A Brief History of Beach Nourishment in South Carolina
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A brief history of beach nourishment in South Carolina By Timothy W. Kana Coastal Science & Engineering Inc. P.O. Box 8056, Columbia, SC 29202 [email protected] ABSTRACT ADDITIONAL KEYWORDS: There were ~59 discrete beach-nourishment events along the South Carolina coast Beach nourishment, South Caro- between 1954 and 2010. These projects encompassed 17 localities ― 62.6 miles lina, fill density, unit volumes, unit ― which is ~65 percent of the developed or accessible-park oceanfront in the state costs. (~33.5% of the ocean coast). The total volume of nourishment through 2010 was Manuscript submitted 4 September ~44.1 million cubic yards (mcy) for an average fill density of 133.3 cubic yards per 2012, revised and accepted 21 Sep- foot (cy/ft) of shoreline. The adjusted cost of all projects in 2010 constant dollars tember 2012. (2010$$) was (~)$351 million for an average unit-volume cost of $7.96/cy (2010$$). Nourishment volumes by decade peaked in the 1990s at 20.7 mcy ― 47 percent of the total. Between 2000 and 2010, nourishment volumes declined to ~12.7 mcy About 53% (~98 miles) of the ocean partly due to reduced need following initial restoration efforts at some sites. Six coast is developed (or accessible park) project areas (North Myrtle Beach, Myrtle Beach, Garden City-Surfside Beach, land. The remainder (~89 miles) is largely Folly Beach, Hunting Island, and Hilton Head Island), comprising 42.6 miles of inaccessible and undeveloped wilderness coast, have received about 70% of the nourishment volume. Most of these sites beaches. Of the developed beaches, fully have measurably wider beachfront area compared with pre-nourishment conditions. 65% have received nourishment at some Hilton Head Island, with five events since 1969, has received 10.6 mcy. Three sites level during the past 55 years as detailed (Debidue Beach, Folly spit, and Hunting Island), comprising ~7% of the nourished herein. shoreline in South Carolina, have not kept pace with erosion and have lost beachfront PURPOSE area. The volume and cost of nourishment applied over project lengths and time pe- As part of a larger effort to track riods yield South Carolina expenditures averaging (~)$39 per foot of shoreline per regional sand volumes at decadal-to- year (2010$$) [range (~)$7–$107/ft/yr]. The present value of developed oceanfront century time scales for community shoreline in South Carolina is roughly in the range $5,000 to $50,000 per linear foot. planning, the author searched for nour- Thus, annualized expenditures for areas nourished have averaged well under 1% of ishment records from numerous sources, property values. particularly the agencies responsible for he first beach nourishment project South Carolina’s nourishment history permitting and executing projects. It soon in South Carolina was at Edisto is as varied as its segmented coast. With became clear that records are incomplete, TBeach in 1954 (Figure 1). That numerous tidal inlets and large ebb-tidal inconsistent, or impossible to find for project involved 830,000 cubic yards deltas in this “mixed-energy” setting some older projects. Nevertheless, to (cy) of poor-quality material dredged (Hayes 1994), the 187-mile ocean shore- track littoral volumes over time, quanti- from the back-barrier salt marsh and line exhibits diverse signatures of erosion, ties placed in nourishment events are an placed by hydraulic dredge along 1 mile development styles, and shore-protection important component of sand budgets at of eroding shoreline (USACE 1969, measures (London et al. 2009, OCRM mesoscales. Cubit 1987). The muddy sediments (vis- 2010). The northeast portion of the coast This paper is an attempt to compile ible as large plumes on historical aerial (the “Grand Strand”) is a relatively stable best-available data on the volumes photographs) quickly winnowed from 35-mile-long arcuate segment between placed, lengths of shoreline directly the beach, leaving in place a concentra- two of South Carolina’s four jettied inlets nourished, and costs of each project. tion of oyster shells, enhancing Edisto’s (Little River and Murrells). The central Source references should be checked reputation as the shelliest beach in South part of the coast around Charleston con- for details on borrow area locations and Carolina. Since 1954, nearly five dozen tains almost a dozen beach-ridge barrier sediment quality, particularly reports by nourishment events have added over 44 islands, several of which have the classic South Carolina Department of Natural million cubic yards (mcy) to 63 miles of drumstick morphology (e.g. Bull Island, Resources (SCDNR) (e.g. Van Dolah et beach at a present-day cost of (~)$350 Isle of Palms, Kiawah Island ― Hayes al. 1998). million (Figure 2). Some projects, like 1979). Mean tide range (6.9 ft, NOAA- Edisto’s first, placed less-than-ideal sedi- COOPS) and the size of inlets reaches a METHODS ments on the beach. However, over time, maximum near Hilton Head Island and Nourishment projects selected