The design team had to meet significant challenges to develop an economical design to span the fast-flowing Ohio River. Inundated with an overabundance of water, the 6.4-kilometer-wide (4-mile-wide) crossing floods at least once a year. In order to protect the Ohio River’s floodplain from further erosion and provide environmental protection to the agricultural lands and wetlands affected by the construction of Natcher Bridge, PB’s design team executed a state-of-the-art finite element hydraulic analysis of a 90-square kilometer (35-square mile) area.

The first of its kind for a United States bridge project, the innovative hydraulic analysis involved recreating and examining flood cycles of 10, 50, 100 and 500 years. More than 100 possible situations were investigated on the Kentucky side of the Ohio River, along with 17 bridge-approach scenarios.

The outcome of the analysis helped PB determine innovative methods of reducing the river’s speed at the bridge’s site, as well as incidences of river overflow. The structure of the bridge was altered to fit into the surrounding wetlands, with nearly all the drilled foundations projecting above the mud line. By project’s end, Natcher Bridge required five flood relief structures.