New Method for Meander-Loop Cutoffs

When a reach of a meandering river becomes very sinuous, and thereby causes significant problems for navigation and flood discharge, cutoff works in the narrow-neck portion of the river bend may be carried out. It is common practice to excavate a small slightly bending cutoff channel, referred to as pilot channel, which is gradually scoured and enlarged toward the concave bank by the river flow. In the design of the Wujiadu cutoff in the Caoe River (already constructed in 1998), the authors proposed a new method for constructing meander-loop cutoffs. Using this technique, the new cutoff channel on the concave bank side and the flood protection embankments are formed during construction, allowing the nonprotected convex bank and the bed of the new cutoff channel to be scoured and be enlarged by flood. Thus, the amount of excavation of the cutoff works can be significantly reduced and the construction period can be largely shortened. In this way, the lines of the new cutoff channel may be unified with the overall river alignment. This paper presents the design philosophy and major points of the method for meander-loop cutoffs.