Rough River Dam in west-central Kentucky is entering one of its most significant construction periods in its more than 65-year history. The U.S. Army Corps of Engineers Louisville District is undertaking a major dam safety modification project that will construct an entirely new outlet works and ultimately install a full-depth concrete cutoff wall through the embankment and underlying karst foundation.

The project combines large-scale excavation, underwater blasting, tunneling, mass concrete construction, hydraulic structures, foundation grouting and deep cutoff wall construction at an operating flood risk management reservoir. The work represents the culmination of more than two decades of investigation, risk assessment, interim risk reduction and design.

Preparation for the project included studying the dam in a 57-feet wide and 100-feet long model at the U.S. Army Engineer Research and Development Center, known as ERDC, in Vicksburg, Mississippi.

Using a model of this size was instrumental in the planning of the work involved in the Rough River Dam Safety Modification project, said Jeremy Sharp, a hydraulic engineer at ERDC, who served as the principal investigator of the Rough River Physical Model study.

“The Rough River physical model was part ofan outlet works study to confirm the performance of a proposed design for the Rough River Dam. The new design will replace the aging and at-risk original outlet work structure,” he said. “Our efforts on the Rough River physical model were critical to evaluating the new tunnel alignment and retreat channel design’s performance and operational projections, enabling the water control team to operate the future prototype structure.”

Jake Allgeier serves as the lead hydraulic engineer on the Rough River Dam Safety Modification project for the U.S. Army Corps of Engineers Louisville District. He said being able to learn in a safe environment has been greatly beneficial in planning for the actual construction.

“One of the main uses of the model is to verify and validate that our theoretical calculations match the real world. Our computer models and simulations of how water behave are very powerful tools, but ultimately these computer models include some assumptions and simplifications about how fluids and turbulence behave,” he explained. “Water is a very complex thing, and we want to make sure we get it right. Being able to use a scale model, that has all the very complicated physics of water baked-in, is a very powerful tool and gives us confidence in the other methods we use to analyze the new dam’s design.”

“In total, we executed more than 200 test runs on the physical model, verifying that the new outlet works will perform safely under routine operational releases as well as rare, extreme flood events,” Allgeier added. “Even in the era of supercomputing, a physical scale model remains an irreplaceable tool for hydraulic engineering.”

“Water behavior inside an outlet works is highly dynamic. Under lower flows, water moves with a free surface in what we call open-channel flow. As gate openings increase and allow higher flows, the conduit fills completely and becomes pressurized,” he added. “That transition to pressure flow significantly alters the hydraulic forces acting on the tunnel, making it a critical focus area in our structural and hydraulic design.”

Sharp said using models for dam projects provides incalculable benefits.

“Dam safety is the most critical high-risk work the USACE enterprise undertakes, so the analysis efforts for a single structure can generate prototype cost savings in the decamillions of dollars,” he said. “Furthermore, it’s only through the modern application of 200-year-old technology, scaled physical modeling, that the ERDC can study nearfield hydraulics on critical hydraulic structures. No numerical code can match the speed and precision of laboratory testing. Furthermore, it is the gold standard in hydraulics.”

Allgeier added that the support from the ERDC team and the model have helped ensure the project brings the dam into the modern era.

“The U.S. Army Corps of Engineers has designed relatively few new dam outlet works in recent decades compared to the major construction boom of the 1950s and 1960s. For the Louisville District, this represents the first new outlet works design since Taylorsville Lake in the 1970s,” he said. “That makes Rough River a rare and critical infrastructure undertaking for our region and nation. These design challenges require modern solutions and time-tested tools that our generation of engineers rarely get to execute from the ground up.”

“It has been a privilege to collaborate with leading national and international experts, pairing advanced computational modeling with proven physical testing to deliver a safe, resilient design built to protect the community for decades to come.”

The Rough River Dam Safety Modification project is a critical mega-project that will repair the high-risk dam and provide permanent flood risk reduction for downstream communities.

Phase 2 of the project will include creating a new outlet works, which will consist of a new control tower and stilling basin with a new tunnel connecting the two features, and a full-depth cutoff wall across the dam. The final portion of work will relocate Kentucky State Highway 79 back to the top of the dam.