| China is one of the country in the world，which flood and drought happenedseriously. It has important significance to research the occurrence of flood anddrought in domestic different areas. This paper focused on coastal area of JingjiangRiver as the study area, collected historical data of flood and drought in coastal areaof Jingjiang River, the data of530years, tentatively established the flood and droughtgrade sequence, combined with the mathematical statistics method and the waveletanalysis method to discuss the regularity, such as frequency, cycle and mutation, usethe t-test to check climate mutation information in coastal area of Jingjiang Rivermore than500years, and make a contrast between the research conclusion and theother authority finally. In addition, listing some major disaster events as example toanalysis, then drawing the following conclusions:⑴530years’flood and drought grade sequence of coastal area of JingjiangRiver，Jiangling site1471-2000a drought and flood level material in China’s NearlyFive Hundred Years of Drought and Flood Atlas, after respectively5-year movingaverage is compared, and found that the fitting degree is very high. Then use SPSS tooperated flood and drought grade sequence of coastal area of Jingjiang River and theDrought and Flood Level of "atlas", a total of530years of data. The correlationcoefficience reached0.695at0.01significant level, further define the climate changepattern of coastal area of Jingjiang River is the main driving factors to control thelocal flood and drought, and at the same time, the establishment of flood anddrought grade sequence preliminary through the verification, can be smoothly forfollowing study.⑵Times and frequency analysis of flood and drought showed that:530years, allkinds of flood in coastal area of Jingjiang River happened a total of208times, in anaverage of1.92years, from high to low is partial water＞water＞heavy water. Allkinds of drought in coastal area of Jingjiang River happened a total of106times, in an average of3.76years, from high to low is partial drought＞drought＞heavy drought.Both floods and droughts occurred in the same year a total of85times, in an averageof4.69years, from high to low is partial water＞alternate happen＞partial drough＞water＞drought＞heavy water＞heavy drought. According to the statistics, since the16th century, in every century, the highest occurred frequency is flood, flood anddrought occurrence frequency is more and more frequent, flood and drought intervalachieve in an average of1.61years, in the republic of China period even high to1.03years, in the19th and20th centuries, flood and drought of coastal area of JingjiangRiver present frequent, serious trend, and mainly to flood disaster pattern. Evolutionof flood and drought in the area，besides controlled by Yangtze river flood,Atmospheric rainfall and other natural environment change, are more related to localpolitical orientation, economic structure, population change, encircling Yuan andfilling lake, agricultural cultivation, dams and many other human activities. In thedifferent historical period, the dominant factors to control the flood and droughtdisaster were different, but many factors above all participated to change the localflood and drought evolution process more or less, resulting in the flood and droughtin the area happened so rampant and with complicated reasons.⑶Flood and drought intensity analysis showed that: diveding the flood anddrought grade sequence of coastal area of Jingjiang River in every decade，bycalculating disaster strength index，showed the serious time of flood in coastal areaof Jingjiang River is the1840s,1860s,1930-1940s, the serious time of drought incoastal area of Jingjiang River is1640s,1940-60s,1970-1990s. Through calculatingflood disaster superposition index, revealed the alternate time of flood and droughtis the1660s,1820-90s and20th century.⑷Flood and drought cycle analysis showed that: use wavelet to analyse floodand drought grade sequence of coastal area of Jingjiang River. Through the threedifferent scale expansion transformation, in the global scale,100a resolution scaleand50a resolution scale, respectively get different wavelet variance and difference wavelet coefficience value，wavelet variance value revealed evolution of coastal areaof Jingjiang River existing a significant cycle of2a，at the same time existing5-6a,8-12a,16-20a and about100a’cycle. Based on the significant correlation offlood-drought sequence and local climate dry-wet sequence, and goodness of fitbetween wavelet coefficience value and mathematical statistics. Revealed theclimate humid center of coastal area of Jingjiang River is the1920-40s,1860s,1940snearby. Dry climate center is the1640s,1940-50s,1970-80s nearby.⑸Flood and drought mutation analysis showed that: Based on goodness of fit ishigher between the t-test of coastal area of Jingjiang River climate change andwavelet analysis on climate change, contrasting t-test and wavelet analysisconclusion, founding11mutation years reached agreement, that is in25scalesresolution, main climate change ages in coastal area of Jingjiang River are: in thebeginning of16century, humid to drought;1540s, drought to humid;1630s, humidto drought;1650s, drought to humid; in the beginning of18century, humid todrought;1730-40s, drought to humid; in the end of18century to the beginning of19century, humid to drought;1820s, drought to humid;1850s, humid to drought; in theend of19century to the beginning of20century, drought to humid;1950s, humid todrought.⑹The R/S analysis showed that: H value of the16-19th century respective are0.5900,0.7285,0.5938,0.6928. H value of the16-19th century is0.4908,16~19century H index are greater than0.5, reveals the flood and drought evolutiontendency in coastal area of Jingjiang River is persistent, flood and drought happeningtrend followed the previous change trend in different intensity, and getting more andmore strong on the whole. In the20th century, H is less than0.5, indicaties that localhuman activity has affected the wanton of local flood and drought evolution, floodand drought happening existing signs of weakening. This may be due to local humanactivities, such as flood drought control and relief measures etc. affect thespontaneous of disaster. However, the local flood control and drought situation is still very serious.⑺Coupling analysis of flood and drought in coastal area of Jingjiang River andthe local natural and social environment change showed that: changes oftemperature, dry and wet, mutation of climate are consistent in the east-central.Plum rains and solar activity have an significant effect on periodic change of floodand drought in coastal area of Jingjiang River. Human activities play a positive rolesometimes, and sometimes play a negative role in occurrence of flood and drought incoastal area of Jingjiang River. Because construction of water conservancy projectswere built, occurrence of flood and drought in coastal area of Jingjiang River will slowdown in the future for a period of time. Yet the rapid development of population andagriculture economy, making occurrence of flood and drought in coastal area ofJingjiang River are more vulnerable to climate influence. Overall, because of thecomplicated human activities in addition to the natural environment change, theflood and drought of the region is uncertainty. |
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