Analysis of long rainfall frequency curve in Changsha urban area of Hunan Province based on climate change

The temperature change in Changsha City of Hunan Province shows a continuous warming trend, and climate change increases the probability of extreme rainfall events in the city, further increasing the risk of urban waterlogging. This study cites the results of future rainfall inversion in Changsha urban area, selects historical (1970—2018) and future period (2030—2069) rainfall sample data as the research object, explores the characteristics and trends of precipitation in Changsha urban area, and based on Pearson III curve fitting rainfall intensity-duration-frequency curve(IDF curve), calculating the design rainfall in Changsha urban area under different return periods of long duration (24 hours). The research results are as follows: overall, the historical annual rainfall days in the urban area of Changsha City have shown a significant downward trend, and the maximum daily rainfall in the future period shows a significant upward trend compared to historical periods. The IDF curve fitting results indicate that the design rainfall with a return period of more than 20 years in the future is higher than the current design rainfall, and the extreme rainfall in the future is showing an increasing trend. The research aims to provide scientific support and basis for the planning and design of the urban waterlogging prevention and control system, as well as disaster prevention and reduction in Changsha city.