Author(s): Zhiwei Li; Zhaoyin Wang; Wenzhe Li
Keywords: Meandering rivers; Neck cutoffs; Cutoff patterns; Bank collapsing; Scour
Abstract: Neck cutoff is a sudden event of meandering rivers and reduces the sinuosity and complexity of meander morphology. Analyzing deeply patterns and mechanism of neck cutoffs is essential in this study. Distinguishing remote sensing images of neck cutoffs, they are divided into three different patterns (rush cutting, bank collapsing and erosion ditch), and theoretically investigating cutoff conditions, process and mechanism. Rush-cutting pattern is the most common way of neck cutoffs. The process of rush-cutting pattern is the overflow surface scouring, forming a new channel and intensively scouring the new channel until reaching the stabilization. Bank collapsing pattern occurs on extremely narrow neck where left and right banks collapsing simultaneously or unilateral bank collapsing cause downstream flow through the neck. Erosion ditch pattern is the first flood scouring forming a new ditch, and subsequent floods along the ditch scouring with the headward erosion until the new channel completely forming to accomplish the neck cutoff.