Chute cutoff is an important process during the evolution of many meandering rivers, but it is seldom incorporated into theoretical analyses of planform evolution due to the paucity of observations of its occurrence and physical controls. We describe a mechanism of chute cutoff that is common along large meandering rivers with uniform floodplain topography. The mechanism occurs independently of non-aqueous perturbations, such as those caused by natural dams, and initiates during a flood by the incision of an embayment located nearly a channel width upstream of the inflection of the meander that will undergo cutoff. Subsequent floods then extend the embayment downstream until forming a chute.
Results/Conclusions
Using sequences of historical aerial photos of the Sacramento River, USA, we found that embayments formed where channel curvature was greatest, or where the channel most tightly curved away from the downstream flow path. Incision occurred only within those portions of the floodplain that were lightly vegetated by grasses or crops. We developed a simple physical model that describes the environmental conditions that can lead to embayment formation. The model considers the role of floodplain vegetation in preventing chute incision and in part explains why chute cutoff is prevalent along some meandering rivers but not others.
