100-Year Flood Event at Konza Prairie Research Natural Area

Network News Spring 1993, Vol. 13 No. 1
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Kings Creek is the principal stream draining the Konza Prairie Research Natural Area, and its 1,046-ha drainage basin lies entirely within Konza boundaries. Since 1979, Kings Creek has been part of the U. S. Geological Survey (USGS) Hydrologic Benchmark Network. In addition to discharge records from the USGS gauging station located on a fifth-order reach of the main channel, discharge has been monitored continuously at weirs on four upstream tributaries since 1986.

A major flood event occurred in Kings , Creek on July 22, 1992 following several days of heavy rain. Floodwaters destroyed the gauging tube and walkway at the station, reaching a height of nearly 5 m above the streambed.

Although direct discharge measurements were not possible at the USGS station, a prediction equation that relates peak flows to water depth indicates a peak discharge of 277 cubic m. Based on flood recurrence models for streams in the region, a flood of this magnitude would have an estimated recurrence interval of 100 years. The previous highest flow recorded at this station was 128 cubic m on July 1, 1982 (see figure).

Although no major changes occurred in the course of the stream channel, large quantities of bed material (mainly limestone and shale gravel or cobble) were scoured and re-deposited along with large debris dams. Rates of periphyton production and chlorophyll a per unit area declined to almost 0 immediately after the flood, but primary production recovered within two weeks, and exceeded pre-flood levels for several weeks after that. Chlorophyll a had not reached pre-flood levels after one-and-a-half months. Data on recovery of invertebrate populations are still being analyzed. We hypothesize that the flood will have minimal impacts on a stream biota that is adapted to the lesser spates and frequent dry episodes common in upland prairie streams.

For more information: Lawrence Gray, Department of Biology. Ottawa University, 1001 South Cedar, Box 83, Ottawa, KS 66067, 913-242-5200, ext. 5467, or Walter Dodds, Division of Biology, Ackert Hall, Kansas State University, Manhattan, KS 66506.