This article first appeared in The Lake Huron Centre for Coastal Conservation November 2012 e-newsletter, released this week. The Goderich-based non-profit charity advocates wise stewardship of Lake Huron’s coastal ecosystems. To learn more about the Centre and sign up for its e-newsletter, please visit online.
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Erosion of Great Lakes bluffs and ravines are pretty straightforward.
If we’re standing at the shore we can see it happening. Sometimes it happens in spectacular fashion – landslides where big chunks of land erode away. Bluff erosion is usually the result of the combination of rain or snow running off the land, groundwater seeping through the bluff soils, and waves eroding the base of the slope. Wave erosion causes the bluff to become over steepened and unstable. Wave erosion is very evident during higher lake levels, when waves rolling in from storms cut away at the base of the bluff. It can make shoreline residents very nervous if their cottage happens to be too close to the action.
The above average levels during the 1970s, 1980s and 1990s were exciting times. The all-time record high levels in 1985-86 were downright vexing for many shore landowners.
So when lake levels dropped in 1999, you could hear a collective sigh of relief that there was a pause from wave related erosion. The lake has remained low since, and wave related erosion has become a non-issue to most shoreline residents. Even with the heavy wave action on Lake Huron during the recent Hurricane Sandy, the waves in most cases weren’t reaching the base of the bluffs. This was in spite of the fact that we were experiencing five- to seven-metre waves.
But before people become too sedate, it’s what we don’t see that matters.
While waves aren’t reaching the shore as much these days, there is wave related erosion still occurring. We don’t see it though because 
it’s happening under water. Erosion of the lakebed (also called lakebed downcutting) is common along cohesive (clay till) shoreline banks and bluffs in the Great Lakes. There are locations along Lake Huron, (some examples are Horizon View, Bluewater Beach, Poplar Beach, all in Huron County) where the rates at which visible erosion (what we see taking place along the shoreline – bluff erosion & landslides) are ultimately controlled by the rates of invisible underwater erosion of the lakebed. This lakebed erosion makes the nearshore area deeper. And where lakebed erosion occurs, it allows ever-larger waves to reach the base of the slope.
During periods of low lake levels, the shallow nearshore means the lakebed is subjected to higher wave energy (the waves touch bottom eroding lakebed soils). So, when high water levels return [don’t worry, they will one day], the water depth close to shore is greater, allowing more wave energy to reach the beach and creating more toe erosion on the beach and bluff.
Coastal erosion has a lot of different complexities. It’s often the ‘invisible’ nearshore erosion that gets overlooked, even though it’s a controlling factor in long-term erosion of the shore.
6 Comments on "What really matters is happening below the surface of the Great Lakes"
Heather Boa, just who wrote this drivel. The reason that the gullys are eroding and collapsing is from the uncontrolled surface and subsurface water from higher elevation i.e. land east of the top of the bluff. The Town of Goderich is 100% responsible for the uncontrolled surface and subsurface water that erodes the Bluewater Beach Gully, the largest and fastest eroding gully on the whole of the west coast of Ontario. Yes this can be fixed and fixed very quickly but there is no leadership available to do the job. So please do not tell those of us who recognize the problem that the erosion has anything to do with lake levels and wave action!
“Heather Boa, just who wrote this drivel.”
According to this article, it was written by The Lake Huron Centre for Coastal Conservation. You must have missed it K. John Hazlitt.
Actually, the Coastal Centre is right, but so are you because both subaerial and subaqueous process are involved in bluff erosion.
THank you, Ann, for the response. Of interest, the engineering to control this erosion at Bluewater Beach Gulley has been done under petition signed by Town of Goderich under the Municipal Drainage Act in 2003. The consulting firms report is by Gamsby and Mannerow of Guelph Ontario. A copy can be obtained at the office of the Town of Goderich Town Hall. This report is still current and all we really need is some leadership from the Mayor of Goderich (also Chair of MVCA) and any councillor and we can fix this Bluwewater Beach Gully erosion problem immediately and of course the money is in place to do this. What, of course, is lacking is leadership and possibly, Ann, you can make a suggestion as to who has the interest to lead this project that will create jobs and put Goderich on the North American map as a leader in the protection of the quality of Great Lakes Water.
I don’t believe erosion issues along the Lake Huron’s coastal bluffs are unique to Goderich. I would be naive to think that what’s happened has happened due to a lack of political leadership over decades. Decades, because that’s how long this has taken to occur.
The solution may start with a lobbying effort on the part of Goderich but it needs to be sustained through much more than that. Up to and including buy-in by both provincial and federal governments because at the end of the day it’s going to take more cash than either Goderich or the county has.
Yes, Ann, the cash to do the job is ready and waiting for a leader to make it happen. Just read and understand the Municipal Drainage Act. Then you will totally understand. The “cash to do the job” does not come from the Town of Goderich for the whole job. Read and understand the Act. Very little of the money required to fix the problem will come from the Town of Goderich. The Municipal Drainage Act does NOT recognize political boundaries. Read the Act.
At Sarnia the lake is still stained by blue clay for miles out into the lake. Those huge waves really chewed up the exposed clay lakebed. I can’t see my fishing lure when it’s only 3 inches down into the water. Dozens of mud puppies were thrown up onto the beaches here during the big blow from “Sandy”.