Earth
Rainfall and runoff
Make it rain over a catchment. Compare permeable soil with rapid surface runoff; then stop the rain and watch drainage.
The model and its limits
40×40 cells, 20 m spacing. Conservative downhill water routing with uniform infiltration; no momentum, erosion or groundwater. Water colour exaggerates shallow films. 1 s = 4 min.
Equations used in the module
Equations Vrain = Vsurface + Vinfiltrated + Vout
