Pennsylvania Legacies #218: Leave It To Beavers

Josh Raulerson (00:01):

Today is Friday, June 28th, 2024. I’m Josh Raulerson and from the Pennsylvania Environmental Council. This is Pennsylvania Legacies. Beavers have been called nature’s engineers and recognition of their instinctive talent for creating dams and lodges on streams and creeks. The presence of beavers is a sign of a healthy waterway, and their structures provide a host of benefits for wildlife and watersheds. But in populated areas, beavers are often seen as a nuisance. Their dams can lead to flooded pastures, farm fields, and roads, and can even disrupt public water supplies At the same time, the loss of beaver populations and the structures they create has exacerbated ecological problems caused by human activity. That’s why Matt Wilson, director of the Freshwater Research Institute and Center for Environmental Education and Research Field Station at Susquehanna University decided to take the engineering upon him himself. He’s been constructing manmade beaver dams or what researchers call “beaver dam analogs” on a stream located on campus. Wilson has partnered with the Department of Environmental Protection to build these structures and study their effects on the landscape, the benefits of which so far have surpassed expectations. Here’s Matt Wilson from Susquehanna University, speaking with my colleague, Derek Maiolo, about his unique approach to watershed restoration and its potential use in watersheds across the country.

Derek Maiolo (01:30):

Matt, thank you for joining us on Pennsylvania Legacies.

Matt Wilson (01:33):

Thanks, Derek. Happy to be here.

Derek Maiolo (01:35):

So I’d like to start by asking what makes beaver dams good for the ecosystem as opposed to larger manmade dams that I know have been criticized for causing issues like disrupting fish and trapping sediment, and that, you know, people are actually trying to get rid of. What makes beaver dams different?

Matt Wilson (01:53):

It’s a good question, and I get that question a lot actually. So one of my favorite responses to it is the saying that I’ve heard a lot from the West that beaver taught salmon to jump, you know, so beaver of co-evolved with every other aquatic critter that we have, and we removed beavers from this system between two and 400 years ago. So our idea of a natural, pristine aesthetic, what we think a pristine stream should look like is this single narrow channel. And, you know, no obstructions, like it’s, it’s got riffles, it’s got pools, riffle, pool all the way down. But in reality, 400 years ago, that stream would’ve probably had a beaver dam every 30 yards, and it would’ve been this big complex of ponds with side channels coming off of them. It would not have been this, this linear path of anything.

Matt Wilson (02:48):

And so I think that, getting to your question, I think that’s the, the difference here is, you know, if you think about a hydro dam or even say a run a river dam, anything like that, it is designed as a hard, permanent structure in one place. So even those shorter dams, the run of river ones, it’s a one physical structure that’s never going to move. And it permanently accrues sediment behind it. It’s usually built much taller. You know, even if it’s only six feet tall, that’s still taller than almost all beaver dams. It’s built in a way that they usually don’t want it connecting to the floodplain, because if it connects to the floodplain, then it’s going around the dam and you’re not storing the energy that’s behind it or storing the water. So in the case of beaver dams, you know, we’re trying to create alternate channels around the dams.

Matt Wilson (03:38):

We want that complexity. We want them to be permeable. We want water to flow through the dam itself, and fish can go through a remarkably tiny spaces. So, you know, that’s one of the, the fears we always get is, well, you’re gonna prevent trout from going upstream. No, they’re gonna be fine. I’ve, I’ve seen trout move through spaces that I would not imagine possible. And the same with smaller fish too, like scalping. So I think the biggest difference is the permeability, the permeability and the impermanence of them. The idea is that the, the structures in their initial form only exist for maybe two to five years. And so as they blow out, that’s actually a good thing. Because, you know, you, you’ve created a new channel wherever the, you know, changes the flow path. And we might put in a new dam downstream with that, just like a beaver would, so that we keep holding back water, but we upgrade the entire system.

Derek Maiolo (04:32):

And, and that re-channelization is how it naturally it would occur, or even really without beavers. Right? Like a stream naturally wants to weave, it’s the, the classic lazy river, right?

Matt Wilson (04:43):

Yeah. I mean, my, my favorite example of that that I use with students sometimes is I’ll zoom in on Google Maps to anywhere in the upper Mississippi where it’s between two states because you see parts of one state on the bank of the other, where the river has moved in the last 200 years. Rivers don’t want to stay in one place, we’re the ones who want them to.

