Muddy Creek Grade Control Structures Muddy Creek, Mississippi and Tennessee

Abstract : Riprap grade control structures were installed at 12 locations along the Muddy Creek drainage system between September 1976 and September 1983 by the US Soil Conservation Service. After scour holes formed immediately downstream of the first four structures, the exit transition of the structure design was changed from a 1:4 exit flare to a 1:8 exit flare. Many of the redesigned structures formed scour holes after completion. The US Army Engineer Waterways Experiment Station used a 1:16-scale model and a 1:24-scale model to study the scour problem and design modifications to the existing structures. Scour was caused by uneven flow distribution due to flow separation in the exit flare. A series of H-pile baffles were designed for the 1:8 and 1:4 exit flares. Additional studies determined that a 1:16 exit flare with no baffles prevented flow separation within the exit transition resulting in a uniform distribution of flow downstream of the grade control structure.