Engineer who worked on flood walls wants to clarify misconceptions

Letters to the Editor

To the editor:

As a civil engineer who was project manager on three levees or flood walls along the Missouri River or a tributary prior to 1993, not one of those failed in 1993.

Therefore, I would like to clarify a misconception that is widely believed.

First, a 100-year or 500-year flood does not mean that it should be that many years before there is another.

Those references are to the percentage (1 divided by the year) of a flood occurring with each flood. Note the “each.”

Imagine a huge dice with 500 dimples numbered from 1 to 500.

For each flood (even if more than one occurs in a year), roll the dice and see what year the flood will be.

I.e., 10-year = 10 percent, 50-year = 2 percent, 100-year = 1 percent and 500-year = 0.2 percent.

Thus, in a year having two floods there could be a 50-year and 100-year flood. Or even two 100-year floods depending on the roll of the dice made by nature. The 1993 flood was considered a 300-year flood.

I’m also amazed that the Valley Park levee keeps growing in size, like a volcano, with each flood.

In 1993 it was three feet, in 2007 it was five feet, now it is eight feet too high?

Three feet is normal levee design to account for subsidence and wave actions.

Omar Feeler, P.E.
Oakville

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