WaterfallsA waterfall is an area where water flows over a vertical drop or a series of steep drops in the course of a stream or river . Waterfalls also occur where meltwater drops over the edge of a tabular iceberg or ice shelf .This list of notable waterfalls of the world is sorted by continent, then country, then province, state or territory. A waterfall is included if it has an existing article specifically for it on Wikipedia, and it is at least 15 m (50 ft) high, or the falls have some historical significance based on multiple reliable references. Wiki info
When the river courses over resistant bedrock, erosion happens slowly and is dominated by impacts of water-borne sediment on the rock, while downstream the erosion occurs more rapidly. As the watercourse increases its velocity at the edge of the waterfall, it may pluck material from the riverbed, if the bed is fractured or otherwise more erodible. Hydraulic jets and hydraulic jumps at the toe of a falls can generate large forces to erode the bed, especially when forces are amplified by water-borne sediment. Horseshoe-shaped falls focus the erosion to a central point, also enhancing riverbed change below a waterfalls. A process known as "potholing" involves local erosion of a potentially deep hole in bedrock due to turbulent whirlpools spinning stones around on the bed, drilling it out. Sand and stones carried by the watercourse therefore increase erosion capacity. This causes the waterfall to carve deeper into the bed and to recede upstream. Often over time, the waterfall will recede back to form a canyon or gorge downstream as it recedes upstream, and it will carve deeper into the ridge above it. The rate of retreat for a waterfall can be as high as one-and-a-half metres per year.