Seafloor characterization offshore of the New York-New Jersey metropolitan area using sidescan-sonar

Schwab, William C.; Denny, Jane F.; Butman, Bradford; Danforth, W.W.; Foster, David S.; Swift, Bree; Lotto, L.L.; Thieler, E. Robert

doi:10.3133/ofr00295

Cited by 10 publications

(21 citation statements)

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“…The amount of 497 migration is more than observed in prior years (Schwab et al, 2013), but otherwise fully 498 consistent with prior observations and with expectations of southwest migration based on the 499 lee/stoss relationship of grain size (Schwab et al, 2000;2013;. This conclusion confirms 500 what has long been hypothesized: that shoreface-attached sand ridges on wave-dominated 501 shelves are storm-generated bedforms (Swift and Field, 1981;Calvete et al, 2001).…”

Section: Bedform Migration In Response To Storm Forcing 495supporting

confidence: 80%

“…Absent 682 any other evident erosion mechanism, we hypothesize that migration of these bedforms 683 constitutes a primary mechanism for evolution of the transgressive ravinement, and that the 684 undulatory morphology of the ravinement underlying the sand ridges is a consequence of such 685 evolution. 686 Schwab et al (2000Schwab et al ( , 2013 have noted that the coastline along western Fire Island is either 687 advancing or stable, whereas along the eastern half of the island it is retreating; they have 688 correlated this observation to observed changes in offshore morphology and modern sand 689 availability along the shoreface and inner shelf. They have further hypothesized that modern 690 sand from the inner shelf is being transported to the shoreface, thereby stabilizing the coastline.…”

Section: Ravinement 662mentioning

confidence: 99%

“…Schwab et al 102 (2000;2013) link this change in shoreface and inner-shelf morphology to the abundance of 103 modern marine sand; much more is available offshore of the western half of Fire Island, because 104 5 sand is being transported westward from a large Pleistocene sand unit mid-island by longshore 105 currents. Schwab et al (2000;2013) also note that the coastline of western Fire Island is 106 presently stable or advancing, whereas to the east it is retreating. To explain this correlation, 107 they hypothesize that shoreward advection of sand from the inner shelf contributes to the 108 replenishment of shoreface sand off western Fire Island; they further suggest that storms 109 contribute to this process.…”

Section: Abstract 14mentioning

confidence: 99%

“…Although our primary focus is on the larger storm, Irene could also have 92 contributed to any observed "storm-induced" component of change. 93The seabed offshore of Fire Island undergoes a significant change in morphology between 94 the eastern and western ends of Fire Island (Figure 1; Schwab et al, 2000;2013;. To the 95 west, the seabed morphology is dominated by shoreface-attached sand ridges, large (~1-6 m 96 high, ~1-3 km wide) dune-like bedforms angled ~20°-50° to shore (acute angle to the east).…”

mentioning

confidence: 99%

“…The resulting unconformity, or ravinement, 526 separates modern sands above from Holocene estuarine sediments or Pleistocene and older 527 sediments below (Bruun, 1962;Swift and Thorne, 1991;McBride et al, 2004;Goff, 2014). The 528 former are typically best preserved in paleo -river channels (e.g., Schwab et al, 2000; Nordfjord 529 et al, 2006). 530…”

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confidence: 99%

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The impact of Hurricane Sandy on the shoreface and inner shelf of Fire Island, New York: Large bedform migration but limited erosion

