- I'm Frank Graff in Asheville's River Arts District.

Coming up on Sci NC, the science behind the recovery from Hurricane Helene.

What we're learning during the cleanup.

- Quality public television is made possible through the financial contributions of viewers like you, who invite you to join them in supporting PBSNC.

- Sci NC is supported by a generous bequest gift from Dan Carrigan and the Gaia Earth Balance Endowment through the Gaston Community Foundation.

- Sci NC is made possible by generous support from Dogwood Health Trust, a private foundation based in Asheville, North Carolina focused on dramatically improving the health and well-being of all people and communities in the 18 counties and the Qualla Boundary of Western North Carolina.

(upbeat music) ♪ - Hurricane Helene slammed into Western North Carolina one year ago, September, 2024.

It brought 30 inches of rain and high winds.

The result, raging rivers wiped out communities.

Mudslides scarred the mountains.

Neighborhoods became debris filled lakes.

The devastation was extreme, but as you can see, the recovery is underway.

Let's start by what the storm left behind in rivers and streams like the French Broad and how cleaning up that debris could affect habitat and the species that rely on it.

Here's producer Michelle Lotker.

- We're in the Mills River.

This is a debris pile left behind by Hurricane Helene that's slated to be removed soon.

And we're looking for endangered mussels because there's a patch of them here and we wanna relocate them before this debris is removed.

- Hurricane Helene left debris in waterways across Western North Carolina.

Anything that could be picked up by the flood waters was washed into rivers and streams and left behind when the water receded.

- People don't realize how bad it actually is.

Western North Carolina as a whole, just everywhere got hammered really hard.

There's a lot of work.

It's gonna be a long process.

- Part of that process is removing debris from waterways.

Cameron is part of the team of contractors working in Henderson County, North Carolina, clearing debris from rivers and streams to mitigate the potential for property and infrastructure damage in future floods.

- When you have this amount of debris in a waterway, it restricts flow on a large scale.

Other homes can get damaged.

Farmers' fields can get damaged.

- Where it can be a major issue is when it starts accumulating and catching and making large debris piles that can either end up damming the river and causing problems that way or putting infrastructure at risk, especially bridges.

- But for aquatic biologists like Luke, who spent the last nine years protecting species in Western North Carolina, not all woody debris is created equal.

Normally, stable woody debris plays an important role in riverbed structure.

- When you get stable woody debris, it basically gets embedded in the substrate or it's anchored in the bank, and it really slows down the flow.

If you take away everything that slows down flow or stabilizes substrate, nothing's gonna be able to stabilize and accumulate, and that's not good for most species.

- Among the river residents that benefit from stability are freshwater mussels, which are critical for water quality in the mills and downstream.

- One of their major roles is they filter water.

It's kind of the foundation of the water quality of the French Broad River in Henderson County.

- Across Western North Carolina, debris removal has been happening, but not always with this need to leave stable structure in place at the forefront.

- I've had a front-row seat living on the Swannanoa River.

I've seen a lot of very extensive debris removal.

There's been a lot of cases where there's nothing that's left.

- After the storm, Luke and his colleagues realized that debris removal was more widespread than they expected.

- Even in places that we weren't quite prepared for there to be any debris removals at all, so we kind of shifted, and that's been near 100% of my focus since then, trying to see what we can do to make sure we don't have further damage of our rivers and make sure they can bounce back, not just the rivers, but the species in them.

- Because contractors in Henderson County are paid by linear foot of stream cleared rather than by volume of debris removed, more selective debris removal and protection of what has been identified as high-quality habitat has been possible in rivers like the Mills.

- It was in our contract of high-quality water habitat.

We had to do a certain protocol.

We reached out to Luke.

He met us that morning.

It's been open arms ever since.

- Luckily, we know a lot of these places really well, and I can tell you individual trees have been there for five, 10-plus years.

It's good to keep that good, stable habitat in place, and sometimes it's not always easy for a contractor to make that judgment call.

What we're trying to do with Cam and them is kind of help speed up that process for them and maximize how much we can protect in the process.

- Communication's key, for sure.

