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The Sensitivity of Hyporheic Exchange to Fractal Properties of Riverbeds
Author(s) -
Lee Anzy,
Aubeneau Antoine F.,
Cardenas M. Bayani
Publication year - 2020
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2019wr026560
Subject(s) - fractal dimension , bedform , fractal , scaling , hyporheic zone , turbulence , surface finish , flow (mathematics) , scale (ratio) , geometry , hydrology (agriculture) , geology , mathematics , materials science , geomorphology , mechanics , geotechnical engineering , physics , geography , sediment transport , sediment , mathematical analysis , cartography , composite material
Hyporheic exchange in riverbeds is driven by current‐bed topography interactions. Because riverbeds exhibit topographic roughness across scales, from individual grains to bedforms and bars, they can exhibit fractal patterns. This study analyzed the influence of fractal properties of riverbed topography on hyporheic exchange. A set of synthetic fractal riverbeds with different scaling statistics was used as inputs to sequentially coupled numerical simulations of turbulent channel flow and hyporheic flow. In the analysis, the maximum power spectrum (dune size) and the fractal dimension (topographic complexity) were considered as independent variables and we then investigated how interfacial fluxes and hyporheic travel times are functionally related to these variables. As the maximum power spectrum increases (i.e., dune height to flow depth ratio), the average interfacial flux increases logarithmically whereas it increases exponentially with an increase in fractal dimension. Hyporheic exchange is more sensitive to additional roughness (larger fractal dimensions) than to bedform size (larger maximum power). Our results imply that fractal properties of riverbeds are crucial to predicting hyporheic exchange. The predictive relationships we propose could be integrated with reduced complexity, large‐scale models. They can also be used to design artificial topographies that target hyporheic ecosystem services.