Fine sediment erodibility in Lake Okeechobee, Florida

Abstract

The critical need to predict the turbidity in water due to fine-grained sediment suspension under wave action over mud deposits for sedimentation and erosion studies, as well as sorbed contaminant transport, is well known. Since fall velocities of fine sediment particles are very small, they can be easily transported by hydrodynamic flows such as waves and currents. The presence of these particles in the water column affects accoustic transmission, heat absorption and depth of the eutrophic zone (Luettich et al., 1989). Because these sediments also have a strong affinity for sorbing nutrients and toxic chemicals, sediments which have been deposited on the bottom may function as a source of contaminants to the water column if they are disturbed by eroding forces resulting, for instance, from wave action. An outstanding example of a water body for these problems is Lake Okeechobee, the largest shallow lake in Florida. This lake shows typical signs of artificial eutrophication mainly due to increased phosphorus loading associated with the surrounding region. Resuspension of sediment at the bottom of Lake Okeechobee composed of fine-grained material has been examined. A sediment transport model was used to simulate likely trends in the evolution of the vertical suspended sediment concentration profile resulting from wave action, and the corresponding eroded bed depth was calculated through mass balance. Requisite information on characteristic parameters and relationships related to fine sediment erodibility were derived from field sampling of bottom sediment in the lake, and through laboratory experiments using this sediment and lake water. (161pp.)