复合洪水多源风险组合关系识别研究OA

Coastal cities frequently suffer from flood disasters,which are often driven not by a single hazard but by the synergistic effects of multiple interacting factors.Under the changing environment,the temporal and spatial scope of compound disasters has shown a trend of expanding year by year,and their disaster combination and diffusion effects pose a major threat to regional sustainable development.To explore the risk coupling relationships of compound flooding under changing environments,this study employed the Mann-Kendall test and wavelet analysis to assess the trends and periodicities of hydrological series.The results indicate that:①extreme values of tide level,rainfall,and discharge exhibit increasing trends,and the driving factors are likely to lead to an upward trend in regional hydro-meteorological elements.② The overall hydrological regime is currently in a wet phase of dry-wet cycles.With TL as an example,the main period of the annual maximum TL sequence at the Denglongshan Station is 22 years,and the subperiods are 5 and 10 years.In the contour diagram of the real part of the wavelet coefficient,negative and positive values in the figure represent low and high TLs,respectively.On the 22-year scale,five oscillations of alternating low and high TLs,including three periods of high TLs and three periods of low TLs,are present.On the 5-year scale,there are 20 oscillations of alternating high and low TLs,including 10 periods each of high and low TLs.On the 10-year scale,13 oscillations of alternating low and high TLs are observed,including six periods of high TLs and seven periods of low TLs,respectively.Additionally,with the combined effect of runoff-tidal dynamics,the compounding of multiple factors will amplify their superimposed impacts;Kendall return periods are applied to compute the compound hazard thresholds of multi-driver flooding.Based on the characteristics of the coupling of multiple disasters in composite floods,a mathematical model of composite disaster risk combination and diffusion pattern integrating the Copula function is constructed by statistical methods,revealing the interaction relationship and diffusion pattern between multiple disasters in composite floods.For compound flooding,the Copula function is first used to establish a two-variable joint distribution probability model,and the Kendall recurrence period under the same recurrence level is calculated;then,the combined disaster threshold of multiple disaster factors is deduced.Results show that:① The joint hazard threshold of multi-driver events is lower than that of single-factor extremes,indicating that interactive amplification effects among multiple drivers expand the impact scope of compound floods compared to univariate extremes.② When the return period is 100 years,the single hazard thresholds for tide level,discharge,and precipitation are 2.89 m,61 600 m3/s,and 253.6 mm,respectively.The combined hazard thresholds of tide level and precipitation are 2.36 m and 164.4 mm,and the combined hazard thresholds of tide level and discharge are 2.23 m and 38 800 m3/s.This study focuses on the superimposed coupling mechanisms of compound flood risks and quantifies their joint hazard thresholds,providing a more robust scientific basis for compound flood early warning systems.