Indicator-based evaluation of spatiotemporal characteristics of rice flood in Southwest China

Abstract Frequent occurrences of extreme rainfall events create severe rice floods. To prevent rainfall-induced rice floods and reduce potential losses, it is important to establish meteorological evaluation indicators and precisely understand the spatiotemporal characteristics of rice floods, to provide support for rice flood monitoring, prevention, and mitigation. In this study, precipitation, disaster and phenophase data of rice in Southwest China (Sichuan, Chongqing, Guizhou, and Yunnan provinces) were integrated to establish meteorological evaluation indicators of single-cropping rice floods, and the rice flood index (RFI) from 1961 to 2012 was thereby estimated to gain detailed information on rice flood disaster characteristics in that region. The threshold of rice flood in the transplanting-tillering stage was 120, 130, and 150 mm for 1, 2, and ≥3 d, respectively. This was 150, 160, and 180 mm for the jointing-booting stage, and 170, 200, and 230 mm for the tasselling-maturity stage, respectively. Identification results by rice flood level were found basically consistent with the historical occurrence of rice flood disasters, with 66.7% of historical records strongly consistent with the flood level assessment, and calculated errors of all validation data were within one level. High RFI was faced by the transplanting-tillering stage, followed by the jointing-booting and transplanting-tillering stages. High-RFI (>1) areas in the whole rice stage were southern and northeastern Yunnan, southern Guizhou, plus Chengdu, Meishan, and Deyang in Sichuan Province. Regional RFI in the whole stage showed a negative trend, with slope 0.0246 (R 2  = 0.1523). RFI at 120 stations, or 62.83% of all stations, decreased over the whole rice stage, while RFI increased at 70 stations, mainly in Guizhou, northeast of Sichuan.