Reflectance factors were obtained for paddy rice at two sites in calibrated TM scenes acquired on two dates for the Kanto district of Japan-1 day after a typhoon inundated the paddies (6 August 1986, when the rice was at boot stage of development) and a month later (7 September 1986, during grain filling). A water turbidity index (WTI), analogous to soil brightness, and the perpendicular vegetation index (PVI) were computed for these data as WTI = 0.91RED + 0.43NIR and PVI = - 0.43RED + 0.91NIR, respectively. Rice yield measured for the inundation-damaged paddies and experimental nondamaged paddies at Tsukuba, Japan, were pooled and related to the PVI calculated from the respective TM scene and ground-measured reflectance factors. The ground and TM data coincided well, and the regression relation YIELD (t/ha) = 0.26PVI - 3.0 for the pooled data. The relation between flood water turbidity at boot stage and yield was also examined for the two test sites; the more turbid the flood water, the greater the damage to the crop. The results demonstrate the possibility of spectrally assessing flood damage to rice and other crops.
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