Stream Realignment Design Using a Reference Reach

This report presents a natural channel design method based on a reference reach approach. This method is termed the Analytical Reference Reach (ARR) method because certain characteristics and features of the design reach are copied or scaled from a reference reach and other characteristics are obtained from analytical relations. The ARR design method offers several advantages over both the Rosgen reference reach method and the analytical approach advocated by the U.S. Army Corp of Engineers and the Natural Resources Conservation Service. Its main advantage over the analytical methods is that the reference reach provides guidance for design of channel features such as meander bends and pools that cannot be designed analytically. Its main advantage over the Rosgen design method is that the channel cross-section is sized analytically to convey an appropriate bankfull discharge, and also the associated bed-sediment load if the channel is alluvial. In the ARR method, several important geomorphic characteristics of the reference reach are preserved in the design reach. These characteristics include the sinuosity of the reach, the ratio of average meander wavelength to bankfull width, and the ratio of pool depth to riffle depth. Applying the sinuosity of the reference reach to the design reach fixes the length and average slope of the design reach. The bankfull discharge for the design reach is obtained either from a hydraulic analysis of a nearby stable reach on the same stream or from a regression equation that relates bankfull discharge to watershed characteristics. Alluvial and threshold channels are sized differently. The design method for alluvial channels equates the bankfull bed-load transport capacities of the design reach and a nearby stable reach on the same stream. The design method for threshold channels scales the cross-sectional dimensions of the reference reach so that the design reach has the desired bankfull capacity. If the computed bankfull velocity exceeds the threshold value, the channel is re-designed using a different reference reach with a higher sinuosity. The ARR design method and the Kansas Analytical Method (K-TRAN Report KU-08-2) are both valid methods for stream realignment design in Kansas. Both methods should yield satisfactory designs for streams with beds composed mainly of sand, gravel or cobble. The ARR design method is preferable to the Kansas Analytical Method for silt- and clay-bed streams. This report provides guidance for reference reach selection and step-by-step instructions for stream realignment design. The Appendix to this report provides essential geomorphic and hydrologic data for 123 potential reference reaches in Kansas. Most of these data were drawn from two previous studies of Kansas streams. The integrated data set is termed the Kansas Reference Reach Data Set (KRRDS).

Language

  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; Maps; References; Tables;
  • Pagination: 66p

Subject/Index Terms

Filing Info

  • Accession Number: 01536566
  • Record Type: Publication
  • Report/Paper Numbers: K-TRAN: KU-09-4
  • Contract Numbers: C1780
  • Files: TRIS, ATRI, STATEDOT
  • Created Date: Aug 26 2014 3:23PM