 Hello and welcome to the board on earth sciences and resources webinar entitled a landscape restoration puzzle when natural isn't what you thought it was My name is Nicholas Rogers. I'm a financial and research associate with the board Our speaker to for today is dr. Dorothy merits a professor in the Department of Earth and Environment at Franklin and Marshall College in Lancaster, Pennsylvania Dr. Merritt is a geologist with expertise in streams rivers and other landforms and on the impact of geologic processes Climate change and human activities on the form and history of Earth's surface Dr. Merritt's received her bachelor's in geology from Indiana University of Pennsylvania Her master's in engineering geology from Stanford University and her PhD in geology from the University of Arizona Dr. Merritt's and her research collaborators have done some really exciting work and unraveling the natural and human processes That have shaped riverine landscapes in the eastern United States and they proposed a surprising pre-industrial scenario that explains high sediment loads in the Chesapeake Bay and other water bodies The work also has significant implications on how we restore our streams The webinar today will look more deeply at dr. Merritt's research and a fascinating story It weaves among geomorphology ecosystems and human history Just a few housekeeping items before we get started the audio for today's event will be streamed through your computer speakers We will be taking questions through the Q&A box located in the lower right-hand side of your screen Simply type your question in the box at any time and click send Please note that your question is limited to 256 characters We ask that you leave the box set to send your questions to all panelists This webinar is also being recorded. Please understand that any questions you submit may be read aloud and included in our recording a Link to the recording as well as a copy of the slides will be posted to our website within the next week or so If you have any technical issues during the event, please contact contact web webx technical support at one eight six six two two nine three two three nine Once again, the number for webx technical support is one eight six six two two nine three two three nine With that I'd like to get started and turn things over to our distinguished speaker dr. Dorothy merits Dorothy Thank you, Nicholas. I'm still transferring over here Give me one moment, please So Nick is my desktop and shared there yet with you Thank you so much Nick It's my pleasure to be talking to some unknown number of people I don't know the number eight right off the hand on myself at the moment But I'm really delighted to have a chance to communicate to all of you From my office and some of my crew is here with me my research collaborators Bob Walters here and others and We're excited about sharing the results of all of this work We've been doing for over a decade and it touches upon many different aspects of the earth sciences Including wetlands and their origins and what formation and restoration of streams and wetlands dams and dam removal Anthropogenic impacts on natural systems water quality permafrost permafrost saw climate change and Of course the recent history of human activity and its impact on landscapes so what touched on a number of those and many of things that I'll talk about today are Discussed in publications and on websites and I'll cite those as I go So you can always go look at those publications or websites And at the end of have a list of the the many collaborators that have been fortunate to work with and many students and the many funders to whom We're grateful and landowners Case in point here. This is Great Mars, Pennsylvania and Jim Moore and the Moore family have graciously allowed us to work here And some 60 years ago they allowed Paul Martin the same paleontologist to work there as well So we're building upon his early work from over half a century ago And when you look at this landscape from the air as Here it appears to be very natural in fact it has amazingly high water quality It's a wetland of wet nettle with sedges toxic sedges. It's an Audubon important bird area It's saturated at the surface year round for that reason it has toxic sedges and it's been a marsh a wet nettle for about 11,500 years However, there are things about it that aren't immediately apparent and one of those is that the pond that you saw in the previous view is actually not natural It was made with dynamite by the Moore family in the 50s and Jim Moore tells us that as a boy He watched the organic mud raining down on those cars. You see in the view So the great clear example of the impact of it in Propostine using dynamite to make a pond in a wetland There were efforts even before that to try to drain this wetland that ditch that flows through the view is actually not a natural stream channel It's a human made ditch from the mid 19th century What's intriguing to us is that this is one of the very few examples we know of not buried by historic sediment and That's how we got involved in this work initially We were looking at the historic sediment that is so ubiquitous in the valley bottoms And it buries nearly every valley bottom in the mid-Atmantic Piedmont region and yet it's not here So what we have here is a rare glimpse into what might have been prior to the burial of so many of the valley bottom landscapes Historically, and I'll come back to that later What's also interesting here is that there's something that's a little more natural than we might have thought it was and That is the actual structure of the landscape is very old It dates back to the Pleistocene It dates to cold climate conditions and the bulk of what we were seeing is the result of cold free spa phenomena And on top of that we have a thinned in here of organic sediment That's the wetland down the valley bottom produced by the accumulation of organic matter from plant matter over time And that's a very thin Capping on it a little film from the Holocene the last roughly 11,000 years So there's a much older legacy here And you can see it if you use LiDAR and get a bare earth view as we're doing here with PA LiDAR So we've made a slope shade You can actually see if my arrow is working for all of you on the slopes There are these low-baked features and these are what we sometimes call drool It's it's fractured crushed up rock material generated by rock fracturing during free-slaw times moving down the slopes Moving down and big alluvial fans after the valley bottom probably blocking the valley bottom down here And then there are places where the refermer card slumps like we see throughout the Arctic today often called retrogressive Faw slumps and these various phenomena from permafrost spa then led to Stuffs from the hillside going to the valley bottoms and making a very good Permutable substrate a rubberly substrate on which wetlands to form during Faw and Paul Martin did his coring and trenching out here Which I'll talk about later There's Paul Martin the more family has pictures of him when he was out there He was a young postdoc at the time and he was digging in coring and he published a marvelous paper that I highly recommend you read In which he talked about the shallow course in this marsh Wondered why this marsh was so rare today And it's got some of the first data on pollen and climate change from that pollen record for this region He was the first to show that adjacent to the last full-blade twice margin We didn't have a temperate forest at that time so