Rapid and widespread dispersal of flood sediment on the northern California margin

Wheatcroft, Robert A.; Sommerfield, Christopher K.; Drake, David E.; Borgeld, Jeffry C.; Nittrouer, Charles A.

doi:10.1130/0091-7613(1997)025<0163:rawdof>2.3.co;2

Cited by 180 publications

(96 citation statements)

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“…Megahan & Kidd 1972, Doeg & Koehn 1990, Fahey & Coker 1992, Davies & Nelson 1993, Grayson et al 1993). Fine sediments which are removed from the land in this way may find their way to coastal areas within hours/ minutes (Fahey & Coker 1992), particularly in association with flood events (Nichols 1977, Wheatcroft et al 1997, Wheatcroft 2000. On mixing with seawater, fine terrestrial sediments flocculate and can settle onto the seafloor; their accumulation on the seafloor can adversely affect the resident benthic communities (Johnston et al 1981, Fahey & Coker 1992.…”

Section: Abstract: Sedimentation · Intertidal Soft-sediments · Terrementioning

confidence: 99%

Terrestrial deposits on intertidal sandflats: sediment characteristics as indicators of habitat suitability for recolonising macrofauna

Cummings¹,

Thrush²,

Hewitt³

et al. 2003

Mar. Ecol. Prog. Ser.

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Section: Abstract: Sedimentation · Intertidal Soft-sediments · Terrementioning

confidence: 99%

Terrestrial deposits on intertidal sandflats: sediment characteristics as indicators of habitat suitability for recolonising macrofauna

Cummings¹,

Thrush²,

Hewitt³

et al. 2003

Mar. Ecol. Prog. Ser.

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“…The bulk of discharged £uvial sediments is transported further o¡shore and deposited below the zone of high turbulence (Wiberg et al, 1996;Cacchione et al, 1999). Subsequently, the sea£oor is signi¢-cantly bioturbated over time causing a downcore coarsening of some deposits until the next £ood deposit recharges this part of the shelf with more sediment (Wiberg et al, 1996;Wheatcroft et al, 1996Wheatcroft et al, , 1997Drake, 1999;Cutter and Diaz, 2000). The lower strata of a £ood deposit from 1995 most likely represent remnants of older £ood deposits which have been partly eroded during storm periods, and reworked by biological processes (Go¡ et al, 1996Borgeld et al, 1999).…”

Section: Regional Settingmentioning

confidence: 99%

“…The stratigraphy of the active Eel margin is signi¢cantly shaped by periodic £ood deposits, which are generated on average every decade during short-term discharge events (e.g., Go¡ et al, 1996Go¡ et al, , 1999Wheatcroft et al, 1996Wheatcroft et al, , 1997Cacchione et al, 1999). Suspended £uvial sediments are carried across-and along-shelf by strong surface and bottom currents in a northward direction during storm events and in a southward direction during storm-free periods, while they mix with coarser-grained shelf sediments (e.g., Drake and Cacchione, 1985;Wiberg et al, 1996;Cacchione and Drake, 1990;Cacchione et al, 1999).…”

Section: Regional Settingmentioning

confidence: 99%

“…1. Bathymetry on the Eel River shelf and the location of a £ood deposit from 1995 (outlined with dotted black lines), which increases in thickness from 0.01 to 0.07 m across the 60-and 90-m isobaths (after Wheatcroft et al, 1996Wheatcroft et al, , 1997Go¡ et al, 1996Go¡ et al, , 1999. All core and Lance stations are marked in the downslope and along-shelf direction.…”

Section: Regional Settingmentioning

confidence: 99%

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In situ acoustic and laboratory ultrasonic sound speed and attenuation measured in heterogeneous soft seabed sediments: Eel River shelf, California

