No Sure Remedy: McLain shoreline erosion plays on
HANCOCK TOWNSHIP — Stopping natural erosion at McLain State Park and other sections of Great Lakes shoreline is a complex process, with possible solutions including sea walls, beach nourishment or simply moving structures, but they often have consequences.
“The beach will take a shape that is the most dissipative to the waves it’s experiencing,” said Great Lakes Research Center Director Guy Meadows. “… There is nothing more dissipative to wave energy than the natural beach. So then if you come in and plunk some artificial thing there, chunks of concrete, big boulders, whatever, they cause more reflection of the waves and more erosion in the long run.”
While that doesn’t mean a structure cannot be saved during high-water cycles using something like a breakwall, problems can easily be moved to a neighbor if the flow of the water is altered.
“When they (high water) come back — and they always will come back — again, the net erosion you will experience will be greater than if you had done nothing,” Meadows explained.
Building a structure to deflect waves away from the shoreline can also block sand from coming in, said James Selegean of the Detroit Army Corps of Engineers Great Lakes Hydraulics and Hydrology Office.
While more of an issue on sandy Great Lakes like Lake Michigan, he predicted armoring a shoreline like McLain would mean the beach disappears, leaving less natural cushion for waves.
Selegean describes the process like a bathtub and drain, with new sand coming in while old sand drains away. If the source of sand or faucet is shut off via a breakwall, it’s going to quickly disappear.
With such setbacks, both Meadows and Selegean lean toward pulling back structures from the water as the first choice for dealing with erosion.
Moving structures has been McLain’s go-to solution, with new campsites and structures moved toward the center of the park.
McLain officials did not respond to requests for comment regarding any additional plans.
The same is true of homes when possible, Selegean said. Moving a structure is often cheaper than armoring the shore and buys owners time.
Some people use stone where the waves hit, or steel sheet sea walls, which come with the additional long-term erosion and beach loss risk.
“The shape of the bottom is like a lens, and they focus wave energy in certain places and not in other places and (depend) on the direction of the waves facing the shoreline, so it’s a really complicated process to do correctly,” Meadows said.
Even piers and jetties disrupt the natural flow of sand, causing it to pile up on one end and bounce off into deep water.
One effective method of shoreline protection known as beach nourishment is a common practice along the ocean, and to a lesser degree, the Great Lakes.
With beach nourishment, new sand is added from somewhere else, often the East Coast. While the process is effective, it is costly, with a cubic yard of sand costing around $30 and a few hundred thousand cubic yards needed.
“You have to change the profile all the way out to the depth where waves are no longer interacting with the bottom, which is 30 feet, and to get 30 feet offshore, you need to be out about 3,000 feet or so or further. It’s a lot of territory to build back up,” Meadows said.
In Michigan, the Department of Natural Resources prohibits taking sand from the deep portions of the lake and putting it on shore, due to concerns about altering wave movement.
“If you dig a big hole out somewhere, then you change the wave patterns, and you might cause somebody that wasn’t experiencing erosion to experience erosion,” he said.