National Park Scouts

The Forest That Floods Without Rain

Host: Jenni · Topic: Congaree flooding, watershed science, wood ducks, alligators, boardwalk engineering

Pretend you're in a forest in South Carolina. Sun is coming down warm through the leaves. The ground under your feet is dry, crunchy, dusty even. About 10 times a year, this exact forest floor disappears. Not the trees, but the ground. It just goes underwater. And sometimes it happens on a day like this, a day that's completely, perfectly sunny.

Today we're heading into Congaree National Park, one of the largest forests of its kind left on Earth. To find out how a forest can flood without a single drop of rain falling on it. Let's go!

Intro

Welcome to National Park Scouts, the show where curious kids discover America's wildest places. I'm Jenni. We're somewhere brand new today: Congaree National Park, right in the middle of South Carolina. This park protects the largest stretch of old, untouched hardwood forest left in the entire United States. Some of the tallest trees east of the Mississippi are standing right here.

We've got four episodes here, and almost everything about this place, the size of the trees, the animals, even the trails, comes down to one wild fact. This forest floods a lot. And it's learned to just go with it. So today, we solve the mystery of the disappearing forest floor.

The Mystery of the Rising Water

Here is the mystery. Clear day, not a cloud in the sky. Didn't rain yesterday either. But when you look down, the water under the boardwalk is rising. If it's not raining here, why would the water be rising? Take a guess.

Here's the answer. The rain already happened, just not here. The Congaree River doesn't start anywhere near this park. It forms when two rivers join together. And those two rivers, they start way up in the hills and mountains of upstate South Carolina and North Carolina, more than a hundred miles away. Every creek and stream up in those hills drains downhill into those rivers after a storm. The whole area that drains into this river system covers more than 14,000 square miles. It's like the size of the entire state of Maryland, and all of it is funneling toward this one river.

So when it rains hard in the mountains, that water has to go somewhere. It runs down the mountains and gathers into streams, and then those streams, they meet up together into a creek. The creek runs to a river, that river to another river, and days later it ends up here. In one flood back in 2015, the Congaree River rose from about six feet to nearly 19 feet in just three days. Almost all of the water fell as rain somewhere else, days before it ever reached the park.

So if you're ever standing on this boardwalk on a sunny day and the water's creeping up, it's not being weird, it's just running late.

It's much quieter. The water rises slowly from underneath, filling the low spots first, then creeping higher between the tree trunks, like a bathtub, filling from the bottom up. Think of a duck paddling in the creek yesterday. The next morning, she might be floating high enough to reach a low branch with her beak. A river otter treats the whole thing like it's a bonus lake that showed up overnight.

And that water isn't just water. On its long trip down from the mountains, it picks up mud and nutrients the whole way, like a delivery truck, collecting packages along its route. When it finally arrives, it drops all of that off, spreading fresh mud across the whole forest floor. That mud is basically plant food. It's a big reason some of the trees here have grown so enormous. Keep that fact in your back pocket for the next episode. We'll be back to it.

A flood usually sounds like a disaster. At Congaree, it's more like a slow-motion delivery truck dropping off dinner for the whole forest.

The Forest as a Giant Sponge

So all this flood water arrives, and what does it do? It doesn't just sit there. This whole forest, the soil, the roots, the fallen logs, they act like a giant sponge. And what do sponges do? They soak up liquid. Think about a kitchen sponge soaking up a spilled glass of water. It doesn't let it keep running everywhere. It stops it.

Congaree does that at a massive scale, soaking up the flood, holding onto it, and then it lets it out slowly over days and weeks. And while it's holding that water, it's cleaning it too, filtering out mud before it ever flows on downstream.

So this flooded forest is quietly doing a job for people nearby who might never even visit, slowing the water down and handing it off cleaner than it arrived.

Guess That Park Sound

Okay, scouts, it's time for guess that park sound. This is the fun part of the show where we take a brain break. I'll play you a sound from right here at Congaree National Park. Listen in and see if you can guess what it is.

Hmm, what do you think? A very small upset kazoo? A noisy gait? Take your guess and I'll let you know right after the break.

Meet the Wood Duck

So that squeaky squealing sound, that is a wood duck. Wood ducks are beautiful. The males have a green head and ornate markings with a rich brown color.

So most ducks, they nest on the ground near water. But not wood ducks, they nest inside tree cavities, sometimes fifty feet up. The morning after a wood duck's babies hatch, they can't fly yet. But mom calls them from down on the ground and they just jump from 50 feet up. Somehow they're totally fine.

Baby wood ducks, they're so light and fluffy at that age, I think they bounce more than they crash.

If a duck built a nest on the ground here, their eggs could get washed away. But if you build your home high up in a tree, it doesn't matter if the ground turns into a lake underneath you. Your home stays dry. Wood ducks figured that thing out a long time ago. Build up high and let the water under you do whatever it wants.

