ARTIFICIAL MANIPULATION OF BEACH PROFILES

A field study was conducted at Myrtle Beach, South Carolina (U.S.A.), to determine the response of natural beaches to artificial manipulation by sand scraping. Between March 1981 and May 1982, a total of 100,000 m3 of sand was shifted from the lower beach to the backbeach on three occasions over a R-km length of shoreline. Fiftyfour profile stations were surveyed to the -1.0 meter contour as many as ten times during the study to determine the effect of scraping and fill along a stable-to-slightly erosional beach. The purpose of the scraping and fill was to provide temporary erosion relief, protect existing dunes and structures, and provide a wider recreational beach at high tide. It was found that scraping and fill had little adverse effect on the beach cycle in the northern zone of the project area, which is fronted by a natural dune system. Fill placed at a gentle slope along the seaward margin of the dunes remained in place for up to ten months before eroding to the prefill surface. In contrast, similar quantities of fill along shore protection structures in the southern zone eroded in several weeks to four months. The study found significant differences in the response of armored versus unarmored shorelines with higher erosion rates and slower recovery of the beach at armored stations.

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Myrtle Beach: A history of shore protection and beach restoration

Shore & Beach ◽

10.34237/1008732 ◽

2019 ◽

pp. 13-34

Author(s):

Timothy Kana ◽

Haiqing Kaczkowski

Keyword(s):

South Carolina ◽

Large Scale ◽

Unit Length ◽

Phase 1 ◽

Property Values ◽

Small Scale ◽

Shore Protection ◽

Beach Management ◽

Myrtle Beach ◽

The City

The City of Myrtle Beach (South Carolina, USA) initiated a three-phase plan for beach restoration in the 1980s: Phase 1 — small-scale beach scraping; Phase 2 — mediumscale nourishment by trucks using inland sand; and Phase 3 — large-scale nourishment by dredge using offshore sand. Phases 1 and 2 were locally funded and served as interim measures (1981-1996) until a 50-year federal project could be constructed (1997 to present). In the course of this work, the city pioneered several approaches to beach management and became a model for the state. These include: the prototype SC beach survey program; the profile volume method for determining shorelines in the presence of seawalls, which was codified in the Beach Management Act (BMA) of 1988; the first locally funded nourishment (1986-1987) and FEMA-funded postdisaster renourishment after Hurricane Hugo 1989-1990; and the first surveys of offshore deposits for nourishment. Before restoration, nearly 65% of the 9-mile (14.5 kilometer) oceanfront was armored with seawalls, bulkheads, and revetments (1981). After nourishment, erosion control structures are now buried and fronted by a vegetated storm berm, while a wider beach accommodates millions of visitors each year. Total volumes and adjusted costs of nourishment from 1986 to early 2018 are 4,997,201 cubic yards (3,820,360 m3) and ~$70.8 million ($2018), respectively. On a unit annual beach length basis, the cost of beach restoration and improvement has averaged $46.80 per one foot of shoreline per year (~$153.50/m/yr) ($2018). Oceanfront property values on a unit length of shoreline basis presently range from ~$15,000/ft (~$49,200/m) for single-family homes to ~$75,000/ft (~$250,000/m) for high-rise buildings, suggesting that beach maintenance has cost well under 0.5% of oceanfront property values per year. Sand loss rates have averaged ~0.8 cy/ft/yr (2.0 m3/m/yr), and the rate of nourishment has been more than adequate to keep up with the ~0.37 ft (0.11 m) sea level rise between 1980 and 2018.

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Unpacking storm damages on a developed shoreline: Relating dune erosion and urban runoff

Shore & Beach ◽

10.34237/1008733 ◽

2019 ◽

pp. 35-45

Author(s):

Patrick Barrineau ◽

Timothy Kana

Keyword(s):

