Man-made waterfalls can be built in backyards using boulders to add sound and motion to the landscape. Waterfalls occur naturally when water cascades over rocks powered by gravity. There are different types of water features like ponds, running boulders, cascading boulders, and ledge waterfalls that can be incorporated into landscapes. Boulder mountain waterfalls are large structures that can include multiple waterfalls, slides, and caves plunging into pools.