Research On Evolution And Countermeasures Of Droughts-floods Abrupt Alternation Events In Huaihe River Basin

Droughts-floods abrupt alternation event is the extreme combination of two kinds of extreme event in water cycle-drought and flood. With the impact of climate change and human activities, the frequency and influence scope of droughts-floods abrupt alternation events have shown an increasing trend, and now it can damage the production, life and ecological environment in many regions. It is practically significant to research on the evolution characteristics of droughts-floods abrupt alternation events, and evaluate the risk of this disaster, and reduce disaster risk through layout optimization of society and economics and scientific management of water resource projects.Affected by the special geographical location and complex climatic conditions, the frequency of drought and flood disasters are very high in Huaihe river basin, and the frequency of droughts-floods abrupt alternation events are also increasing in recent years. The sharp change from drought to flood disaster in the short term will lead to more serious damage than drought or flood disaster. Droughts-floods abrupt alternation events will cause tremendous losses to the high density of population and industrial and agricultural production in Huaihe river basin. So the research on the evolution and comprehensive response of droughts-floods abrupt alternation events in Huaihe river basin is very urgent and necessary.Based on water cycle theory and regional disaster assessment theory, this paper built the theoretical and technical framework for dealing with droughts-floods abrupt alternation events, and then it was applied to Huaihe river basin. The principal conclusions of this study can be drawn as follows:(1) The theoretical system and technical framework have been put forward to study on evolution rule and response strategies of droughts-floods abrupt alternation events. Connotations and formation mechanism of droughts-floods abrupt alternation events were analyzed from hydrology, meteorology and water circulation perspective. An integrated method system including quantitative recognition, evolution analysis, risk assessment, trend prediction and integrated strategies was put forward to study on evolution rule and response strategies of droughts-floods abrupt alternation events. Quantitative identification index for droughts-floods abrupt alternation events will be established by daily precipitation data in order to improve time resolution of index. Index system and assessment model for risk assessment of droughts-floods abrupt alternation events were built based on disaster risk assessment theory. Future spatial-temporal evolution of this event was forecasted by the Global Climate Models. An integrated strategies coping with droughts-floods abrupt alternation disaster was presented based on history and future evaluative characteristics and disaster risk assessment results.(2) Spatial-temporal evolution of droughts and floods and the damage in Huaihe River Basin were analyzed. The results show that droughts and floods occur frequently in Huaihe river basin, bring out serious damage of life and property. So it is necessary to research on the evolution characteristics and response strategies of droughts-floods abrupt alternation events in order to reduce the losses of flood and drought disasters in Huaihe river basin.(3) Temporal and spatial distributions of historical droughts-floods abrupt alternation events were analyzed. Quantitative identification index of droughts-floods abrupt alternation events was constructed, and the rationality of this index was also validated. The calculation shows that, the droughts-floods abrupt alternation events occurred widely with average range of 17.35% in Huaihe river basin. These events were also occurred frequently in this basin. The frequency in south bank of upper Wangjiaba and most of the Rigan area is up to 29%-43%. From the perspective of intra-annual distribution, about 84.77% of droughts-floods abrupt alternation events occurred in the 6-8 month.(4) Risk assessment and zoning of droughts-floods abrupt alternation disaster were carried out. The results show that, the high risk areas are mainly distributed in the south bank of upper Wangjiaba and most of the Rigan area. The high and middle risk areas are mainly distributed in the north bank of upper Wangjiaba, north bank of Benghong interval and most of the Yishusi area. Compared with 1961-1980, droughts-floods abrupt alternation disaster was at elevated risk in 1981-2011. The main reason is increased frequency and exten of droughts-floods abrupt alternation events leading to rising danger. While water conservancy and irrigation water-saving facilities to be effective to alleviate the risk(5) Future evolution tendency of droughts-floods abrupt alternation events were predicted.5 CMIP5 models were selected to forecast the future temporal and spatial distribution of droughts-floods abrupt alternation events in RCP2.6, RCP4.5 and RCP8.5 scenario. The results show that, droughts-floods abrupt alternation events will occur at a lower frequency in the future. There are large differences of prediction results among 5 models, and the estimated uncertainty is significantly.(6) An integrated strategies dealing with droughts-floods abrupt alternation disaster risk was put forward in Huaihe river basin. The controllability and corresponding control approaches of droughts-floods abrupt alternation disaster risk were analyzed from the formation process of disaster risk. Specific risk response programs in Huaihe River basin were presented from reducing disasters, controlling exposure, reducing vulnerability, improve ability of damage prevention and mitigation, and promoting management levels.This study will further develop the theory and method of droughts-floods abrupt alternation events. The findings are expected to provide methodological support for the study on quantitative identification, the spatial-temporal evolution, and risk assessment and risk zonation about this disaster, and to provide scientific basis for prevention and mitigation droughts-floods abrupt alternation disaster risk.