South Carolina ◽

Storm Events ◽

Near Surface ◽

Dune Erosion ◽

Groundwater Flux ◽

Impact Scale ◽

Cape Hatteras ◽

Myrtle Beach ◽

Rain Events ◽

Elevation Model

Hurricane Matthew (2016) caused significant beach and dune erosion from Cape Hatteras, North Carolina, USA, to Cape Canaveral, Florida, USA. At Myrtle Beach, South Carolina, the storm caused beach recession, and much of the southern half of the city’s beaches appeared to be overwashed in post-storm surveys. Around half of the city’s beaches appeared overwashed following the storm; however, the Storm Impact Scale (SIS; Sallenger 2000) applied to a pre-storm elevation model suggests less than 10% of the city’s beaches should have experienced overwash. Spatial analysis of elevation and land cover data reveals dunes that were “overwashed” during Matthew drain from watersheds that are >35% impervious, where those showing only dune recession are <5% impervious. The densely developed downtown of Myrtle Beach sits on a low seaward-sloping terrace. Additionally, indurated strata beneath the downtown area can prevent groundwater from draining during excessive rain events. As a result, the most continuous impervious surface cover and near-surface strata lie within a half-kilometer of the beach and drain directly to the backshore. Along the U.S. Southeast coast, this is somewhat rare; many coastal systems feature a lagoon or low-lying bottomland along their landward border, which facilitates drainage of upland impervious surfaces following storm passage. At Myrtle Beach, all of the stormwater runoff is drained directly to the beach through a series of outfall pipes. Many of the outfall pipes are located along the backshore, near the elevation of storm surge during Matthew. Runoff from Matthew’s heavy rains was observed causing ponding on the landward side of the foredune and scouring around beach access walkways. Based on these observations, the severe dune erosion experienced near downtown Myrtle Beach during Hurricane Matthew may have been caused by runoff and/or groundwater flux rather than overwash. These results highlight an unexpected relationship between upland conditions and dune erosion on a developed shoreline. That is, dune erosion can be caused by mechanisms beside overwash during storm events.

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Water quality in the Withers Swash Basin, with emphasis on enteric bacteria, Myrtle Beach, South Carolina, 1991-93

10.3133/wri954125 ◽

1995 ◽

Keyword(s):

Water Quality ◽

South Carolina ◽

Enteric Bacteria ◽

Myrtle Beach

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Comparing Tropical Cyclone and King Tide Impacts on a South Carolina Coastal Dune System

Journal of Coastal Research ◽

10.2112/jcoastres-d-21-00025.1 ◽

2021 ◽

Author(s):

Ellis

Keyword(s):

South Carolina ◽

Tropical Cyclone ◽

Coastal Dune ◽

Dune System ◽

Coastal Dune System

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Hydrodynamic Drivers of Dissolved Oxygen Variability within a Tidal Creek in Myrtle Beach, South Carolina

Water ◽

10.3390/w11081723 ◽

2019 ◽

Vol 11 (8) ◽

pp. 1723 ◽

Cited By ~ 2

Author(s):

Douglas M. Pastore ◽

Richard N. Peterson ◽

Diane B. Fribance ◽

Richard Viso ◽

Erin E. Hackett

Keyword(s):

Water Quality ◽

South Carolina ◽

Dissolved Oxygen ◽

Tidal Creek ◽

Water Levels ◽

Beach Erosion ◽

Shear Stresses ◽

Myrtle Beach ◽

Do Concentration ◽

Face Morphology

Beach erosion and water quality degradation have been observed in Singleton Swash, a tidal creek that traverses the beach-face connecting land and ocean in Myrtle Beach, SC. The objective of this study in Singleton Swash is to explore relationships between water quality and hydrodynamics, where the latter are influenced by beach face morphology. We measure water velocities, water levels, and dissolved oxygen concentrations (DO) (a proxy for water quality) and apply correlation analysis to examine the relationships between physical processes and dissolved oxygen variations. Results show that larger tidal ranges are associated with higher mean levels of DO in the tidal creek. The larger tidal ranges are linked to larger magnitude currents, which increase both the DO transport via larger fluxes of oxygenated oceanic water into the swash and the magnitude of Reynolds shear stresses; due to tidal asymmetries, flood currents are stronger than ebb currents in this system. Based on these results, it is concluded that the combined transport of oxygenated waters into the tidal creek from the ocean on large flood tides and subsequent mixing due to large Reynolds shear stresses result in the observed net DO concentration increases in the creek over tidal cycles.

