Just how high was the Big Thompson Flood? And how often will a flood like that occur?

June 30, 2016
Geoff blog_lightened

Geoff Krall

Recently, the family and I were taking in an afternoon in Boulder, CO. After taking in a lunch at the lovely Dushanbe Tea Room we took a stroll along Boulder Creek. Right by a retaining wall stands this object.

This monument demarcates how high the waters rise for a flood of various magnitude. Zooming in a bit to the demarcations we see the following (from bottom to top):

Version 2

Version 2

Version 3

The thing that makes flood levels so interesting mathematically is that in addition to height, they’re measured in probabilistic time. That is, every 100 years we can expect one flood to reach as high as the demarcation of the “100 Year Level”. Every 500 years we can expect one flood to reach as high as the “500 Year Level” and so on.

So… what does that suggest for the marker near the tippy top of this monument, marking the height of the Big Thompson flood of 1976?

Version 4

Suggested Facilitation

Provide the following (enhanced) picture.

Follow up with your favorite problem kicking off protocol. I’d suggest either a Notice/Wonder or a Know/Need-to-Know.

Potential Questions

  • How high did the water level get during the Big Thompson flood?
  • How often does an event like that happen?
  • How high are these markers off the ground?

For this last one, you’ll probably need some sort of base level unit to measure the heights, for perspective’s sake. Allow me to provide one additional picture.

(Hey, if it’s good enough for Stadel, it’s good enough for me.)

This blog originally appeared on Emergent Math.

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