– Welcome everyone to Wednesday Nite @ the Lab. I’m Tom Zinnen. I work with the UW-Madison Biotechnology Center. I also work for the Division of Extension Wisconsin 4-H. And on behalf of those folks and our other co-organizers, PBS Wisconsin, the Wisconsin Alumni Association, and the UW-Madison Science Alliance, thanks again for coming to Wednesday Nite @ the Lab. We do this every Wednesday night, 50 times a year. Tonight, it’s my pleasure to introduce to you Adam Bechle. He’s an engineer with the Wisconsin Sea Grant. He was born in Green Bay, Wisconsin, and went to Green Bay Preble High School. Then, he came here to UW-Madison to study civil and environmental engineering as an undergrad and stayed on to get his master’s and PhD, also in civil and environmental engineering here.

And then in 2016, he joined the Wisconsin Sea Grant as a post-doc, and then in 2019, became a permanent member of the staff there. Tonight, he’s gonna talk with us about adapting to a changing Great Lakes coast. Would you please join me in welcoming Adam Bechle to Wednesday Nite @ the Lab?

– Thank you, Tom, for that introduction, and thank you Wednesday Nite @ the Lab for inviting me to speak about this important issue facing our Great Lakes coasts. Fluctuations in Great Lakes water levels are very challenging for our coastal communities and coastal residents, particularly when we see extremes, Extremes like extreme low water levels that were seen in record lows in 2013 on Lake Michigan and extreme highs that have been seen on Lake Michigan and Lake Superior in 2019 and 2020. But before I get into talking about adapting to those changing coastlines, I’d like to give a little bit of a background on Wisconsin Sea Grant and why Wisconsin has something called the Sea Grant program. So Sea Grant is a federal university partnership between the National Oceanic and Atmospheric Administration and university partners around the nation. In total, there’s 34 Sea Grant programs on all of our oceanic states and Great Lake states, as well as Puerto Rico and Guam. Wisconsin’s Sea Grant is based at UW-Madison, with satellite offices at the UW campuses in Superior, Green Bay, Manitowoc, and Milwaukee. Wisconsin Sea Grant focuses on research, education, and outreach for the sustainable use of Great Lakes coasts. And so we fund basic research on a number of Great Lakes issues, and as well have outreach specialists and communication specialists like myself who talk about issues like Great Lakes water levels, coastal engineering, fisheries, aquaculture, water quality, social science, tourism, and a number of other issues in the Great Lakes.

So why do we have a Sea Grant program in Wisconsin? Well, one thing I like to point to is the length of the coast that we have in the United States. The Great Lakes has 4,530 miles of coastline along the United States. That’s more than the Atlantic coast and the Gulf coast combined. Not quite as much as the Pacific coast when you factor in Alaska and Hawaii, but still quite a substantial amount of coastline in the Great Lakes. Wisconsin itself has over 800 miles of shoreline between Lake Michigan and Lake Superior, and the Great Lakes are extremely important to the state of Wisconsin. It’s where we live. Some of Wisconsin lives near coastline. There are $6 billion of improved property within a quarter mile of the Great Lakes coasts. Great Lakes are also a great economic driver for the state. The Great Lakes ports in Wisconsin generate over $1.

5 billion of revenue annually. And the Great Lakes are a place that we recreate. There’s over 200 coastal beaches along Wisconsin’s Great Lakes shoreline, and those coastal beaches are not only important for our recreation, but they also drive tourism to those communities that depend on them. And so we have a really valuable resource in Wisconsin in our Great Lakes coasts. How did we get them? Well, the coasts and the Great Lakes in general are intertwined with our glacial history. Over 2 million years ago, the Laurentian Ice Sheet descended into the Great Lakes region from the north and over time, advanced and retreated numerous times. And as it did that, it started to carve out the Great Lakes Basins. The Great Lakes Basins mostly were old river beds with softer sediments, and really carved out the basins that we see today. The last glacial advance in Wisconsin, in the Great Lakes in general, was the Wisconsin glaciation about 25,000 years ago. Then the glaciers started to retreat for good out of the Great Lakes, and we were left with the landforms we see today.

Now, when the Great Lakes retreated, we didn’t see exactly the configuration of Great Lakes that we have today. The drainage patterns and water levels of the Great Lakes changed over that following thousands of years. As water changed course throughout the Great Lakes, the land surface in the Great Lakes area rebounded from having the heavy weight of the glaciers on top of it. The northern part of the Great Lakes are rebounding faster than the southern part, so we’re having a tilting effect because the northern parts were under thicker ice and for longer periods of time. And so all those changes, the tilting land surface, the water flowing out through channels and rivers, have changed the drainage outlets over time until about 4,000 years ago, when we ended up with approximately our current configuration of the Great Lakes. So what were we left with? Well, we have five Great Lakes. We have Lake Superior, Lake Michigan, Lake Huron, Lake Erie, and Lake Ontario. And the Great Lakes are all connected through a series of connecting channels flowing all the way from Lake Superior out to the Atlantic Ocean. So Lake Superior sits about 600 feet above sea level, flows out the St. Marys River, and through a series of dams and power plants up there through the St.

