Fate and Effect of an Experimental Mixed-Sediment Mound

An Experimental mixed-sediment mound has been constructed 7 km south of the mouth of the Cape Fear River, NC. The objectives of the study include: (1) document the fate of the mound, (2) document sediment characteristics over the long term; and (3) investigate the generation of turbidity associated with the mound. Directional wave information, vertical current profiles, surface-sediment samples, suspended-sediment concentration measurements, and repetitive high-resolution bathymetric and sub-bottom surveys have been obtained since April 2001. Results to date indicate that the mound has remained intact while the mound crest may be creeping toward shore in response to the prevailing wave and current conditions. Sedimentary characteristics appear to be cyclical in response to local processes. The general trend is that over time the high concentration of fines winnow out leaving a predominantly sand pavement on the mound surface until the next storm event. In addition, turbidity levels over the mound were found to not be anomalously high in comparison to ambient levels. This study is important for model development and dredging operations implementation.