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Comparison of Amino Acid Racemization Geochronometry with Lithostratigraphy, Biostratigraphy, Uranium-Series Coral Dating, and Magnetostratigraphy in the Atlantic Coastal Plain of the Southeastern United States

Quaternary Research ◽

10.1016/0033-5894(82)90078-3 ◽

1982 ◽

Vol 18 (3) ◽

pp. 337-359 ◽

Cited By ~ 53

Author(s):

L. McCartan ◽

J. P. Owens ◽

B. W. Blackwelder ◽

B. J. Szabo ◽

D. F. Belknap ◽

...

Keyword(s):

South Carolina ◽

Amino Acid ◽

Coastal Plain ◽

Atlantic Coastal Plain ◽

Amino Acid Racemization ◽

Uranium Series ◽

Myrtle Beach ◽

Atlantic Coastal ◽

North And South ◽

Integrated Study

AbstractThe results of an integrated study comprising litho- and biostratigraphic investigations, uranium-series coral dating, amino acid racemization in molluscs, and paleomagnetic measurements are compared to ascertain relative and absolute ages of Pleistocene deposits of the Atlantic Coastal Plain in North and South Carolina. Four depositional events are inferred for South Carolina and two for North Carolina by all methods. The data suggest that there are four Pleistocene units containing corals that have been dated at about 100,000 yr, 200,000 yr, 450,000 yr, and over 1,000,000 yr. Some conflicts exist between the different methods regarding the correlation of the younger of these depositional events between Charleston and Myrtle Beach. Lack of good uranium-series dates for the younger material at Myrtle Beach makes the correlation with the deposits at Charleston more difficult.

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Longshore variation in coastal foredune growth on a megatidal beach from UAV measurements

10.5194/egusphere-egu2020-8059 ◽

2020 ◽

Author(s):

Iain Fairley ◽

Jose Horrillo-Caraballo ◽

Anouska Mendzil ◽

Georgie Blow ◽

Henry Miller ◽

...

Keyword(s):

Wave Energy ◽

Point Cloud ◽

High Tide ◽

Tidal Range ◽

Dune System ◽

Wave Heights ◽

Upper Intertidal ◽

Rtk Gps ◽

Swansea Bay ◽

Dune Area

Coastal dunes are both a vital natural coastal defence and a key ecological habitat; therefore, understanding their evolution is important to inform coastal management. Megatidal environments are the world largest tidal ranges and hence provide a unique endmember of the tidal range continuum. A study site at Crymlyn Burrows, Swansea Bay, UK is monitored here; the area was originally of applied interest due to its identification as a key receptor of the Swansea Bay Tidal Lagoon project. The study site comprises of 2km of dune frontage bounded to the west by hard sea defences and to the east by the River Neath estuary. The intertidal is characterized by a shallow slope and crescentic intertidal bars. Mean spring tidal range at the nearby Mumbles tide gauge is 8.46m; mean wave heights at a wave buoy offshore of the site (depth 9m LAT) are 0.66m and storm wave heights exceed 3m; predominant wind direction is in an alongshore &#8211; onshore direction.A Sensefly Ebee-RTK drone with a Sony RGB camera has been used to map the dune system and the mid to upper intertidal beach on a monthly &#8211; bimonthly frequency since October 2018. Initial post-processing was conducted in the Sensefly Emotion3 software; Pix4D was then used to generate a point cloud from the georeferenced images. RTK-GPS surveyed ground control points distributed over the study area were used to improve the accuracy of the solution. Point clouds were cleaned to remove noise using Cloud Compare, an open source point cloud editor, before being interpolated onto a gridded surface. Comparison of the gridded surface against RTK-GPS surveyed points gave a vertical mean absolute error (MAE) of 0.05m over the beach area. Comparison in the dune area is more complex since the raw point cloud includes the vegetation and hence over-estimates height compared to the bare earth. Based on the raw point cloud, MAE over the dune area was 0.22m; however, when vegetation points were removed using artificial neural network based colour discrimination, the MAE was 0.05m.Longshore variation in dune evolution is clearly evident. At the eastern and western ends of the dune system, dune progradation can be observed whereas in the central portion the frontal dune is cliffed and the dune foot position is static or eroding landward. Pressure transducers have been deployed in a longshore array at the neap high tide level to assess variation in wave energy reaching the upper intertidal over the study area.This presentation will explore whether this variation in behavior is due to longshore variation in wave energy (erosion potential), variation in sediment availability (accretion potential) or the persistence of antecedent morphology.

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