River Discharge Measurement Under High Flow Velocity Condition Using UHF Radar

Noncontact flow measurement methods have been popular among hydrographers for their convenient and safe operation in recent years. Ultrahigh frequency (UHF) radar is an essential flow measurement instrument that is normally deployed on the river bank to monitor flow velocity and discharge. However, when the river flow is too high, some frequency points of the Doppler spectrum are aliased. The frequency point in the aliased first-order peak region may contain more than one current signal, which cannot be distinguished by the previous radial current extraction methods. The consequent poor radial current decreases the estimation performance of cross-sectional surface velocity and river discharge. This letter first interprets the mechanism of the aliasing phenomenon according to the relationship between Bragg frequency and Doppler shift. Then, a radial current extraction method based on the classification of Doppler frequency points is proposed to solve the aliasing problem. Experimental results demonstrate that the proposed method outperforms the other two radial current extraction methods in calculating discharge with a reduction in a root-mean-square error (RMSE) of 364 and
$574 \mathrm {m^{3}/s}$
, respectively.