He doesn't hold us up.

They're there to help.

It takes one phone call.

- Cameron and his team also have to work closely with landowners to gain access to the river, which often runs through private property.

By having stream bank access for entry and exit and debris collection, they can minimize how much machinery is driving back and forth in the riverbed.

- A lot of this stuff's so big, you can't do it by hand.

We're minimizing the erosion because we're coming in, we're doing a section, then we're getting out, and we're not running that one route way too much.

It's a lot easier to repair a stream bank versus a riverbed.

So we try to navigate in between openings on the riverbank so we're not tearing trees down on the riverbank.

The landowner's working with us, the farmers are working with us.

It's a big help to minimize the eco damage.

I knew there was mussels in the Mills.

I didn't know how important they were.

- The Mills River is home to the slipper shell mussel.

It's a state endangered mussel.

Mills River's really the only place that we have them in any good number.

- We're about to go into the Mills River and try and find some slipper shell mussels so we can move them out of harm's way.

- The debris pile we were visiting illustrated how complicated it is to remove storm-related woody debris while leaving behind stable trees and branches.

- The orange marks are marks for, that's things we wanna keep there if possible.

There's clearly debris piling up there and it didn't look like that three weeks ago.

So I'm trying to see what we can do to cut down on that kind of thing happening while also protecting that bank and also protecting the in-stream habitat.

- Luke swam into the debris pile to locate the slipper shells.

- There's at least a couple mussels right here.

- They just kind of look like another kind of rock on the bottom of the river.

- Mike Perkins always describes them as rocks that suck.

(laughing) A cheeky reference to their filtering abilities.

We started collecting the mussels Luke had spotted and quickly noticed they were tagged.

- This is the originally mussel that we took and held at the hatchery and then put it back and still have it.

- I watched as Luke spotted mussels amongst similar-looking rocks on the riverbed and looked down and noticed one that had been stirred up out of the sand.

I did my part.

- Yeah, there you go.

- I spotted one.

- 20% increase.

- I mean, he came all the way to the surface.

That was way easier to spot than the first ones we got.

- This is the only good population we have for the species in the state, the Mills River.

This is like one of the only places that you can find any at all, let alone several.

- After collecting all of the slipper shells we could find, we headed downstream to a spot where debris removal had already happened to relocate our haul in a spot where Luke found a wild slipper shell already happily embedded in the sand.

And just like that, our transplants had a new home.

Being able to relocate mussels like these and protect river habitat creates hope for future populations of species important to the health of the river.

But still, the debris removal process is not always straightforward.

- There's an impossible amount of considerations when you're talking about what to protect and what to take.

There's a lot of situations where stable woody debris even has a new tree on it that's collecting debris.

And with the heavy machine that's required for some of this, it's like really hard to just pick and choose.

So there's just a lot of challenges trying to make sure that we protect what we can, but also do what needs to be done to meet in the middle, protect people, protect property, protect the animals.

Every situation is different, but that's why it's really important for me to get really involved with Cameron, L&S, and all those folks.

And they've been really good about understanding and listening to my concerns while still trying to get the job done.

For Cameron and a lot of his crew, the future of rivers like the Mills hits close to home.

- I mean, I grew up fishing this river.

Born and raised here.

Everybody loves this river.

A lot of people fish it, float it, snorkel in it.

They do a little bit of everything.

It's something that we need to protect and we need to be cautious of how we do the cleanup.

- Now to the forest.

Producer Evan Howell explains how scientists are trying to understand how the destruction changed the forest ecosystem.

(Bird Cawing) - This is what devastation looks like.

This is what happens when 30 inches of rain over three days combined with 100 mile per hour winds slam into Western North Carolina mountains.

(bird cawing) Hurricane Helene was like a giant monster crashing through the forest, bringing down 100,000 acres of trees.

80 foot oaks and maples were splintered, root systems torn away, landslides scraped away entire sides of mountain.

Scientists say the forest structure of the Blue Ridge Mountains suffered damage never before recorded, leaving one of America's most diverse ecosystems hanging in the balance.