Marys River out into Lake Huron. Now, Lake Huron is connected to Lake Michigan through the Straits of Mackinac, and this connection is so wide that the water levels of Lake Michigan and Lake Huron are pretty much the same. In fact, we call it Lake Michigan-Huron, and we treat it as one large lake when we’re talking about water levels. Out of Lake Michigan-Huron, the water flows through the St. Clair River into a small lake called Lake St. Clair near Detroit and out the Detroit River into Lake Erie. Now, there’s no dam or human control structure on that flow, but that river is dredged periodically to allow navigation, and so that does change how much flow does go through that river when that dredging operation does occur. And then Lake Erie outlets over the Niagara Falls, drops over 300 feet into Lake Ontario, of course, through a river, and then Lake Ontario sits about 243 feet above sea level. Lake Ontario outlets through the St. Lawrence River through a series of dams and out to the Atlantic Ocean.

And so this is a large, interconnected system of water and those water levels in the lakes change over periods of years and seasons and months and even days. And so our period of record of water levels in the Great Lakes extends back from about 1918 to the present day. And in that water level record, we see highs, lows, periods where water levels are above the long-term average, periods where water levels are below the long-term average. And these variations are on the order of feet. Recently, in the late 2010s, all the five Great Lakes have been above their long-term average, and each Great Lake has broken some form of water level record. Water levels, in their extremes, especially, can really change our coastline. When we have low water levels, things like navigation shipping are stressed because water depths can be insufficient to pass large ships or even recreational craft, and things like water intakes for our drinking water treatment plants sometimes can be stressed not having enough water depth to function properly. At high water levels, especially at the extremes, we have a higher probability for flooding along our coasts, as well as erosion of our coasts. So today, I want to talk a little bit about what is going on with Great Lakes water levels, what drives them up and drives them down, how is that changing the coast, and then what are some strategies that are being used to adapt to this change? So first, what is a water level or a lake level in the Great Lakes? When you hear about it in the news, or hear about it in maybe a scientific publication, really we’re talking about an average over a daily, monthly, or annual period. And typically, monthly average is what’s used to describe the lake levels.

That’s because we can see water level changes on a scale of time scales. We see inter-annual variations where water level goes up and down over a period of years. We also see seasonal changes in water levels, where we have, typically on an average year, our highest water levels in the summer and our lowest water levels in the winter. We also have changes out there on the lakes all the time. Wind waves, which if you went to go look at the lake right now, you’d see that rippling and maybe white-capping. That changes on the order of seconds. And then when we have large coastal storms, big winds blowing in, we get storm surges, seiches, those change water levels on the order of minutes to hours, and sometimes even up to days. But in general, when we talk about lake levels, we’re talking about that monthly average. That can kind of remove some of those short-term fluctuations and really help us focus on how much water is in the lake. So let’s take a little bit more detailed look at the water levels in Lake Michigan-Huron.

So again, we have a period of record of just over a hundred years. Lake Michigan-Huron has experienced a record high in October of 1986, a record low in January of 2013, and the range between those two is about 6. 4 feet. Now, within the water level record, we see a seasonal fluctuation. Again, kind of peaking out in the summer and being lowest in the winter. And on average, that’s about one foot. Some years may be more, some years may be less, but the average variation seasonally is one foot. As I said before, we have periods of high and periods of low. We’ve seen rapid changes in water levels on Lake Michigan-Huron. In the ’50s, we had a rise of over three feet in just a year and a half, and then in the ’80s, we saw a drop of over four feet in just over two and a half years.

So we can experience pretty quick changes in water levels. We can also see prolonged periods of high and low water levels, like the 1970s, where we had eight years of prolonged high water levels or the early 2000s, where we had 15 years of prolonged low water levels. It’s a bit similar story when we look at Lake Superior. Lake Superior has a slightly smaller range between its record high, which was set in October of 1985, and its record low, which was from 1926. That range is about 3. 9 feet, but we also experience rapid changes, rapid increases, rapid decreases, periods of high and prolonged periods of low. So this is something we definitely need to expect when we live on the Great Lakes coast, is that high water levels and low water levels, based on history, will always be coming back. So what drives the Great Lakes water levels up and down? Well, it’s helpful to think of the Great Lakes kind of as a budget, thinking of water going in and out of the budget. And one of the big drivers is rainfall, precipitation falling directly on the lakes. That is quite a substantial amount of water.

We also have rainfall that falls on the surrounding lands and runoff into the lakes. The lakes are also very big surfaces of water, and so we get quite a bit of evaporation directly off the surface of the lake and back into the atmosphere. Those three terms, precipitation, runoff, and evaporation, when lumped together and added up, are called the net basin supply, the supply of water into and out of the lakes. So precipitation and runoff add water, evaporation takes it away. So if precipitation and runoff exceed evaporation, then the Great Lakes in general will rise. If precipitation and runoff are lower than evaporation, we have more water leaving the basin than entering, then generally the water levels will lower. Now, there’s other components to the water budget. We have, as I mentioned, connecting channels connecting the Great Lakes. So in the instance of Lake Michigan-Huron, flow comes in from the St. Marys River out of Lake Superior, and out through St.