Derek Maiolo (05:06)

What were the ecological issues or conditions that you were seeing that led you to studying beaver dams?

Matt Wilson (05:14):

So, I read a paper a few years ago about how beneficial beaver dam analogs were in Washington and Oregon, and how much they’d reduced temperatures by increasing groundwater storage, diversity in bugs, biomass of fish. Everything was better. And so I was really curious about this. We don’t see these artificial beaver dams on the east coast really much of anywhere.

Derek Maiolo (05:39):

Is there any reason why that is? Like why, yeah, why that started in the west and hasn’t hadn’t moved east?

Matt Wilson (05:45):

Fear of beavers or, or hatred of beavers might be a more accurate term, frustration with beavers?

Derek Maiolo (05:52):

I see. Yeah. I’ve heard some comments from people who yeah, maybe are not too happy with when they see a beaver in, in their backyard or in their, in their stream.

Matt Wilson (06:00):

Oh, I’m, I’m thrilled when I see them. That means that something’s working.

Derek Maiolo (06:03):

I am too, but I’m also from the Northwest, so that might be my, my Oregon roots. But so, but sorry. So you were mentioning you had, this is something that was, you’ve seen in Washington and Oregon, that this is what got you on that path?

Matt Wilson (06:13):

Yeah, so it sent me down wanting to know more and wanting to figure out why it didn’t happen around here. I saw this sad little stream that we have at our field station on campus. It is the most deeply incised stream I’ve ever seen outside an urban area on the East Coast. And what I mean by that is basically the stream forms of deep U, and so the banks are really steep, comes down to a flat bottom, and it’s completely disconnected from the flood plain. So when it rains, when there’s a big storm, all that energy, all that force is kept inside the channel. It can’t dissipate outward. And so it just keeps down cutting and keeps eroding more and more every time it rained. So that’s what got me thinking about beaver dams again.

Derek Maiolo (06:55):

And so you said you had read some papers on the beaver dam analogs. How did you go from reading about these to starting to implement this into your own work?

Matt Wilson (07:04):

As far as we know, it’s the first time it’s been done in Pennsylvania. Or the very least the first time it’s been done working with state agencies to make sure that they’re aware of the process. It is been a great conversation working with Department of Environmental Protections, DEP, on this project because we’re doing it on a stream that’s ephemeral, so it doesn’t flow year around. There’s no, you know, risk if it fails of doing harm to aquatic life or any kind of damage. So it’s, it’s a perfect proving ground for this. But we had a long conversation to figure out, you know, how do we get to the point of actually getting it in the ground and following regulations and doing all of that. So I’ve wanted to do it for about two and a half years, and last fall is when we actually installed them.

Derek Maiolo (07:55):

And what is the name of the creek where you installed this first dam?

Matt Wilson (07:59):

There, there are, there’s no name on the creek. It’s so small, so it’s it flows into Pence Creek.

Derek Maiolo (08:03):

Okay. But this is the one, is this this stream that you were talking about that was—

Matt Wilson (08:07):

Yeah the one on campus. Okay

Derek Maiolo (08:08):

So can you describe what these beaver dam analogs look like and how they are installed?

Matt Wilson (08:16):

Yeah, there’s actually a handbook for how to build beaver dam analogs and other related structures out West that Utah State came out with it. It’s fantastic. But the designs that they have, like, they gave me great ideas, but they’re for places where you have a lot of willows, what they’ll usually do is put posts in the stream perpendicular to flow a few feet apart, and then take willow branches and sort of make a wicker weave between the, the posts and the willows. I mean, you add more, make it more dense than that, but it, that’s sort of the base is this weave between the posts where our dams are, we don’t really have any willow available, but we have far more Bradford pears than I ever hoped for. So for anybody who doesn’t know, that’s an invasive species, that can cause a lot of problems around here.

Matt Wilson (09:05):

So we thought, you know, why not two birds with one stone and use the Bradford pears, but they are very brittle. So we actually ended up creating two lines of posts parallel to each other, but perpendicular to the flow about a foot apart from each other, and stuffing these branches and these trunks in between and sort of using them to just hold everything in place until we get a few storms and material flows into the dam and gets caught and trapped. And then it all sort of settles in. But in general, the construction isn’t very complicated.

