This is scientific American 62nd science. I'm Julia Rosen. Got a minute?

In 2013, a rare September storm swept across the plains of Colorado.

When it hit the Rockies, it dropped more than a foot of rain in places like Boulder,

as much as the city sees in an entire year.

The rain unleashed deadly floods and landslides that swept away roads and buildings.

In fact, a new study found that a century's worth of erosion and sedimentation

took place in a matter of a few days.

Once the flooding started, you haven't quickly and took a lot of people, you know,

unawares.

Sarah Rathburn, a geoscientist at Colorado State University in Fort Collins,

who experienced the storm herself.

On top of the damage to man-made structures,

Rathbren knew that the floods moved huge amounts of sediment,

wood, and the organic carbon they contain. She saw a unique

opportunity to put hard numbers on what went where.

At the base of one of the watersheds that flooded,

a reservoir captured everything that flowed downhill.

I was thinking about being able to track the sediment from the source

to what I'm calling this anthropogenic sink, the reservoir,

and really quantify it.

We don't have a lot of controls on absolutely capturing everything that these large storms produce.

And so the fact that the reservoir was capturing everything really seemed like a unique opportunity.

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