Flooding on the Des Plaines River has become more and more frequent. Why?

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Dear Tom,
Flooding on the Des Plaines River has become more and more frequent. Why?
— Mike Sobey
Dear Mike,
It’s certainly true that the Des Plaines River (and other rivers and streams in the Chicago area) are flooding more frequently. It’s mainly because most of them flow into the metropolitan area from surrounding areas that are now experiencing development.
Riverfront facilities at a given spot within developed areas are designed to handle river floods of a given magnitude. But as urbanization proceeds upstream, more water pours into rivers than previously because urbanized land produces more runoff more quickly than undeveloped land. This is resulting in higher river crests downstream in areas whose earlier development did not anticipate upstream development.

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