The palette
Green has a real part on this sheet: the slopes are wooded, the woods are in the data, and they make bands along all three rivers. Choose a green clearly apart from the water, so that each bank reads in two layers, the river and the slope above it. The three rivers share a single ink; take it deep enough for the bridges to cross it as clean lines. The winding streets of the hills need nothing more than the line weight of the streets themselves.