A landscape is a memory surface. The contours of the surface offer an accumulated memory trace of the water that has fallen upon it. The rainfall forms little rivulets which combine into streams and then into rivers. Once the pattern of drainage has been formed then it tends to become ever more permanent since the rain is collected into the drainage channels and tends to make them deeper. It is the rainfall that is doing the sculpting and yet it is the response of the surface to the rainfall that is organizing how the rainfall will do its sculpting.
Just, wow!