Derek Maiolo (09:38):

Yeah, I, I saw a photo of you with like a power drill at one point, right? Is that how you got the stakes into the ground?

Matt Wilson (09:45):

Yeah, so we actually had a post pounder, a gas-powered post pounder that we started with to do this, and about a third of the way through the, the cast iron on it broke. So most of the dams were just human power with a sledgehammer.

Derek Maiolo (10:00):

Just like the beavers use, right? <Laugh>

Matt Wilson (10:02):

Yeah. They don’t have iron, so a little more industrious for them.

Derek Maiolo (10:06):

But I am curious, like how, how much of this design do you know, was based on how actual beavers are, are engineering their dams? Like how, how close is this to a true beaver dam? Are the benefits the same too?

Matt Wilson (10:19):

Yeah, so structurally they obviously look human made, like beavers don’t put posts in the middle of their dams, but it’s remarkable. I’ve seen some out west that have been in streams for a long time, and they start to look like beaver dams after a while because they accrue all of this material in front of them, you know, leaves and sticks that are flowing and the stream will get trapped. And eventually that just sort of creates this like sheet over the, what we had built originally. And it starts to look a lot like the dam would have anyway. If you can ignore the posts that stick up every once in a while so visibly we get kind of that same aesthetic after a while. But ecologically the whole intent is that they perform the same functions as a natural beefer dam would.

Matt Wilson (11:07):

These aren’t, you know, dams in the sense that we think of with human construction where they’re impervious. These are are permeable things that water can flow through but also retains most of it during a storm. And so that retention slows down the flow trap sediment pulls that out of suspension in the stream, prevents it from flowing downstream, especially in our watershed toward Chesapeake Bay. And at the same time, by building these dams up to bank full in this deeply incised stream, we’re now pushing water into the flood plain, which in the five years I’ve been here did not happen once, and now it happens every single storm. So we’re sort of getting that reconnection of the floodplain creating complexity of the habitat inside the channel. And hopefully by retaining all this water and slowing down the flow, we’re going to recharge the groundwater and maybe make the stream perennial again.

Derek Maiolo (12:03):

And why aren’t the beavers doing this work for us? Right? Like, why aren’t, why aren’t there natural beaver dams in this area?

Matt Wilson (12:10):

So there are where we let them, and I think that’s the key here, is if you go to any remote stream in Pennsylvania, you’ll find beavers and you’ll find dams everywhere. And you’ll find this wonderful complex of ponds and deeply saturated soils and complex braided channels with trout everywhere. Everybody’s happy. Now, if you go to half the tributaries to Pine Creek they all have this look to them, and it’s amazing how much beaver activity there is in places like that. But, you know, down here next to small town in a stream that doesn’t flow year round. So our, our case is a little bit different because without water, it’s tough to have the beavers, they’re not here because we won’t let them be.

Derek Maiolo (12:57):

Why, especially in the East, is there an animosity towards beavers?

Matt Wilson (13:00):

Yeah, I think it’s definitely a perception thing. There are cases where like, there’s infrastructure problems with beavers. You know, you build a dam next to a culvert, and there’s all kinds of problems for a road. But we know how to deal with that. There’s a consulting company that started all of this at this point, I think about 25 years ago in Vermont, coming up with ways solutions to allow beaver coexistence with infrastructure. And so they have all of these structures called “beaver deceivers” that will prevent them from blocking the culvert or prevent, you know, if there’s a blowout of the dam, prevent it from blocking the culvert and, and keep water flowing. Like we, we know how to deal with this. We know how to coexist with them.

Derek Maiolo (13:48):

In the stream where you have installed one of these beaver dam analogs, what effects have you started to see on the ecology?

Matt Wilson (13:56):

The effects have been really astounding to me because we installed eight of these in the fall, just what, seven, eight months ago. And I thought it would be a couple years before we really saw changes in the stream from the dams. And we’re already seeing the first dam in the system. So the one that you know, is going to catch the most coming down into the system from upstream at this dam itself, we’ve already collected enough sediment that it’s almost up to bank full again. So the stream has almost upgraded back to where we want it to be. You know, that’s, it’s a very small area within the whole stretch that we’ve done this, that that’s happened, but we’re already seeing literal tons of sediment trapped by these dams and preventing it from going downstream. And we’re seeing where we’ve extended the dams and where we’re pushing water into the floodplain, we’re seeing a secondary channel start to form, which is exactly what we want.

