The dendritic (tree-like) pattern shown in this image of the The Snow-capped Rockies gives clues about the underlying geology and topography of the region. The linear features are stream channels, where precipitation has struck the ground and flowed downhill. If a small amount of precipitation strikes a level, somewhat porous surface, it tends to be absorbed into the ground and flows underneath the surface.
Although larger amount of precipitation strikes the same type of area, it will tend to create pools on the surface. As well as it losses to the atmosphere via evaporation. If the ground isn’t very porous or the ground is already sloped, precipitation will flow over the surface as runoff. Therefore carving stream channels out of the rock. The tree-like pattern is caused by the surface is fairly homogenous. Also the rock is weathering at the same rate throughout. If the ground consisted of several rock types, weathering would be uneven, forming a trellis pattern.