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Title: Levee design profiles for the Williamson, West Virginia, Flood Protection Project
Authors: United States. Army. Corps of Engineers. Huntington District.
Williams, David T.
Keywords: Discharge rating curve extrapolation
Computer program
Mathematical model
Numerical model
Levee elevation design
Flood protection
Flood control
Tug Fork River
West Virginia
Publisher: Hydraulics Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Miscellaneous paper (U.S. Army Engineer Waterways Experiment Station) ; HL-88-4.
Description: Miscellaneous Paper
Abstract: This report describes a hydraulic study of the Tug Fork River, West Virginia, from the Kermit gage to the town of Williamson. Williamson is the site of a major flood protection project and is to be protected to the Standard Project Flood (SPF). The objectives of the study were to aid in updating and recalibrating the original HEC-2 model of the US Army Engineer District, Huntington, identify and incorporate into the model important hydraulic parameters, develop a procedure for extrapolation of the stage-discharge rating curve to the SPF discharge at Williamson, and determine the SPF water-surface profile under project conditions. With mylar overlays of the maps as guides, overbank reach lengths of the HEC-2 model were adjusted to reflect the length of the centroids of the flow lines. Representation of buildings was made by adjustments to the geometry points, and the most recent bridge surveys were used to update the geometry. Geometric adjustments were also made in the town of Williamson to allow flow through the central business district (CBD). Because the 1977 discharge estimates (flood of record) of the Huntington District and the US Geological Survey (USGS) differed (117,000 cfs versus 94,000 cfs, respectively), different calibrations of the HEC-2 model were performed based upon the two discharges. Examination of the calibrated 1984 flood water-surface elevations resulted in reexamination of the rainfall data, and the 1984 flood was reconstructed. This changed the main stem discharge from 82,000 cfs to 58,000 cfs for the 1984 flood. Analyses of the detailed USGS discharge/velocity measurements of the 1984 flood indicated significant flow through the Williamson CBD during the 1977 flood. The HEC-2 model was adjusted to reflect the geometry of the buildings and streets. Checks were made to assure that the side flow over the existing floodwall into the CBD was sufficient to meet the CBD conveyance potential. Analyses of the 1984 and 1977 floods and pre-1984 USGS rating curves suggested that winter and spring foliage conditions produced different rating curves which resulted in the adoption of winter and spring rating curves. The rating curves were extrapolated to the SPF by the following method: (a.) Plot composite channel roughness k𝗌 versus water-surface elevation for known conditions. (b.) Extrapolate ks to the estimated water-surface elevation for the SPF event but not less than the minimum k𝗌 for the bed material grain size under plane bed conditions. (c.) Estimate the water-surface elevation of the SPF event and from the extrapolated curve, determine the k𝗌. (d.) For the k𝗌 and estimated water-surface elevation, calculate the Manning's η value and input to the HEC -2 model. (e.) Check the resulting HEC-2 water-surface elevation against the estimated elevation and, if different, make additional estimates until the computed and estimated water-surface elevations match. The HEC-2 model was modified for project conditions by adjusting the geometry and roughness associated with floodwalls and channel modifications and taking into consideration the containment of the water discharge within the floodwalls and levees.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Miscellaneous Paper

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