Submitted to: Laboratory Publication
Publication Type: Government Publication
Publication Acceptance Date: 7/15/1999
Publication Date: N/A
Technical Abstract: The Yalobusha River System has responded similarly to other channelized stream systems. In downstream reaches, main stem channels are characterized by aggradation, sediment accretion on channel banks, and proliferation of "pioneer"woody-riparian species such as willow, river birch, and sweet gum. In these reaches, banks gradually regain stability, and beds are covered with fine to medium sand. Upstream from the aggradational reaches, channel conditions deteriorate rapidly. Channels are dominated by degradation and rapid channel widening by mass failures on both the Yalobusha River (above river kilometer 28.6) and Topashaw Creek (above river kilometer 22.1). Tributary streams entering in these reaches are also characterized by bed degradation and unstable banks. Knickpoints, marking the upstream migration of the degradation process, have formed in the cohesive beds. Although incision of more than 1 m has occurred in some of these clays, other beds composed of the Porters Creek Clay formation have formed relatively stationary knickpoints as high as 1.8 m. Unique features of the stream system include: (1) Almost the entire channel network has been channelized, but the straightened and enlarged Yalobusha River mainstem terminates in an unmodified, sinuous reach with a much smaller cross section; (2) the lower end of this channelized reach is completely blocked by a plug of sediment and debris causing frequent flooding; and (3) relatively erosion-resistant cohesive streambeds occur over much of the watershed.