Rapids

The strongest visible features that serve to distinguish rapids from other waterbodies, without surrounding landscape context, are turbulence of water and the white foam created by this turbulence, the water appearing to be moving quite quickly, and other areas close to these ‘rapids’ that appear more still. This white foam visible in what we would consider labeling as ‘rapids’ is known as whitewater, which is caused by “differential erosion” of the streambed. The “streambed wears away,” and “stronger rocks remain to break up the flow of the stream” [1]. Another feature common in rapids are large, strong rocks that are present in the river or stream, emerging from the waterbody’s surface. These emerging rocks cause the flow to change directions and crossing flow directions and areas of swirling water help us recognize rapids. Furthermore, these eroding rocks and their smooth surfaces are quite recognizable, too.

In situations where rapids are present, the nearby or connected waterbody sections are often labeled ‘river’ or ‘fjord’ depending on the general setting and scale of the extended waterbody. These labels are chosen where the streambed has been worn away in an even manner, or in other words, where the rocks on the streambed are of similar strength. Rapids are also visually identifiable with different features depending on their strength and size, such as “whirlpools, fast currents, obstacles, and waves of different strength” which are directly related to how rapids are classified [1]. It was mentioned above, as well, that the water in rapids appears to be moving quite quickly, which sets rapids apart from other waterbodies, as rapids occur where “the bed of the river has a relatively steep gradient,” which directly contributes to the river’s turbulence and velocity [2].

References

[1] National Geographic Society. (2011, January 21). Rapids. Retrieved (2021, July 21), from https://www.nationalgeographic.org/encyclopedia/rapids/

[2] Internet Geography. (2020). Landforms in the Upper Course of a River. Retrieved (2021, July 21), from https://www.internetgeography.net/topics/landforms-in-the-upper-course-of-a-river/