Guidelines for Stream Realignment Design

KDOT occasionally finds it necessary to realign short reaches of small streams in connection with highway improvements or to protect the highway embankment against stream encroachment. A realigned stream reach should be stable and should resemble a natural stream in its cross section, profile and planform. The Kansas Analytical Method or natural stream design, developed in this report, follows the general approach recommended by the USACE and the NRCS, and incorporates hydrologic and geomorphic data from natural streams in Kansas. The realigned reach is designed to convey the same bankfull discharge and sediment load as a stable reach directly upstream. The channel length, slope, and cross-sectional dimensions are obtained from an analytical solution to Manning's equation for uniform flow and a simplified version of the Meyer-Peter and Muller sediment-transport equation, along with hydraulic-geometry relations for the bankfull width. A meandering planform with the computed length and an appropriate meander wavelength is constructed of circular arcs and line segments. A saw-tooth bottom profile with riffles and pools at appropriate locations is recommended to provide aquatic habitat during periods of little or no flow. Step-by-step instructions for stream realignment design by the Kansas Analytical Method are provided. An example illustrates the practical application of the method.