Allie the Alligator

Deep in Congaree, there's a quiet stretch of dark water called Weston Lake, a bend of the river that got cut off and left behind. Scientists call that an oxbow lake. And somewhere down in it, there might be an alligator. Let's call her Allie.

So, Allie the alligator, she's not bothering anyone. She mostly just wants to float around and be left alone. But here is a twist. Alligator moms, they can never build a nest inside this park. Why do you think? Alligator nests are big mounds of mud and plants right on the ground. And they need to stay dry for about two whole months while the eggs develop. Two months of dry ground is not guaranteed at Congaree. Remember, this park floods roughly 10 times a year. If a nest flooded, the eggs wouldn't survive.

So, as far as anyone's found, alligators don't nest inside Congaree at all. They live here, they might grow up here. But when it's time to start a family, they head off somewhere higher and drier outside of the park.

Allie the alligator calls this flooded forest home, but if she ever wants kids, she's gotta move to the suburbs.

Engineering the Boardwalk

So if the ground here floods roughly 10 times a year, how does anybody walk through this forest? The answer is a 2.6 mile loop called the boardwalk trail, built to solve one big problem. How do you build a trail through a forest that keeps disappearing underwater?

For a long time it didn't solve it perfectly. About half of the boardwalk sat low and closed every time the water came up. So the park just finished a huge project to fix that problem. Crews built the low sections higher, using tall supports twisted deep into the swampy ground like a giant screw, so they wouldn't just sink into the mud. Now, three-quarters of the entire boardwalk sits above the average high water line during a flood.

Picture a hallway in your house that floats above your basement, so even if the basement floods, you can walk through your whole house completely dry. That's basically what this boardwalk does for the forest. People couldn't stop the flooding. They didn't even try. They just built something smart enough to rise above it. Same idea as the wood duck, just with a lot more lumber.

Wild Card: Flood Survivor

Okay, scouts, it's time for the wild card. This is the part where we play a game, and this one is called Flood Survivor. I'm going to describe an animal that actually lives here at Congaree. You tell me: when the flood comes, does this animal thrive or not?

Question 1: This animal builds its nest inside a hole in a tree trunk, sometimes 50 feet off the ground. Does it thrive or not thrive? Thrive. That's an easy one. We just met this duck. It's the wood duck. Its whole nest is already sitting way above anywhere the water could reach.

Question 2: This animal spends its whole life walking around on the forest floor. When it senses danger, it pulls completely inside its shell and waits it out. It's called the Eastern Box Turtle. Does it thrive or not thrive? It does not thrive. And that's surprising, isn't it? Box turtles are surprisingly bad swimmers. Their shells are round and heavy, built for walking, not paddling. So deep water is genuinely risky for them. When a flood comes, a box turtle's best move is getting to higher ground fast.

Question 3: This animal looks exactly like an ordinary bunny popping through your backyard. Does it thrive or not thrive? It thrives. And this one is surprising. It's called a marsh rabbit. And unlike a backyard cottontail, marsh rabbits are excellent swimmers. So when the water rises, they paddle right through like it's nothing.

So, scouts, next time you picture a flood, remember it's not always the animal you'd expect that ends up in trouble. Sometimes it's the one that looks totally ordinary that's secretly built for it.

Scout Question

Okay, it's scout question time. We get to hear from a kid just like you. I asked: if you had to survive a flood, which animal would you want to be? And why? Let's hear what some of you had to say.

Lydia, age 5

If I had to survive a flood, I would be a bird that could fly higher than a flood.

I love hearing from you so, so much. Do you want to be on our podcast next? It's so easy, I promise. You can contact me on social media or through my website. Just say that you want to answer a scout question, and I'll get you on our next podcast adventure.

What I Learned Today

What did you learn today that most adults don't know? I learned that flooding doesn't kill this forest. In fact, it's healthier because of it. The rich mud and sediment gives these plants the nutrients they need to flourish. And then the forest lets the clean water flow right on down the river.

Scout Mission

Every scout needs a mission. Here's yours.

If you're at home, find a sponge in your kitchen. Pour a cup of water onto it and watch what happens. Does the water go all over? Or does the sponge hold onto it and let it out slowly? That's what the forest does every time it floods at Congaree.

If you are visiting Congaree National Park, walk the boardwalk trail and look for flood evidence. A muddy watermark high on a tree trunk, or sticks and leaves caught in low branches, or fresh mud on the forest floor. That's the forest delivery truck, and you're looking at exactly where it dropped things off. Water that fell as rain somewhere else, days ago. It keeps showing up here right on schedule.

Outro

Next time, the actual giants that grow out of all that mud and flooding. Trees so enormous, some hold the record for the biggest of their kind on the entire planet. Your next adventure is waiting.