Coastal Oceanographic effects of summer 1993 Mississippi River flooding




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U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Weather Service


The Great Mississippi River Flood of 1993 caused significant changes to the landscape throughout the Midwest and ultimately to the coastal ocean. Normal late summer Mississippi River flows are markedly lower than the large amounts of freshwater that flow into the northern Gulf in spring and early summer. Since the flooding occurred at the time of year when flows into the Gulf of Mexico are normally lowest, the timing of the event and its oceanographic effects are of particular interest because of the exposure of marine ecosystems to abnormally large amounts of diluted seawater and the associated pulse of land-based pollutants.... This event has been well-documented by researchers in Gulf and East Coast states. A concerted effort to track the effects of this major natural event on the coastal ocean required a broad spectrum of information from Federal and state agencies and universities. This report provides information on weather, streamflow, and oceanography, and describes detectable impacts in the coastal marine environment from the Mississippi-Atchafalaya River outflows to the coast of North Carolina. This assessment was jointly produced by the NOAA Coastal Ocean Office and the National Weather Service.... While this report focuses upon the detectable changes in the coastal marine environment immediately following the flood event, longer term effects of the flooding will be better understood as scientists continue to study the coastal environments where the immediate effects were seen.


77 pgs.


floods, flooding, flood damage, oceanography, coastal