The Role of Hydro-Environmental Conditions in Modulating Streambank Erodibility Parameters

Abstract Submission: Streambank erosion is a ubiquitous morphodynamic process. However, high rates of streambank erosion are detrimental to the stability and function of restored streams. Over time, such high rates can lead to excessive bed erosion and deposition, increased loading of fine-grained material and nutrients, and poor water quality and habitat conditions. Therefore, there is a need to advance assessment and prediction of streambank erosion rates. The objective of this work was to characterize the temporal variability of streambank erodibility parameters in response to rapidly changing hydro-environmental conditions and hydrological fluctuations. Specifically, the Jet Erosion Test (JET) was used to perform in-situ, repeated measurements of critical shear stress (τc) and erodibility coefficient (kd) in seven banks along two creeks in Raleigh, NC, USA. JET testing was performed over a period of 14 months, for a total of 90 tests. Concurrently with JET testing, the characterization of hydro-environmental conditions (e.g., moisture content and soil temperature), soil physical properties (e.g., size distribution and bulk density), and stream-flow metrics for each runoff event (e.g., volume, magnitude, and duration) were also considered. Results indicated that, for a given site and soil type, streambank erodibility parameters vary as a function of hydro-environmental conditions, with physical properties modulating initiation of motion (as indicated by changes in τc) and hydro-environmental conditions impacting the functional form of detachment rate (as indicated by changes in kd). Ultimately, this work aims to advance understanding of the inherent variability and uncertainty that mark drivers of streambank erosion in nature.

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