Gorgas

Wilkens

et al. 2002

Marine Geology

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We compared in situ and laboratory velocity and attenuation values measured in seafloor sediments from the shallow water delta of the Eel River, California. This region receives a substantial volume of fluvial sediment that is discharged annually onto the shelf. Additionally, a high input of fluvial sediments during storms generates flood deposits that are characterized by thin beds of variable grain-sizes between the 40-and 90-m isobaths. The main objectives of this study were (1) to investigate signatures of seafloor processes on geoacoustic and physical properties, and (2) to evaluate differences between geoacoustic parameters measured in situ at acoustic (7.5 kHz) and in the laboratory at ultrasonic (400 kHz) frequencies. The in situ acoustic measurements were conducted between 60 and 100 m of water depth. Wet-bulk density and porosity profiles were obtained to 1.15 m below seafloor (m bsf) using gravity cores of the mostly cohesive fine-grained sediments across-and along-shelf. Physical and geoacoustic properties from six selected sites obtained on the Eel margin revealed the following. (1) Sound speed and wet-bulk density strongly correlated in most cases. (2) Sediment compaction with depth generally led to increased sound speed and density, while porosity and in situ attenuation values decreased. (3) Sound speed was higher in coarser-than in finer-grained sediments, on a maximum average by 80 m s 31 . (4) In coarse-grained sediments sound speed was higher in the laboratory (1560 m s 31 ) than in situ (1520 m s 31 ). In contrast, average ultrasonic and in situ sound speed in finegrained sediments showed only little differences (both approximately 1480 m s 31 ). (5) Greater attenuation was commonly measured in the laboratory (0.4 and 0.8 dB m 31 kHz 31 ) than in situ (0.02 and 0.65 dB m 31 kHz 31 ), and remained almost constant below 0.4 m bsf. We attributed discrepancies between laboratory ultrasonic and in situ acoustic measurements to a frequency dependence of velocity and attenuation. In addition, laboratory attenuation was most likely enhanced due to scattering of sound waves at heterogeneities that were on the scale of

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“…On the Eel shelf, observations of the Eel River plume, boundary layer sediment transport processes, and the distribution of seafloor sediment properties revealed that wave-supported turbidity flows were the dominant mechanisms for creating midshelf flood deposits. Tripod and hydrographic survey observations showed that the Eel River delivered sediment to the inner shelf and that wave-supported turbidity flows were responsible for transporting to a depositional locus in 60 to 100 m water depths (Wheatcroft et al, 1996(Wheatcroft et al, , 1997Wheatcroft and Borgeld, 2000). Seafloor sampling studies on the Eel shelf showed that the flood deposits emplaced by wave-supported turbidity flow had a stratigraphic signature consisting of relativity thick deposits (5 to 15 cm) of terrigenous mud (Wheatcroft and Borgeld, 2000).…”

Section: Introductionmentioning

confidence: 99%

Observations and modeling of wave-supported sediment gravity flows on the Po prodelta and comparison to prior observations from the Eel shelf

Traykovski

Wiberg

Geyer

2007

Continental Shelf Research

181

195

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Abstract:A mooring and tripod array was deployed from the fall of 2002 through the spring of 2003 on the Po prodelta to measure sediment transport processes associated with sediment delivered from the Po River. Observations on the prodelta revealed wave-supported gravity flows of high concentration mud suspensions that are dynamically and kinematically similar to those observed on the Eel shelf . Due to the dynamic similarity between the two sites, a simple one-dimensional across-shelf model with the appropriate bottom boundary condition was used to examine fluxes associated with this transport mechanism at both locations. To calculate the sediment concentrations associated with the wave-dominated and wave-current resuspension, a bottom boundary condition using a reference concentration was combined with an "active layer" formulation to limit the amount of sediment in suspension. Whereas the wave-supported gravity flow mechanism dominates the transport on the Eel shelf, on the Po prodelta flux due to this mechanism is equal in magnitude to transport due to wave resuspension and wind-forced mean currents in cross-shore direction. Southward transport due to wave resuspension and wind forced mean currents move an order of magnitude more sediment along-shore than the downslope flux associated wave-supported gravity flows.

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Rapid and widespread dispersal of flood sediment on the northern California margin

Cited by 180 publications

References 0 publications

Terrestrial deposits on intertidal sandflats: sediment characteristics as indicators of habitat suitability for recolonising macrofauna

Terrestrial deposits on intertidal sandflats: sediment characteristics as indicators of habitat suitability for recolonising macrofauna

In situ acoustic and laboratory ultrasonic sound speed and attenuation measured in heterogeneous soft seabed sediments: Eel River shelf, California

Observations and modeling of wave-supported sediment gravity flows on the Po prodelta and comparison to prior observations from the Eel shelf

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