Clair River out on its way to Lake Erie. We also, in some cases, have man-made diversions into and out of the lake system. So Lake Michigan-Huron has the Chicago River diversion. So around 1900, the Chicago River, which once flowed into Lake Michigan, was reversed with the Chicago Sanitary and Ship Canal to flow out of Lake Michigan-Huron. That is a diversion of water, diversion from the natural pattern. So it’s interesting to kind of consider how much water is actually being diverted through that specific diversion. So the Supreme Court decreed in the 1960s the flow of the Chicago River flowing out, and that is 3,200 cubic feet of water per second. Now, if we take that over the course of a year, that adds up to 750 billion gallons of water. Which sounds like a lot, and it is a lot of water, but when average that amount of water over the surface area of Lake Michigan-Huron, which is 45,000 square miles, that amounts to just under an inch of water out of Lake Michigan-Huron going out through the Chicago River. Definitely not negligible, but certainly small compared to what Mother Nature can do to water levels on the Great Lakes.

There are other diversions into Lake Superior on a similar order of magnitude, and humans also have some control in some of the connecting channels where we do have locks and dams where flow is regulated, but in general, Mother Nature is really what drives these many-feet rise and fall in water levels. Humans do have some control, but that’s more on the order of inches. So speaking of Mother Nature putting water into our Great Lakes, precipitation, as I mentioned, is one of the big components to the water budget. We have precipitation records dating back just before 1900 all the way to present day. Over this long period of time, the wettest five years in history occurred from 2015 to 2020. In fact, we set our all-time record for water precipitation in the Great Lakes Basin in 2017, and then almost broke that record in 2019, so the two wettest years in history in that five-year span. That’s a big reason why, as I mentioned, we’ve had record-high water levels throughout the Great Lakes in 2019 and 2020. So taking a more detailed look at this road to record-high water levels, let’s drill down in Lake Michigan-Huron and kind of see how that lake went from January 2013, new record-low water level, all the way up to new monthly high records in 2020. So in the years preceding that record-low water level, there was quite high evaporation on the Great Lakes, which drove water levels down and kept them low. Then in 2013, we hit that all-time record low on Lake Michigan, followed up with a spring and summer that had very high precipitation and therefore high runoff as well that raised the water levels, but they were still below our long-term average, shown in red here.

Then we had a low evaporation winter. We didn’t get much seasonal decline in water levels that we normally see in the winter, and that seasonal decline is usually driven by increased evaporation in the winter and low precipitation in the winter. Well, we didn’t have a whole lot of evaporation that winter, so we didn’t see much seasonal decline. Followed up with a wet spring and wet summer that drove water levels just about average, and then that again was followed by a winter of low evaporation, bringing water levels from those record lows in 2013 up to around average. Things were a little calm for a few years, and then we had that record-setting precipitation year in 2017 that drove water levels well above average. Followed it up in 2019 with a near-record level of precipitation, and then we stack those up with another winter of low evaporation that really set the table for 2020 to break records on Lake Michigan-Huron, and we set new monthly record highs from January all the way to August in 2020. July of 2020 was just two inches off the all-time record-high water level in Lake Michigan-Huron. So really, an unprecedented rise from record-low water levels in 2013, almost setting our new record all-time high in July of 2020. Since, we’ve sort of topped out there. 2021, at the time we’re recording this, we’ve had a slight drought in the area, and that’s had low precipitation, not a whole lot of water entering the lakes.

Gotten some relief from those record-high water levels. Sitting here, September of 2021, we’re still well above average, but definitely not in that record territory. So where can you go to find out about Great Lakes water levels today? The Army Corps of Engineers every month puts out a monthly bulletin of Great Lakes water levels. A web search for that term, Monthly Bulletin of Great Lakes Water Levels will bring it up, and with it is a graphic showing a two-year history of where we’ve been with water levels, as well as a six-month forecast of where water levels are predicted to go. So to orient you of this monthly bulletin, I’ve got here a Lake Michigan-Huron bulletin from September 2021. So across the top, we see time, we see years going back to 2019 and months going back two years. On the vertical axis, we have the lake level elevation, and on the left-hand side is feet. The dashed blue line there is the long-term average water levels, and you can see that seasonal cycle in there, peaking out in the summer and bottoming out in the winter. The red line here is where we’ve been. This is the recorded water levels over the last two years.

And then those little lines across the top with years on them, those are the monthly record highs, and then on the bottom are monthly record lows. And so you really get a full picture of where water levels have been and how that compares to our record levels. So we can see here, 2020, as I mentioned, set new monthly record highs from January to August in 2020. And since then, we’ve kind of been steadily declining, as I mentioned, been in a drought. The supply of water coming into the lakes has been a little bit lower, bringing us to where we are right now, again, as we’re recording in September of 2021, kind of halfway between the long-term average and the monthly record high. The forecast for the next six month is shown in the dashed green line, and around it is kind of a cone of uncertainty of where those water levels might go. It’s kind of like a hurricane forecast. The further out you get, the less certain we are of where water levels will be, but looking forward, we’re likely gonna be sticking in that above-average range, at least for the next six months on Lake Michigan-Huron. We can also look Lake Superior, this monthly water level bulletin. We can see where Lake Superior was, setting monthly records in 2019 and 2020.

