Rip Current Characteristics and Velocities
Although rip currents are not caused by tides, the water level (tide elevation) at the coast may have an impact on rip current speed and strength. Generally, rip current velocities increase as water levels (tide elevation) decrease.
Rip current velocities also typically increase as wave heights increase. An increase in the height of incoming waves can result in sudden increases in water depth and rip current velocities. These sudden changes or pulses in water depth and current speed can catch bathers off-guard. Rip current pulsations are extremely dangerous to all swimmers!
While average rip current velocities of 1 to 2 feet per second do not pose serious hazards to strong swimmers, rip currents may rapidly reach or exceed velocities of 3 feet per second. Also, rapid fluctuations or pulses in wave groups can quickly generate rip currents with extreme velocities that have been measured up to 8 feet per second - this is faster than an Olympic swimmer can sprint! If a swimmer is caught in a rip current, attempting to swim directly back to shore against the seaward flowing current can result in exhaustion and possible drowning.
Rip currents are usually narrow (~ 20 to100 feet in the alongshore direction), may extend hundreds of feet offshore, and generally span the entire water column. However, offshore, or outside the surf zone, they tend to be confined near the surface.
Rip currents do not pull people under water - they pull people away from shore. Drowning deaths usually occur when people are unable to keep themselves afloat and swim back to shore. This may be due to fear, panic, exhaustion, a lack of swimming skills, or any combination of these factors.
Rip Current Duration
Some shorelines are characterized by permanent rip currents which may be found in a fixed location such as a break in a reef or other hard structure. Some rip currents are persistent, lasting for many days or months in one location. Rip currents may also migrate along a stretch of coastline. Rip currents may also be ephemeral, forming quickly and lingering for a few hours or days before dissipating and disappearing.
Source: NOAA
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