for 20,000 years ago The rather we had take a tundra and he says in the paper We probably had bare soil affluxion slopes and it's a marvelous insight of his he recognized based on the vegetation What the landscape must have looked like He also did early in a really example of radiocarbon dating He was able to show that this marsh became established somewhere at the end of the last place to see and going to the earlier Holocene Here's an example of permafrost Faw and jello affluxion lobe were cell affluxion lobe formation today and you can see that it moves material of all sides even bolder size down slopes even at very low gradients and That's the stuff we now see throughout the mid-atlantic Piedmont region and in the region Valley in the Valley bottoms as well as on the side slopes And that's what then Holocene what and we're able to form upon once the ground had thawed What we're seeing in lidar then with the bare earth views is the low-baked structure these forms That when they're active there they're moving during times of fall when the active layer is fine They move very slowly a few centimeters a year perhaps down slope But always during times of fall Here's an example of our lidar analysis from central Pennsylvania again a slope shade You can see the fall material from fall moving down the slope into the Valley bottoms in places as many tens of meters thick It's often better developed in one valley side than it on one hill slope side than another given that The aspect and the facing of the Sun But what's neat here is you can also see that going down the main Valley in this Valley within the region Valley It's a shale Valley that there are these large step-like features going down and these are also gel affluxions So even the Valley bottoms themselves acted as hill slopes during these cold times It's the advancing and retreating of the ice sheets that we often are most familiar with and the glacial legacy of that Kind of advancing and retreating But at the same time the last two million years or so We've had advancing retreating permafrost boundaries And that's what we're looking at in this area here in the Atlantic region primarily Pennsylvania, Maryland It's what's the record of that advancing and retreating of frozen ground it might have been over a hundred meters thick in places And we're trying to estimate that So we need to keep in mind then that this is happening over and over for the last Here only I'm only showing 600,000 years, but cold times warm times cold times warm times is the proxy record then For the warm and cold times at the moment we're in a warm period So it's very I'm tempting at times to think that landscapes always look the same But of course it hasn't it's actually been much colder most of the last 600,000 years ago than it is today And note also that there was a very abrupt warm warming circa 18,000 years ago and within that warming period since end of last glacial maximum There have been some brief episodes of rapid warming So here what I'm showing is the position of the last glacial maximum ice sheet with its margin Circa 21,000 18,000 years ago And then I'm showing the works in French and Miller that is a record of where there would have been perhaps Continuous permafrost with some kind of permafrost They can't quite tell from the record they compiled in 2013 It's largely a record of people finding collusion and so forth, but also some other periglacial features But now what I'm showing is today where there was continuous permafrost the darker blue down to an isotherm of about minus 8 degrees Celsius then discontinuous down to about minus 1 degrees Celsius and then sporadic or isolated We'd have to go that far north today to get to a place where there is permafrost And it's all through the news at the moment on what's happening as permafrost falls with modern warming So the mid-Atlantic region is a very good analog or in some ways an analog For how what happened down here farther to the south when this landscape was Had permafrost and then warmed and that permafrost began to retreat or to fall and disappear so that on the previous due to the a line going from north to south and in Anderson Anderson the book written by Anderson Anderson they show along that line from north to south very thick permafrost at about 400 meters too much thinner getting to the zone where it goes from continuous to discontinuous and then sporadic and What we are finding is that this is probably a very good analog for paleo Pennsylvania where there was continuous permafrost and then going into Maryland it becomes discontinuous We're basing that on the landforms that we're studying and mapping and investigating and then going into Virginia We have to go to higher altitudes to get find evidence of permafrost although there is some at higher altitudes So the landscape is a record of that paleo temperature gradient The best modern analog we have found for what this region might have been like is actually Antarctica There are some differences of course, but what's common is that both places were very dry modern-day and our gets very dry in the dry valleys and Paleo Pennsylvania paleo Maryland was very dry and that's based on other people's work Not just our own so it was very windy very dry frozen much of the time And so we don't see on fluvial processes acting in some of the main valleys because they're frozen We do see lots of thermal contraction polygons is cold enough for the ground to crack and that's diagnostic It's a clear indicator of continuous permafrost We see many gel affluxion lobes and benches nivation hollows Etc. A thermocarpons and those we see all of those in Pennsylvania paleo Pennsylvania So now going back and looking at Great Marsh what we should keep in mind is we're looking at a landscape that at the moment is flawed But has been frozen from much of the last two million years probably or at least the last hundred thousand the work of T. C. Hale's Josh Brewing others on Joe Marshall is showing that The time the landscape spends in the frost cracking window down here at minus three to minus eight degrees Celsius Is very important because that affects the intensity of frost cracking so the more time it spends in that window That's the maximum conditions for getting frost cracking and the deeper that that gets the more Shattered material will be produced in Pennsylvania has a lot of shattered material as you'll see in Pennsylvania has some as well So looking here at the work of Joe Marshall what she has done is taking global Climate models and downscaled them and then use them with frost with can't use the temperature to look at frost cracking into estimate frost cracking Intensities you can see the scale board down here from her work So showing frost cracking intensity and degrees Celsius per centimeter It's not over a year and annual year of basis And so using various climate models We can show that in the region we're working But it's likely that given the climate modeling that we would have had conditions for conducive time intense very intense frost cracking And of course the landscape verifies that and supports it because we have many shattered rocks on the slopes You can trace these shattered rocks up to the ridge crest in the forest areas and many previous workers have mapped this colluvian What's new and different now is being able to use LiDAR to actually see the shapes of these Deposits and then to track how they move down slope to look under the trees for example We have some very exciting and new independent evidence that supports that the ground was indeed that was indeed that cold here And that is the existence of thermal contraction polygons But I showed those in the anodic earlier in that previous photograph and a researcher by the name of gal in 2014 published a map in which he showed all these little red dots as places where he had found thermal contraction polygons in New Jersey and Napa less etc and We realized that we would surely have them here because we had seen some of these in outcrops and quarries and other workers had Without sure we could do it if gal did and he was using Google Earth to do it So here's his Google Earth work It was published in his paper in 2014 and he showed that he could find these polygons He could map them and sketch them and at certain times we are he could not so all depends on soil moisture and the dryness of the soil So we began looking at he had done you have to get close down to the earth's surface I'm sure enough we found them very quickly We knew where to look initially because we'd seen evidence of these and others had in outcrops and quarries You can see the polygons along the hillsides here up and over these little mazes like summits This is the shale hills of central, Pennsylvania We got more and more excited began using satellite imagery and we could do an even better job This is the same area looking straight down using satellite imagery What this tells us then is it certainly was very cold minus three to minus eight degrees Celsius may be even colder But it certainly would have had continuous permafrost and it explains then why Bob Walter and I and our colleagues have had a very hard time finding Deposits that we would consider to be truly fluvial in origin and it's because the landscape has been frozen so much as a time Here's a good view then we just found this summer of one of those polygon Boundaries in outcrop along the road cut and what what's exciting to us is that it's filled with sand and the sand tells us then that it was That was Aeolian dust blowing about we've sampled this now and are getting ready to do some OSL work and other work with it It tells us a little bit more about the conditions at the time It tells us also that it was not very wet We would have had ice wedge more typical ice wedge cast instead We just have the cracking of the ground and then the opening of it We're working with Mark Demetros and others on this and it's a really neat new part of our work We find these all the way down to the valley bottoms except that in the valley bottoms as here We often find these darkened swales now They're actually dark because they're moist and we can only see these at certain times of the years and They they're in a loose way connected with these networks with the polygons and cells and They're filled with white silk which we interpret to be a reworked look and on that white silk There's an organic rich layer that has formed and so these were wetlands and throughout the Holocene Although today this area is farmed and I'll show that in a moment. Here's another view of the same area. It's near Carlisle, Pennsylvania You can see that the tributaries and these are not really streams They're just low swales that are moist are all parallel or sub parallel They follow bedrock fractures and then there's this other fracture pattern from the polygons itself Here we are looking at a different time of the year and you can see we can't see that that phenomena which is so remarkable We began wondering about these and wondering why would we have these silk-filled moist swales that are branching and spatially Extensive and interconnected with the polygons And we then came across a paper by Joe Levy and his colleagues from Antarctica again That the dry valley region or Taylor Valley region and we realized that this explains very well what we're seeing Because they're not truly gullies. They're not cut down by flowing water. They're seepage gullies They're seepage from permafrost spa and from the active layer of thawing and water seeping out, snow melting, etc And it brings down some small relatively small amounts of the finer material into the valley bottom where it accumulates So these are widespread we think in this region and can be found now with Google worth another imagery We find all sorts of retrogressive slums as I had mentioned we can find them on the LiDAR as well as the field We find they're more original gullies We've seen evidence that these lakes, permafrost lakes that had dried they're around the state college area and Of course in the Mid-Atlantic Piedmont what we've had begun to realize is that Various types of stens or wet meadows had become ubiquitous then would fall such as Great Marsh So we went back out with Candace Grand III, Chris Bernhardt and others and Aaron Markey our post-pac researcher And we've done some coring and we've done a lot of redid carbon dating You can see here we have a number of cores and we're using them for different purposes All of them have at the top this thick dark organic rich layer This particular layer appears human disturbance and then they all have basically the same strategic be going down And this one in the middle here is one we're looking at for seeds There are some we're looking at the pollen that's Chris Bernhardt's work at the USGS and then of course the dating You can see the dates here on the left this light colored silty layer down here We interpret as loss of some sort in the valley bottom about about 20,000 years old All right, here's some of the seeds we extract. This is a one millimeter square grid They all in the case of Great Marsh and the other black soils organic rich soils that we look at are consistent with wet meadows Wet marshes sometimes we find the submerged aquatic organisms indicating that there were pools of water But always it indicates a low energy environment And much like what we're finding today in the Arctic as permafrost fuzz So in the simple so they can we could take one of these cores and look at it from bottom on the down here in their lower Right to top and we can see these very sharp stratigraphic boundaries And we can bite interpreting the pollen the seeds the radio carbon dates et cetera other things in there Well, these determined is that we essentially had some sort of from a karst pond at the end of last full glacial Last glacial maximum and then a transition which is we refer to as the great far or the big far because we often see some Evidence of erosion at that service or lack of deposition or both then we typically see what we're beginning to realize is a period of warming that we have dated to the timing of the bowling Allerad and it has Wetland formation that had begun and then a period of cooling which correlates to the younger dryest and they have less organic matter and drier conditions it seems and then again warming and wetter conditions and you're really hold a scene and from these cores and our other sites These whole of seen what and remained stable and sustained throughout the whole of seen and in fact They can today retain carbon over that time period. So they're major reservoirs of carbon So we're going then from frozen to solid to warm cold warm for the last 18 19,000 years Looking in more detail Ignoring the human disturbance zone here You can see then that record of carbon accumulation We're using a proxy for it loss on admission, but it's basically showing us a lot of carbon stored in the upper 40 centimeters You can also see here in the middle from the oxygen ice from the oh 18 dated from my and our agreement Excuse me this period of warming here with is the bowling Allerad and then the cooling here, which is the younger dryest and You'll see in a moment that we can pick up evidence of that some of our sites including Great Marsh The pollen data from Chris Bernhardt showing the change from pine to oak and note the hemlock We do actually find hemlock commonly at the very base of the whole of seen wetlands that around 10 11,000 years We actually find small cones from the hemlock Here's a seed work that Aaron Markey and colleagues have done And they won't go into the details of it except to point out that these are all Consistent with a wet nettle with open pools put them again. There's a lot of karex tussig sedges There are many different sedged species So really a remarkably wonderful landscape for 10,000 years or so a little bit longer 1112,000 years And here are the dates over here But notice that we actually had wetland plants before carbon began to accumulate And we're not quite sure yet how to interpret that but that is the record We pick out our our associates are picking out thousands of seeds from this and other sites It's a great record of what was happening locally I'll talk briefly about this abrupt climatic transition right here the bowling all around this Relatively sudden warming from about 12.7 to 14.7 thousand years ago Which we see stratigraphically and we see that during that period of warming there actually was some wetland formation And then you can see here in the plot of depth versus age. Here's a disconformity we have older sediment then right here and Rejects pose right on top of it on this much younger sediment So a disconformity and then starting about the middle end of the bowling all around accumulation that was steady of Organic rich sediment up through the time of modern human disturbance and there was compaction of the wetland That's great much wetland which looks so beautiful was dynamite it and gets that cetera Actually also with a cow pasture for a long time. So there's some compaction in it I want to show you another site now because Great March is not our only site we actually have well over 120 sites and There each one of them is a new record for us There's a lot of similarities, but a few differences from here to there Many of them have sewer lines running through them as this one does a long tiny run in Maryland And this is the boulder the boulders that are used to protect the sewer line And many of them have had no dams and no ponds and have been buried as this one has so this one has had a record of burial of Organic rich sediment and a Pleistocene rubble and a bowling all the rod deposit that and so forth we've been using Geosics and it's determined that in places of up to 10 meters or so of valley still which is all collusion from Material coming off the side slopes and it's quite bouldery in places in fact right over here There are large piles of boulders quartz boulders that a farmer had dragged over there at some time in the past So there's clear evidence that material hadn't moved sediment had moved off these slopes sediment produced by frost shattering into the valley bottom and Gradually filling the bottom and then in places Wetlands form within that substrate. We'll look at a few of those. Here's one right here And then we've done some trenching out here about I think eight or nine trenches by now at this site You can see that we're looking I'll go back and show you where we are here We're looking right along. There's a slope nearby here going that way in the lower left there We're looking at collusion which came off the hill slope in the background and as we condone that slope Which is now buried by historic sediment anthropogenic sediment That's that slope had gradually merged with a wetland which had begun forming at about 11,500 years ago at this location And then it had accumulated organic matter and filled up with time and kept growing and growing and getting thicker and Thicker that that wet soil with wet metal speeds and then something happened that it was buried by historic sediment and what happened then was that European settlers arrived and began clearing the land that was mining in the area charcoaling They were building dams for various purposes. They were manipulating the streams the valley bottom of the wetlands and So you can see that this once Amazing what in which would have looked much like great marsh now is buried by several four or five feet or so of historic clay and silt Which came off the hillside as well There's largely a fine sediment record in contrast to the colluvial record from the Pleistocene which is much coarser and poorly sorted And you can also see with the brick that I've sampled here how amazingly cohesive and organic which this material is Recently we were very fortunate after some flooding to see the oldest wetland We have yet been able to sample so well, which is right down here by Bob Walter and Bill Hillgartner They're done. There's tamping it was exposed during a low water of the time right after some flooding And I'll show a close-up in a moment And what's exciting to us is that under sediments that is mass movement in origin Which came off the slopes in the background and you can see it has low bait shapes to it In fact part of it's blocked behind the bank slump a lot of the banks here are slumping But I'm back here underneath and I'll show a close-up is this organic rich material. It's just under the water It's still at groundwater level. This water level in fact is base flow essentially It is the long-term groundwater table level So that wetland would have been forming from their dating We have multiple dates here at roughly thirteen thousand five hundred to thirteen thousand four hundred years ago During the bowling allurad warm phase and we found oak leaves in it I'm a lot of fed seeds and also a black spruce needle, which is according to Bill Hillgartner consistent with other findings in ecology paleo ecology that show that during this transition from cold to warm during the bowling allurad That you can actually we can actually have both cold and warm species co-existing There's not no modern analog quite like that today We'd have to go much further north to find black spruce But this wetland this early wetland it was forming on top of the pysosine rubble Actually then had within it some cold and warm species Farther downstream along piney round there's a very thick and spectacular exposure much like what we see in the trenches of a Holocene wetland soil, which again is very much like the Great Marsh soil and Which is not buried in the case of Great Marsh And it's formed on this rubble of boulders and so forth from the Pleistocene last glacial maximum and earlier Probably multiple repeated events of this permafrost and permafrost spa And we see every now and then we see this slightly finer lens of rubble Which appears to be associated with maybe some winnowing and some pulses of material coming out of debris flow like flurries Down the valley You can also see here some of this set the seeds were pulling out multiple tusk etched seeds and so forth Potomage eatin so we know that it was a wet meadow Again in this case the ecology With the seeds is very helpful to as much as with Paul for Paul Martin the poem was used would have given a sense of the regional climate But we're looking at local landscapes and local hydrology these wet meadows would have been wet much of the year In fact, they would have had water at the surface throughout the year Why does this matter then to modern streams and to stream restoration today? So I urge you