KnowraRapidsRapidsRapids are shallow, fast-flowing sections of a river where water moves turbulently over rocks or other obstructions.BriefConnectFroude number: A dimensionless ratio comparing flow speed with the speed of surface waves in a fluid. It distinguishes subcritical flow from the rapid, wave-dominated conditions common in rapids.River: A natural flowing body of water that moves through a channel toward a larger body of water. Rapids are energetic sections within rivers, not separate watercourses.Whitewater rafting: A recreational activity in which people navigate turbulent rivers aboard inflatable rafts. Rafting uses rapids as routes and obstacles, with difficulty shaped by their flow.Lava Falls: A difficult rapid in the Grand Canyon section of the Colorado River in Arizona. Its powerful waves and hazards make it a well-known example of a major rapid.Fluvial geomorphology: The study of how rivers shape landforms and transport sediment. Rapids are active sites of erosion and sediment transport within river systems.Hydraulic jump: An abrupt rise in water depth where fast, shallow flow changes to slower, deeper flow. Rapids can contain hydraulic jumps where turbulent water dissipates flow energy.River channel: The landform that confines a river’s flowing water. Channel width, depth, and shape influence where rapids form.Whitewater kayaking: Paddling a kayak through turbulent river water, often including rapids. Kayakers read rapid features to choose a line and manage hazards.Crystal Rapid: A rapid in the Grand Canyon section of the Colorado River in Arizona. Its shifting hazards illustrate how river conditions can change a rapid’s character.River erosion: The wearing away of riverbanks and beds by flowing water and transported material. Fast, turbulent flow can intensify erosion around rapid-forming obstacles.Show all 26Linked from 3 pagesKhone Phapheng FallsRelated: Rapids and cascades combine across the river’s rocky bed at Khone Phapheng.Xiling GorgeNarrower topic: Rapids historically made some stretches of Xiling difficult for boats to traverse.Show all 3