Black Bayou Cutoff Culvert Sizing using Unsteady Flow HEC-RAS
Calcasieu Parish, Louisiana
FTN assisted the NRCS in designing culverts for the Louisiana Highway 384 crossing of the Black Bayou Cutoff in Calcasieu Parish south of Lake Charles, Louisiana. This crossing lies in a marshy area just south of the Gulf Intracoastal Waterway (GIWW). The purpose of the culverts is to open up Black Bayou Cut to improve east-west drainage in the vicinity, lowering marsh water elevations to the east of Highway 384. FTN developed an unsteady-flow HEC-RAS model of Black Bayou Cut and Old Black Bayou in the vicinity of the GIWW and the Calcasieu River. The goals for the model simulations were to determine the discharge capacity of the proposed culvert design and to evaluate channel conveyance and flow velocities in the channel reaches. If required, FTN was to make recommendations for changes to the culvert design or channel geometry to ensure that the desired discharges could be achieved at acceptable velocities. The model consisted of four channel reaches, a storage area representing the common low-lying floodplain between two of the reaches, seven lateral weirs connecting the two channels to the storage area, and the culverts. Simulations also included use of the channel improvement routines in HEC-RAS.
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