And actually as we sit now, Lake Superior is right about its long-term average water level, and the six-month forecast has the lake sitting right in that area of long-term average. Certainly this can change if we get a wetter fall or winter than expected or lower evaporation than expected, but this is the current forecast as far as it’s provided. So you can go and do a web search for that any time and find the latest water level bulletin as well as the water level forecast. So what’s gonna happen with water levels under a changing climate? Well, one thing we do know, we know that we expect a warmer climate going forward, as well as a wetter climate going forward. So what does that mean to the Great Lakes water level budget? Well, that suggests an increase in precipitation and an increase in runoff to the lakes, but that warmer weather will likely lead to an increase in evaporation from the Great Lakes. So an increase in water coming in and an increase in water going out. So prior to about 2013, the general consensus running through climate models and routing them through models of water levels in the Great Lakes was that evaporation was gonna win and that lake levels are going to trend lower. However, it was discovered that the treatment of how runoff from the land was making its way into the lakes in those models was under-predicting how much runoff was happening. And so more recent studies, including one from Michael Notaro and collaborators at the UW-Madison have shown that we don’t have a clear trend anymore of where we expect water levels to go under a changing climate. Really, it depends on how much warming we anticipate or will actually get, and how much increase in precipitation we get, because those two signs are kind of fighting with each other.

So depending on which climate model you use, they see slight decreases in water levels, slight increases in water level. So not a clear conclusion anymore, like we had prior where we thought water levels were gonna go lower. But one thing we do want to stress is that historical variability is likely to remain. We’re still likely to see extreme highs, still likely to see extreme lows, possibly higher highs and lower lows than we’ve seen before. With more extreme precipitation, more extreme evaporation, we could be in for greater periods of those extremes than we’ve seen before. So looking forward, it’s really best to anticipate those extremes to continue. So I’ve covered a bit about what is going on with Great Lakes water levels, and now I wanna talk a bit about, so how are the coasts changing in response? As I mentioned before, when we have extreme low water levels, that really puts stress on our navigation facilities. In some cases, particularly when we had those record-low water levels in the early 2010s, there were marinas that had to dredge continually, boats were having a hard time getting in and out of the facilities, ships could not contain a full load and were losing money based on having to not be fully loaded just so that they had enough water depth to travel. Lots of dredging was going on in those low water levels, and of course, concerns about drinking water intakes, whether there was enough water depth for those to function as designed. With high water levels, the concerns become more with flooding and erosion and infrastructure damage from our high water levels.

And so I wanna focus a bit on coastal flooding first, and then I’ll talk a little more about erosion. So coastal flooding doesn’t happen just with high water levels. It’s a combination of high water levels and coastal storms. So when a coastal storm blows in with strong winds blowing towards the shore, those strong winds can push up a storm surge, so piling up water against the lake, the shoreline. That moves in water on the Great Lakes that can be anywhere from a foot to several feet of storm surge. On top of that are waves. Those waves, when they hit the shoreline, waves typically will break when they get to shallower water and will run up the slope and cause additional water to get close to inundating, say a home, especially in low-lying areas. Now, at average water levels, a given storm may not cause flooding, may not bring the water up to a level of a home, but when we have high water levels, that storm has a head start at causing flooding. And so the same storm under average water levels may not cause flooding, may cause quite a bit of inundation and flooding for a home and for a wide stretch of homes. One place where this happens in Wisconsin is along the bay of Green Bay.

The bay of Green Bay is long and shallow, oriented to the northeast, so that when strong northeast winds come, quite large storm surges can pile up at the end of the bay and cause problematic flooding for the city of Green Bay, as well as some of the cities along the bay, particularly the western arm of Green Bay. Places like Suamico, Oconto, they’ve all been dealing with flooding during this record-high water level period. I want to talk about two events in Green Bay in particular that were notable in this high water period, December 1st of 2019 and April 28th of 2020. Those were some notable flooding events, but to put those in context, let’s actually go back in time. April 8th, 1973, the worst coastal flood recorded in Green Bay history. The headline from the Press-Gazette was “Floods Force 800 From Their Homes. ” Large storm, northeast winds blew down the bay, brought in cold April icy water into those homes and flooded out a large area of low-lying land near the bay. So what was going on here with storm surge and water levels? Well, those northeast winds kicked up about a 3. 3-foot storm surge. Pretty big.

Water levels were above average, no record highs, but they were quite above average. That brought the water level in Green Bay up to about just over 584 feet above sea level, and so that caused that widespread flooding. So that 584-foot mark I’ve marked here on the graph and is an important number to keep in mind when we’re comparing to this event. Shortly after this devastating flood, the city of Green Bay constructed a dyke along its Green Bay coastline in hopes to not experience that sort of devastating flooding again. And it’s functioned quite well, and there hasn’t been that bad of flooding from a coastal flood since, but let’s look at what has happened since then. Well, let’s take us to December 3rd of 1990, and this storm surge was the big one. The strong northeast winds coming down the bay kicked up a 5. 4-foot storm surge. Compared to the next-highest storm surge in the historical record, which was four feet, this is a foot and a half higher than anything that’s been recorded in modern history. This was the big one.

