MICHIGAN CITY — The bad news? Lake Michigan's water is exceeding record high levels set more than 30 years ago, consuming a large chunk of many Northwest Indiana beaches in the process.
The good news? The high waters and smaller shores aren't here to stay, if past geological data is any indication.
Indiana University Northwest's Erin Argyilan shared more about the Great Lakes' rising water levels at Thursday's Northwest Indiana Green Drinks event. The geology professor's talk, "Lake Michigan: High Levels and Beach Erosion," drew nearly 100 area residents to Shoreline Brewery, a record for the monthly lecture series.
Argyilan – who gave a presentation on Mount Baldy at a previous gathering – has studied the evolution of the Great Lakes for more than 20 years, and opened her presentation with data from the federal Great Lakes Environmental Research Laboratory on Lake Michigan's water levels. Data ranged from 1918 – the first year the U.S. Army Corp of Engineers began recording – through today.
The figures show levels comparable to those seen in 1986 and 1987, the last time the water was so high, she said. While this year's annual mean has remained below those from 30 years ago, some daily values this past summer set new record highs, Argyilan said.
The climb is especially dramatic given that the lake experienced record low water levels just six years ago, she said. The geologist attributes the surge to a 10-15% rise in Midwest precipitation over the past decade, caused by an increase in storms tracking from the Gulf of Mexico.
Historical data suggests the elevated water levels aren't permanent, though, Argyilan said.
Midwest geologists have poured years into studying the age and elevation of beach ridges around Lake Michigan, she said. Thanks to this work, scientists have plotted the rise and fall of water levels as far back as 4,500 years.
Looking at the data, Great Lakes experts believe water levels reach a crescendo every 30 years or so. The recent rise appears to be a continuation of this pattern, she said.
"We are happy to see the high lake levels right now," Argyilan said.
Fluctuating water levels aren't the only explanation for the shifting landscape of area beaches, however.
The Northwest Indiana coastline is home to many drift cells, localized erosion zones in which sand and gravel move from one part of the shore to another. Human development along the coastline causes these cells to develop, as structures like harbors and breakwalls interfere with the natural movement of sand, Argyilan said.
Each drift cell consists of an erosional zone, the original location of the sand and gravel; a transport pathway, which carries the sediment elsewhere along the shoreline; and a depositional zone, where the material finally ends up.
"Each of one of these sections is just simply trying to get straight," she said. "Once you put that harbor structure out, it creates a little eddy and it erodes behind it. It's going to create erosion. It's going to move sand somewhere else until it is even and happy."
One of these cells exists in the Michigan City area, Argyilan said. The Long Beach community is where the erosional zone is located, with the sand moving down and ending up in the Washington Park beach area.
This drift cell, when combined with Lake Michigan's rising waters, has exacerbated the decline of the shoreline of Long Beach properties, she said. Meanwhile, homeowners living on the other end of the system are experiencing a growth in beachfront property – and encroachment from nearby dunes, in some cases.
At least one beach in the Long Beach area has been closed to the public for the last two summers because of high water levels.
Knowledge on how these drift cells operate is changing how scientists approach beach stabilization, Argyilan said.
In the past, engineers would employ "hard stabilization" measures, such as concrete seawalls, to deal with fluctuating water levels. These structures fail to prevent erosion, however, creating new drift cells where sediment moves from one part of the shore to another.
"There's a really well-respected scientist named Orrin Pilkey who says 'Just rip 'em all off. Rip everything out,'" Argyilan said. "That will probably never happen, but you understand his point."
Instead, geologists are looking at "soft stabilization" measures, like laying down new sand – either on a temporary or permanent basis – to serve as a buffer when water levels spike.
"I would hope people look at these records and lake level behavior and think about it in those types of scales, and be a little more fluid in their thinking," she said.