The set-up of a rip current creates an unstable condition. When the instability is relieved, it provides circulation cells within the surf zone. Waves break in a water depth of 1.3 x height. This is lessened in an underwater channel. Also, rip currents diminish the power of incoming waves.
Rip currents are a shore-normal current.
This means that they are perpendicular to the longshore current. At certain beaches, rip currents can almost meet up with the longshore current. Erosion also occurs at areas where a seawall has been built to protect structures from storm surge and storm waves. Studies done in Narrabeen Beach, Australia Rips are characteristic of intermediate beach types. Four mechanisms of rip development have been proposed.