Matt Wilson (14:53):

So the smaller storms, smaller rainfall events will push water into the floodplain than what’s required now. And every time that happens, it helps recharge the groundwater, it helps add complexity and slow down the energy that’s making its way downstream, which is really what we’re after here. And in channel, what we’ve noticed that’s really incredible to me — before we did this, the entire channel itself was scoured out so much. There’s so much energy going through it that the only substrate, the only rocks in the stream were fist sized or bigger and they’re all completely loose. You know, you’d twist an ankle trying to walk through the stream channel, and just in a few months now, we actually have a layer of fine sediment across the entire channel for 200 yards, and it’s a stable, all the substrates now embedded. It’s, it’s stable, it’s in place, it’s not moving during a storm, which has even increased some plant growth along the edges of the stream too.

Derek Maiolo (15:53):

Okay. Yeah. What is the benefit of keeping that fine sediment and keep keeping sediment in the stream and not letting it rush down?

Matt Wilson (16:00):

Yeah, so it, it’s twofold. One is the big picture Save the Bay mentality of that. We, we don’t want to export our problems downstream, sort of the, we all live upstream and we all live downstream problem. But the other one in this system in particular is that we want the, the stream channel, the bed of the stream channel to be higher in elevation so that we don’t have this deep edge between the floodplain and the channel itself. So we want to upgrade the stream channel, and the only way to really do that is to trap sediment or plant material, anything else that’s flowing downstream. So through time, you know, we hope that a grade’s up high enough that the dams that are now there are mostly buried. This is my dream, 10, 15 years from now, right? It’s not, it’s not something that’s going to happen overnight. And, and as that channel degrades, then the dams may not be as critical for connection for recharging groundwater. You know, they’re not designed to be permanent either. The whole point of using wooden stakes is that at some point they do decay and they do change because natural beefer dams don’t stay in place forever. They move.

Derek Maiolo (17:15):

Interesting. I never thought of that. And, and you were using a term, I want to make sure I understand. When you say aggrade, is that when you are, is that the that seems to me the antonym of degrade, right? Like is that a rebuilding up of—

Matt Wilson (17:26):

Yeah, basically the option opposite of eroding in this context.

Derek Maiolo (17:29):

The Pennsylvania Environmental Council and our affiliate organization, the Pennsylvania organization for Watersheds and Rivers we work a lot with community watershed organizations that are often small volunteer groups. So I’m wondering how replicable these beaver dam analogs are. Like, is this something that anybody, you know, with, with some stakes could do on their own? Or is, is this something that people should leave to the professionals?

Matt Wilson (17:55):

So I’m going to say a little bit of A and a little bit of B. We actually did the install of these dams with entirely volunteer work. So we did almost all the dams. I did the first couple with a couple faculty here just to make sure we knew what we were doing before we trained anybody else. But we did six of the dams in one day with about 20 to 40 volunteers, depending on time of day. You know, they filtered through in and out. But we had six complete in one day, and the only expense was the wooden stakes that we bought, which ended up costing about a thousand dollars in total for, for eight dams like that. In terms of your, your accessibility for a restoration project, I’d say this is about as low lift as it gets if you’re going to do, you know, some kind of large-scale restoration.

Matt Wilson (18:47):

So absolutely feasible for a small watershed group. The other side of that that I was thinking about, the technical part is the, they’re not a one size fits all, everywhere, all the time solution. The whole point is to flood a floodplain. So, you know, sometimes that’s just not feasible. And we were just having, I was talking to someone from DEP the other day about this, you know, we actually don’t know enough about how when we create these ponds, when we create the, the beaver dams, how the water infiltration rates and sort of the improvement of groundwater quality and temperature of the water changes depending on the soils. So if you have, say, an area where it’s all cast limestone which is pretty common in central pa, especially in farmland, you know, this is really porous. Water will infiltrate really quickly, and then you have a large area that can store that water underground and keep it cool most of the year so that when the groundwater comes out, it’s going to be cold.

