Rip Current Monitoring System

Rip Currents - A Killer on the Beach

Rip Currents are powerful, channeled currents of water flowing away from shore. They typically extend from the shoreline, through the surf zone, and past the line of breaking waves. Rip currents generally form when waves approach normal to the shoreline or at a slight angle. Rip currents can occur at any beach with breaking waves, including the Great Lakes.

The mechanics of rip currents are a result of complex interactions between waves, currents, water levels, nearshore bottom (bathymetry), as well as wave-wave interaction. As waves travel from deep to shallow water, they eventually break near the shoreline. As waves break, they generate currents that flow in both the offshore (away from the coast) and the alongshore directions. This offsore or seaward flow of water typically occurs through a break in the sandbar, where water is channelized into a narrow current known as a rip currents.

Basic Rip Current Mechanics Waves break on the sand bars before they break in the channel area. Wave breaking causes an increase in water level over the bars relative to the channel level. A pressure gradient is created due to the higher water level over the bars. This pressure gradient drives a current alongshore (the feeder current). The longshore currents converge and turn seaward, flowing through the low area or channel between the sand bars.

Rip Current Types

There are several ranges and variations in the formation of Rip Currents. The following illustrations are some of the types of rip currents:

Firgure 1 Rip currents developed by bar trough channel flow	Figure 2 A series of rip currents (~100m apart)
Figure 3 Formation of intermittent rip currents	Figure 4 Rip currents influenced by a near-structure

Click here to see more images of rip currents.

Rip Current Monitoring - Critical Factors in Determining the Risk

The MDL Rip Current Predictor uses the following critical factors to determine the risk of occurence:

-Waves (breaker height, peak, direction, period)
-Beach (slope, orientation, material)
-Water levels (tide)
-Other (local coastal configuration)

An index of surf zone hazards will help determine the modal beach state and surf zone wave level.

The Rip Current Hazard Index indicates the probability of rip current occurence. The rip current outlook is classified as high, moderate, or low.

Rip Education Resources: Survival Kits

-Rip Current Saftey Tips

-Rip Current Awareness