Evaluating causal factors that influence the spatial and temporal variability of streambank erosion in Iowa

Authors: WILSON, CHRISTOPHER - University Of Tennessee; SCHILLING, KEITH - Iowa Geological Survey; Papanicolaou, Athanasios - Thanos

Submitted to: Journal of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/22/2022
Publication Date: 12/1/2022
Citation: Wilson, C.G., Schilling, K.E., Papanicolaou, A.N. 2022. Evaluating causal factors that influence the spatial and temporal variability of streambank erosion in Iowa. Journal of the ASABE. 65(6):1465-1473. https://doi.org/10.13031/ja.14894.
DOI: https://doi.org/10.13031/ja.14894

Interpretive Summary: Rural infrastructure near floodplains and rivers is affected by bank erosion and ultimately bank failure. The implications to US agriculture can be unbearable with annual damages nearing 1-2 billion dollars. Farmers loose productive land near floodplains, and rural infrastructure such as country roads near embankments and bridges become not operational and may require maintenance. Data suggest that till-derived soils in north-central and northeast Iowa lack cohesion compared to loess-derived soils in southern Iowa. This study provides simple means to quantify loss of riverbank across Iowa using soil moisture and soil temperature information. This information will be valuable to scientists and natural resources managers to predict areas that are prone to bank failure and preemptively provide mitigation strategies.

Technical Abstract: Streambank erosion exhibits high variability both spatially and temporally, and few studies have attempted to characterize the causal factors of the variability at regional and seasonal scales. This study combines geotechnical field measurements with historical trends of soil moisture and temperature to quantify the spatial and temporal variability of critical shear stress and erodibility in streambanks of the Major Land Resource Areas of Iowa (MLRAs). The data suggest that till-derived soils in north-central and northeast Iowa lack cohesion compared to loess-derived soils in southern Iowa. Thus, critical shear stress values from northern parts of the state were significantly less than those from western and southern Iowa. A multi-variate regression equation was developed using properties of texture and bulk density to quantify critical shear stress values for all stream bank soil series in the state. Cumulative distribution functions of these values visually reflect the separation between the critical shear stress values of the different MLRAs with the loess-derived soils in western and southern Iowa having similar, overlapping patterns, in contrast to MLRAs in north central and northeast Iowa with the till-derived soils. Temporally, the critical shear stress reaches minimum values during March when soil moisture is high and there are several freeze-thaw events. This is most apparent with bank soils in eastern Iowa.