And admittedly, yes, it is a little bit underwater right now

because, well, that river there is in flood.

But 50 years ago, this would've been open water

and I would've been jumping off this boat up to my neck.

And yes, I was extremely nervous

about that little jump [laughs]

'cause that's the first time I came off here.

But yeah, this is the Wax Lake Delta.

50 years ago: no trees, no plants, nowhere to put your feet,

I would've been swimming, on a coastline that's famous

not for building up but for eroding.

And to explain why, we have to go just a little bit inland.

The Mississippi River is so murky and brown

because it's filled with silt and sediment.

Throughout history, roughly every thousand years or so,

deposits of that sediment build up enough

that the river basically blocks itself

and then takes a different and steeper route to the ocean,

at least until silt builds up on that new route

and the river moves again.

That massive and relatively sudden change

is called an avulsion.

And avulsions were fine until modern times,

when the industry that you can hear

and the livelihoods of untold numbers of people

rely on the river being exactly where it is.

But in the past, every time that humans

have tried to fix the rivers around here,

there have been unintended consequences.

We built levees like this one

to protect towns like Baton Rouge here,

but they make the river flow faster and higher

because all the water is now concentrated into one channel.

And because they restrict water flow, they move the flooding upstream,

which means the next neighbourhood over

has to build their levee higher to deal with it.

There are regulations to prevent 'levee wars',

when communities have to keep building their levees higher

because their neighbours are doing the same.

Those regulations aren't always followed.

And downstream, levees mean that instead of a wider river during floods,

you get a faster river, eroding away those silt and sediment deposits,

literally washing away the land that it once created.

And now, the river doesn't flood as much,

so the ground next to it dries out and settles and sinks.

Louisiana's coastline is disappearing.

In 2011, government cartographers retired 35 placenames,

taking them off the maps

because those islands and bays just don't exist anymore.

They're just open water.

But there is one place on the coastline, a couple of hours south of Baton Rouge,

where land is appearing again,

and that is also an unintended consequence,

which brings us back to where I was standing

at the Wax Lake Delta.

- The Wax Lake Outlet is a channel off the Atchafalaya River.

The Atchafalaya River is a channel off the Mississippi.

So, a channel off a channel off the Mississippi River. [thunder booms]

Excuse me, I heard a little thunder.

- Okay, no, we-- - Let's get out of here.

- The Wax Lake Outlet was built in the early 1940s

and it was designed to pull water off the Atchafalaya River

and reduce flood stress on Morgan City.

One of the unintended consequences

was the development of a delta at the mouth of the Wax Lake Outlet.

And so, the Wax Lake Outlet and the Atchafalaya River

carries a lot of sediment,

and then when it gets to the coast, the river flow slows down

and all of the sediment in the river settles out.

We're talking tens of millions of metric tonnes of sediment every year.

This is solid enough land that you can walk on it

and you can stand on it.

Louisiana has lost nearly 2,000 square miles' worth of land over the last century,

and there's a large effort to rebuild the coast.

A big part of that effort is to try to partially divert

the flow of the Mississippi River

to create new deltas that are like the Wax Lake Delta.

And so, people like myself want to study the Wax Lake Delta

so we understand how deltas build

so we can better design coastal restoration projects.

It's important to restore the coast,

one, to push back the sea to enhance flood protection in Louisiana,

and it's also a place where you could potentially bury carbon.

We have too much CO2 in the atmosphere,

and highly productive deltas like the Wax Lake

may be one of those places where we can do that.

I often feel like the numerical models

that we have to understand the coast are pretty darn good.

The much more difficult thing to model is to understand people

and how people are going to behave with this changing coast.

And I feel like, that, we barely even know the equations.

We don't necessarily know even what the rules are

to govern how do people deal with a stressful changing environment.

- So, yes, it's still wet underfoot here right now

because this whole area's still in flood.

But that just means there's more mud, more sediment being deposited.

This land is going to be a couple of centimetres higher

and this coastline is going to be just a little bit safer.

I've sunk about an inch into the mud

and it's gone in my shoes. It's in my shoes.

Right, I should totally have gone with the sandals.

[laughing]

[grunts] All right.