When the Army Corps of Engineers analyzed coastal flooding in Green Bay, they estimated this was about a 1-in-300-year storm, or to put it in other terms, in an average year, there’d be a 1-in-300 chance of a storm surge like this occurring on Green Bay. The biggest one that we’ve seen in the historic record. Fortunately, Lake Michigan was at roughly average water levels here, depicted on the graph by the red line. So when you add those average water levels with this extreme storm surge, that brought the water level in the bay of Green Bay roughly to about 584 feet, similar territory to that 1973 flood. With the dyke in place, there wasn’t that devastating, widespread flooding, but if water levels had been above average, things could have been worse. When we look at the timing of water levels and storm surge specifically in Green Bay, looking at the top five storm surges that have occurred in our modern history, the only one that really occurred at elevated water levels was that 1973 event. Otherwise, they’ve occurred at near-average or below-average water levels, which brings us to our current period where we’ve had record-high water levels. So December 1st, 2019, strong northeast winds coming down the bay created a 2. 4-foot storm surge on the bay of Green Bay and caused local flooding right along the bay there. In terms of how large this storm surge was, this was about an average large storm that you would see in a given year.

Obviously some years, there’ll be bigger storms, some years may not see a storm this big, but roughly, this is about what you’d call a big storm that you’d see in a year. Then in April of 2020, another storm surge, a little bit larger, about 2. 6 feet, came down the bay. Again, strong northeast winds caused localized flooding around the bay area and a little bit into the city. Green Bay Metro Boat Launch was swamped. This storm was a little bit bigger. This is roughly a storm you’d see every two or three years. So not a remarkable storm. Certainly a big one, but nothing compared to that 1990 storm. But when you add it on top of record-high water levels, brought the bay up to just about that 584-foot mark, causing localized flooding.

Again, that dyke’s in place, so the widespread flooding that was seen in 1973 didn’t happen, but it just underscores how much coastal flooding is impacted by our Great Lakes water levels. So when we’re at record-high water levels, it doesn’t take a remarkable storm to cause issues, but when at average water levels, it took the largest storm surge ever recorded in Green Bay to get to that same level compared to high water levels. So really, flooding is problematic, especially when we have high water levels, something we’ve seen in the last few years. Green Bay is definitely a spot where coastal flooding is concerning. It’s low-lying, and it’s like I said, the bay is long and shallow, which is really conducive to large storm surges. Most of Wisconsin Great Lakes shoreline is not that low-lying. In fact, a lot of it is up on coastal bluffs, 10 feet high, 100 feet high, 130 feet high, and not really subject to flooding from the coast, but there are other issues that come with a coastal bluff, and that is erosion and bluff failure. So what happens there? Well, much like with flooding, coastal storms come into the mix, creating storm surge and waves. And when those storm surge and waves reach up high enough that the waves can touch the bottom of the bluff and start to impact it, those waves bring a lot of power and force and start to wear away sediments there. And so again, at average water levels, it’s harder for those storms to reach the base of a bluff.

But when we have higher water levels, it’s that much easier for the same coastal storm to bring waves up and impact the base of the bluff. If the water level gets up and over the beach, we don’t have that benefit of the beach being able to have waves break over it nicely. Those waves can come in and strike the bluff at an even higher height in that case. And so sediment is continuing to be worn away at the base of the bluff. It can steepen that toe up up to a point where the soils that comprise that bluff can no longer stand at a stable angle. Each soil has sort of a natural angle that it will remain stable at and not be at risk of collapse, and as you steepen up further and further from that angle, you increase the likelihood that there will be a slope collapse. And so as waves continue to remove material away and steepen that toe, that risk becomes greater and greater. Now, depending on the type of soil that a bluff is made of, it may fail in a number of different ways. Some places experience a deep-seated slumping, where the whole slope will kind of slide out into the lake. That’s not the most common form of slope failure in Wisconsin, but it does happen in a number of places.

More common is called sliding or translational sliding. That’s where we see a series of smaller failures on that unstable, over-steepened part of this slope. So we’ll see a smaller section of the slope kinda collapse and fall off down to the base of the bluff, and that leaves a steeper portion up the bluff. That steeper portion further up the bluff is now unstable and subject to potentially collapsing. This can be worsened if the high water levels and waves continue. They remove the material that had just eroded down at the bottom of the bluff, and then start to continue to work on that bluff and steepen up the slope. Eventually, the upper part of the bluff slope will collapse and slide, and this failure works its way up the slope of the bluff. Even if there was no more wave erosion once we’ve destabilized the bluff, that slope is gonna want to get to a more stable configuration, a more shallow angle. And how does it do that? Bluff failures and collapses. So that is how we eventually see recession of the coastline at the top and where our bluffs start to encroach upon things that we value like homes, businesses, parks, and things like that.

