Erosional Cyclic Steps Governed by Plunge Pool Erosion

Erosional Cyclic Steps Governed by Plunge Pool Erosion: A Parametric Study Based on Field, Laboratory, and Model Data

Zeng, X. (TU Delft Rivers, Ports, Waterways and Dredging Engineering; Tsinghua University)
Blom, A. (TU Delft Rivers, Ports, Waterways and Dredging Engineering)
Czapiga, Matthew J. (TU Delft Rivers, Ports, Waterways and Dredging Engineering)
An, Chenge (Tsinghua University)
Parker, Gary (University of Illinois at Urbana Champaign)
Fu, Xudong (Tsinghua University)

2021

For upland ephemeral gullies, gully erosion is strongly related to the formation and migration of cyclic steps. It is necessary to provide insight into the process of cyclic step development to accurately predict the pace of landscape evolution and soil loss. Information on the geometry of cyclic steps in subaerial environments is limited, and, to our knowledge, no model of cyclic step development considers plunge pool erosion. In this study, we analyze the geometric features and controlling factors of erosional cyclic steps through meta-analysis of measured data including new measurements in the Loess Plateau, China. We focus on cyclic step dynamics of fluvial beds controlled by bed shear stress and local plunge pool erosion. We develop a new theory to incorporate plunge pool erosion through adapting existing cyclic step and plunge pool models. Our method agrees with measured data, showing that a larger flow rate leads to larger step length L_d and height H_d and increasing erodibility increases step aspect ratio L_d/H_d. The method is also able to predict how the step length, height, and aspect ratio change with the average channel slope. Our results indicate that plunge pool erosion is an important mechanism of cyclic step evolution. However, plunge pool development alone is not sufficient to explain the wide range of L_d/H_d in the measured data. The posed theory relates to equilibrium conditions and thus cannot consider temporal adjustments in step geometry.

controlling physics
erosional cyclic steps
geometric features
plunge pool erosion
the Parker-Izumi model
the plunge pool model

http://resolver.tudelft.nl/uuid:b1a956b2-e9c7-452b-94ff-2a9f92ed070f

https://doi.org/10.1029/2020JF006034

2022-05-08

2169-9003

Journal of Geophysical Research: Earth Surface, 126 (11)

Institutional Repository

journal article

© 2021 X. Zeng, A. Blom, Matthew J. Czapiga, Chenge An, Gary Parker, Xudong Fu