Backwater at bridges and densely wooded flood plains, Yockanookany River near Thomastown, Mississippi

Floodflow data that will provide a base for evaluating digital models relating to open-channel flow were obtained at 22 sites on streams in Alabama, Louisiana, and Mississippi. Thirty-five floods were measured. Analysis of the data indicated methods currently in use would be inaccurate where densely vegetated flood plains are crossed by highway embankments and single-opening bridges. This atlas presents flood information at the site on Yockanookany River near Thomastown, Miss. Water depths, velocities, and discharges through bridge openings on Yockanookany River near Thomastown, Miss., for floods of April 12, 1969, January 2, 1970, and March 15, 1975, are shown, together with peak water-surface elevations along embankments and along cross sections. Manning 's roughness coefficient values in different parts of the flood plain are shown on maps, and flood-frequency relations are shown on a graph. (Kosco-USGS)