Rapids

Causes:
1.Geology resistant/less resistant rocks (ridges of hard rock create an uneven slope)

2. Remains of a waterfall

3. Remains of a knick-point

A rapid is a section of a river which has a relatively steep gradient leading to an increase in water flow and turbulence. It is a hydrological feature between a run (smooth part) and a cascade (a drop). It is characterized by the river becoming shallower and exposed rock.

Example:
The zambezi river where white water rafting is known as 'commercial suicide'. The main attraction is the 27km of gorge below the falls, a one day run.