Matt Wilson (19:54):

So in an area like that, it might be the perfect solution, but if you’re in a spot where it’s primarily clays or you know, entirely clays, which is some other parts of the state, and you don’t have any infiltration, are we just creating some bath water? And I’m not saying that we are, but the, the reality is we don’t know. We haven’t done enough research on that part of things. So, and I think definitely in systems where you’ve got infiltration where you’re going to recharge groundwater, they’re a great solution. They’re a great idea from what we’ve seen so far. They’re great on really small ephemeral systems for just trapping sediment and creating complexity for habitat. But scaling that up I think is the next big challenge that I really want to tackle.

Derek Maiolo (20:40):

And you had said too that you, the, one of the reasons you tested on this stream is that, there isn’t really much aquatic life. Am I remembering that right? So is the next step to build up to that level or like, what, what’s next as far as your beaver dam analog goes?

Matt Wilson (20:57):

I would love to do this on a flowing system in PA now and think more about doing this once has created all kinds of ideas and discussion and data. We’re doing this at a university, so we’ve got every measuring device I can imagine stuck in the, the system, but using what we’ve learned so far to try it again somewhere with flowing water, you know, start small, right? But see what kinds of outcomes we can generate. And if they are, the benefits we hope and expect for.

Derek Maiolo (21:28):

I’d read some articles where your students had gotten involved. What was their experience like?

Matt Wilson (21:33):

Their involvement has been a very wide breadth of parts of the project. I’ve had a couple students working with me who have just really gone headfirst into the dams themselves in terms of construction and maintenance. So we built these in a dry system where we have to guess where flowing water’s going to go after you’ve added an obstruction to the system and then a storm happens and you look and say, oh, that’s not what we thought would happen. And so there has been this iterative process of going back out and doing some repairs on the dams and extending them to places, sort of stabilizing the edge of the dams to make sure we’re not eroding the banks, that sort of thing. And so I’ve had a couple students who have really taken to that and have been going out and working as the human beavers to do these repairs.

Matt Wilson (22:27):

We’ve worked with a couple of other students who are really into the, the data side of things. So one of the things we did is put in a permanent photo point at each dam that’s a fixed stake, so we know exactly the right height, the angle, everything, so it can take the same photos over time and do some analysis of those to see how it’s changing. And so we have one student who’s got really excited about that part of things. We have, if I’m counting right, three research students working with us on into the fall on these one who’s thinking about as we create these new channels in the floodplain, are we changing the plant community that’s there? And as we’re inundating the floodplain again, are we changing the, the plant community? We’re doing everything that I can possibly imagine. We even painted some rocks in marine paint that we’re going to release into the stream and see how fast they move downstream. So we’ve got these, you know, neon turquoise rocks that are going to find their way downstream.

Derek Maiolo (23:25):

Are you teaching a class on beaver dam analogs, or how, how does this work fit into your courses that you’re teaching?

Matt Wilson (23:31):

I wish I was teaching a class on beaver dam analogs. That would be my favorite class. I do teach a course on restoration ecology. I teach that every other year, so I’m actually not teaching it this coming fall, but I will the year after. And I, I plan on spending a lot of time in the beaver dams for that.

Derek Maiolo (23:48):

There was a report recently that came out that was looking at the, a number of severe rainstorms that Pennsylvania is getting has increased pretty significantly in recent years. And the reports that I’ve seen similar to as far as the effects of climate change show that we are going to be, be getting more precipitation and in particular, more intense precipitation events. So how do you think something like a beaver dam analog, what role could that play in, you know, in a climate change scenario?

Matt Wilson (24:20):

That I think is above all else the biggest reason to start putting these everywhere in the state there, there’s been a lot of research recently actually about natural beaver dams, beaver streams that are essentially beaver systems, beaver complexes now out west. And the effects of those on wildfire spread because you create this green ribbon, even when the upland areas are dry, you’ve created a much wider floodplain that’s wet year round. So when a forest fire hits that, it becomes a fire break. And, and in the worst case scenario, it jumps the floodplain altogether. So there are these images, especially I think from Idaho is the last one I saw of you see this green ribbon surrounded by burnt land. So there’s that part of it in terms of water storage is huge because you mentioned, you know, the more, the more rainfall and fewer events, it’s that in between the events.