to please look at the website that Kayla Schulte put together for us last year BSR stands for Big Spring Run It's one of our key sites for a restoration experiment that we're doing with NSF funding with many collaborators and Also to look at the website that we've developed with Sophia Gelotti and others of our research team and Noah Snyder For some new NSF funding we have to look at anthropogenic sediment and Anthropocene streams throughout New England and the big Atlantic region and then a paper be published on this a few years ago All right, so why does it matter? It turns out that when people see these deeply in size streams and hide banks and collapsing banks They attribute the problem almost always to whatever they can see happening today in the landscape and that might be cows it might be Urbanization might be the building of Walmart's parking lot and They tend to restore them are often associated with putting boulders along the banks That was more commonly done a few years ago than now fortunately And it can cost quite a bit of money and it doesn't seem to be very successful It's slowing the rate of bank erosion and reducing the amount of fine sediment going into waterways That ultimately might go to the various bays and be impaired water bodies such as the Chesapeake Bay And when we first began working on the origin of the sediment that we saw in the stream banks You can see me back here in the background of Mike Browneson the foreground We were wondering about these various types of deposits This is probably a reworked look right here And we went down to look at some of the sites where a reds woman of Johns Hopkins and Luna Leopold from the USGS and then Berkeley had worked throughout the 50s 60s 70s 80s and 90s and We began to realize that every one of their sites that we went to We could find evidence of a mill and in fact at this site the restoration was called Whitton's Mill Park after it was done And we began to realize that all these places where they could see this record of the story of sediment burying a Holocene wetland and then a deeper Pleistocene rubble layer were associated with some kind of recent human activity that caused Ponding of water or flowing of water and rapid sedimentation And of course there was plenty of sediment coming off the hillside during early land clearing and farming and charcoaling Etc that requires us to think a little differently about landscapes things that happen to be stream banks today Haven't always been and in fact in this particular case nothing here is really truly smoothial and origin It's in fact the base of it was a hillside essentially and then a wetland So we've been recommending that people might want including ourselves And I want to reconsider how we've used things and I use an example now this quote anamorphosis Which we can best illustrate with a painting from Hans Holbein the younger We can see here is there's some object. We don't recognize and if we if we really go to the right and look 90 degrees Along it and get next to it and look right along the painting. We see it's a skull So we have to shift our view we have to view things from a different perspective And instead of saying look at that screen channel and look at the bank erosion Which might be from excess stormwater runoff et cetera rather could it be from a history of land use change and a Periglacial history of rubble formation, et cetera that it is ultimately controlling these trajectories are controlling what's happening in the landscape Not just the most recent few decades or centuries of human impact and There are many classic papers which are quite phenomenal in terms of the detail the observations The writing is beautifully it's beautifully written and they talk about the origin of these valley bottoms as being natural So that this particular surface here was described as a natural ruler floodplain and Luna and red to recognize that they're very common and very typical But and they try to explain it as this meandering thing you can see here Which is Seneca Creek migrating back and forth and depositing rubble on one side as a gravel bar Depositing fine sediment above as an overbank floodplain system and many streams that west or are like that in fact But it doesn't explain in the long term the streams in this region It explains the modern and sized Anthropocene streams, but not ultimately all the rubble down there or even the bulk of the historic sediment Right and so here's an example then of the mill that we actually found evidence of that would existed downstream from where Reds and Luna had done quite a bit of their work along Watts Creek Watts branch So the mill dam was here in the mill building was here This is a painting at the Smithsonian that we were able to go look at and photograph and it was painted by William Henry Holmes It was one of the early associate directors of the Smithsonian So the early work where Reds and Luna had done protections with actually along one of these and size streams where there had been races and so forth What happens when a dam is built in a valley bottom? There are many examples. There were some 16,000 dams in Pennsylvania in the 17 and 1800s state has pretty good records of many thousands of those And when a dam is built you can see one under construction here a base level is the base level is raised There's a higher level to the water surface Which you can also see over here with an older mill and that raised water level and that ponded water that are used to help Turn a wheel in the case of the early mills and later turbines So these are quite charming and they were ubiquitous and we associate them with a kind of bucolic landscape But they're actually industrial that's an industrial landscape and they were associated with a lot of activity and economic Turnover what happens in humorically is a dam is built perhaps where there was a wet meadow as in the case of mid Atlantic Piedmont Valley Bottoms and Sunridge Valley Bottoms The dam is built. There's the ponded water level the incoming sediment is trapped behind that maybe not all but some and it Rises up to that level and we can actually test that using airborne LiDAR So here's a pro that we've made using LiDAR for one example There are many we can see that Harris surface, which is the historic sediment and note that it's not just a horizontal level graded to the dam But there's a sediment wedge buildup that is a new transport slope Mike run us to put together some very nice stuff about this since this PowerPoint will be online You'll be able to you have a copy of you can go and check out this website. He also has On our website he's even showing how you can locate some of the mill dams it used to be in the region We published on this work in 2008 in the cover of science here's a LiDAR derived image showing the various steps in the Valley bottom Associated with the dropping below different dams. So there are multiple dams often today They're the sites of bridges and road crossings and so forth and the modern streams are cut into that historic sediment Which buries tow slope? We were shocked to find how many of these dams existed And they're not usually in the National Infantry of Dam's database that your network of engineers had because they're too old Too small usually, but there are many of them State of Pennsylvania is one of the leaders in the nation of low-head dam removal. Many are unsafe. They're obsolete They're expensive to maintain and this is just the ones we know about These are actual locations in the straight maps and it was Bob who first began