path to path gradient

I try to make a bumpmap of a mountainside. My current idea is to trace the isohypse as paths and then fill them with a gradient from path to path.

I have not found a function that does exactly this, but I then tried it with the gradient mesh and only changing the colour of the nodes I already have. Unfortunately it then keeps messing the gradient up, if I make it with a freeform path, and creating each shape by modifying a rectangle is just horrible (especially trying to fit multiple adjecant contours.
Working with one big rectangle does also not feel like an option, because I cant create enclosed circles within a gradient mesh.

Does anyone has an idea, how to solve this?