Functional Evaluation of Paddy Field Dam Devices with Different Characteristics Using Generated Heavy Rainfall Data

Six combinations of drainage equipment for paddy fields dam were prepared to evaluate the peak cut functions of discharge from paddy. First, a hydraulic experiment using artificial channels was conducted to determine the flow coefficient in each device used to calculate discharge. Next, paddy models which can simulate water balance on paddy field were built and set the determined flow coefficient for each device. The discharge and water depth of paddy models were calculated using generated rainfall with nine different rainfall scales ranging from 100 to 500 mm/3d. As a result, all devices effected a peak cut function on discharge from the paddy field, at the same time, the peak water depth on the paddy was increased. The characteristics of the effect are dependent on the type of device. The peak cut effect using a “function-integrated” device was maximized at 100-150 mm, and the effect of a “function-independent” device was maximized at 300 mm. Simultaneously, the device of function-integrated type required time decreasing water depth until initial condition compare with the device of another type. To structure a sustainable framework for paddy field dam activity, it is important to assume the target rainfall scale for disaster prevention, understand the characteristics of the devices, and the conditions of paddy fields in the area, and then consider in advance how to install them.