Lake Michigan Current-Related Incidents

77 Fatalities, 230 Rescues: 2002-2012

     Lake Michigan has the highest number of current related fatalities and rescues of all the Great Lakes, with 77 fatalities and at least 230 rescues (GLCID, 2002-2012). These numbers are relative to the number of people that visit the beaches of Lake Michigan each year, which is on the order of millions.

 

Lake Michigan has the majority of current-related incidents on the Great Lakes (GLCID, 2002-2012).

 

The eastern side of Lake Michigan sees a majority of the incidents. What factors allow for such a high incidence of dangerous currents on Lake Michigan? Why are these incidents primarily occurring on the Michigan side of the lake? The image below (left) shows a map of current-related incidents occurring on Lake Michigan, with darkest red color indicating 15+ incidents. On the right, is a map of the most popular tourist destinations along the shoreline from the Pure Michigan website. In addition to favorable rip current locations and conditions, western lower Michigan sees a large number of tourists each summer, which accounts for the higher number of incidents.

 

Red colors (left map) indicate the number of rip current related incidents from 2002-2012 in the GLCID. Right map shows most popular tourist beachtown destinations from puremichigan.org

 

Locations of Rip Current Incidents on Lake Michigan

Rip currents on the Great Lakes and the ocean occur near shoreline structures, complex sandbar terrain (such as longshore sandbars), and river mouths. On Lake Michigan, most of the beaches have some combination of complex sandbars or shoreline structures such as breakwalls (see the image below of beaches along the Lake Michigan shoreline). Complex sandbar terrain and breakwalls help water to 'pile up' on shore, leading to rip current development.

 

Areas with Rip Current Incidents. Top: right to left: Grand Haven State Park, South Haven Harbor, Holland State Park,

Bottom: Muskegon State Park/Pere Marquette Park, Silver Lake State Park, and Charles Mears State Park.

Note the presence of sandbars and breakwall-like structures. Images from Googlemaps.com, 2011.

 

Looking at all of the 307 current-related incidents on Lake Michigan from 2002-2012, 64% of the cases occurred on a beach with a shoreline structure. In fact, some of these structural rip current incidents have occurred under lower wave heights, and that is why it is important not to swim along piers or breakwalls-even during seemingly benign conditions!

This pie chart illustrates that the majority of incidents occurred near a shoreline structure. Sandbar/Structure indicates the incident occurred at a beach with both features, however it was not known where the victim was swimming. This is similar to River Mouth/Sandbar(SB)...which indicates both features were present on the beach where the incident occurred but it was not know exactly where the person was swimming. GLCID, 2012.

 

Conditions Supportive of Rip Current Development on Lake Michigan [based off current-related incidents]

 Like any beach on the ocean, strong onshore winds and high waves are the conditions most observed during rip current related incidents on Lake Michigan. On the eastern shores of Lake Michigan, this occurs frequently during the summer and early fall as cold fronts pass through the area. Looking at data from the GLCID, the most common wave height rante observed during rip current (and channel current) incidents was "2 to 4 ft." This is likely due to the fact that at these heights rip currents become stronger, and people feel comfortable going into the water (versus 10 to 12 feet where rip currents are occurring, but less swimmers are present).There are also a large number of incidents in the "1 to 3 ft" range, and even some in the "0 to 2 ft" range. This is because a majority of Lake Michigan rip current incidents are structural, and this type of rip current does not require as active of a wave pattern to develop. Additionally, channel currents were included in this count, and typically developed during lower wave height incidents.


Wave heights during rip current  and channel current incidents on Lake Michigan 2002-2012 (GLCID).

 

What sort of weather pattern is conducive to rip current formation on Lake Michigan?

     Looking back at the drowning deaths and rescues in the database, we can see there are typical set ups. The most common set up over Lake Michigan is the passage of a cold front across the area, bringing strong onshore winds to the eastern shoreline of the lake. Any situations in the weather that cause moderate to strong southerly to northerly oriented flows on Lake Michigan can cause problems, especially near the breakwalls (a common feature at beaches). Westerly flow can also be a concern because it is directly onshore (supportive of sandbar type rip currents). Below are some weather maps from the days of rip current incidents on Lake Michigan:

 

July 25, 2010 around 2:00 PM EDT. High pressure is seen over Lake Michigan...bringing strong onshore

northwesterly flow. This was actually five hours prior to the drowning. When the drowning occurred,

the high was more directly overhead. Waves were only one to three feet at the time of the drowning, but

hours prior to that they were between two and four feet. There was one drowning associated with a sandbar

rip current. Image obtained from the HPC surface analysis archive.

