Indicators and Changes of Extreme Rainfall, Flooding and Sediment Events in the Middle Reach of the Yellow River

In the context of climate change, the frequency and intensity of extreme events may increase. In recent years, the measured water and sediment in the middle reach of the Yellow River has been significantly reduced. In addition to the impact of human activities, it is also necessary to analyze the impact of extreme rainfall on water and sediment changes. According to the characteristics of rainfall in the middle reach of the Yellow River and the extreme precipitation index recommended by the World Meteorological Organization, it is divided into two categories which are sessions and accumulation to analyze the variation trend of different precipitation indexes, the extreme rainfall indicators related to water and sediment changes and their changes. It is analyzed on the indicators of extreme flood and sediment events in the middle reaches of the Yellow River and their changing characteristics. Based on the standard of the occurrence probability of less than 10%, the extreme values criterion of sessions and cumulative indicators in extreme rainfall, flood and sediment events were determined. This paper analyzed the frequency and variation of extreme events in different times and the response relationship between extreme rainfall and extreme flood and sediment events. Preliminary analysis shows that the average numbers of days, total amount, and intensity of extreme rain from 2000 to 2015 have not exceeded the maximum in the series from 1956 to 1999. In addition to the significant increase in individual indicators of the maximum ,1day rainfall in June, 5-day rainfall in June ，the number of rain days in 1-10 mm, there has been no significant change in the indicators of sessions and cumulative extreme rainfall. Affected by factors such as underlying surface conditions and rainfall areas, there is no significant quantitative relationship between extreme rainfall and extreme flood events, extreme sediment events.