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84-8 Cutoff Geometry Dictates the Infilling and Longevity of Oxbow Lakes

Session: Riverscapes in transition: Advances in fluvial geomorphology, sediment transport, deposition, river health, and urban rivers (Part II)

Presenting Author:

Douglas Edmonds

Authors:

Edmonds, Douglas¹, Jing, Ye², Shoemaker, Dylan³, Li, Yuan⁴, Islam, Muzahidul⁵, Konsoer, Kory M.⁶, Constantine, Jose⁷r> (1) Earth and Atmospheric Science, Indiana University, Bloomington, IN, USA, (2) Earth and Atmospheric Sciences, Indiana University, Bloomington, IN, USA, (3) Geography and Anthropology, Lousiana State University, Baton Rouge, LA, USA, (4) Earth and Atmospheric Sciences, Indiana University, Bloomington, IN, USA, (5) Geography and Anthropology, Lousiana State University, Baton Rouge, LA, USA, (6) Geography and Anthropology, Louisiana State University, Baton Rouge, LA, , (7) Geosciences, Williams College, Williamstown, MA, USA,

Abstract:

Oxbow lakes are critical ecological habitats and effective sediment and contaminant sinks on meandering river floodplains. However, the factors driving the wide variation in their lifespans—ranging from a few years to several centuries—remain unclear. Oxbow lakes are formed when plug bars seal each channel entrance, stopping the flow of sediment into the channel. Several hypotheses have been proposed to understand what controls the creation, and the persistence of oxbow lakes. Classical work suggests that plug bars form when the bifurcation angle from the main channel into the soon-to-be abandoned channel is large, whereas further work has suggested that the angle asymmetry, the upstream bend and the length ratio of the new cutoff and soon-to-be abandoned channels can also be important to the formation of plug bars. Here, we analyze Landsat imagery (1984–2025) to quantify infill histories and cutoff geometries for recent cutoffs in the Amazon Basin (1985-2021), supplemented by 57 global control cases. We show that oxbow lakes formed by neck cutoffs exhibit half the short-term (10-year) infill proportion of those created by chute cutoffs, leaving a larger open-water fraction that directly promotes long-term (30 years) lake persistence. Among candidate controls, channel length ratio clearly differentiates cutoff types and serves as the primary control on infill proportion (R² = 0.6), with higher length ratios predicting lower infill; angle asymmetry acts as a secondary control. Using a one-dimensional numerical model, we reveal the underlying mechanism that how the length ratio controls the creation of oxbow lakes: a higher length ratio creates a slope advantage in the new channel, generating a diffusive wave that scours the upstream reach and transfers sediment into the abandoned bend to form the plug bar. These findings demonstrate that initial cutoff geometry exerts fundamental control over oxbow lake longevity, providing essential insights for managing water resources, biodiversity vulnerabilities, and carbon storage in the Amazon basin.

Cutoff Geometry Dictates the Infilling and Longevity of Oxbow Lakes

Description

Session Format: Oral

Presentation Date: 10/11/2026

Presentation Start Time: 03:25 PM

Presentation Room: CCC, 108

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