City of Waco

On May 17, 1989, Waco experienced a 50-year flood event which overtopped IH-35 through the downtown area to the extent that the Interstate was closed and traffic was rerouted. Today, the Texas Department of Transportation (TxDOT) is embarking on a robust widening project for IH-35 in Waco from 12th Street northward to North Loop 340. The photograph, at left, excerpted from the Waco Tribune Herald, depicts flooding conditions between 12th and 8th Streets on IH-35 within the Waco Creek watershed resulting from this 50-year rainfall event.

The City of Waco retained Walker Partners to determine if this new highway widening Project will have any adverse flooding impacts on the Waco Creek watershed. After many meetings with TxDOT and their consultants, the Walker Partners’ Team prepared a HEC-RAS 2-D computer model to analyze potential increased flooding conditions within the Waco Creek watershed resulting from the new Project.

The findings from this Study are as follows:

 Raising the elevations of the IH-35 main lanes (by as much as four feet) worsens the “dam” effect of IH-35 by obstructing overland stormwater flow and casting water back onto private properties on the west (upstream) side of IH-35 to depths of 3.8 feet. This condition is non-compliant with TxDOT’s Hydraulic Design Manual and is a public safety hazard.

The raising of the main lanes on IH-35 worsens the “dam” effect of IH-35; thus, forcing more stormwater through the 4th and 5th Street “at grade” crossing and increasing both the flow velocity and flood depth. This condition is non-compliant with TxDOT’s Hydraulic Design Manual and is a public safety hazard.

completion date: 2019

location: waco, tx