Goff

Flood

Austin

et al. 2015

Continental Shelf Research

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14We investigate the impact of superstorm Sandy on the lower shoreface and inner shelf 15 offshore the barrier island system of Fire Island, NY using before-and-after surveys involving 16 swath bathymetry, backscatter and CHIRP acoustic reflection data. As sea level rises over the 17 long term, the shoreface and inner shelf are eroded as barrier islands migrate landward; large 18 storms like Sandy are thought to be a primary driver of this largely evolutionary process. The 19 "before" data were collected in 2011 by the U.S. Geological Survey as part of a long-term 20 investigation of the Fire Island barrier system. The "after" data were collected in January, 2013, 21 ~two months after the storm. Surprisingly, no widespread erosional event was observed. Rather, 22 the primary impact of Sandy on the shoreface and inner shelf was to force migration of major 23 bedforms (sand ridges and sorted bedforms) 10's of meters WSW alongshore, decreasing in 24 migration distance with increasing water depth. Although greater in rate, this migratory behavior 25 is no different than observations made over the 15-year span prior to the 2011 survey. 26Stratigraphic observations of buried, offshore-thinning fluvial channels indicate that long-term 27 erosion of older sediments is focused in water depths ranging from the base of the shoreface 28 (~13-16 m) to ~21 m on the inner shelf, which is coincident with the range of depth over which 29 sand ridges and sorted bedforms migrated in response to Sandy. We hypothesize that bedform 30 migration regulates erosion over these water depths and controls the formation of a widely 31 observed transgressive ravinement; focusing erosion of older material occurs at the base of the 32 stoss (upcurrent) flank of the bedforms. Secondary storm impacts include the formation of 33 ephemeral hummocky bedforms and the deposition of a mud event layer. the New York City metropolitan area was heavily damaged, and the Long Island barrier island 46 system was both breached in places and seriously eroded . 47The impacts of this storm on the shoreface and inner shelf, which are permanently 48 submerged and therefore primarily accessible only through acoustic mapping, are harder to 49 observe. However, although the shoreface and inner shelf are neither populated nor veneered 50 with human infrastructure, they are nevertheless critical to both people and their structures, 51 because they are the first line of defense of barrier island systems against a naturally retreating, 52or "transgressing," coastline. Under rising sea level conditions, the natural condition today along 53 most of the U.S. east coast, barrier islands will back-step (retreat landward) by erosion on the 54 seaward side and deposition on the landward side (Bruun, 1962;Swift and Thorne, 1991; Thorne 55 and Swift, 1991). Large storms, with consequent high waves, strong currents and above-normal 56 tidal ranges/surges, are thought to be primary drivers of such shoreface erosion (Swift, 1968; 57 Swift and Thorne, 1991). Such storms...

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Section: Bedform Migration In Response To Storm Forcing 495supporting

confidence: 80%

Section: Ravinement 662mentioning

confidence: 99%

Section: Abstract 14mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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The impact of Hurricane Sandy on the shoreface and inner shelf of Fire Island, New York: Large bedform migration but limited erosion

Goff

Flood

Austin

et al. 2015

Continental Shelf Research

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Holocene sediment distribution on the inner continental shelf of northeastern South Carolina: Implications for the regional sediment budget and long-term shoreline response

Denny

Schwab

Baldwin

et al. 2013

Continental Shelf Research

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a b s t r a c tHigh-resolution geophysical and sediment sampling surveys were conducted offshore of the Grand Strand, South Carolina to define the shallow geologic framework of the inner shelf. Results are used to identify and map Holocene sediment deposits, infer sediment transport pathways, and discuss implications for the regional coastal sediment budget.The thickest deposits of Holocene sediment observed on the inner shelf form shoal complexes composed of moderately sorted fine sand, which are primarily located offshore of modern tidal inlets. These shoal deposits contain $ 67 M m 3 of sediment, approximately 96% of Holocene sediment stored on the inner shelf. Due to the lack of any significant modern fluvial input of sand to the region, the Holocene deposits are likely derived from reworking of relict Pleistocene and older inner-shelf deposits during the Holocene marine transgression. The Holocene sediments are concentrated in the southern part of the study area, due to a combination of ancestral drainage patterns, a regional shift in sediment supply from the northeast to the southwest in the late Pleistocene, and proximity to modern inlet systems. Where sediment is limited, only small, low relief ridges have formed and Pleistocene and older deposits are exposed on the seafloor. The low-relief ridges are likely the result of a thin, mobile veneer of sediment being transported across an irregular, erosional surface formed during the last transgression. Sediment textural trends and seafloor morphology indicate a long-term net transport of sediment to the southwest. This is supported by oceanographic studies that suggest the long-term sediment transport direction is controlled by the frequency and intensity of storms that pass through the region, where low pressure systems yield net along-shore flow to the southwest and a weak onshore component.Current sediment budget estimates for the Grand Strand yield a deficit for the region. Volume calculations of Holocene deposits on the inner shelf suggest that there is sufficient sediment to balance the sediment budget and provide a source of sediment to the shoreline. Although the processes controlling cross-shelf sediment transport are not fully understood, in sediment-limited environments such as the Grand Strand, erosion of the inner shelf likely contributes significant sediment to the beach system.Published by Elsevier Ltd.

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Seafloor habitat mapping of the New York Bight incorporating sidescan sonar data

Lathrop

Cole

Senyk

et al. 2006

Estuarine, Coastal and Shelf Science

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Seafloor characterization offshore of the New York-New Jersey metropolitan area using sidescan-sonar

Cited by 10 publications

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The impact of Hurricane Sandy on the shoreface and inner shelf of Fire Island, New York: Large bedform migration but limited erosion

The impact of Hurricane Sandy on the shoreface and inner shelf of Fire Island, New York: Large bedform migration but limited erosion

Holocene sediment distribution on the inner continental shelf of northeastern South Carolina: Implications for the regional sediment budget and long-term shoreline response

Seafloor habitat mapping of the New York Bight incorporating sidescan sonar data

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