Catastrophe Distinction Index of Oilseed Rape Vernal Waterlogging in Hunan

Focusing on the oilseed rape waterlogging in Hunan, several waterlogging process samples are picked out from historical disaster information to build the impending hazard sample set and affected sample set. As disaster-causing factors in different status have significant difference, t-test is used to quantify the significance of precipitation factor difference in different attenuation coefficients and create effective accumulation preparation (P_E). According to P_E and continuous cloudy days (D), the critical line is derived from Fisher principle to build oilseed rape vernal waterlogging catastrophe distinction index which can distinguish the affected status day by day. The waterlogging catastrophe index is verified by inverting waterlogging process samples and calculating the value of independent samples. By calculating the affected frequency of waterlogging in each site, and the waterlogging catastrophe index, the relationship between the frequency of waterlogging damage and the relative meteorological yields is studied, and the waterlogging impact evaluation model is constructed. Results show that current precipitation and antecedent precipitation have significant effects on the formation of the waterlogging disaster in Hunan. When the influence attenuation coefficient is 0.899, the difference between P_E of the impending hazard sample set and affected sample set is most significant. The oilseed rape vernal waterlogging catastrophe distinction index can be used to monitor the waterlogged catastrophe process on a daily basis, and indicate the catastrophe time and the intensity of the disaster, providing theoretical support for the dynamic monitoring of regional oilseed rape waterlogging process and a new idea for the real-time monitoring and early warning of the precipitation process. In the independent sample verification, the maximum value of waterlogging catastrophe index shows a similar distribution with disaster records, and can reflect the actual disaster situation. It can be a better scientific basis for regional disaster controlling and preventing. According to analysis results, the waterlogging-affected frequency of oilseed rape in Hunan shows an overall trend of high in the southeast and low in the northwest. The waterlogging-affected frequency is higher in flowering and fruiting period and lower in mature period. The waterlogging disaster in fruiting period has the most significant effects on the oilseed rape relative meteorological yields. Oilseed rape vernal waterlogged disaster influence index shows a trend of high in the southeast and low in the northwest. The rape yield is most affected by waterlogged disaster in the east of Changsha, central and north of Zhuzhou, Xiangtan, Yongzhou and the middle of Chenzhou.