Flood Profiles of Iowa Streams

PROJECT PERIOD: Continuous since 1957
PROJECT CHIEF: David Eash Email David Eash
STUDY AREA: Statewide
COOPERATING AGENCY: Iowa Highway Research Board and the Project Development Division of the Iowa Department of Transportation (Iowa DOT Project HR-140)

NEED FOR STUDY:

Flood peak and water-surface-elevation profile information is needed for the economical and safe location and design of bridges and other structures on or over streams and the adjacent flood plains. Defining the limits of flood inundation and establishing encroachment limits on flood plains are related problems needing this information. Data for major floods are needed to compute flood-peak discharges and calibrate water-surface-elevation profile models at ungaged sites along streams.

OBJECTIVES:

Define the water-surface-elevation profiles and corresponding discharges along streams in basins with at least 100 mi2 of drainage area for selected floods. Evaluate the flood characteristics and hydraulics at existing and proposed flow structures in basins of all sizes when requested.

PROGRESS:

A new flood-profile report was published in November 2012. The report documents the August 11-16, 2010, flood on the South Skunk River in central and southeast Iowa. The report citation is:

Barnes, K.K., and Eash, D.A., 2012, Flood of August 11-16, 2010, in the South Skunk River Basin, central and southeast Iowa: U.S. Geological Survey Open-File Report 2012-1202, 27 p. with appendix. [Available online at URL http://pubs.usgs.gov/of/2012/1202/]

ONLINE INFORMATION:

Map and Chronology of Iowa flood-profile reports prepared by the USGS.

Summary of U.S. Geological Survey Reports Documenting Flood Profiles of Streams in Iowa, 1963-2012

This report summarizes 47 U.S. Geological Survey flood-profile reports that were published for streams in Iowa during a 50-year period from 1963 to 2012. Flood events profiled in the reports range from 1903 to 2010. The report summarizes flood-profile measurements, changes in flood-profile report content throughout the years, streams that were profiled in the reports, the occurrence of flood events profiled, and annual exceedance-probability estimates of observed flood events. A total of 94 stream reaches have been profiled in U.S. Geological Survey flood-profile reports. Floods were profiled for June flood events for 18 different years, followed by July flood events for 13 years, May flood events for 11 years, and April flood events for 9 years. Multiple large flood events exceeding the 2-percent annual exceedance-probability discharge estimate occurred at 37 of 98 selected streamgages during 1960-2012. Five large flood events were recorded at two streamgages in Ames during 1990-2010 and four large flood events were recorded at four other streamgages during 1973-2010. Results of Kendall's tau trend-analysis tests for 35 of 37 selected streamgages indicate that a statistically significant trend is not evident for the 1963-2012 period of record; nor is an overall clear positive or negative trend evident for the 37 streamgages.