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<br />;r <br />~ <br />I <br />~ <br /> <br />related runoff were felt both in upland areas and in the <br />floodplains. Pre-flood rainfall saturated the ground and <br />swelled tributary rivers. Subsequent rains quickly filled <br />surface areas, forcing runoff into the lower lands and <br />creating flood conditions. The recurrence interval of <br />the flood ranged from less than 100 years at many <br />locations to near 500 years on segments of the <br />Mississippi River from Keithsburg, Illinois, to above <br />5t. Louis, Missouri, and on segments of the Missouri <br />River from Rulo, Nebraska, to above Hermann, <br />Missouri. At 45 U ,So Geological Survey (USGS) <br />gaging stations, the flow levels exceeded the lOO-year <br />mark. The duration of the flood added to its <br />significance. Many areas were under water for months. <br /> <br />. Rainfall and floods like the 1993 event will <br />continue to occur. Floods are natural repetitive <br />phenomena. Considering the nation's short history of <br />hydrologic record-keeping as well as the limited <br />knowledge of long-term weather patterns, flood <br />recurrence intervals are difficult to predict. Activities <br />in the floodplain, even with levee protection, continue <br />to remain at risk. <br /> <br />. The loss of wetlands and upland cover and <br />the modification of the landscape throughout the basin <br />over the last century and a half significantly increased <br />runoff. Most losses occurred prior to 1930, but some <br />are related to more recent drainage, flood damage <br />reduction, and navigation development. Although <br />upland watershed treatment and restoration of upland <br />and bottomland wetlands can reduce flood stages in <br />more frequent floods (25 years and less). it is <br />questionable whether they would have significantly <br />altered the 1993 conditions, <br /> <br />. Human activity throughout the basin has <br />caused significant loss of habitat and ecosystem <br />diversity. Flood damage reduction and navigation <br />works and land use practices have altered bottomland <br />habitat adversely. <br /> <br />. The costs to the nation from the flood were <br />extensive, Thirty-eight deaths can be attributed directly <br />to the flood and estimates of fiscal damages range from <br />$12 billion to $16 billion, Agriculture accounted for <br /> <br />EXECUTTVES~ARY <br /> <br />over half of the damages. More than 70 percent of the <br />crop disaster assistance payments were made to counties <br />in upland areas where ground saturation prevented <br />planting or killed the crop. Nearly 50 percent of the <br />approximately-lOO,OOQ homes damaged, suffered losses <br />due to groundwater or sewer backup as opposed to <br />riverine flooding. Flood response and recovery <br />operations cost the nation more than $6 billion. In <br />addition many costs can not yet be quantified. Impacts <br />on businesses in and out of the basin have not been <br />calculated. Tax losses to governments are unknown, <br />The impacts of the flood on the population's physical <br />and mental wellbeing are just being identified and are of <br />concern. <br /> <br />. Flood damage reduction projects and <br />floodplain management programs, where implemented, <br />worked essentially as designed and significantly reduced <br />the damages to population centers, agriculture, and <br />industry. It is estimated that reservoirs and levees built <br />by the U.S. Army Corps of Engineers (USACE), <br />prevented more than $19 billion in potential damages. <br />Large areas of Kansas City and St. Louis were spared <br />the ravages of the flood, although several suburbs <br />suffered heavy damages. Watershed projects built by <br />the Soil Conservation Service saved an estimated <br />additional $400 million. Land use controls required by <br />the National Flood Insurance Program (NFlP) and state <br />floodplain management programs reduced the number <br />of structures at risk throughout the basin. . ~ <br /> <br />. Many locally constructed levees breached <br />and/or overtopped. Frequently, these events resulted in <br />considerable damage to the land behind the levees <br />through scour and deposition. <br /> <br />. Flooding during the 1993 event would have <br />covered much of the floodplains of the main stem lower <br />Missouri and upper Mississippi rivers whether or not <br />levees were there. Levees can cause problems in some <br />critical reaches by backing water up on other levees or <br />lowlands. Locks and dams and other navigation related <br />structures did not raise flood heights. For more <br />frequent floods -- less flow -- navigation dikes may <br />cause some minor increase in flood heights. <br /> <br />ix <br />