(dramatic music) - This is the Elk Mountain area just north of Asheville.

What you see here is just a small part of what went down September 27th when Hurricane Helene came through.

Trees are down everywhere.

In fact, 17% of the trees in Buncombe County were lost during the storm.

What we should be seeing right behind me is green, not sky or barren bark.

And infrastructure was hit hard too, roads, bridges, power.

But what about the infrastructure of the forest?

There are experts on the mountain right now trying to find out just what went down.

It's all about what's called the tree canopy and keeping our forest ecosystem healthy.

- So I've always loved plants.

When I was a kid, my grandparents lived up in the mountains and we'd come out and I just always was really fascinated by the little things on the ground actually were my sort of first love.

- Margaret Woodbridge is senior ecologist at the Bent Creek Experimental Forest southwest of Asheville.

She's in the place where science meets the soil.

She says with a disappearing canopy, that which doesn't belong quickly takes their place.

- So invasive species come in and they take over an area.

They, in some cases, can kill trees.

But my biggest concern is the understory becomes dominated completely by maybe one or two invasives and you lose all that diversity.

- Worse are more than trees.

Beneath the canopy on the ground lies what's called the understory.

Ferns, mosses, and native plants, all vital to the ecosystem.

But Hurricane Helene changed everything, stripping entire mountain canopies off in a way scientists say they've rarely seen before.

And on an unprecedented scale, it's shifting the balance.

- The conditions now are putting us kind of on a track to not return to normal, but maybe return to something completely different that we don't fully understand.

- It might be a little scary.

- Yes, it is scary.

And it's hard because of the scale and how do you begin to approach that?

So for example, we see here our native flame azalea that's been taken over by oriental bittersweet.

- Wow.

- And so eventually this shrub may die.

- This right here?

- Yeah, so this is the bittersweet and we see these orange flowers.

This is that native flame azalea.

It's a beautiful native shrub, but the bittersweet has almost completely overtopped it.

- Just wraps itself around the... - When forest canopies fall, sunlight floods the ground and what begins as light can lead to the gradual elimination of a forest's natural identity.

- So we're looking at violetwood sorrel as a native.

And the concern here is that beautiful natives like this are gonna be out-competed by invasives like the multi-flora rose we see right beside it.

This is multi-flora rose, an invasive introduced to the US in 1867.

So this is a southern red oak.

It's gonna take quite a bit of time for seedlings that are this small to move up into the canopy.

Depending on the species, some that highlight environment allows them to grow more quickly and some really struggle because they're either out-competed by those species that grow really fast or they just struggle in that higher light, usually drier condition in the soil that's created by that loss of canopy.

I really like the kind of petals with the almost fringy red petals.

It's a little bit sticky.

It's very hairy.

(laughs) We have thousands of native plant species, so I can't imagine how many we have overall.

I think just in the Smokies, there's at least 140 native tree species.

- And the trees cradle about 1,600 native plants and around 200 bird species, along with a range of woodland animals.

They all depend on their own formula for survival.

Woodbridge says you don't even need a total canopy loss.

Even small disturbances in the forest can invite newcomers that overshadow these native species and slowly reshape the ecosystem from the understory up.

- You'll see species that like different light environments because that smaller gap creates different lights environments, like spots of highlights, spots of low light, wetter spots, drier spots, so you get that diversity.

You don't necessarily get that when you have just kind of a completely simplified condition.

So we're seeing a couple of invasives here, and it's a good example of some of the most concerning ones.

So we've got multiflora rose here, and that's the white flowers you see coming up on the tree.

We have English ivy also growing well up into the tree, and if you look up, you can start to see how expansive and kind of prolific the multiflora rose and the English ivy are.

- In the mountains, survival is not solitary.

Trees, plants, animals are all connected within a complex system where every living thing depends on another and nothing thrives alone.

- I guess we're all part of it, aren't we?

- Yeah, I mean, we're a part of these systems, and part of our job is to look at how to manage them.

Helene scares me because that makes that job so much harder.

- There is hope.

By studying which trees can return and where, they're testing ways to slow invasive spread and help native species recover.

