Streamflow confers on society both benefits and hazards . Runoff downstream is a means to collect water for storage in dams for power generation of water abstraction . The flow of water assists transport downstream . A given watercourse has a maximum streamflow rate that can be accommodated by the channel , and which can be calculated . If the streamflow exceeds this maximum rate , as happens when an excessive amount of water is present in the watercourse , the channel can not handle all the water and flooding occurs . The 1993 Mississippi river flood , the largest ever recorded on the river , was a response to a heavy , long duration spring and summer rainfalls . Early rains saturated the soil over more than a 300,000 square miles of the upper watershed , greatly reducing infiltration and leaving soils with little or no storage capacity . As rains continued , surface depressions , wetlands , ponds , ditches , and farm fields filled with overland flow and rainwater . With no remaining capacity to hold water , additional rainfall was forced from the land into tributary channels and thence to the Mississippi . For more than a month , the total load of water from hundreds of tributaries exceeded the Mississippi ’s channel capacity , causing it to spill over its banks onto adjacent floodplains . Where the flood waters were artificially constricted by an engineered channel bordered by constructed levees and unable to spill onto large section of floodplain , the flood levels forced even higher
1993 Mississippi river flood
Great Flood of 1993
Streamflow