Risk Analysis Of Flood Disaster To Single Cropping Rice And Summer Corn In The Middle And Lower Reaches Of The Yangtze River

Based on the daily meteorological data from 426 weather stations located in the middle and lower reaches of the Yangtze River during 1961 to 2010, the single station flood indicator was built. The flood level standards of single station in Hubei Province were selected as an initial indicator. Then the threshold of precipitation in the process was Increased or decreased in the range of-50~+100mm. Flood indicator was gradually selected by combining with historical flood records and agricultural areas suffered from flood disaster. The provincial agricultural flood indicator was built and its rationality was further verified. The temporal and spatial change of agricultural flood disaster in the area for nearly 50 years was analyzed. Based on the daily precipitation data of 297 stations located in the planting region of single cropping rice and 91 stations located in the planting region of summer corn in the middle and lower reaches of the Yangtze River from 1961 to 2015, combination of the growth period data and flood disaster data of single cropping rice and summer corn, the different flood disaster grade samples was counted during different growth periods. By using partial correlation analysis, multiple linear regression, normality test, and sample mean interval estimation with SPSS and ArcGIS software, the flood disaster grade indexes of single cropping rice and summer corn during different growth periods was respectively constructed. Their rationality were verified. The temporal and spatial changes and risk distribution of flood disaster to single cropping rice and summer corn from1961 to 2010 were analyzed. The main results are as follows:(1) The occurrence of agricultural flood in the middle and lower reaches of the Yangtze river region has increased in recent 50 years, but regional and decadal differences are obvious. The areas in which agricultural flood occurred most were the middle and north of Jiangxi, Jianghan plain, Zhejiang coastal areas, the junction of Anhui, Jiangxi and Zhejiang provinces as well. There was more agricultural flood occurrence in the south of the Yangtze River than the north. Agricultural flood had occurred less during 1960s-1980 s, and significantly increased in 1990 s, and then decreased relatively since the 21 st century.(2)The high incidence area of flood disaster to single cropping rice is mainly located in Poyang Lake, Zhejiang coast, Enshi and Zhangjiajie. In the last 50 years, the occurrence of waterlogging disaster generally showed an increasing trend, especially during transplanting to booting stage. High risk probability area is mainly located in Poyang Lake, Mount Huangshan, Enshi and Huanggang during transplanting to tillering stage. Flood risk is less than 4% in most areas during jointing-booting and heading-mature stage. Risk index of flood disaster is generally high, and most of the area is more than 0.6. During jointing-booting and heading-mature stage, high value area of risk index mainly located in the coastal areas of Zhejiang, most other areas are in low value area, which risk index is less than 0.3.(3) At the same growth stage, the waterlogging frequency decreased with the increase of waterlogging disaster grade.The waterlogging disaster high frequency zone mainly concentrated in the area along Yangtze River, the area along Huaihe River and coastal area, and would northward move gradually with the rainbelt when the growth process increasing. In the last 50 years, the occurrence of waterlogging disaster generally showed an increasing trend in the emergence-tasseling stage, but it mainly reduced during tassel to mature stage. At the same growth stage, the risk probability distribution of each grade waterlogging disaster is basically same, and high risk probability areas gradually reduced. The high value area of risk index gradually moved from southwest to northeast with the increase of the birth process.