Physical changes due to navigation in the UMRS Bhowmik, N. G. 1991. Physical changes due to navigation in the Upper Mississippi River System. In Proceedings, 1991 Governor's Conference on the Management of the Illinois River System, Third Biennial Conference, Peoria, Illinois, October 22-23, 1991. Reprinted by U.S. Fish and Wildlife Service, Environmental Management Technical Center, Onalaska, Wisconsin, April 1993. EMTC 93-R019. 9 pp. (NTIS #PB94-108917) ABSTRACT The Mississippi, Illinois, Ohio, and Missouri Rivers are used extensively for the transport of goods and commodities, as well as for recreational activities. The Upper Mississippi River System, extending from its confluence with the Ohio River to its headwaters near St. Paul, Minnesota, is used extensively by commercial barge traffic with typical configurations of about 32.1 by about 335.5 meters in plan form, with a draft of 2.74 m. A barge convoy such as this can move up and down the river at speeds from about 1.35 to 4.4 meters per second. Movement of such a body through a river whose cross section in low-flow conditions can be as little as 275 by 3 to 4 m creates significant disturbances of the river environment. The changes in the river environment resulting from the movement of such traffic may include creation of waves and drawdown, altered velocity and pressure regimes, resuspension and lateral movement of sediment, and temporary changes in flow direction due to the return flow. Research has been initiated to determine the physical changes associated with navigation within the Illinois and Mississippi Rivers. Field data on various hydraulic and sediment resuspension characteristics have been collected and analyzed to determine functional relationships. These physical relationships will be used in the biological models to identify and determine changes in the aquatic environment due to navigation traffic. This paper discusses some of the physical changes in a large river environment due to navigation traffic. KEYWORDS physical changes, navigation, Upper Mississippi River System, Mississippi River, Illinois River, Ohio River, Missouri River