The research of composite measurement method to estimate river discharge

River flood control and water management highly prioritize the use of high flow data. New measurement instruments have been adopted in field discharge measurement recently to acquire discharge data in safety during flooding events. However, previous studies using this instrument assuming that the vertical velocity distribution consistent with theoretical law will affect flow estimation accuracy. This work presents a composite measurement system, composing of Acoustic Doppler Current Profiler (ADCP) and continuous wave radar, as an alternative flow measurement. Based on field data, exactly how mean velocity and surface velocity is also examined. Experimental results indicate that the velocity ratio is equal to 0.83. Moreover, analysis of field velocity data and log-law reveals that k_s is equal to 3.5D₇₅. Above results are difficult to obtain by traditional flow measurement. Experimental results also demonstrate that different measurement methods to estimate the river discharge differ in accuracy. The composite measurement method in different flow conditions is developed as follows. The direct measurement method can be used in low discharge (<50 cms); direct and non-contact measurement methods can be used in medium discharge (50 cms̃1,000 cms); and the non-contact measurement method can be used in high discharge (>1,000 cms). This finding implies that the composite measurement system is practical for river flow measurement. Moreover, the accuracy of high flow measurement is evaluated by taking flow measurements at the high discharge during typhoon Tembin. Furthermore, the discharge measurement system has already been successfully implemented during a typhoon. Therefore, in contrast with the traditional measurement method, the proposed composite measurement method is more safe, acceptable and feasible in flood discharge applications.