Trends in the Frequency of Extreme Flooding Events

Trends in the Frequency of Extreme Flooding Events: Trends in the frequency of precipitation events in which precipitation over a 7-day duration exceeds a 1-year recurrence interval for each particular climate division. Blue circles are positive trends, red circles are negative trends. The magnitude of the trend is linearly proportional to the radius of the circle. A 100% trend is equal to a doubling of the average yearly frequency, from 1 to 2 events per year. Check marks indicate positive trends with a local significance at the 5% level.

Credit: Figure reproduced from Kunkle and Andsager (1999), which did not consider Mexico, and excluded climate divisions in the U.S. lacking sufficient data.