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High Water Impacts on Coastal Erosion

Published May 19, 2020
Erosion at Grand Mere Lakes on the southeastern shore of Lake Michigan.

Erosion at Grand Mere Lakes on the southeastern shore of Lake Michigan.

Glaciers covered most of the Great Lakes basin approximately 14,000 years ago. During the glacial retreat, the glaciers eroded rock and soil and carried it along with moving ice to the glacier edge where it was released from the melting ice and deposited as till, a mixture of sand, silt and clay.

When the glaciers receded, there were many minor re-advances of the ice edge. Each ice advance deposited till with a different compositions. Between these till layers are layers or lenses of sand and gravel that were deposited in water in front of the retreating glacier. Between glacial advances there were also layers of silt and clay deposited on the lake bottom.

These varied layers and lenses are now exposed in eroding bluffs and banks in many places along the shores. Water drains through the porous, sandy, gravelly layers to the shore, creating slope instability during normal conditions. Erosion at the toe of the bluff due to wave action causes a collapse of the upper soils, typically creating a near vertical slope in the clayey soils that may trigger further slope failures.

Record high lake levels in 2019 on Lake Michigan have increased the height of the wave impact and accelerated the erosion. Holland, Michigan reported a loss of 50 feet of beach since last summer. Many homeowners and communities have been caught off-guard with the dramatic increase in erosion along the coastline, with numerous homes lost to the collapsing bluff.

The water levels for Lake Michigan are projected to be at or above the levels seen in 2019 this spring and summer. Coastal erosion in 2020 could be similar or worse than what was seen last year.

The Detroit District has been actively engaging with local stakeholders and congressional delegates to determine how the U.S. Army Corps of Engineers could provide assistance.