Waterfalls always occur together with rocks. One never sees a waterfall going over an earth cliff. water can erode soil in a very short time, but takes millions of years to wear down rocks. Signs of it can nevertheless be seen in the surfaces of rocks, polished smooth by the continous flow of water.

Some waterfalls may also be found in limestone, which is a sedimentary rock. This is not common in Malaysia. The local climate and conditions have caused very rapid erosion leaving few limestone surfaces around to present sufficient drainage for a sustainable stream. Thus Malaysian limestone normally has waterfalls during or after rainstorms, occuring both outside and inside the limestone, the latter being found in caves.