes the animate button to continuously changes the spin slider, as well.
The false-color? switch causes the model to use a different coloring scheme, that exposes the elevations differently.
The altitude? switch alters the way the water is colored.
THINGS TO NOTICE
Notice how water flows downhill! I'm a fricken genius!
THINGS TO TRY
What conditions will cause the river to overflow it's banks? How do you think this compares to real-world flood conditions?
EXTENDING THE MODEL
Add additional terrain generators: cistern, septic field, mountain.
Generate a terrain that has one straight river and one curvy river. Is the flow rate different?
Then put boats or flotsom in the water, moving with the currents!
Z-order clipping: Hide nodes that should be behind other nodes.
CREDITS AND REFERENCES
Thanks to Boyce J Baker, who by seeking assistance on a model of his own, got me thinking about the fun of modeling a watershed.
COPYRIGHT & LICENSE
(back to the NetLogo User Community Models)