A recent study out of the UW Geosciences and Wisconsin Geological and Natural History Survey by Russell Krueger, Luke Zoet, and Elmo Rawling looked at bluff evolution in response to high water levels using some real advanced methods, drone surveys, and slope stability modeling to really understand how fast these failures work their way up a bluff. And they found that unstable services progress up the bluff at a rate of about 4. 4 meters per year, or roughly 15 feet per year. So kind of to put that in context, a low bluff, maybe 10 or 15 feet high, can really experience failure in recession at the top of the bluff almost immediately. Our higher bluffs in the state, over a hundred feet, now, we’re talking on the order of a decade before erosion that occurs at the toe of the bluff works its way all the way to the top of the bluff. And we can kind of see that visually if we look at a couple different sites in Wisconsin. So first looking at a shorter bluff from the Kenosha area in Somers. This is about 30 to 40 feet tall. 1970s to 2012, there wasn’t a lot of change in this bluff. 2012, as you’ll recall, we were almost at record-low water levels.

So not a whole lot of erosion happening at the toe. Well, from 2012 to 2017, we had quite a rise in water levels on Lake Michigan, a lot of wave erosion reaching the toe, and that recession happened at the top of the bluff pretty readily. Just in that five-year window, went from having some distance between the edge of the bluff and the house to by 2017, the back porch of that house falling in the lake. One more year down the road in 2018, the foundation is exposed of that house and unfortunately had to be removed, demolished by crane for safety reasons. But this house was lost to erosion in Wisconsin. A big impact of erosion here. If we look at a taller bluff, this is from Milwaukee County. We see in 2012, reasonably stable configuration. Lake levels are close to record lows. By 2017, lake levels have risen, waves have impacted the toe of this bluff, and we see some erosion and failures working their way up, maybe a third of the way up the bluff.

Much taller bluff here, using maybe some of those trees as a reference point as we move forward in time. By 2018, we lose some of those evergreens on the bluff slope. 2019, still, the failure’s working its way up. And then by 2020, we don’t see much vegetation on the bluff slope anymore. Those failures have worked their way to the top of the bluff, but it took a lot longer than our low bluff example, so really demonstrating that failure process. So lower bluffs, typically we’ll see those impacts quicker, definitely at the top where we have homes and things we care about. The taller bluffs, we’ll see them eventually, but it may go a little unnoticed because it can be kinda hard to see what’s going on down at the lake, but we know that failure is working its way up the bluff. So definitely something to be aware of, no matter what the coastal configuration. Water levels and waves are a big impact on Great Lakes coastal bluff erosion, but they’re not the only thing that affects Great Lakes coastal bluffs. One thing we need to think about is water coming from the land surface.

So as water flows down from the top of the bluff to the base, that can erode soil particles directly off the surface of the bluff. Groundwater in the bluff slope. When it comes out in the middle of the bluff, it’s coming out at a high enough rate, it can cause sapping or erosion of the soil particles there. Also, groundwater in a slope reduces its stability. It’s not as strong, and that stable angle will have to be shallower or less steep. And so high groundwater conditions can also factor in to bluff failure and bluff erosion issues. And so we really need to think about all these natural processes at a bluff site. Certainly lake levels and wave erosion a main driver, but we can’t ignore other factors. Now, as humans, we live on the coast and we make changes, and some of those aren’t exactly the best thing for bluff stability. One thing we do is we build.

We add surfaces where water can no longer be absorbed. It runs off, and possibly causing increased surface water erosion problems. So we have to be mindful of where those impervious surfaces go. Vegetation on the bluff naturally occurs on a bluff. The roots of that vegetation, beneficial for a few reasons. One, the roots hold the soil, at least to some depth, let the roots go and add strength to the soil. They also absorb water from the soil and put it up into the atmosphere, and so they help remove excess water from the bluff. So if we come along and we remove that vegetation, we’re decreasing that stability of the bluff. And then another thing we do is when we see toe erosion at the base of the bluff, oftentimes we try to stop it to save the properties at the top. This can be done by adding erosion-resistant materials like concrete, oftentimes armor stone, rock, to sort of keep that wave energy from being able to erode the bluff slope.

However, this kind of fundamentally changes how those waves interact with the bluff, and instead of eroding sediment away and sort of being absorbed maybe on a beach, they’re striking a hard surface. And changing that near-shore dynamics can, in some cases, have negative impacts at neighboring properties, sometimes increasing erosion around the structure. And so it’s something to be aware of and definitely something that does happen in some cases. You can look at these changes yourself on a great tool that we have in Wisconsin called the Wisconsin Shoreline Inventory and Oblique Photo Viewer. You can either search that name online, or you can type in the web address, no. floods. org/wcmp. This is something that was put together by the Association of State Floodplain Managers, the Wisconsin Coastal Management Program, and Dave Mickelson, who is a professor emeritus at UW Geosciences, compiling historic aerial photos of the coast and putting them in a viewer for everyone to take a look at. So up there are photos from the 1970s, the 2007, 2008, 2012 photos that were acquired by the Army Corps of Engineers, and then since 2017, the Coastal Management Program has been working with the Wisconsin wing of the Civil Air Patrol to routinely acquire photographs of the coast. And these are extremely valuable in being able to track changes on the coast, see how certain bluffs and structures have responded over time, and really get a good picture of how things have changed.