And maybe that quiet promise of recovery, like the forest, begins from the ground up.

- Hurricane Helene scoured Hickory Nut Gorge, and it washed millions of tons of natural and man-made debris from the gorge into Lake Lure.

The big digout hopes to restore the lake.

(Siren) - The water was rising, so we were seeing things floating, and then I was like, "What is that floating there?

It looks like the top of a boathouse."

And then it would go right over the dam.

And then that's when we were all like, "Oh my goodness, this isn't good.

Something's not right.

There's no way a whole home should be going over the dam in the waters."

- Ashton Bowles' mind still reels from experiencing Hurricane Helene tearing through Lake Lure in September 2024.

- So then you would see a boat or a tractor and a trailer, and it just got very overwhelming after a while, after seeing thing after thing.

- Life is slowly returning to normal at Bowles' Lake Lure Pottery Studio.

Online orders saved her business the first few months after the storm.

The studio has reopened for customers.

But memories of the storm are haunting.

- Even the wind right now, with it being, it still gives me, I get tight-chested.

I don't like strong winds.

I don't like seeing the signs swaying.

I don't like hearing sirens go by.

I don't like hearing a helicopter above.

I think everyone's still on edge.

- Miraculously, the dam that was built in 1926 and created Lake Lure held.

This is the Lake Lure Dam.

The lake's on that side.

- Yes.

- We're on this side.

- Yes.

- When Helene hit, we would be-- - Underwater.

- Underwater?

- Underwater.

- How far underwater?

- About 20 feet underwater at this point right here.

- Wow.

- Think of it as Niagara Falls coming over the dam.

As you look at the dam, the powerhouse is in the middle.

The dam, when it was built, is designed to have sequential areas where the water, as it was rising, would go along the sides and come over the sides.

- Water did pour over the dam.

The power plant was flooded.

The centuries-old generators are being repaired.

But there was so much water, the earthen banks on both sides of the dam gave way.

The crushed stone you can see on the edges of the dam filled those breaks in.

Lake Lure officials believe those breaches helped ease pressure on the dam and kept it from failing.

- That's the road, right?

- Yes.

- That's the roadbed.

- Yes.

- So is that an example of how much dirt was washed out of here?

- Absolutely.

You can see the original bedrock, which hasn't been visible to anybody in Lake Lure since 1926.

- This was all covered?

- This was all covered up.

- Oh my gosh.

- All the way up to the dam.

When the water broke through and came down this side, it washed all that sedimentation with it.

And you can see that it's about eight or nine feet thick, uncovering the bedrock.

And that gave us a sense of security 'cause we knew that the dam was stable, sitting on rock-solid stone that had been here for time immemorial.

And that dam was not gonna go anywhere.

- What debris didn't go over Lake Lure's dam covered the lake surface.

- The debris that came into the lake was probably 30 acres of solid debris.

Now, the whole lake was full of debris, but there was solid debris.

They know from doing sonar, some of that was 50 feet deep.

So it was a debris pile, unlike anything Lake Lure's ever seen, and of course, hopefully we'll never see it again.

- We pulled vegetation debris out, construction debris from businesses and homes.

We pulled propane tanks out.

Even the propane tanks that were below ground, they got eroded out during the storm as the water's coming down the valley and they ended up in our lake.

- What were you thinking when you pulled that out?

I mean.

- You don't know what, I mean, it's just, I still have problems grasping, you know, the magnitude of it, how big it was, and what we're still finding in here.

- Most of the debris floating atop the lake has been removed.

It took almost four months to clear it out.

All that debris ends up here.

Look closely and you'll discover images of life frozen in time.

You're looking at just a portion of the almost 26,000 cubic yards of debris pulled from the lake.

That's about 3,000 dump truck loads, and that's not counting what was removed from roadways and property.

The debris that can't be recycled will be trucked to hazardous waste landfills.

It's what is still in the water and under the water that is concerning.

- What you can't see is so much of the damage that was done to our infrastructure, and that's because we have a sub-aqueous sewer system, so if the water's in the lake, you can't see the sewer system, right?

