Sediment Load during Flood Events for Illinois Streams. Long Term ResourceMonitoring Program

摘要

A large percentage of the annual sediment yield from a watershed is transportedby a stream during a small number of floods that occur in a relatively short period of time in a year. The sediment load during flood events are examined and relations between the annual sediment yield and the sediment load during the major floods in a given year are developed based on available stream sediment data from the state of Illinois. On the average, the annual flood transports from 20 percent (for large rivers) to 23 percent (for small streams) of the annual sediment load, while the two highest floods in a year transport from 32 to 43 percent of the annual sediment load. The average duration of the annual flood is only 9.2 days which is 2.5 percent of the whole year. The average duration of the two highest foods is 17 days which represents only 4.7 percent of time in a year.