Stability of Relocated Stream Channels

Federal Highway Administration1981PDFTech ReportBrice, J. C.Geological Survey (U.S.). Water Resources DivisionUnited States. Federal Highway AdministrationGilje, Stephen A.United States. Federal Highway AdministrationUnited StatesStreamflowScourBank protectionChannel stabilizationFHWA-RD-80-158Stephen A. GiljeFinal ReportData gathered to documen t the stability of streams at 103 sites in different regions of the United States where stream channels were relocated for the purposes of highway construction indicate varied responses. In comparison with prior stream stability, bank erosion of the relocated channel was the same at 45 sites, better at 28 sites, and worse at 14 sites. Channel degradatioqrmstly minor, was discerned at 17 sites. Iength of relocation contributed significantly to channel stability only at sites where its value exceeded 250 channel widths: below 100 channel widths, the effects were dcxninated by other factors. Among the factors identified as critical to the stability of relocated channels are: growth of vegetation on banks (40 sites); bank revetment (33 sites); and stability of prior channel (19 sites). Factors identifed as critical to instability are: bends in the channel (21 sites); ercdibility of bed-bank materials (16 sites); and instability of prior channel (8 sites). Documented case histories of stream relocation projects on the scale done by highway agencies do not indicate the disastrous effects cmmonly associated with much larger scale river channelization projects.104