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Surface Turbulence Reveals Riverbed Drag Coefficient
Author(s) -
Branch R. A.,
HornerDevine A. R.,
Chickadel C. C.,
Talke S. A.,
Clark D.,
Jessup A. T.
Publication year - 2021
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl092326
Subject(s) - drag coefficient , turbulence , turbulence kinetic energy , drag , surface finish , geology , beach morphodynamics , surface roughness , hydraulic roughness , environmental science , flow (mathematics) , seabed , hydrology (agriculture) , meteorology , geomorphology , mechanics , sediment transport , geotechnical engineering , sediment , oceanography , materials science , physics , composite material
Flow in rivers and the coastal ocean is controlled by the frictional force exerted on the water by riverbed or seabed roughness. The frictional force is typically characterized by a drag coefficient C d , which is estimated from bulk measurements and often assumed constant. Here, we demonstrate a relationship between bed roughness and water surface turbulence that can be used to make remote estimates of C d . We observe that regions with larger bed roughness result in greater turbulent kinetic energy (TKE), which is transported upward by river boils to the water surface. We present a relationship between surface TKE and C d , and validate this relationship by comparing remotely sensed estimates of C d to those from in situ measurements. Thus, our results provide an approach for estimating bottom roughness and C d based entirely on remotely sensed data, including their spatial variability, which can improve modeling of river discharge and morphodynamics in data‐poor regions.