Unifying Advective and Diffusive Descriptions of Bedform Pumping in the Benthic Biolayer of Streams

Journal Article · Tue Oct 27 00:00:00 EDT 2020 · Water Resources Research

DOI:https://doi.org/10.1029/2020WR027967· OSTI ID:1690305

Grant, Stanley B. ^[1]; Monofy, Ahmed ^[2]; Boano, Fulvio ^[2]; Gomez‐Velez, Jesus D. ^[3]; Guymer, Ian ^[4]; Harvey, Judson ^[5]; Ghisalberti, Marco ^[6]

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1. Occoquan Watershed Monitoring Laboratory, The Charles E. Via Jr. Department of Civil and Environmental Engineering Virginia Tech Manassas VA USA, Center for Coastal Studies Virginia Tech Blacksburg VA USA
2. Department of Environment, Land and Infrastructure Engineering Politecnico di Torino Torino Italy
3. Department of Civil and Environmental Engineering Vanderbilt University Nashville TN USA
4. Department of Civil and Structural Engineering, Sir Frederick Mappin Building University of Sheffield Sheffield UK
5. U.S. Geological Survey, Earth System Processes Division Reston VA USA
6. Oceans Graduate School University of Western Australia Perth Western Australia Australia

Abstract

Many water quality and ecosystem functions performed by streams occur in the benthic biolayer, the biologically active upper (~5 cm) layer of the streambed. Solute transport through the benthic biolayer is facilitated by bedform pumping, a physical process in which dynamic and static pressure variations over the surface of stationary bedforms (e.g., ripples and dunes) drive flow across the sediment‐water interface. In this paper we derive two predictive modeling frameworks, one advective and the other diffusive, for solute transport through the benthic biolayer by bedform pumping. Both frameworks closely reproduce patterns and rates of bedform pumping previously measured in the laboratory, provided that the diffusion model's dispersion coefficient declines exponentially with depth. They are also functionally equivalent, such that parameter sets inferred from the 2D advective model can be applied to the 1D diffusive model, and vice versa. The functional equivalence and complementary strengths of these two models expand the range of questions that can be answered, for example, by adopting the 2D advective model to study the effects of geomorphic processes (such as bedform adjustments to land use change) on flow‐dependent processes and the 1D diffusive model to study problems where multiple transport mechanisms combine (such as bedform pumping and turbulent diffusion). By unifying 2D advective and 1D diffusive descriptions of bedform pumping, our analytical results provide a straightforward and computationally efficient approach for predicting, and better understanding, solute transport in the benthic biolayer of streams and coastal sediments.

• Sponsoring Organization: USDOE
• OSTI ID: 1690305
• Alternate ID(s): OSTI ID: 1786790
• Journal Information: Water Resources Research, Journal Name: Water Resources Research Journal Issue: 11 Vol. 56; ISSN 0043-1397
• Publisher: American Geophysical Union (AGU)
• Country of Publication: United States
• Language: English