reset the drains to their initial stateĮnd to flow patch procedure find the neighboring patch where the water is lowest the DIFFUSE command is useful for smoothing out the terrain Show-water? whether the water is visibleĭrains agentset of all edge patches where the water drains offĮlevation elevation here (may be negative) The project gratefully acknowledges the support of the National Science Foundation (REPP & ROLE programs) - grant numbers REC #9814682 and REC-0126227. To inquire about commercial licenses, please contact Uri Wilensky at model was created as part of the projects: PARTICIPATORY SIMULATIONS: NETWORK-BASED DESIGN FOR SYSTEMS LEARNING IN CLASSROOMS and/or INTEGRATED SIMULATION AND MODELING ENVIRONMENT. To view a copy of this license, visit or send a letter to Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.Ĭommercial licenses are also available. This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License. Center for Connected Learning and Computer-Based Modeling, Northwestern Institute on Complex Systems, Northwestern University, Evanston, IL. If you mention this model in a publication, we ask that you include these citations for the model itself and for the NetLogo software: Thanks to Greg Dunham and Seth Tisue for their work on this model. Here is an eroded volcano in Kamchatka with a strong resemblance to this model: The code depends on agentsets always being randomly ordered. What would it take to get river deltas to form? You'd need to model sediment being carried by water and then deposited. Would a more elaborate rule produce different results?Īdd multiple soil types to the terrain, so that the land is of varying hardness, that is, varying speed of erosion. Currently, all of the water simply flows to the lowest neighbor. Does this alter the behavior of the system in interesting ways?Īdd "springs" - point sources from which new water flows.Īdd indicator turtles to show the direction and magnitude of flow on each patch.Įxperiment with the rules for water flow. See what happens when you start with a hill. (Is what happens realistic, or does it reveal limitations of the model?) See what happens when you start with a perfectly flat terrain. Use the HIDE-WATER button to make the water invisible, and observe the terrain.Įxperiment with the effect of the different sliders on the appearance of the resulting rivers. Gradually, these rivers grow until they have drained all the lakes. Then rivers start to form at the edge of the world. Initially, the world is covered by lakes. A value of 1.0 means that the soil will not erode at all. Higher values will cause the soil to be harder, and less likely to erode, while lower values will cause the soil to erode more quickly. The SOIL-HARDNESS slider controls how "hard" or resistant to erosion the soil is. For example, if RAINFALL is 0.1, then each patch has a 10% chance of being rained on at each time step. The RAINFALL slider controls how much rain falls. You can use the HIDE-WATER button to make the water vanish so you can see the terrain beneath. The GO button runs the erosion simulation. If you want to start out with a hill in the middle, turn on the HILL? switch. If you want a perfectly flat terrain, turn off the BUMPY? switch. Lower values give rougher terrain, with more variation in elevation. The smoothness of the terrain is controlled by the TERRAIN-SMOOTHNESS slider. The amount of erosion is proportional to the amount of flow. ![]() ![]() The amount of flow is proportional to the difference in level, so that the water level on the two patches is (if possible) equalized.Įrosion is represented by decreasing the elevation of the source patch a bit when flow occurs. Water flows to the adjacent patch where the water level is lowest, as long as that patch is lower than the source. The model uses the following naive model of flowing water. If it does receive rain, its water depth increases by one. Around the edge of the world is a "drain" into which water and sediment disappear.Įach patch has a certain chance per time step of receiving rain. Deeper water is represented by a darker blue. The lighter the patch, the higher the elevation. The patterns of water flow change as the terrain is reshaped by erosion. As it flows, it erodes the terrain below. Rain falls on the terrain and starts to flow downhill. The user is presented with an empty terrain. This model is a simulation of soil erosion by water. Do you have questions or comments about this model?
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