2026 CSDMS meeting-057
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Floodplain slope organizes chute and neck meander cutoffs across rivers in the Amazon Basin
Yuan Li,
Indiana University Bloomington Bloomington Indiana, United States. yl246@iu.edu
Douglas Edmonds, Indiana University Bloomington Bloomington , United States.
Kory Konsoer, Louisiana State University Baton Rouge , United States.
José Constantine, Williams College Williamstown , United States.
Ye Jing, Indiana University Bloomington Bloomington , United States.
Dylan Shoemaker, Louisiana State University Baton Rouge , United States.
Md Muzahidul Islam, Louisiana State University Baton Rouge , United States.
Channel cutoff is a fundamental mechanism by which meandering rivers of the Amazon reshape their courses, and yet it remains unclear how their frequency and type vary across the river basin. This knowledge gap limits the development and evaluation of numerical models that aim to capture cutoff dynamics at large spatial scales. Using satellite images from 1984–2021, we identified 1,132 cutoffs across single-threaded channels wider than 90 m. We find that cutoff types are unevenly distributed across the basin: neck cutoffs (n = 594) dominate low-slope floodplains, while chute cutoffs (n = 456) are more common in steeper regions. Bimodal distributions of cutoff geometries indicate fundamentally different processes associated with neck and chute cutoffs. We introduce a mechanistic framework that includes impacts of local floodplain topography, discharge, and landcover on cutoff types. Data reveal that floodplain slope is a first-order control on cutoff type. The planform geometry of chute cutoffs is more scale-free than necks. This basin-wide perspective illustrates how cutoff type changes systematically across the Amazon, suggesting that floodplain attributes related to lentic habitat availability. More broadly, these observations provide data-driven constraints that can inform the representation of cutoff processes in morphodynamic models.
