Abstract: Effects of Dredging and Handling Techniques on Sediment Texture
Richard D. Hobson
Offshore sand and gravel deposits are an extensive mineral resource whose importance and economic value increase steadily as onshore and lagoonal sources become unavailable. One major use of these marine deposits is for beach nourishment where the amount of initial fill material required and the expected periodic renourishment requirements usually are estimated using fill-factor and renourishment-beachfill models, respectively. Textural properties of borrow site and native beach sediments are used as the basic input for beachfill model calculations. Alterations to borrow sediment texture properties by dredging and handling techniques could affect significantly both the predicted response of the sediments after placement in the beach environment and the economic aspects of the project.
A field experiment was conducted to identify and quantify some effects of dredging and handling techniques on sediment textural properties. Sediments from the entrance channel to New River Inlet, North Carolina, were surface sampled by SCUBA divers prior to suction dredging and then resampled by coring the hopper-barge loads before their discharge at the beach dump site. Beach samples also were collected at the project site to evaluate native-beach composite properties. Comparisons of dredged and predredged sediments textures indicate average handling losses of about 13% of the sediments dredged. These losses are from the medium to fine-sand sizes (½ to 1/16 mm) and should be considered in terms of dredging and handling processes, and the economic and physical implications from t e standpoint of beachfill-model calculations.
AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC