Risk analysis of combinations of short duration rainstorm and tidal level in Guangzhou based on Copula function

Guangzhou is a waterlogging-prone city, and short duration rainstorm, floods and tides are three key factors of its urban waterlogging. Using Archimedean Copula functions, this study calculated three joint distributions for annual maxima of one-hour rainfall and tidal level, annual maximum tidal level and the corresponding one-hour rainfall, and annual maximum one-hour rainfall and the corresponding tidal level. Then, for the different combinations of rainfall and tide in Guangzhou, we developed a risk probability model and calculated various risk probabilities and return periods, including conditional risk probability, simultaneous risk probability, and waterlog prevention risk probability. Results show that the Copula function gives a good fitting to the joint distribution of rainfall and tide and the combined risk analysis is reliable. This study would provide useful information for risk analysis of waterlogging in Guangzhou.