There’s also data layers up there looking at assessing bluff stability. In some cases, we have erosion measurements up there as well, but really a great resource to help understand how specific areas have been responding to changing water levels. Again, that’s the Wisconsin Shoreline Inventory and Oblique Photo Viewer, no. floods. org/wcmp. A great resource to check out when we’re trying to explore the coast. So I covered how the coasts are changing with specific emphasis on how water levels are behind some of that change. Now, I want to talk a little bit about what strategies are being used to help adapt to these changes. So when I talk to folks in my job, talking to property owners, to municipalities, people who are dealing with erosion, I’d like to start with a top-down approach to protecting coastal investments. And part of that is the top is where, typically, what we care about is.

That’s where homes are, businesses are, infrastructure. And so starting up at the top and trying to see what is the problem, how close is erosion or flooding to causing an issue, and work our way down towards the lake, because, as I’ll talk about in a moment, fighting with Lake Michigan and Lake Superior is tough and it’s very expensive, so if we can work our way from the top down and see if we need to do that, that’s usually the best course of action. So what can we do at the top of the bluff? Well, managing our land use, managing where water flows, and managing vegetation are all great things that we can do. In terms of managing land use before something’s built in siting things intelligently, not having them too close to the edge of the bluff and trying to keep them out of nature’s way. As we’ve covered, erosion and flooding, these are natural processes on the Great Lakes. It’s what the lakes want to do, but it’s problematic when we put things we care about in the way. And so if we can stay as far out of nature’s way as possible, that can usually be the most effective solution. So in terms of doing this in a policy perspective, some of our counties and municipalities in Wisconsin have enacted building setback ordinances that try to keep new development out of harm’s way. These will often include things like erosion rates over a certain amount of time for a life of a building. They range anywhere from 30 years to 100 years, depending on how conservative you are.

And then slope setback, if a slope is going to fail to its natural stable slope angle, accounting for having that distance in that setback. And then oftentimes they include somewhat of a buffer to provide a little bit of breathing room in case erosion happens at faster rates than they have in history. And so these can be really effective ways at keeping new development safer from the threat of erosion and keeping them out of harm’s way so we don’t have to try and fight these problems with Lake Michigan. For existing buildings, obviously they can’t be sited initially further away from the coast, but relocating a building can be a pretty effective strategy at getting out of harm’s way. Requires you to have somewhere to move the building, but as this example shows from Sheboygan County, a home was pretty close to the edge of the bluff and a bluff failure precipitated the homeowner to really consider their options. And since they had a large enough lot, they were able to hire a house mover to pick up and move the house back sufficient distance away from that erosion threat, reconnect the utilities, put in a new septic system. All of that totaled up, of course, but it was probably cheaper than trying to stop the erosion and keep the house where it was. Again, building relocation is not maybe necessarily always an option, but it’s something to keep in the toolbox when we’re trying to adapt to changing coasts, staying out of nature’s way. Other things we can do at the top of the bluff, managing healthy vegetation. As I mentioned, certainly not clear-cutting the vegetation we have there, but encouraging deep-rooted native vegetation for the benefits of holding the soil and removing water.

Keeping a no-mow buffer near the edge of the bluff will help those roots grow deeper and help slow down any water that wants to flow over the edge of the bluff. Views of the lake are high value when we’re at properties that are close to the coast. So obviously, if we’re covered with vegetation, some of those views may be impeded on, but really a good way to get those views back is to frame views and have low-growing vegetation over those sight lines. If there’s trees in the way, rather than cutting them down, exploring if they can be pruned up to give you those viewing corridors, trying to maintain as much healthy vegetation as possible and balancing that with the use of the site. Management of water at the top is also important. Knowing where drainage is flowing, making sure gutters aren’t pointed directly over the edge of the bluff, things like that. Rain barrels are a popular choice to really hold that water and avoiding putting things like rain gardens or tilled beds right near the edge of the bluff where water can go right into the bluff. As we work our way down the slope, a lot of those principles still remain good practices. Managing water, making sure it’s slowed down so it’s not picking up speed as it goes down the bluff and eroding the bluff surface. One good way to do that and slow that down is to, again, ensure there’s good, healthy vegetation on the bluff surface as possible.

Sometimes the bluff is too steep to be stable. That steepness may be threatening a property. If a house can’t be moved, reshaping an unstable slope is sometimes needed. Oftentimes this is done by cutting back the slope of the bluff to a shallower angle, back to that stable angle of whatever the bluff material is. If space is an issue, retaining walls in building terraces can also be an effective option to increase that slope stability. In some cases, adding fill to get that stable slope is possible, but that can oftentimes be expensive and hard to get permitted because then that fill would encroach upon the lake. So things that would be considered if bluff stability is really threatening a home. Then as we work our way down to the shoreline and these other options aren’t a solution, the home is still at threat, it can’t be relocated, then we start thinking about trying to slow toe erosion if that’s absolutely necessary. And so the concept here is putting erosion-resistant material or reducing the wave energy reaching the toe to kind of stop that process of erosion at the toe. There are a number of ways this is done in the Great Lakes.

