Neosho River
Flooding Exercise

James S. Aber
Emporia State University


The Great Flood during the summer of 1993 was the largest flood of the 20th century in the north-central United States. Many stream gauging stations in the Mississippi and Missouri basins set all-time historical records. For example, on August 1, 1993, the Mississippi River at St. Louis peaked at 1,080,200 cfs (30,588 m3/s) flow. Rivers in eastern Kansas also experienced high flows and significant local flooding.

Prior to 1993, the largest historical flood in eastern Kansas occurred during the summer of 1951. This flood resulted in widespread damage and economic loss. It led to construction of several flood-control reservoirs, levees, and other drainage structures. These structures were largely successful in lessening the impact of flooding during 1993. Reservoir operation has the general effect of reducing peak downstream discharge by spreading the high flow over a longer time interval--weeks or months instead of days.

For this exercise, students will analyze the history of flooding on the upper Neosho River in east-central Kansas--see drainage maps. We will utilize peak annual flow data from the Americus and Iola gauging stations. These stations are located respectively above and below John Redmond Reservoir. This lake is a flood-control reservoir located in Coffey County; it began operation in 1961. River flow at the Iola gauging station is fully regulated by John Redmond Reservoir; flow at the Americus gauging station is partly controlled by the upstream Council Grove Reservoir (Morris County).

View northward over the Neosho River and floodplain at Emporia, a few miles below the Americus gauging station. Note the broad floodplain with agricultural land use. The area of this scene was inundated completely during the flood of 1998. Kansas highway 99 is visible in the distance. Kite aerial photograph, © J.S. Aber (5/02).
Closeup view over the Neosho River channel in low-flow stage at Emporia, Kansas. A gallery of trees follows each side of the channel. Kite aerial photograph, © J.S. Aber (5/02).
Overview of Neosho River floodplain at Harford, just above John Redmond Reservoir. Floodplain to left; city of Hartford (right background) is situated on a low terrace. Kite aerial photograph, © J.S. Aber (4/01).
Low-flow view of gravel riffles in the Neosho River channel at Neosho Falls, northeastern Woodson County. The riffles are composed almost entirely of chert pebbles derived from the Flint Hills. Such riffles are important for maintaining fish habitat. Photo date 3/94, © by J.S. Aber.

U.S. Geological Survey--peak streamflow for the nation.

Locate and download annual peak flow data values for the Americus station (07179730) and Iola station (07183000). Click "site number" and submit, then enter the site number and submit again. Finally click on the site number to see a graphical display of peak annual discharges.

To see the actual yearly values, click on the "table" option. You also can obtain a "tab-separated file" of the numerical values. The Iola record is one of the longest available on the Neosho River, beginning in 1885. The Americus record began in 1964.



  1. Construct (or download) graphs showing peak annual flow values for the Neosho River for the intervals indicated below.

  2. Calculate the mean annual flood for the following time intervals. The mean annual flood is simply the average value of peak stream flows for the period of record.

  3. Bank-full discharge at the Iola gauging station is 32,300 cfs (Byerley 1995). Does this figure correspond to any results of step 2? Explain the significance of the mean annual flood.

  4. How many out-of-bank floods took place at Iola during the period of record prior to John Redmond Reservoir (1918-1960)? What is the recurrence interval for out-of-bank flooding during this period? Hint: divide number of years by number of out-of-bank floods.

  5. How many floods exceeded 50,000 cfs at Iola during the period of record prior to John Redmond Reservoir (1918-1960)? What is the recurrence interval for floods of this magnitude?

  6. How many out-of-bank floods took place at Iola during the period of record after John Redmond Reservoir (1961-present)?

  7. Characterize and contrast the great floods of 1951 and 1993 for the Iola gauging station.

  8. Characterize and contrast floods at both gauging stations during the period since John Redmond Reservoir went into operation (1961-present). Note: out-of-bank flood discharge at Americus gauging station is stage height 26 feet or ~10,200 cfs (Putnam, USGS WRD).

  9. Discuss how operation of John Redmond Reservoir has changed the downstream behavior of the Neosho River. Consider flooding, overall stream hydrology, and sedimentation, as well as impacts on fish and riparian habitats.

Turn in:


Return to wetland syllabus. Text and imagery © J.S. Aber (2007).