The Research on Disastrous Law of Drought and Flood in Hubei Province in China

Using the daily precipitation and disaster census data of 76 meterological stations in Hubei in China from 1960 to 2005, we studied the temporal-spatial distribution and disastrous laws of drought and flood. The results show that the frequent occurrence area of drought appeared zonal distribution of east to west, with the location of high value center in Xiaogan, Anlu and Yingcheng of 0.93, 0.75, 0.71 yr^-1, respectively. While the annual occurrence frequency and area of flood were significantly less than those of drought, with the location of high value center in Tongshan, Chibi and Chongyang of 0.78, 0.57, 0.56 yr^-1, respectively. The annual variations of drought and flood experienced three different tendency periods, which were from 1960 to 1969, from 1970 to 1995, and from 1996 to 2005,especially after 1996, two kinds of disaster showed an opposite variation trend, with an increase of stations of drought and a decrease of stations of flood. The drought and flood mainly occurred in June, July and August. From 1960 to 1995, the disastrous intensity of drought had an oscillation variation, with a high value period, while the agricultural economic loss was gradually increasing. Some areas of Hubei province experienced a strong drought disaster period from 1996 to 2001, and the agricultural economic loss had leapfrog growth and reached the maximum value in 2001 as the cumulative effect of drought. The agricultural economic loss was depended on the damaged area of crops, with the correlation coefficient of 0.41. The variation tendency of flood’s disastrous intensity was quasi periodic oscillation, governed by 8~12 years’ and 3~5 years’ time scales. Both of the damaged areas of crops and agricultural economic losses reached maximum values in the 1990s, but showed obvious decrease after 2000. Compared to drought disaster, the impact of flood on agricultural was more directly and quickly, causing the damaged area of crops was correlated with agricultural economic losses clearly, with a correlation coefficient of 0.80. There was good relationship between the flood-affected population and direct economic losses. From 1960s to 1990s, the slope of the fitting curves between the flood-affected population and direct economic losses decreased by age, illustrating that the increasing speed of direct economic losses was accelerated with the growth of flood-affected population. The value of ratio between total flood-affected population and total flood-death toll from 1990 to 2005 was far less than that from 1960 to 1989, showing the abilities to prevent flood disaster were strengthened. The drought-flood abrupt alternation mainly occurred in summer in northwest and southeast of Hubei province. During the sharp-turn disaster process, as the former disaster would strengthen the vulnerability of crops and reduced the economic value of crops in early period, the increasing speed of agricultural economic losses was accelerated with the growth of disaster-affected areas and the economic losses would be less than normal value in latter disasters.