Landscape evolution involves many complex processes related to the fluid motion, granular materials, vegetation and so on. Furthermore, its dynamics covers a wide range of length and time scales. Therefore, almost all models tend to rely on empirical formulas. We now propose a more principled model using shallow water equations combined with mass conservation of sediment. In our simulations, we show that a sheet flow forms the stripe pattern called a gully, not the channel network, and that a channel without banks builds the banks on both sides.
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