Public-works agencies are keeping a careful lookout for rising water from this week’s heavy rain, and it’s not just pools and puddles they’re concerned about. Norm McDonald is Director of Bridges and Structures for the Iowa Department of Transportation.
A new bridge is designed to handle the volume of water a river might carry in a hundred-year flood, but some older ones are in the "scour-watch" program. The program looks at rainfall predictions and calculates whether the volume of water added to the river may be enough to "scour" earth away from the bridge supports.
When the program calculates that there may be a problem at the bridge, the system automatically places a phone call to the maintenance people in that area. They’ll go out to look at the bridge and see if indeed there’s a high-water problem — and if there is, they’d close the bridge.
While rushing rainwater can hide potholes or even sweep cars off the road, there are also hidden dangers like the ground washing out from under pavement, or supports eroding until a bridge is at risk of approaching. McDonald says they want to find such trouble spots and close the road or bridge before people discover it by driving over it.