 

August 1, 2009 at 5:00 PM EDT. Here is a more common example of the weather pattern over Lake

Michigan when rip currents develop. A cold front is seen passing across the Lake. Typical winds

ahead of the cold front are southwesterly, which is onshore. These winds are also optimal for

strong longshore current development, which intersects the piers (stretching east to west) and causes

structural rip currents. The incidents on this day took place around 6:00 PM EDT. There was one

drowning and five rescues near a pier. Image obtained from HPC surface analysis archive.

 


August 11, 2009 at 2 PM EDT.  Here is the perfect example of why not to swim near a structure. Winds were

observed to be north to northwest at about 15 mph gusting to 22 mph at South Haven, MI

(which was the closest observation site to Holland, MI at the time). This was due to the passage of

the cold front seen in the actual data...where winds and waves were generally between two and four

feet. On this day, 23 people had to be rescued between noon and 5:00 pm near the pier (on the north side)

at the park. This was the incident that caused the unusually high number of rescues for 2009...and all were associated

with the pier. Red Flags were flying at the park warning the swimmers of the dangers of rip current development and crashing waves. 

Keep in mind, this is a good example of where high waves also played a part in these incidents.

Image obtained from HPC surface analysis archive.

 

     One last situation that is most common to Lake Erie, but does occur on Lake Michigan is the Seiche. The simplest definition of a seiche is water sloshing back and forth in a basin. When strong winds or pressure differences move across the lake, they cause a buildup of water on one end of the lake (surge). As the influencing system leaves (such as thunderstorms, strong cold fronts, etc), the water will slosh back to the other side, and continue sloshing until it reaches equilibrium. The uneven distribution of water on the shore can cause rip current problems.

Diagram of how a seiche works. Image was obtained from...

July 4, 2003: Rip Current-Seiche event

     On July 4, 2003, rip currents developed along the Lake Michigan waterfront in Berrien county, MI from a seiche caused by a strong thunderstorm that passed earlier that morning. One can actually observe this seiche occurring by looking at the water level data from the National Ocean Service Observation Stations.

 

July 4, 2003. This radar image from the Grand Rapids National Weather Service was observed around 8:00 AM EDT.

You can see the line of thunderstorms moving across the lake. With its strong winds and pressure changes, this storm

caused the seiche that lasted throughout the day.

 


 

NOS observation stations. Those boxed in red at Milwaukee, Wi and Holland, MI were used to closely

examine the water level data. Image is from the National Buoy Database Center.

 

Observed water level data.

A seiche is observed in the water level data. Milwaukee, WI was down at 577.00 ft. Holland

was up at 577.68 ft. This is not a dramatic difference, but it was enough to cause problems. Images are from the NOS

weather stations.

 

     As a result of this storm induced seiche that lasted most of the day (as seen in the graphs), moving rip currents developed along the beaches of Berrien County in Southwest Michigan. Seven people drowned along a three mile section of beach in three hours when they were trapped in rip currents. This accounts for seven of the incidents in the database where wave heights were 2 feet or less at the time. The fine sand was manipulated into a complex bar-rip current system during the storm. When water levels receded (in the seiche), rip currents increased to dangerous speeds and captured unsuspecting swimmers.

 

A Rip current that developed in Berrien County, MI. Picture courtesy of The University of South Florida. Note the current by the muddy color in the water.

 

 

Summary

     The majority of rip current incidents occur along the eastern and southern shoreline of Lake Michigan. Numerous factors play a part, but the primary explanation is that the prevailing wind direction is westerly, or onshore, across the eastern shore of Lake Michigan, making it more prone to rip current development. Secondly, there are a higher number of recreational locations on the Michigan side of the Lake, therefore more people are at risk. Rip currents do develop on the western side of Lake Michigan, however they are less frequent. The main type of rip current on Lake Michigan is the structural rip current, where the longshore current interacts with a pier or breakwall extending out into the lake. The typical weather pattern for the development of these rip currents is any that involves onshore flow or flow parallel to the shore, which enhances the longshore current. This typically manifests itself as an approaching or exiting cold front, where onshore winds are either southwesterly (ahead of the front) or Northwesterly (behind the front). Lastly, seiches can cause uneven distributions of water in the nearshore environment, leading to rip current development. To read more about rip currents on the Great Lakes, go to our table of contents.

 REMEMBER: INCIDENTS IN THE DATABASE ARE CURRENT-RELATED: MEANING INCIDENTS COULD HAVE BEEN A RESULT OF A COMBINATION OF HIGH WAVES AND CURRENTS. ADDITIONALLY, THESE NUMBERS SHOULD BE COMPARED WITH THE HIGH NUMBER OF VISITORS TO THE PARKS AND LOCAL BEACHES PER YEAR-WHICH IS ON THE ORDER OF MILLIONS.

References

 

 

 

 

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