McLaughlin Whitewater Design Group was developing a new course at Coweta Falls on the Lower Chattahoochee River near Columbus, Georgia. McLaughlin hired Alden to build a scaled physical hydraulic model of the course to make sure it would perform as designed.
The whitewater course is part of an aquatic ecosystem restoration project involving the removal of the Eagle and Phenix Dam and the City Mills Dam and construction of a series of environmental, recreation, and aesthetic features. The overall goal of the project is to restore riverine and shoal habitat. The two dams will be removed with oversight by the Army Corps of Engineers to reveal natural whitewater rapids. MWDG plans to enhance the whitewater experience by adding a combination of grouted boulder structures, newly excavated channels, a tunable wave-shaper and upgraded river access.
The physical model study evaluated a number of proposed site modifications to be installed for optimization and enhancement of whitewater features within the river, including the installation of the tunable wave-shaper. The model was used to perform visual qualitative evaluations of the whitewater features. as well as to quantitatively track the water surface elevations throughout the model at different river flows and varying river tailwater elevations.
The model simulated the Coweta Falls portion of the river to a geometric scale of 1:12, and included a small portion of the Eagle and Phenix dam that will remain on either side of the river after the dam is removed and the two naturally formed channels within the modeled portion of the river. The proposed site modifications were also modeled including the channel entrance sills, invert sills, whitewater sills and tunable wave-shaper. The model was primarily tested at prototypical river flows ranging from 900 to 13,400 CFS, but was capable of flows of 20,000+ CFS. The model also included provisions for adjusting tailwater over the range of expected river tailwater elevations.