Flood Recurrence Intervals

Norlene Emerson, University of Wisconsin-Richland
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Initial Publication Date: May 19, 2012 | Reviewed: June 4, 2013


This lab activity has students use stream discharge data obtained from the USGS Water Resources Division web site in order to calculate recurrence intervals for a local stream. Using the recurrence data generated, the students then make recommendations to the residents of a local town as to what they might do to reduce their loss from the effects of frequent flooding in their community.

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This activity has been developed for an introductory-level Environmental Geology course that has both a lecture and lab component. Most of the students who take the course are non-majors and are at the freshman or sophomore level.

Skills and concepts that students must have mastered

Students should have some basic knowlege of streams and floods. Prior experience with using excel to make graphs is helpful but not manditory.

How the activity is situated in the course

This lab is given to students after they have been introduced to the topics of streams and floods in the lecture portion of the course.


Content/concepts goals for this activity

Following completion of this activity, students should be able to:

  • define the terms "recurrence interval" and "flood stage"
  • calculate recurrence intervals given peak flow data for a particular stream
  • calculate annaul flood exceedance probability
  • determine land area covered by floodwater on a topographic map given the river flood stage and discharge values

Higher order thinking skills goals for this activity

interpret a flood frequency chart, extrapolate a trendline in order to make predictions concerning larger future floods

Other skills goals for this activity

Students should have prior experience using Excel software to make spreadsheets, create charts, and enter formulas.

Description and Teaching Materials

In this lab, students calculate recurrence intervals for various flood records on a portion of the Kickapoo River in southwest Wisconsin based on historical data obtained from a gaging station on the Kickapoo River maintained by the USGS. The historical data is accessed from the USGS Water Resources Division . Students create Excel tables to calculate discharge ranks, recurrence intervals, and annual exceedence probablilities. The students use the data they generate in order to create a recurrence interval graph and to map the extent of a flood event.

Student Handout (Microsoft Word 85kB Jun11 13)
Map of Gays Mills (Microsoft Word 229kB May19 12)

Teaching Notes and Tips

This lab activity as presented can be completed during a two hour lab period. Students will need access to the internet and Excel.


Students will each turn in their Excel data tables, their flood frequency graph, a map of the Kickapoo River valley near Gays Mills, WI, and their answers to questions on the activity sheet.