Floodplain trapping and cycling compared to streambank erosion of sediment and nutrients in an agricultural watershed

Journal of the American Water Resources Association
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Abstract

Floodplains and streambanks can positively and negatively influence downstream water quality through interacting geomorphic and biogeochemical processes. Few studies have measured those processes in agricultural watersheds. We measured inputs (floodplain sedimentation and dissolved inorganic loading), cycling (floodplain soil nitrogen [N] and phosphorus [P] mineralization), and losses (bank erosion) of sediment, N, and P longitudinally in stream reaches of Smith Creek, an agricultural watershed in the Valley and Ridge physiographic province. All study reaches were net depositional (floodplain deposition > bank erosion), had high N and P sedimentation and loading rates to the floodplain, high soil concentrations of N and P, and high rates of floodplain soil N and P mineralization. High sediment, N, and P inputs to floodplains are attributed to agricultural activity in the region. Rates of P mineralization were much greater than those measured in other studies of nontidal floodplains that used the same method. Floodplain connectivity and sediment deposition decreased longitudinally, contrary to patterns in most watersheds. The net trapping function of Smith Creek floodplains indicates a benefit to water quality. Further research is needed to determine if future decreases in floodplain deposition, continued bank erosion, and the potential for nitrate leaching from nutrient-enriched floodplain soils could pose a long-term source of sediment and nutrients to downstream rivers.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Floodplain trapping and cycling compared to streambank erosion of sediment and nutrients in an agricultural watershed
Series title Journal of the American Water Resources Association
DOI 10.1111/1752-1688.12624
Volume 54
Issue 2
Year Published 2018
Language English
Publisher Wiley
Contributing office(s) National Research Program - Eastern Branch
Description 18 p.
First page 565
Last page 582
Country United States
State Virginia