Ž . Marine Geology 162 1999 133–144 www.elsevier.nlrlocatermargeo A preliminary sediment budget for the Winyah Bay estuary, South Carolina, USA Soraya M. Patchineelam a , Bjorn Kjerfve a,b, ) , L. Robert Gardner a,b ¨ a Department of Geological Sciences, UniÕersity of South Carolina, Columbia, SC 29208, USA b Marine Science Program and Belle W. Baruch Institute for Marine Biology and Coastal Research, UniÕersity of South Carolina, Columbia, SC 29208, USA Received 22 June 1998; accepted 12 May 1999 Abstract Winyah Bay, a 65-km 2 coastal plain estuary in South Carolina, has an average freshwater input of 557 m 3 s y1 and presently receives 0.43 =10 6 t yr y1 of suspended sediments from its watershed, corresponding to a yield of 12.7 t km y2 yr y1 . However, 20 dams have been constructed on the upper rivers, primarily on the Yadkin and Pee Dee rivers, which serve to capture an additional 0.40 =10 6 t yr y1 of sediment, implying a gross sediment yield of 24.5 t km 2 yr y1 for the watershed although almost 50% never reaches the coast. Continuous dredging in the estuarine channels removes 0.107 =10 6 t yr y1 of silt and clay from the estuary. Sediment coring and 210 Pb analysis indicate that the sedimentation rate in Mud Bay, a high accretion area in the lower estuary, is 5.5 mm yr y1 , which together with previous estimates of marsh sedimentation rates of 2.7 mm yr y1 in the tidal marshes surrounding the estuary leads to a total estuarine mud sedimentation estimate of 0.24 =10 6 t yr y1 . Thus, 80% of the fine-grained sediment reaching Winyah Bay is either accumulating in adjacent marshes or on estuarine mud flats or is being dredged and deposited offshore. Although these budget calculations need further confirmation by direct measurements and additional coring, Winyah Bay apparently delivers only a minimal amount of suspended fine-grained sediments to the coastal ocean. q 1999 Elsevier Science B.V. All rights reserved. Keywords: suspended sediment budget; estuary; 210 Pb coring; sedimentation rates 1. Introduction Estuaries are ephemeral geological environments located at the interface between rivers and ocean ) Corresponding author. Department of Geological Sciences, University of South Carolina, Columbia, SC 29208, USA. Tel.: q1-803-777-4600; E-mail: bjorn@sc.edu where they receive sediment input from both. Farm- ing, deforestation, surface mining, and urbanization in drainage basins change the natural sediment deliv- ery to estuaries. These activities increase the riverine sediment discharge to estuaries, causing shoaling and higher turbidity. On the other hand, dams and reser- voirs decrease the river-sediment discharge, which has contributed to coastal erosion in some areas during this century. Because estuaries serve as har- bors and ports, it is commonly necessary to dredge 0025-3227r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S0025-3227 99 00059-6