| Autor: |
Bandini, Filippo, Lüthi, Beat, Peña‐Haro, Salvador, Borst, Chris, Liu, Jun, Karagkiolidou, Sofia, Hu, Xiao, Lemaire, Grégory Guillaume, Bjerg, Poul L., Bauer‐Gottwein, Peter |
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| Zdroj: |
Water Resources Research; Feb2021, Vol. 57 Issue 2, p1-22, 22p |
| Abstrakt: |
Image cross‐correlation techniques, such as particle image velocimetry (PIV), can estimate water surface velocity (vsurf) of streams. However, discharge estimation requires water depth and the depth‐averaged vertical velocity (Um). The variability of the ratio Um/vsurf introduces large errors in discharge estimates. We demonstrate a method to estimate vsurf from Unmanned Aerial Systems (UASs) with PIV technique. This method does not require any ground control point (GCP): the conversion of velocities from pixels per frame into length per time is performed by informing a camera pinhole model; the range from the pinhole to the water surface is measured by the drone‐borne radar. For approximately uniform flow, Um is a function of the Gauckler‐Manning‐Strickler coefficient (Ks) and vsurf. We implement an approach that can be used to jointly estimate Ks and discharge by informing a system of two unknowns (Ks and discharge) and two nonlinear equations: i) Manning's equation and ii) mean‐section method for computing discharge from Um. This approach relies on bathymetry, acquired in situ a priori, and on UAS‐borne vsurf and water surface slope measurements. Our joint (discharge and Ks) estimation approach is an alternative to the widely used approach that relies on estimating Um as 0.85·vsurf. It was extensively investigated in 27 case studies, in different streams with different hydraulic conditions. Discharge estimated with the joint estimation approach showed a mean absolute error of 19.1% compared to in situ discharge measurements. Ks estimates showed a mean absolute error of 3 m1/3/s compared to in situ measurements. Key Points: Drone‐borne sensors can measure stream water surface velocity and water surface slopeWe developed a new method to estimate stream roughness and discharge from drone‐borne water surface velocity and slope measurementsDrone‐borne discharge measurements compared well with in situ measurements in 27 different field sites [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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