going to the straight maps at his local Society and digging these out and plotting them up in GIS and then later Micrones worked with us and many students We were just astonished to see that the milling had affected so much of the waterways Well, we went and checked the laws the early laws We read about the mill ax and then the mill crowding ax We saw that it was actually to be expected because these were ways to make money And it was and there was no other major sources power at that time So of course people would put in as many mills as they could so again This is just the ones we know about here in Pennsylvania in these three counties on The connoisseur and the brandy wine at other rivers We also used 1840 census data and found that there have been 65,000 water powered mills as of that point in time with a very large Concentration right here in the bit Atlantic region with the dot size proportional to the number of mills in a given county at that time And you can see then compared to the glacial limits Where we're located here in the bit Atlantic region and the Chesapeake Bay and it matters because we have a lot of Thoracic sediment which is now washing out of the waterways as these dams breach and and also as the dams breach Streams are generally incising down to that place to see in rubble and exposing these Holocene wetlands And that's giving us outcrops that might not even have even existed 50 years ago As Thomas Jefferson said no neighborhood has no there's no neighborhood without a mill That's the ice margin All right, so you can I'll show you what happens when a dam breaches if it's filled with sediment as these older ones are This is based on the work of Alessandro Contelli at University of Minnesota Get back and get that again So a dam breaches as an experiment and there's a vision a nick point propagates up the valley There's bank erosion down here now and no bank erosion up there Once that drop in base level makes it up through that reservoir that former reservoir We'll then see that there's channel widening going on all along it You can see the bank collapse of this non relatively non cohesive weak material And that's what we have here although in our case there's some cohesion to it You can see the buried black soil. That's the Holocene wetland. It's this big spring where we're now doing that long-term restoration monitoring And so the bank retreat here the bank lateral bank erosion is Not the result of any change in land use the land use here has actually been the same for centuries It's the result of the fact that downstream the mill dam had breached a number of other smaller dams They've been built in the valley had also become obsolete and failed more along with no longer maintained So this allows us to see that black buried soil Like the one of Great March, but the one of Great March is not buried and the modern streams can now pick up some of that Hope Pleistocene gravel and sand and so forth and use it to build some small inset bars There are many efforts to try to plant trees along these unstable banks In the effort to make riparian corridors and there were 3,500 plants here at the big spring run site But by the by the mid 2000s most were gone. There were a dozen a dozen left So we were approached about what to do about this site We recommended a new approach based on our and our interpretation It's a very young stream actually where there used to be a very old wetland. In fact, so we proposed this to the state and EPA We said that in the Pleistocene that valley bottom would have looked much like this frozen with some solid lakes and Then in the whole scene would have looked much like the right a whole of seen wet nettoe And that's based on our thousands of seeds that Ali new beverage extracted and identified with Bill Hill Gortner and Jeff Hartran and So what's the Pleistocene period with tundra to post the whole of team wetland and then it was buried with colonial no pond sediment and Then that was in size as the dam breach and then trees were planted on top of that stack of reservoir sediment and Then it's quite dry actually up on the stack of sediment We proposed just remove that sediment rather than try to stabilize the banks with boulders Let's just remove 20,000 tons of historic sediment So we did that and on the right you see this is the wetland today That is the post restoration wetland and that's the same view these trees are those trees So that's it during restoration Prior to the establishment of all the vegetation and we tried to establish a vegetation week It's very similar to what we have today It looks a bit aggressive to glad there was this Equipment even though it's on a very full of threads that have very low pressure per square inch The guy in the cab actually was getting RTK GPS and was digging down to the level of the black soil based on our survey data This is land studies did the restoration working with us and many others So they simply removed that 20,000 tons of sediment and prior to that We had done eight years of monitoring with the US Geological Survey and other agencies and we're still continuing that Monitoring we selected just like to site because there had been monitoring there in the past But here's an example standing along the screen channel before Restoration and the exact same view after restoration. So all that's been done really is remove sediment lower the banks And then we often are asked where did that sediment go? It ended up by half a stance after a few years outside our backdoor practically near Franklin and Marshall campus It's a Brownfield redevelopment site and they needed top soil good top folks. We seem to have lost audio with Dorothy We're gonna get it back. Just give us a couple minutes. Nick. Can you hear me? I'm being told that there's no audio right now Yeah, Dorothy. We can hear you go ahead Go ahead. All right. Thank you. Should I back up do you think? Yeah, about two slides. I think but all right. Thank you Thanks to my crew can running into tell me All right, so let's get back here. All right back there you guys Yeah, that looks right. All right So before and after restoration all the sediment on the left is now gone There's bank for no longer there to a road and we're actually by the way I should mention we kept track of those erosion rates and There's a sediment now. It's posited nearby in a Brownfield. It's been spread out since then and revegetated So we're doing all these things to try to understand Whether or not we can actually make a shallow vegetated flow system that will be Sustainable and stable much the way the Holocene wetland was and we're trying to enhance hydrologic exchange Hyper re-exchange between service and ground water improve water quality by reducing sediment loads by Increasing hyper re-exchange we're getting de-nextrication and we're monitoring that remote monitoring carbon retention, etc So please check the website to get many more details There's a lengthy report there and many publications that are in the works will be coming out and a lot of updates of data So with the USGS we had a gauge station up here at the Coming into the restoration site which begins right there and then it's restored all the way down to that fence line We have another gauge station over here monitoring what's coming in at this end and then a third at the downstream men monitoring What's leaving the restoration reach so we're keeping track of what's coming in and what's going out and how that's changed with time From eight years prior during the eight years prior to restoration and then ever since