Study On The Characteristics Of Strong Wind And Rainstorm And The Encounter Joint Distribution In Large Reservoirs Along The Coast Of Guangdong

Affected by global warming,the frequency and scale of typhoons and rainstorm in many coastal areas have undergone significant changes in recent decades.These changes have brought great challenges to the safety of design and management of reservoirs.Most of the reservoirs in our country did not consider the encounter of strong wind and rainstorm in the past construction process;the calculation of design wind speed and wave run-up in the current standard did not involve too much encounter analysis,so whether the current dam elevations that have been built and current standards still meet the safety requirements under the conditions of climate change has become an urgent problem for water conservancy projects in coastal areas.Therefore,this article will take 10 large coastal reservoirs in Guangdong Province as the research object,analyze the temporal and spatial characteristics of wind speed and rainfall in Guangdong,discuss the correlation and encounter law between strong wind and rainstorm,and comprehensively evaluates the impact of the encounter of strong wind and rainstorm in coastal reservoirs on dams and the applicability of the calculations of current standards about the design wind speed in the coastal area of Guangdong.The main research contents and conclusions are as follows:(1)Analyze the tropical cyclone and typhoon data in Guangdong Province from 1949 to2020,and summarize the typhoon activity law of typhoon in recent decades;MK mutation,wavelet analysis and other methods are used to analyze the time variation characteristics of the average wind speed,maximum Wind speed,maximum 1d rainfall,maximum 3d rainfall and maximum 7d rainfall and summarize the temporal and spatial changes of wind speed and rainfall.The results show that the number of tropical cyclones landed in Guangdong Province from 1949 to 2020 shows an insignificant downward trend,but the typhoon frequency shows an insignificant upward trend(P<0.05).The rainfall in the large reservoirs along the coast of Guangdong is generally increasing,and the wind speed is generally decreasing.(2)Taking ten large reservoirs in the coastal area of Guangdong as the research object,three edge distribution functions are used to fit the distribution of wind speed and rainfall and evaluate the goodness of fit to select the best fit function.A wind speed-rainfall Copula joint distribution model is established to calculate the wind speed and rainfall recurrence levels in different return periods,and determine the design wind speed values under different recurrence levels.The wind speed values of the joint return period and the univariate return period are compared and analyzed to analyze the difference between the wind speed under the two conditions with and without considering the encounter of strong wind and rainstorm.The results show that when considering the encounter of strong wind and rainstorm,the maximum wind speed during the joint return period is about 10% larger than the maximum wind speed considering only a single variable.When there is no rainfall data,the water level data in front of the dam can be used to analyze the encounter situation and calculate the design wind speed.(3)According to the current standard for rolled earth-rock fill dams and stone masonry dams,the dam crest elevation of 10 reservoirs are calculated respectively under the standard design wind speed and the maximum 1d,3d,7d rainfall samples with the condition of considering the encounter of strong wind and rainstorm,and compared with the actual dam crest elevation to analyze the applicability of the design parameters of the current standard in large reservoirs in coastal areas.The results show that the two standards are basically reasonable for the calculation of design wind speed in Guangdong coastal areas.However,considering the possibility and potential danger of the encounter of strong wind and rainstorm,in the future.The encounter of strong wind and rainstorm can be considered to increase the safety redundancy of the reservoir when it is designed according to the standard for rolled earth-rock fill dams.