Matt Wilson (25:19):

That’s the bigger problem in my mind because if all of our rain’s falling at once and we don’t have these complexes that slow flow and recharge groundwater, then we’ve got expressways and all of the rain goes straight back out to the ocean, in which case, you know, you’re getting with every year less recharge in the groundwater because you get sheet flow during these big events, you know, it’s not filtering in, and you also get more erosion, you get more downcutting of the stream because you’ve got more force from more storms. And if you down cut the stream more, you’re also pulling groundwater out that was below the stream channel before that’s now getting sucked out so your groundwater table gets even lower. And so it becomes this negative feedback lube, unless we do something to slow down the energy and keep that water in place. So that’s where I think beaver dam’s really add not just resistance, but resilience in urban areas. It’s actually tougher because you, you’re so confined by hardscapes,

Derek Maiolo (26:21):

There’s so much impervious surface, right?

Matt Wilson (26:23):

Yeah. And, and you can’t really, you know within a, the stream system, you’re really not thinking about, you know, there’s very few places where you can allow the floodplain access to the stream or vice versa, just because of hardscapes that are in place. You know, there’s, there, there are only so many things we can do within the bounds of an urban system and city planning. Now new city planning can take an account for that, you know, it’s the old structures that are tough to deal with.

Derek Maiolo (26:49):

I don’t know if you can speak to this, but have you noticed policy or conservation efforts look to the natural world more as time goes on?

Matt Wilson (26:59):

Yeah, I think we’re getting there. Like all things, when it comes to policy, it moves slower than we hope. But even in the past five years that I’ve been working on related restoration work, I’ve seen a lot of change. Some NPA, but mostly like for example, Maryland has started doing beaver dam analogs, you know, these are things that I, I did not expect to start popping up all around the same time in different places, sort of independently of one another. So I think there’s been some, I don’t know if grassroots is the right word, but some independent upwellings — how’s that? — of process-based approaches sort of creeping into the restoration world, which has been great.

Derek Maiolo (27:39):

You did the first beaver dam analog in PA, is that right? As far as you know?

Matt Wilson (27:43):

Yeah, as far as we know.

Derek Maiolo (27:44):

Have there been other instances since the fall of this? Has this started to expand anywhere else in the state or

Matt Wilson (27:50):

Nobody else that at least has gone through the state that we know of and, and they should. You know, I’m going to say that like, it has actually been a great process working with DEP on this and, and throwing ideas and back and forth that has made it better. There’s been a lot of interest though. I, I’ve had folks reach out to me and I know that north Central region has gotten questions too about doing installs in places. So I think we’re, we’re starting to build interest in doing more of it. And the next step is coming up with a, a thoughtful process and approach for deciding when and how to do more. The other good thing about a lot of these processes is that when we restore them, if we do it right, they’ll start to self-propagate and perpetuate. So oftentimes when folks put in beaver dam analogs in flowing systems, so we’re not quite that case, but a lot of the time when they put them in normal streams, if there’s beavers anywhere nearby, they’ll find them and move in and they’ll actually start to use the, the analogs as the sort of seed material for their own dams. So it’s really funny sometimes that I’ve seen photos where, you know, it looks half natural and half artificial, and that’s because it is. So once the beavers move in, like you can walk away because they’re going to take care of the dams for you.

Derek Maiolo (29:12):

I’m glad that you mentioned that. That was actually the last question I had is what might be the prospects of reintroducing beavers. And you’re already well on your way, I guess.

My guest today has been Matt Wilson, director of the Freshwater Research Institute and CEER Field Station, and a member of the faculty at Susquehanna University. Matt, thank you so much for being on Pennsylvania Legacies.

Matt Wilson (29:36)

Thanks, Derek.

Josh Raulerson (29:41):

That’s all for this time on Pennsylvania Legacies. You can learn more about PEC’s own work to protect and restore watersheds on our website at pecpa.org. There, you can find all past episodes of this podcast, including our most recent one, which looked at new funding, going to water quality improvements in southeastern Pennsylvania. Listen in your web browser, or if you prefer, you can always download episodes directly to your mobile device and your preferred podcast app. Learn all about PEC’s program and policy work across Pennsylvania, everything from trail development to clean energy and climate on the podcast and on the website, which again is at pecpa.org, pecpa.org. And we’ll be back after the July 4th holiday with more Pennsylvania legacies conversations. Until then, for the Pennsylvania Environmental Council and Derek Maiolo, I’m Josh Raulerson and thanks for listening.