Estimation method of flood damage on rice paddies for watershed management as flood risk mitigation
2016
Minakawa, H. (Institute for Rural Engineering, NARO, Tsukuba, Ibaraki (Japan)) | Kitagawa, I. | Masumoto, T.
Reduction scales in rice yield, which show the decrease in both weight and quality of rice grains caused by flooding, were formulated. A pseudo-flooding experiment of rice plants was conducted for three years to collect basic data of the scales. In the experiment, a paddy field was dug to three depths to construct a flood zone. Therefore, the zone can reproduce a variety of flood conditions without water management. Reduction of the weight of whole rice grains, which is calculated by multiplying the gross weight of brown rice by the weight ratio of whole rice under each flooding condition, was used as fundamental data for making the scales. As a result, the scales indicated that flooding caused damage to rice yields at all growth stages, but the degree of yield reduction differed significantly depending on the stages. In particular, the booting and heading stages of rice were vulnerable to submergence, the yields reduced approximately 50% from just 1 day of flooding at these stages. At the same time, flooding with incomplete submergence mitigated damage to yields. Assessing these flooding conditions is important in order to use the scales to estimate damage on rice. The scales are available for easy estimation of basin scale flood damage to rice, and are also useful tools for risk assessment of climate change impact on agriculture by applying them to output of flood analysis.
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