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Title: Multi‐scale drivers of spatial patterns in floodplain sediment and phosphorus deposition

The capacity for floodplains to capture sediment and filter pollutants is spatially variable and depends on the complex interactions of geomorphic, geologic, and hydrologic variables that operate at multiple scales. In this study, we integrated watershed‐scale and local assessments to improve our understanding of floodplain depositional patterns. We developed a dataset of event‐scale observations of sediment and phosphorus deposition rates distributed at 129 plots across large environmental gradients of floodplain topography, valley geometry, and watershed characteristics in the Lake Champlain Basin, Vermont. Plot‐scale observations were used to evaluate the cross‐scale influence of environmental factors and were summarized into site‐scale averages to explore regional trends. Consistent with other studies, floodplain deposition generally scaled with drainage area, but trends were longitudinally discontinuous and depended on variations in valley width and slope. While variability in deposition patterns at the watershed‐scale was large (average of 2.0 (0.2–9.8) kg sediment m−2 yr−1; average of 1.4 (0.2–6.5) g phosphorus m−2 yr−1), the range in deposition rates locally across a floodplain was greater (average of 4.6 (0.06–21.7) kg sediment m−2 yr−1; average of 6.4 (0.1–41.1) g phosphorus m−2 yr−1). Local variables that described the proximity to water and sediment sources, and frequency with which the plot was activated by a more » flood, had the greatest relative contribution to boosted regression tree models of phosphorus deposition rates, highlighting the importance of river–floodplain connectivity for floodplain functioning and the profound impact of human activities that limit such connectivity. Patterns identified in our study may guide prioritization of restoration and conservation practices designed to capture sediment and phosphorus on floodplains.

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Publication Date:
Journal Name:
Earth Surface Processes and Landforms
Page Range or eLocation-ID:
p. 801-816
Wiley Blackwell (John Wiley & Sons)
Sponsoring Org:
National Science Foundation
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