Narrator: Of all the projects in the Master Plan, the proposal for the Rio Hondo Confluence is the most ambitious.

Located at the intersection of the 710 and Imperial Highway, there are 12 projects planned, including a cultural center and two large platform parks that would be built over the river channel.

These projects were designed by the team at Gehry Partners and Olin Studio.

Here, the dreams of removing the concrete ran up against the reality of the channel system, which became a surprising learning process for Frank Gehry and his team.

Gehry: So I looked at it, and there was a group called FOLAR, Friends of the Los Angeles River, that was run by Lewis MacAdams, and Lewis and I talked and he still, when I first met him, believed the concrete could be taken out, and that could be created into a beautiful, idyllic landscape that connects 51 miles of the city.

In our study, I looked at that for two years.

I believed you could do it, too.

It seemed like such a right thing to do.

It had to be true.

It had to be the right way to go.

Our values were similar.

What a wonderful man.

What a wonderful vision.

Unfortunately, it had no reality.

He was led to believe that you could take the concrete out.

I don't know who led him to believe that.

It certainly wasn't the Corps of Engineers.

It certainly wasn't the water districts or anybody.

Maybe it was wishful thinking.

Man: We started the project as similar to many people who have worked and continue to work on the river, which is this idea of a 51-mile connected green space, which is still our goal.

It's just a matter of what's possible.

Our Corps colleagues on the project were Jessica Henson at Olin and Mark Hanna at Geosyntec, and Mark is one of the foremost experts on the hydraulics and hydrology of the Los Angeles River, and he really had to give us an education on how the hydraulics worked.

[Music playing] Henson: And so we come here to the LA River, you see this, like, what, 400-foot-wide concrete channel, and you're like, "I'm a landscape architect.

We are going to make it vegetated and green, and it is going to be, like, cool.

Like, who doesn't want a green river, right?"

And so we started building, like, these 16-foot-long models of a widened channel, of different terraced options.

You start to look at it and you start to see some of the issues with that.

Hanna: Well, right, of course.

Most of the time you come down here, and this is what you're looking at, and you really feel like the opportunities to make moves are enormous.

It's those very rare events that you really need the channel to function the way it was designed.

Rivers in nature are not straight.

They meander, right?

They meander based on their flow rates, based on the vegetation conditions, based on the sediment load, and the slope of the actual channel itself.

So people look at this and say, you know, "Why can't we green this river up?"

And, really, greening this river up means bringing back those meanders.

And this river is a piece of infrastructure that was built to move water as quickly as possible.

If the idea when the flood control system was really developed, they were thinking, "We also want trees, we also want groundwater recharge, we also want open spaces and places for people to wander and experience nature," this channel would have been much larger.

They would have pushed back the levees much wider.

Henson: So if you bring this into where we are today, in the 21st century, we have a lot of critical infrastructure along the river, we have a lot of residents, like, a lot of people live along the river, and they love that.

By and large, the LA River is very tightly hemmed in, and so one of the struggles with saying, "Let's take all 51 miles and create that more natural condition" is it would cause a lot of displacement.

You'd be talking about displacing maybe tens of thousands of people if you did it for all 51 miles.

But the problem with it is, as a river, it's a system, and when you widen a river in a section, it's--the water slows down, so water stacks.

And when that water stacks, you create usually other flood issues for people upstream or downstream.

So you start to get into this situation of like, OK, well, this neighborhood gets this widened river, vegetated amenity, and then we're going to actually make flooding worse for this community just downstream, and they're not going to get a park.

And so it starts to become a real equity issue along the Los Angeles River as we stand here in our current conditions of the 21st century.

Historically, across the United States, communities of color have disproportionately borne the burden of that type of displacement when freeways have been built, when other infrastructural systems have been created, and unfortunately, we would see that repeated if we did something at that scale along the Los Angeles River.

So what innovative things can we do to bring that into the 21st century in a way that's actually going to support local communities, not displace local communities?