for in- the quality of nourishment material has Daufuskie Island at the southwest end clusion were implemented between 1954 improved, the volume of projects has in- of the state with nearly every foot of and December 2010, nominally a “55- creased, and the condition of many South “ocean” shoreline influenced by ebb-tidal year” period. Each project was assigned Carolina beaches is better. delta shoals (Hayes and Michel 2008). to the decade completed, particularly Shore & Beach Vol. 80, No. 4 Fall 2012 Page 9 those straddling different decades dur- had to be apportioned from the totals. In ing construction. Primary data sources some cases (given in italics), a cost estimate in order of importance include: is based on similar unit-pumping costs for • Unpublished project records and the time period of execution. While these final reports of quantities, costs, and estimates are ripe for future revision, the placement limits. author found that they constitute a small • Interviews and correspondence with proportion of the overall expenditures. The project engineers, particularly USACE large projects, accounting for the majority officials. of nourishment volumes and costs, are • State permitting records. generally well documented. • Pre-project planning documents. English units and original project • Third-party scientific publications. costs at time of construction are listed • Media reports. herein for consistency with the source To keep the present paper brief, no documents. This is to facilitate cross- more than two sources are listed for each referencing of quantities in the future. project. Future researchers many uncover The original cost of each project was con- more precise archived records for some verted to 2010 constant dollars (2010$$) projects. In the detailed tabulations that using the USACE Civil Works Construc- follow, volumes that are considered im- tion Cost Index System ― Base Year precise are given in rounded amounts. 1967 (CWCCIS 2012). The tabulations The lengths and volumes given with give the index normalized to the Year greater precision are “in-place” measures 2010 (i.e. = 1.0), which yields an adjusted as documented by post-nourishment cost in 2010 dollars for each project. surveys as reported by engineers and Applicable lengths published in final reports or other un- and project durations published project documents. Where Project lengths (in feet) are as docu- pay volumes and “in-place” volumes mented in the original sources. In cases are available from source documents, of multiple nourishment events and over- the volume listed is the best-available lapping areas within a particular locality, “in-place” volume since the goal is to the maximum length of shoreline nour- account for actual quantities added to the ished over time was used as the “project beach. For example, several Hilton Head length.” For example, Hunting Island has Island projects have involved consider- been nourished eight times since 1968 ably higher “in-place” volumes than the with individual projects ranging from pay volumes for the benefit of the com- 2,484 to 12,160 linear feet. Upon review munity (OA 1992, 1999). of the stationing and limits of these Cost information was similarly com- Figure 1. Vicinity map of the South projects, it was determined that ~15,700 piled from project records to the extent Carolina coast. linear feet (~75% of the Hunting Island possible. The “federal” projects executed ocean shoreline) have received nourish- by USACE generally include engineering, bypassing projects associated with jetty ment. This “impact” length was adopted planning, and related “soft costs” whereas construction at Murrells Inlet (1977) and for calculation of unit rates. most of the locally-sponsored projects only Little River Inlet (1980) were rolled into all The applicable years of project im- include construction costs. Some of the capital costs. The nourishment component pacts were assumed to begin around the time of the first nourishment at a site and to extend through 2010. These pe- riods were arbitrarily rounded in nearest five-year increments so as to provide measures of annualized unit volumes and costs. The longest duration project is, therefore, Edisto Beach, at 55 years while the shortest duration project is Daufuskie Island (ATM unpublished data), which was constructed in 1999. The annualized expenditures for proj- ects are highly sensitive to the applicable duration, of course, but some time period must be assumed. In the case of Edisto Figure 2. Beach nourishment volumes (in cubic yards [cy]) by decade. Beach, the second and third projects did Sources listed in Tables 1-2. not occur until 40-50 years later (1995 Page 10 Shore & Beach Vol. 80, No. 4 Fall 2012 and 2006), so the annualized expendi- ture is relatively low compared with Daufuskie Island. Omission of the 1954 project brings Edisto’s expenditures more in line with statewide averages. Unit measures The fundamental unit of littoral sedi- ment budgets is a volume per unit length of shoreline within defined cross-shore boundaries (Kraus and Rosati 1998, Ro- sati 2005).