Remote Sensing of River Bottom Roughness

Ruth Branch, University of Washington, Civil and Environmental Engineering, Seattle, United States, Alex R Horner-Devine, University of Washington Seattle Campus, Department of Civil & Environmental Engineering, Seattle, United States, Chris Chickadel, Applied Physics Laboratory, University of Washington, Seattle, WA, United States; University of Washington, Seattle, WA, United States, Andrew T. Jessup, University of Washington, United States and Stefan A Talke, California Polytechnic State University, Department of Civil and Environmental Engineering, San Luis Obispo, California, United States
Abstract:
River bottom roughness is a key parameter in hydrodynamic modelling of river flow, yet it is often estimated and assumed constant over long sections of the river. The bottom roughness modifies the drag and therefore the turbulence statistics of river flow. If the relationship between the bottom roughness and the surface turbulence statistics is known, then a remote measurement of the turbulence statistics can be used to estimate the bottom roughness.

Sonar measurements of river bottom roughness are combined with in-situ and remotely sensed velocity data at ten sites in a river to investigate the relationship between surface turbulence and bottom roughness. The bottom roughness features examined in this experiment were dunes with amplitudes varying from 3 to 50 cm. The in-situ velocity measurements were made with ADVs and an ADCP mounted on the front of a moored barge which floated up and down with the tide. The remotely sensed velocity data was extracted from infrared images of the water surface. Remotely sensed surface turbulence data from one site was shown to be well-correlated to turbulence data 2 cm below the surface but its relationship to bottom roughness has not yet been studied (Chickadel et al. 2011). Here we present the turbulence data throughout the water column at each of the ten sites and show how it and its remotely sensed surface signature is related to the bottom roughness.

Chickadel, C. C., S. A. Talke, A. R. Horner-Devine, and A. T. Jessup (2011), Infrared based measurements of velocity, turbulent kinetic energy and dissipation at the water surface in a tidal river, Geosci. Remote Sens. Lett. 8(5), p. 849-853.

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