ABSTRACT
The short-term general scour is significant phenomenon in Taiwan’s river due to non-equilibrium sediment transport, steep channel slope, and river basin geology; so that the measurement of hydro-graph of riverbed changes during a flood is an important issue. The river bed elevation measured before and after a flood were close, but the severe riverbed scour were also monitored during the rising limb of a flood and often led to the disaster, such as levee foundation exposed, land loss and bridge failures. In this research, Zhuoshui River is a study area for analysing short-term general scour by field measurement and numerical simulation.
The measurement technology of wireless tracer real-time riverbed scour monitoring is used here, show as Figure 1. It can record the scoured-riverbed elevation and water surface velocity during a flood. The short-term general scour and hydro-graph of bed change were measured in 2016. A maximum scour depth of 2.9 m was measured during Typhoon MEGI, Sep. 2016. Besides, the riverbed changes of study reaches in 2016 were simulated by SRH-2D for estimating the riverbed change hydrograph, show as Figure 2.
Based on the investigation and numerical analysis, the short-term general scour dominates the river course change in Zhuoshui River. Also a flow chart of short-term general scour analysis was developed with the collected data and gave reasonable predictions. In conjunction with the real-time ultrasonic water level measurements, the formula can be used as a potential tool for the emergency evacuation purposes.
