by Alan Marble, September 24, 2019
At the September 2019 level Lake Michigan is very close to the all-time high recorded in 1986, when Wildewood responded by building retaining walls. Most cottages and homes were built on tiny lots platted generations ago: lots 50’ or 100’ wide, and 100’ in depth. Many of those owners face a serious threat to their homes today, with no room to move their cottages away from the bluffs. The concerns are of property loss, cottage loss, and a restriction (or for less physically able folks, the loss) of beachcombing, a solitary activity that pulls many of us to the shore. The same bluffs we find so attractive during “normal” water years now loom as an eroding threat to future generations walking the beach and roaming the dunes.
There are inevitable questions arising from any discussion of altering or reinforcing the shoreline of Lake Michigan. Perhaps foremost is the concern with what may happen to an “unprotected” property shoreline when retaining walls or seawalls are constructed on adjacent shoreline. As described in more detail below, nature will be the primary driver of what happens to the CSA dunes:
- If waters remain high or continue to rise, further erosion on CSA common grounds is inevitable, whether or not a wall protects adjacent properties.
- If the lake level recedes over time there may be a period of time during which the trading of winds, waves and sand may result in short-term erosion to CSA common ground. But this should be mitigated as wind-blown sand, the primary element of our dunes, accumulates and once again secures the shoreline. That was the case after Wildewood built retaining walls in 1987 and the water level started dropping soon thereafter.
Any CSA baby boomer who wandered the beach as a child, bent over in search of Petoskeys and chain corals, could stand at the foot of the old concrete stairs and look south, and see nothing but shoreline. Today, a view from the base of the mostly-collapsed stairs clearly reveals the Frankfort lighthouse, two miles distant. Millions of tons of sand, till and clay have eroded away, carrying forests, bluff-top fences and parts of some dwellings with them. It is a natural process, probably accelerated by man’s activities, that will continue long after we are gone.
Shoreline erosion along these fragile shorelines is inherent to the nature of the bluffs. Formed by glaciation thousands of years ago, our soaring dunes are comprised mostly of wind-born sand atop layers of glacial till (gravel) and clay. There is little resilience to this composition... erosion is an everyday thing, regardless of the lake level, from wind, rain and, occasionally in winter, ice (which can form a barrier against erosion, or be a powerful destructive force). When high water levels are added, the erosion is visible daily, and even hourly, during sustained high winds. The winds along the western Michigan shore vary constantly, both seasonally and on a day-to-day basis, with infamous Lake Michigan fall storms doing the most damage.
Lake Michigan erodes all unprotected shoreline equally. On a local view, the 1987 Wildewood retaining walls (and also a short stretch at the north end of the CSA grounds, constructed by CSA residents at/about the same time) served the primary purpose by retaining soil as it collapsed, trapping it and providing a base for sand dune recovery as the lake receded. Its other purpose, preventing further erosion from wind and wave action, has been apparent as the water crested this spring. The adjacent CSA common ground to the north of Wildewood has been adversely affected this spring, primarily from the relentless wind and wave action, not from any “scouring” effect.
The potential for increased erosion to adjacent CSA common ground may go up as the water level recedes, but only to a point. With alternating prevailing winds (NW to SW) the effect is muted, and windblown sand will aggregate to rebuild the dunes accordingly. There is proof of this alternating effect in that, prior to the sudden surge in the level of Lake Michigan in the early spring of 2019, the Wildewood shoreline and CSA grounds shoreline were even.
Should the CSA join the proposed Wildewood project? Currently there are no buildings on CSA common grounds threatened by erosion. History tells us the shoreline is as dynamic in rebuilding as it is fragile when under attack. The dunes and bluffs will rebuild, with astonishing speed, if the lake level goes down. If the lake level continues to rise, most human efforts to stop erosion of the fragile shoreline will be to naught.