'Seiche' phenomenon hits often, sometimes kills

The Muskegon Chronicle has an interesting article about a little know Great Lakes phenomena called a "Seiche". With effect similar to a tsunami, a seiche can cause high waves and dangerous rip tides. Although generally not well known, seiche's occur with some frequency:

Thousands of tourists crowded the scenic beach to enjoy a long holiday weekend, unaware of the approaching tidal wave that would sweep them into a deadly natural disaster. That was the scene one month ago, when a killer tsunami raced across the Indian Ocean and killed more than 225,000 people in South Asia.

It also was the scene on July 4, 1929, at Grand Haven State Park, when killer waves swept 10 people to their deaths on one of the deadliest holidays in West Michigan history. The culprit here was not a tsunami, but a seiche (pronounced "saysh"). Created by high winds or squall lines that exert intense downward pressure, seiches can make Lake Michigan slosh back and forth like water in a bathtub, sending powerful waves racing to the shorelines.

"A seiche is a smaller version of a tsunami, with a different cause. A seiche is caused by wind; tsunamis are caused by earthquakes," said David Schwab, a research oceanographer at the National Oceanic and Atmospheric Administration's Great Lakes office in Ann Arbor. Schwab said most Great Lakes seiches only produce subtle changes in lake levels. But given the right weather conditions, a seiche can unleash huge storm surges that endanger human life and coastal structures.

Bob Beaton, a longtime Grand Haven resident and surfer, said the scariest thing about seiches is that they can strike when the lake is calm. "Some of the deadliest seiche incidents have happened on calm days," said Beaton, who has spent years researching seiches and is a member of the Great Lakes Beach and Pier Safety Task Force.

Seiches also create fierce rip currents below the surface when the lake level rises and then recedes rapidly. "The waves don't scare me, it's the current that drowns people," Beaton said.

A seiche that struck Chicago without warning on a June morning in 1954 increased the lake's water level by 4 feet in just 30 minutes. The rising water was followed by a massive wave, 25 miles wide and as high as 20 feet in some areas, that swept dozens of people off piers. Eight people drowned. Schwab said the killer wave bounced off the Michigan coast before pounding Chicago, pushing water in some areas 100 feet inland of some beaches.

Two years later, a seiche triggered a 10-foot swell in Ludington that sent anglers and beachgoers scrambling for safety. The first swell knocked several anglers off the pier and pushed water 150 feet past the normal water line. The water then receded beyond the water line before a second, larger wave crashed ashore.

Beaton, who has surfed the Great Lakes since 1962, said he sees several seiches each year. His most recent encounter with a seiche came while surfing north of the Muskegon breakwater last October. Beaton said listening to weather forecasts is the only way to know if conditions are right for a seiche. He said it's impossible for a lay person to anticipate a seiche by observing the lake or approaching storms. "It's like trying to predict an earthquake," he said.

Who knew? For more information about seiche's see this explanation at Wikipedia.