Streambed median grain size (D50) across the contiguous U.S.

Authors: ASAMEN, DAWIT - North Carolina A&t State University; JHA, MANOJ - North Carolina A&t State University; ALLEN, PETER - Baylor University; Arnold, Jeffrey; White, Michael; BIEGER, KATRIN - Aarhus University

Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2022
Publication Date: 10/25/2022
Citation: Jha, M.K., Asamen, D.M., Allen, P.M., Arnold, J.G., White, M.J., Bieger, K. 2022. Streambed median grain size (D50) across the contiguous U.S. Water. 14. Article 3378. https://doi.org/10.3390/w14213378.
DOI: https://doi.org/10.3390/w14213378

Interpretive Summary: The median particle diameter (D50) is an important factor in the prediction of stream stability and sediment transport. Unfortunately, these data are not available for the vast majority of stream segments in the U.S. In this research we combined monitoring data from five sources to identify spatial patterns across the U.S. These data were summarized using three regional frameworks: Physiograph Regions, Level III Ecoregions, and Hydrologic Landscape Regions (HLR). Statistical summaries of D50 within zones of each framework are presented. These summaries may prove very useful to parameterize hydrologic models for streambed stability analysis.

Technical Abstract: The streambed D50 represents median grain size of surface and subsurface materials located along the channel bed. It has been used as an integral part in sediment transport and stream power equations that sought to characterize stability conditions of stream reaches. However, the applications of D50 data are prone to the constraint of regional applicability, localization of datasets and limited number of datapoints. This research attempts to fill this gap to some extent by presenting a quantitative information on the data availability with regional level of analysis examining the spatial distribution of D50 data across the contiguous U.S. Five sources were used to develop a dataset that contained more than 2400 data points with various hydrological parameters including D50. The dataset was first examined for duplicates and possible outliers. Spatial distribution was analyzed based on the three regional frameworks: Physiograph Regions, Level III Ecoregions, and Hydrologic Landscape Regions (HLR). Physiographic region-based assessments allowed identification of dominant streambed material with gravel constituting the largest part in bed composition of majority of the regions. Box plot analysis of HLRs elucidated prevalence of higher average D50 for regions with humid climate, permeable soil, and Plateaus terrain. Smoothed spatial maps showed the dominance of sand and fine gravel in streams located in the central and southern part of the U.S. while the northeastern part exhibited abundance of coarse gravel and cobble. In addition, correlations between the long-term aggradation/degradation trends and streambed material were also examined, although no apparent geographical discriminations were identified. The D50 dataset and the analysis presented here may prove very useful as a source of readily available large dataset as well as in hydrological studies for streambed stability analysis.