Wednesday, May 28, 2008 - 1:45 PM
435

Impacts of, and recovery from, a catastrophic flood on a southeastern Missouri stream

Samuel B. McCord1, William J. Elzinga1, and John C. Pozzo Jr.2. (1) Ecology Department, MACTEC Engineering, Inc., 3199 Riverport Tech Center Dr., St. Louis, MO 63043, (2) Environmental Safety and Health, Ameren Services, 1901 Chouteau Ave., St. Louis, MO 63116

On December 14, 2005, a reservoir in southeastern Missouri failed and suddenly released over 1.5 billion gallons of water into a tributary of the Black River.  Upper segments of the tributary experienced flow conditions estimated to be comparable to a 1 in 10,000+ year flood, while lower segments of the tributary and the river downstream of its entrance experienced only 1 in 3 to 10 year floods.  We surveyed macroinvertebrate assemblages throughout the system to estimate the magnitude and geographical extent of the impact.  Taxa richness and EPT richness in the upper segments were considerably lower than reference conditions in the spring and fall following the flood.  In lower stream segments, however, these metrics increased to reference levels or greater.  Shannon diversity and a pollution-tolerance index were less effective in distinguishing between reference and impacted segments.  Reduced relative abundance of EPT organisms combined with increased abundance of chironomids and simuliids were also evident in the upper stream segments.  But despite obvious sediment deposition, macroinvertebrate assemblages in middle and lower segments were, at worst, similar to those of reference locations within the Black River system and in an adjacent river system. 


Web Page: flood, Black River, macroinvertebrates

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