Physical characteristics of sediment and habitat Roseboom, D. P., R. M. Twait, and T. E. Hill. 1992. Physical characteristics of sediment and habitat affecting aquatic plant distribution in the Upper Mississippi River System: FY 90. Report by the Illinois State Water Survey, Peoria, Illinois, for the U.S. Fish and Wildlife Service, Environmental Management Technical Center, Onalaska, Wisconsin, December 1992. EMTC 92-S011. 77 pp. (NTIS #PB94-109964) ABSTRACT The initial phase of this project was a literature review of the relationship between a sediment's physical characteristics and the ability of that sediment to sustain aquatic vegetation. The review included methods of determining sediment cohesiveness or shear strength under field conditions. A limited field survey investigated physical characteristics of vegetated and unvegetated sediments near proposed HREP sites and LTRMP monitoring sites on the Illinois and Mississippi Rivers. Preliminary results of 17 sites reveal possible relationships between sediment shear strength and the presence or absence of aquatic vegetation. Related site characteristics were also noted-- degree of shelter from wave action, Secchi disk transparency, depth, and visual characterization of sediment composition. Graphing of the sediment shear strength at each site and the degree of shelter around each site indicated that physical sediment characteristics determine the presence of emergent vegetation. The presence of submerged aquatic vegetation appeared less dependent on physical characteristics of sediment but more dependent on light penetration. Only when the major physical factors were considered simultaneously did a clear pattern of plant occurrence become evident. KEYWORDS submerged aquatic vegetation, aquatic plant growth, sediment, Illinois River, Mississippi River, wave action, Upper Mississippi River System