May 10, 2017

High Streamflow is Increasing, Raising Flood Risks

by
Climate Central
  • States that with the frequency of heavy precipitation increasing across most of the U.S., it follows that streamflow levels may be increasing as well
  • Analyzes streamflow data at more than 2,100 active gauges 
  • Finds that the number of days with high stream flow (the top 25 percent of readings) has risen over the past 30 years (1987-2016) in the largest rivers of the U.S., including the Ohio, Missouri, and Mississippi
  • States that heavy precipitation is the key element driving streamflow, although urbanization and the reduction of permeable surfaces also play roles, as does the engineering of dams and levees
  • States that the increasing number of days with high streamflow indicates that the risk for stream and river flooding is also on the rise
  • Examines the streamflow data for additional seasonal trends
  • Finds that in addition to heavy rain, spring snow melt can also play a role in streamflow
  • Finds some of largest increases in high streamflow days in Upper Mississippi River Valley and the Northwest during the spring