You can't see all the subsurface debris and sedimentation that's underneath the lake.

Those are things that, look, the optics are great, and that's both good and bad, isn't it?

It's good because it certainly looks better here, but the downside is people feel like, all right, you're okay, we need to move on to something else now.

- So with the lake lowered by almost 30 feet, exposing debris that sank close to shore, the U.S.

Army Corps of Engineers is entering the next phase of its Lake Lure mission, dig out the lake itself.

- So our scope here within Lake Lure is to remove the debris, the storm-related debris, back to preexisting condition or up to 20 feet deep, whichever we come to first.

We've got sand, we've got silt, we've got sediment, and this is the remains of a car that came from upstream.

As you can see, it's been tumbled, it's been rolled.

Just the awesome force of Mother Nature as this thing came down the river.

- The Corps estimates almost 1 1/2 million cubic yards of sand, silt, and debris fill the lake that washed down from the Rocky Broad River watershed and through the Hickory Nut Gorge.

That's enough material to fill almost four NFL stadiums.

- We hit a little bit of everything out here in the lake.

As the storm worked its way through or down the French Broad River, it picked up rock, silt, sediment, and then as it hit those towns, it pulled everything in from those.

So you have everything you can imagine to build a house with, everything that's in your garage.

- Lake Lure has a maximum depth of 104 feet.

Hurricane Helene's flood waters filled in almost half of that depth with silt.

In some more shallow areas, the lake is almost completely filled.

Sonar readings taken for routine lake maintenance before the storm hit are being compared to readings taken after the storm.

The findings will guide the big dig out.

- So I'm looking here, so the river's out there, but if you look at the map, we're standing in what was the river at one point.

How far is the river gonna go?

How far are you guys gonna dig out?

- So in the current scope of our contract, it is to restore the lake to that preexisting condition, remove the event-related debris.

So off to our left, you can see where the boathouses were, where we're standing, this is all gonna come out.

- This is all gonna come out?

- Oh yeah, every bit of this.

- So water will be flowing here?

- Yeah, the idea is to get the water back to where it was in the bottom of the lake, back to that similar contour.

- In areas where the lake is still filled with water, sonar readings will indicate high concentrations of debris and silt on the lake bottom.

Cranes on barges will be utilized in those places to lift out whatever is found.

- You're seeing how the water moved, the river moved, the bank moved, the debris that we're seeing.

It's quite amazing the magnitude of the storm that took place in this area.

I think the reason this mission is so much harder than other missions that we've had is just the terrain, the roads to get in and out, but you also have the community here that still needs to live and move around and get in and out.

And being cognizant of that as we are doing the mission to clean and reopen up stuff, but also there are people here and they also are very important on making sure that they're able to continue rebuilding as well.

Our motto is [speaks Latin], we try, we'll knock it out, we will complete the mission, so we figure out a way.

- The Hickory Nut Gorge in particular has been scoured back to the time of the ice age when the glaciers came through.

The scar that was placed in Hickory Nut Gorge will be lasting for time immemorial.

We're saying that we are open with restricted access to the lake until we can get the lake safe and clean enough to make sure there won't be a long-term environmental impact.

The wildlife, as I mentioned, is still here.

The people that lost property along the shore or had damage to their homes, all that's recoverable in a short period of time.

We were most worried about the environmental impact and we're pretty confident now that we're going to emerge from this even better than we were before.

- As Western North Carolina continues to recover, our thoughts remain with those affected by the storm and we will continue to cover their stories.

I'm Frank Graff, thanks for watching.

(upbeat music) ♪ - Sci NC is supported by a generous bequest gift from Dan Carrigan and the Gaia Earth Balance Endowment through the Gaston Community Foundation.

- Sci NC is made possible by generous support from Dogwood Health Trust, a private foundation based in Asheville, North Carolina focused on dramatically improving the health and well-being of all people and communities in the 18 counties and the Qualla Boundary of Western North Carolina.

- Quality public television is made possible through the financial contributions of viewers like you who invite you to join them in supporting PBSNC.