Potential hazard analysis from the viewpoint of flow measurement in large open-channel junctions

A robust and reliable risk assessment procedure for hydrological hazards deserves attention. The transport of mixed material in the types of hazard, such as flash floods and debris flows, plays an important role and should be taken into consideration. At present, however, the mixed material transport phenomenon is not systematically and simply included in the procedures for the elaboration of hazard analysis. The consequence is the risk of losing prediction accuracy and of underestimating hazard impacts. The phenomenon of open-channel junction flow such as in irrigation ditches and at wastewater treatment facilities is an important aspect of hydrological engineering. Extensive experimental studies of the flow characteristics have been conducted. In this study, an Acoustic Doppler Velocimeter is used to monitor the flow in large open-channel junctions at the Chihtan purification plant in Taipei. The condition of the experiment is made up of different discharge. The result of the measurement data shows that the mean velocity profile, aspect ratio, measured vertical line location and the ratio of the distance of the vertical line maximum velocity from the bed to water depth. An artificial neural network (ANN) is used to simulate the mean velocity profiles in this study. The results show that the ANN can accurately and reliably simulate the mean velocity profiles. The result is believed to provide hints for the consideration of the effects, induced by mixed material transport, in the elaboration of hazard analysis.

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