Flow discharge measurement using small unmanned aerial system
Arizona State University
Abstract
The accurate measurement of river discharge during flooding events has long been a challenging and dangerous task in the Southwestern United States, where flashy flow has high velocity and sediment concentration. Small unmanned aerial systems (sUAS) can be deployed to access unsafe field sites and capture flow images remotely for estimating flow velocity and discharge. Turbulence energy dissipation (TDR) rates derived from measured surface velocity have been applied to estimate flow discharge in laboratory flumes. This research aims to examine the accuracy of TDR for estimating discharge in natural rivers. Eight field sites, including concrete lined canals, earthen canals, and natural channels, were selected near established USGS gaging stations. Flow discharges at each site were measured using two cameras: one mounted on a small UAS, and the other stationed at one bank, in addition to an acoustic Doppler current profiler (ADCP). The ADCP measurements were treated as accurate discharges for evaluating the accuracy of the measurements from two cameras. The velocity index was calculated using several approaches and verified using the ADCP data. The results showed the method that uses the turbulence dissipation rate at the surface to calculate the velocity index achieved discharge estimation errors as small as 2%. However, this approach shows significant errors at rivers of irregular cross sections, especially at the presence of vegetation and suspended sediment. Among eight sites, the conventional approach that assumes a constant velocity index yields better results than using the turbulence dissipation rate. Further researches on turbulence dissipation rate in open channel flow of irregular cross sections, complex boundary conditions, and high sediment concentration are needed for the application of turbulence dissipation rate approach in natural rivers.
About the speaker
Dr. Jennifer G. Duan is a professor in the Department of Civil and Architectural Engineering and Mechanics. Her research area is hydraulics and sediment transport focusing on computational simulation of morpho-dynamic processes of river meanders, sediment transport, flood flow dynamics, vegetated channels, scour at bridge piers, and microorganism transport in irrigation canals. She had led many federal, state, and local agency funded research projects, including an NSF Career Award, and she is also a consultant to World Bank and Battelle Memorial Institute. She has also served several leadership ositions (Chair/co-Chair of Technical Committees) in EWRI-ASCE and CAWRA (Past President of Chinese American Water Resource Association).