By far the most common is what’s called a rock revetment. This is a sloping face of erosion-resistant, most often rock, stone, that will resist movement by waves and those are large rocks. And on the Great Lakes, especially on the open coast of the Great Lakes, we’re talking about ton rocks, multi-ton rocks, to be able to resist the force of waves. And under those large rocks are smaller stone, so that when water gets in between the gaps in those large rocks, it doesn’t undermine the structure from underneath. Again, revetments, most common type of structure to reduce toe erosion. Other ones that are used sometimes are a seawall, which is a vertical structure, either made out of steel or concrete, functions somewhat similar to a revetment, but when waves hit them, they reflect a lot more wave energy and can cause some more issues in the near shore. But again, the concept there is to directly resist erosion from the lake. Breakwaters are sometimes used to reduce wave energy at the coast. They’re built out into the water and waves hit them, either blocking the wave energy or reducing the wave energy that the coast sees to reduce the erosive capacity. And then an emerging area in the Great Lakes is something called nature-based shorelines.

This is trying to work with nature or mimic nature to provide some protection of the coast. Oftentimes it’s a hybrid with some harder structures with rock or concrete, but in the example that I show here, this is what’s known as a marsh sill. There’s a little bit of rock sill, kind of like a small breakwater out in the water. The waves hit those and that reduces wave energy a little bit. We’ve got marsh vegetation growing. As the waves hit those, reduces a little bit of wave energy. And then it’s backstopped by some smaller rocks for whatever wave energy reaches the shoreline to stop erosion there. Nature-based shorelines have been much more developed on our nation’s ocean coasts and internationally on ocean coasts. The Great Lakes, we’re still developing here. We’ve got ice, we’ve got freshwater species that don’t work the same as our ocean coasts, so it’s definitely an area that’s growing in the Great Lakes and something to keep an eye on, whether or not this sort of solution is suitable at a site.

It has more habitat benefits to aquatic and terrestrial habitats than conventional armoring of the shoreline with just rock. So it’s definitely gaining a lot of interest. Where can you learn more about these sorts of options? Well, Wisconsin Sea Grant, we’ve just published two new guides, one, “A Property Owner’s Guide To Protecting Your Bluff,” going into more detail about a lot of the concepts I talked about, going from working your way from the top down to the bottom, good practices to use, managing land use, vegetation, water, and then slope stability, and, if needed, shore protection. And then we’ve also put together a guide called “Nature-Based Shoreline Options For Great Lakes Coasts. ” As I mentioned, this is a developing area in the Great Lakes, and so we’ve put together some basic techniques that are being used now in the Great Lakes, as well as some case studies of where they’ve been implemented in the Great Lakes to help folks wrap their head around what nature-based shorelines are and kind of how they can be used in the Great Lakes. We also have two guides called “Adapting to a Changing Coast. ” These are a little higher-level views. One is written for Great Lakes coastal property owners, covering some of the options they can use to address flooding and erosion, and one is more geared towards local officials thinking about policy, funding options that might be helpful for adapting to a changing coast. All those can be found on the Wisconsin Sea Grant website, seagrant. wisc.

edu, or a web search for Wisconsin Sea Grant. It has lots of information about these issues, as well as the whole profile that Sea Grant has: fisheries, aquaculture, water quality, tourism. Lot of great information out there, both from Wisconsin Sea Grant, as well as from many of our partners at the state and federal and local level. One thing I’d like to point out on the website that might be particularly useful to some of the viewers, a website called “Resources for Property Owners. ” This is where we’ve collected a number of useful resources for Great Lakes coastal property owners to help understand what’s going on on the Great Lakes. Waves, erosion, sediment transport, how to assess vulnerability to some of these hazards, how to pick options going forward. And then when it comes time, if you need to work with an engineer, a contractor, some resources to help understand that process and a list of known contractors and engineers to start from when trying to do that sort of work. Again, seagrant. wisc. edu, can find a lot of great information about water levels and more there.

As I close out, I’d really like to acknowledge that I don’t do this work alone and Sea Grant doesn’t do their work alone. We have strong partnerships at the state and federal, university, regional, and local level. Just to name a few, we work closely with the Wisconsin Coastal Management Program, Wisconsin Department of Natural Resources, NOAA, the Army Corps of Engineers, UW-Madison researchers, UW-Milwaukee researchers, researchers at universities across the state. The Southeast Wisconsin Regional Planning Commission, Bay-Lake Regional Planning Commission, Association of State Floodplain Managers, and a lot of local partners as well. And so really we’d like to acknowledge and thank them for their work with us on these issues. I’d also like to acknowledge a lot of this information that was shared today was developed under a NOAA Regional Coastal Resilience grant that was funded by NOAA through the Office of Coastal Management, helped make a lot of this information and the guides I mentioned possible. With that, I’d like to leave you with just a reminder that the Great Lakes are really important to Wisconsin, both economically, as a sense of place, a place we recreate, and they face challenges, particularly when we have extreme water levels, high and low. And from history, we kind of anticipate we’ll continue to face these challenges in the future. They may be made worse by climate change, but working to adapt to them is in the best interest of everyone in Wisconsin, because of how important that that resource is to our state. With that, I’d like to again thank Wednesday Nite @ the Lab for having me, and thank you for your attention and have a great day.