Assessing the applicability of flow measurement by using non-contact observation methods in open channels

River discharge is one of the important hydraulic data to evaluate and manage the regional water resources. Estimating river discharge is generally based on field measurements. The measurement data are then applied to construct water level-discharge rating curves. However, it is sometimes difficult to obtain accurate discharge data due to the high uncertainty of flow. A commonly used technique is the propeller-type flowmeters (PTF), which average the results of 1-, 2-, or 3-point methods to obtain a vertical mean velocity. In this study, three types of flowmeters were employed to compare the accuracy of flow measured. The devices were calibrated using a tow tank testing: PTF, acoustic Doppler profiler (ADP), and radar surface velocimeter (RSV). To assess the applicability of the non-contact observation method, a series of 16 experiments in channels were conducted. Surface velocity measurement using the RSV was compared with the measurements obtained by PTF. The relationship between measured surface velocity of RSV and measured vertical mean velocity of PTF was established. The results show that the RSV can effectively estimate the river discharge in the open channel flow.