Hydraulic changes in rivers due to navigation Bhowmik, N. G. 1992. Hydraulic changes in rivers due to navigation. Pages 10-22 to 10-40 in Proceedings, Fifth Federal Interagency Sedimentation Conference, March 18-21, 1991, Las Vegas, Nevada. U.S. Fish and Wildlife Service, Environmental Management Technical Center, Onalaska, Wisconsin, December 1992. EMTC 92-R001. (NTIS # PB97-104657) ABSTRACT Movement of river traffic such as tows, barges, or recreational craft in navigable rivers and streams can temporarily alter the hydraulic characteristics of the river cross section. These changes may include bow, stern, or transverse waves; resuspension of bed sediments; changes in velocity structures either in close proximity to the moving vessel or within the water body; altered flow direction; and transport of sediment and water into side channels, sloughs, or backwater lakes. Research is being conducted at the Illinois State Water Survey to determine and evaluate the changes that may accompany the movement of river traffic within the Upper Mississippi River System (UMRS). The UMRS extends from Cairo, Illinois, at the junction of the Mississippi River with the Ohio River, to the headwaters of the Mississippi River in Minnesota. The major tributary of this system is the Illinois River. Data were collected on waves, drawdown, sediment, and velocities by using state-of-the-art equipment and instrumentation. Analysis of the data has shown that barge traffic can temporarily increase the concentrations of suspended sediments; that it will alter the two components of the velocities, the magnitudes of which are dependent upon the relative distances of the measuring points; and that it can generate waves and drawdown. The duration of the increases in suspended sediment concentrations and velocities is dependent on the traffic characteristics and ambient flow conditions of the river. It was also observed that flows near the shore zone can change direction as a result of the movement of loaded or unloaded barges. Physical changes associated with the river traffic may alter some biological habitats. Research on physical changes resulting from river traffic is geared toward determining the relative importance of alterations in the river environment and how they may affect the aquatic habitats. KEYWORDS navigation, Upper Mississippi River System, hydraulic changes, Illinois River