Rapids is a general term for the stretches of a river on which the water flows rapidly and rapidly through an increased gradient, shoal or narrowing of the river bed. Artificial rapids are created by weirs or river slides . The word is usually used in the plural.
Rapids formed by blocks or rocks are known as cataracts . Very steep rapids are sometimes referred to as waterfalls , even if the typical characteristics of a waterfall are not given. Well-known examples are the Boyoma Falls and especially the Inga Falls in the Congo , the largest rapids in the world.
Numerous rapids, especially the large or heavily traveled rivers, were eliminated in the past as a danger to river navigation , but also in the course of river straightening , river widening and dam construction . For example, the then notorious St. John's rapids of the Vltava (which Bedřich Smetana musically portrayed in the symphonic poem Die Moldau in 1874 ) disappeared with the construction of the Štěchovice Dam (built 1937–1945) in the floods. The Rhine cataract at Binger Loch was also blown up and leveled out by means of tail units , and the Laufenburg rapids on the Rhine were dammed to use water power .
The word running for rapids became the name or part of the name of a number of places, such as B. Laufen (Salzach) , Lauffen am Neckar , Laufen-Uhwiesen with Laufen Castle on the Rhine Falls, Laufen in Laufental (Basel-Land) or Laufenburg on the Baden and Aargau side of the High Rhine .
The speed of a river can increase so much in certain areas that the hydraulic form of movement shooting occurs. The criterion is the exceeding of the fastest propagation speed of waves.