Hydrologist Tom Over predicts floods, better prepares Illinois

Floods can be devastating. Closed roadways, collapsed infrastructure, property damage ― you name it. Imagine being able to predict a flood before it even happens. That’s what Tom Over, hydrologist with the United States Geological Survey does. 

Tom Over, hydrologist with the United States Geological Survey, currently serves at principal investigator on the Illinois Center for Transportation and Illinois Department of Transportation's joint project R27-181: Updated and Unified StreamStats Peak Discharges for Streams of Illinois.

Over will measure and implement updated estimates of the streamflow peak discharges that correspond to a given probability of occurrence (100-year floods, for example, which are the peak discharges expected to be exceeded in a given year with a probability of 1 percent) for Illinois.

These values are computed using discharge data collected at USGS streamgages and include equations developed from statistical relationships on different drainage basin characteristics, such as basin area and land use that will allow estimates to be obtained at ungaged stream locations throughout Illinois.

“These estimates at ungaged locations will be applicable to urban and rural watersheds in northeastern Illinois and rural watersheds elsewhere in the state,” Over said.

The updated peak-discharge estimating equations will be implemented in SteamStats, an online tool disseminating peak-discharge estimates at nearly all stream location in Illinois.

USGS’ David Soong and Amy Russell are co-principal investigators. StreamStats for Illinois is the result of a previous ICT-IDOT project, R27-006: Internet-Based Flood-Peak Discharges Determination for Rural Streams — Illinois StreamStats, led by Audrey Ishii, Soong, and Jennifer Sharpe.

Ishii, Over, and Soong were co-principal investigators of a recent Phase 2 ICT-IDOT project ― R27-144: Development & Implementation of Updated Urban Regional Flood Frequency Equations for Illinois. The result of this project included peak-discharge quantile estimates at gaged and ungaged locations in northeastern Illinois, accounting for the effects of urbanization. The estimates were included in StreamStats.

Prior to this online alternative, IDOT used a 1979 paper study, so the update brought the data forward into the new century.

“As is well-known, extensive development occurred in many parts of northeastern Illinois since 1979, and the design standards for storm-water runoff have changed,” Over said, “so an update was very much needed.”

Over was co-investigator with Tim Straub, a USGS hydrologist, on two previous ICT-IDOT projects ― R27-019 and R27-105, which focused on bridge scour, both the measurement of and estimation methods. The most common cause of bridge failure results from floods scouring bed material around bridge foundations.