and it was restored in 2011 We fly over it repeatedly. We also use a drone We have web cameras that we have used Jim Moore and Bob Johnson Robert Johnson had set up a web camera here and another one up here You can see the end of the restoration reach right there This is not restored and then down here. This is not restored So in the restoration reach there are multiple little channels some of them are hard to see but there are many little Multi-branching channels and it has become a wet meadow system We're fortunate to work with the NASCO with Marianne O'Call and Keith Brendan Hodge and Keith Williams and others and the store zoo here at F&M Who's been doing pieces work on this and post-back work using ground-based lighter a repeat scanning of ground-based lighter To actually try to look at vegetation over time and we're also doing a lot of repeat RTK GPS surveying But with the ground-based lighter what's fascinating is we're able door is actually working on trying to quantify the vegetation And then working with Lara Larson and Danielle Watson as a Berkeley we clip the vegetation We weigh it we compare those estimates of the the volume and mass of vegetation And then we're also monitoring with the USGS and part of door thesis work the amount of carbon accumulating in the soil Because there is some very fine sediment accumulating in this part of the restoration reach with time So it's a really neat way of using ground-based lighter are to assess what's going on And then we've done some flow modeling with our parola at University of Louisville and Ward or both for at land studies What we're doing I won't show the before Restoration flow modeling, but by taking a given flood event we can look then at What happens during a flood we take a given gauge record for a given flood from our USGS gauge stations You can see it out here during a flood and the water spreading out over bank And then we can model that to see how the shear stresses change along the valley when the blues are showing That's very low shear stress is because the water shallow and spread that wide Whereas prior to this if you go check our website, you'll see the previous on restoration modeling We had a deep narrow channel. It was carrying this size gravel so place where the headwaters You can see the drainage divide in the background a place that was headwaters limestone spring many springs Was carrying this size gravel because of deep incision into a storage sediment. So it's remarkable So I'd like to end just by saying that we are really enjoying working on all these projects It's the I was I'm very happy to see that there are so many people who are involved in this work and contributing in so many ways Looking at this plant and animal species that the bog turtles, but they've been bound to work and so forth It's been very rewarding and we look forward to your questions and future communication. You can email us You could check our website, etc. Thank you very much Great. Thanks Dorothy right now. We're going to open it up to questions again. I'll Tell you down in the lower right-hand side of your screen there in the Q&A you can put questions in there And then I'll read them aloud as appropriate Just to get a start I have a my own question You touched on it a little bit in your presentation Dorothy But you talked about all the sediment you removed in your latest project and you're using it now on F&M Can you explain a little bit more about what that is and what you're doing with it? Yes, and as I did mention at the beginning that Bob Walter is here So I'll be looking towards him in case you have any more comments to add to this But we had done a lot of testing Bob's a geotemist and we had done multiple tests one that sediment over many years It's largely silt and we actually think it's largely windblown silt that is a legacy of Glacial activity and post-lacial activity and then that silt which had been worked into the soils on the hillsides Had moved down the slopes during European land clearing and farming and grazing and so forth and ends up in the Valley bottom So the fairly uniform in size and fairly organic rich in fact And so it would be it's a shame to not do something good with it and we've long thought that it could be put to a very high purpose hopefully and There one could put it back on the hillside and that's happened to some restoration sites There are others now like this particular restoration project just not as advanced in terms of the monitoring and the many collaborators But there are others Because it was high quality sediment high quality fine-grain silt It was valuable and it could be used for these sorts of brownfield redevelopment sites But there is the cost of trucking and that is a limiting factor during times of low gas prices That's much easier to do than during times of high gas prices But in this case for this one brownfield redevelopment They were looking for soil and our soil happened to be relatively close by so it was bought along with some other top Soil and then hauled here great, thanks Question from the audience What nutrients have you found in your monitoring and is there a temporary water or sediment quality effect during restoration? yes There are relatively high nitrate levels in the groundwater at the big spring site and In the surface water, they were also picking up in addition to the nitrates relatively high levels of phosphorus And Bob had determined that there is quite a bit of phosphorus in this historic sediment absorbed on to the Particles and clay particles and that during bank erosion it was actually then transported along the surface water during flow events So there were both there was phosphorus there carried along with the particulate matter and then nitrates in solution and The phosphorus is one thing that we think we've been able to reduce quite a bit because it's no longer that the amount That was in the stream banks is no longer there and Bob has done some fingerprinting work with Alan Gellis and others some chemical fingerprinting They've been able to show that in fact there is now Much less of a signal of phosphorus in the the sediment load than there was prior to restoration The nitrates work will take much longer time to resolve we think because we have groundwater wells with EPA and USGS If some 30 I think and we have to be zometers And they're they're still working on all that water quality data to try to determine if there's been a Change post restoration and one of our hopes is it was the increasing carbon retention going on and we know that's happening that there is carbon retention We hope that that will lead to greater denitrification in that wetland valley bottom Places like Great Marsh have some of the highest water quality in the state of Pennsylvania an example of how these wetlands can really do great things for Reducing nutrients reducing nutrient lows below the abnormally high levels in many places today Okay, the next question I have Paul Stacey he's asked I wonder beaver damming on the first order first and second order streams during pre colonial times might have build up big reservoirs of Headwater sediments, and then that was released as beavers were hunted down in that area. What might Is this coincidental with the mill dam construction and rapid filling of those sediments do you have any insights into that? Yes, we do and I'd love to talk more with that person later, too We really like we like the beaver questions and we get them often during talks Well, um, Bill Hull Gardner also is doing some research on this idea colleges. He's