Shintaro Koike

Research about flood mitigation function of the paddy field

Minjiao LU

Now, the storage capacity of the paddy field is considered as one of the flood measures. Paddy field can storage the water. Other agricultural land has not this characteristic capacity. This study attempts to estimate the effect of basin paddy field storage over Igarashi River in Sanjo city, and examine its technical characteristics and the future possibilities.
From viewpoint of flood control, the practice to use paddy field storage capacity is referred to as the " Paddy Field Dam (PFD)". PFD can store the rainfall in paddy fields, a limit the outflow of the river. It is possible to suppress the runoff increase due to rainfall. However, the mechanism of the paddy field dam, stores the rainfall from the beginning of the rain. And when the rain reaches the peak, because the water level in the paddy fields is increased, decrease the storage capacity. So, it cannot effectively store the rainfall peak. Therefore, we consider a gate to fully control the water level in a automatic way. Since the cumulative rainfall of 200mm from the river improvement plan was found to be a danger. If Igarashi river basin exceeds the cumulative rainfall of 200mm, it was assumed to start store the rainfall in paddy fields. After waking runoff analysis, reduction in the outflow amount of 130m3/s was observed at the maximum. The runoff analysis was carried out against the observed 2004 Niigata and Fukushima heavy rain and the 2011 Niigata and Fukushima heavy rain. The result is 2004 Niigata and Fukushima heavy rain runoff of 80m3/s at the maximum was reduced. And in 2011 Niigata and Fukushima heavy rain runoff of 95m3/s at the maximum was reduced.

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