at Johns Hopkins We have never found evidence of beaver Except for it may be one case and any of the valley bottoms we've worked in and I mean when I say evidence I mean in the black soils the buried Holocene black soils. We don't find the beaver dams We don't find chewed logs one site we might have and we always wondered about that We're certain that even if they had been there Which we think they might have been that there wouldn't have been large amounts of sediment trap because we need the land Clearing to get the silk released from the hillside that was very stable in the tree covered and grassland covered hillside So that the silk was stable in the Holocene There's no record of a sedimentation in the Holocene in any of these valley bottoms prior to European arrival So that there was no still to accumulate behind a beaver dam We wonder whether there might have been beaver here and one of the ideas that Bill has come up with based on some extensive literature review now is that Where there is evidence of beaver It's usually in headwaters where it's more mountainous headwater streams for example in western Maryland Rather than out in the peat the lowland peed months of Lancaster County, you know parts of Maryland and York County So maybe the beaver didn't like those wet meadows very much for some reason. They're wide They're very maybe they prefer to go off into the side ravines, so we might we might find them over there in the steeper sides would be teres There's no archaeological evidence of them yet that we know of Thanks for the the next question is what time of year did you see that thermal contraction polygons on your Google Earth imagery? Yes, we have well we look usually and it's what Gow did in September August September when it's getting drier and crops have been harvested if they're still crop standing we can't see them and We have found that in a given area we can see them on one field and not on another even at that same time of year and Yet we know they're there in both cases and maybe in another year We can see them in the other field and it has to do them with the timing of cropping we think So that's important and it's and the things that they're growing it seems matter One of my students has been saying in fact that she thinks we need to focus on a certain type of field where they might have had I think she said corn maybe that drives the soil more than soybean I'm not sure but certainly September October, but not every September August September. Excuse me some years We've done maybe the soils wetter The next question is could you speak to the Applicability of the methods and approaches that used in Pennsylvania, Maryland for red for river restoration to other areas in the US that might not have That might have other types of anthropogenic influences not necessarily just dance Yes, what I would say is From what we've learned it's so important to understand the the entire trajectory of landscape development And how it's related to the hydrology in our case That it was a combination of a lot of sediment from frost shattering Moving down the slopes into the valley bottoms and then with saw having high groundwater tables because it's a you know Mid-latitude temperate humid temperate region so groundwater is high and in fact I didn't go into the details But we see different types of wetlands Based on their position with respect to the long-term groundwater table So in another region if there weren't if there hadn't been a high groundwater table and a wet meta That would matter in terms of restoration if there were steeper slopes and greater sediment supplies You know it's coming off the Rockies for example that would matter New England North Carolina though seem to be have many similarities to this region Albeit in New England it was glaciated the going down to North Carolina where it's certainly much warmer And it probably didn't have much permafrost if any except at higher altitudes up in the higher mountainous areas We still see this Carl Wegman's work for example shows that and other people now Dan Richter is working there at Duke and with his colleagues that there is plenty of historic sediment and That if the incision and bank erosion is largely the result of a recent dam breach And if the storage of that sediment is largely the result of a dam that was built sometime in the past Then that would really matter to the restoration approaches So we often say it's important to diagnose the problem correctly to not immediately assume that it's You just stormwater runoff that really to look carefully at the history of that landscape and to try to understand How did the sediment get there in the first place and when and what was this landscape for the last so many thousands of years? And it would be different in each part of the country You know we as we go south in fact we know we're going into the zone of discontinuous permafrost We can tell that geologically and stratigraphically and as we come out of that we get into much more chemically weathered rocks for example So there is a difference although we still see ubiquity of wetland valley bottoms great Next question is you mentioned that this wetland restoration can be more successful than using boulders to protect the bank erosion What about compared to regrading the banks that are planting a riparian buffer? You think this would be unsuccessful in this area? I Wouldn't say unsuccessful and it would depend on the bank heights But when we're close to a dam downstream close to them and dams vary in height of course So some the mean dam height for Lancaster County was about I think it was 12 feet But in other places we've seen dams as high old dams as high as 30 feet So in those places it's it's a lot of grading there's an exam a dam along Gunpowder Falls for example, it's 30 feet high Hoffman dam that would be a lot of grading in that case But in lower in lower dam heights or way up the reservoir way up the valley where it's only a few feet of historic sediment That could work and it might be a cheaper alternative Just to remove some of the sediment and one of the restoration sites We've been to with land studies. They couldn't remove all of the historic sediment due to the cost But they remove some it was more than just grading the banks back They actually removed tried to remove down to a wetland level for a swath down the valley It's been very successful at maintaining a wetland and environment down there but I think in some cases where there's not a lot of historic sediment that Grading back some distance and planting riparian species could be helpful certainly The triage approach will be would be a best I think find a site We've often said if you can if you find a site We have lots of bank erosion There's a possibility of doing what we did here for example and making it a park and so forth One could reduce a lot of sediment loads in that case other places it might be people living there buildings etc. That can't be done Thanks, it looks like that's all the time we have for questions today as you I wanted to thank you Dorothy and For our participants as you sign off the webinar, you'll be reject redirected to our website This is where you'll find the information on today's webinar And we'll be posting the presentations and recording in about a week or so With that I'd like to thank our speaker again. Dr. Dorothy merits and thank you all again for participating This concludes the webinar and have a great day Thank you everybody, and I'll just end with great work one more time to have a happy landscape Good day