Sand transport by the Eel River and its effect on nearby beaches

Ritter, John R.

doi:10.3133/ofr73236

Cited by 9 publications

(4 citation statements)

References 4 publications

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“…For the Elwha and other SMRs, sands play an important role in coastal sediment fluxes. Suspended sediments in the Elwha River on 6 March were 32–35% sand, similar to values measured in the Têt River, Eel River, and southern California rivers (~25% during storms; Bourrin et al, ; Ritter, ; Warrick & Milliman, ), and the Choshui River (35–40% during a typhoon; Milliman et al, ). Sands settle rapidly in the river‐mouth region but can also be transported limited distances seaward and reworked in longshore transport cells.…”

Section: Discussionsupporting

confidence: 74%

Formation and Removal of a Coastal Flood Deposit

2019

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During floods, small mountainous rivers transport large sediment loads to the coastal ocean. This sediment often deposits near shore, and if conditions allow, various types of gravity flows (including hyperpycnal river plumes) can transport the sediment across the shelf within minutes to months of delivery. The stochastic and energetic nature of small‐mountainous‐river flood dispersal presents challenges to observations of transport processes and flood‐deposit formation during events, however. In this study, the removal of two dams on the Elwha River afforded an opportunity to closely monitor coastal sediment dispersal using boundary‐layer instrument systems during 4 years of intense sediment loading. A flood in March 2014 generated fluvial sediment concentrations of 14–20 g/L, coastal boundary‐layer concentrations of up to 14 g/L, and 23 cm of muddy sand deposition in a few days. Limited evidence exists for a gravity flow lasting <2 hr during slack tide, coinciding with the waning phase of the secondary flood peak. However, rapid sediment deposition over the 4‐day event period was dominated by advection of sediment in the boundary layer and by suspension settling from turbid river water, which never exceeded the well‐established 35–40 g/L required for hyperpycnal river plume formation. Within 3 weeks, the entire sandy flood deposit had been eroded by strong tidal currents. This system highlights the difficulty in forming hyperpycnal river plumes within tidally energetic systems, even from an extremely turbid river, and the conditions that can erase major sediment delivery events from the sedimentary record.

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Section: Discussionsupporting

confidence: 74%

Formation and Removal of a Coastal Flood Deposit

2019

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“…Littoral drift is believed to be dominated by northern, storm-driven transport in the winter, and by southern, wind wave-driven transport in the summer (Dingler and Clifton, 1994;Winkelman et al, 1999), with net northern transport during SW storms and El Niño events (U.S. Army Corps of Engineers, 2017a). On the basis of mean grain size and mineralogy, Ritter (1973) hypothesized that the Little and Mad Rivers provide sand to the beaches and barrier north of the Humboldt Bay inlet, while the Eel River provides sand to the south of the inlet. However, patterns of erosion above the North Jetty and accretion below the South Jetty, along with the northward migration of the spits at Mad and Little Rivers, are evidence of northward littoral drift.…”

Section: Sediment Dynamicsmentioning

confidence: 99%

Spatio-temporal geomorphological and ecological evolution of a transgressive dunefield system, Northern California, USA

Pickart

Hesp

2019

Global and Planetary Change

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A series of historic aerial photographs in addition to the U.S. Coast Survey 1870 map were used to document evolution of the coastal barrier and transgressive dunefield system at the Lanphere-Ma-le'l Dunes on Humboldt Bay, California, USA, between 1870 and 2016. Geomorphic units (shorelines, foredunes, nebkha, blowouts, parabolic dunes, deflation basins, and dunefields) as well as vegetation alliance were mapped in ArcGIS at approximately decadal intervals and compared among three subareas delineated based on large scale geomorphic differences that coincided with contrasting biological invasion and management histories. Sand inundation events in the 1930s and 1940s led to deterioration of the foredune and burial of deflation basins in the south, with the transgressive dunefield directly abutting the backshore in places. The transgressive dunefield in the north differentiated into parabolic dunes that decoupled from the foredune complex earlier than in the southern subareas, which have retained undifferentiated transgressive dunefields. Shoreline progradation increased dramatically following the historic

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“…This pattern is a consequence of hydraulic sorting by wave-generated currents, which partition terrigenous sands and muds above and below storm wave base, respectively (Fan et al, 2004). Lower Eel River suspensions contain as much as 20% sand (and nearly equal parts silt and clay; Brown and Ritter, 1971), but most of the sand initially settles near the river mouth and adjacent surf zone before being reworked to the inner shelf during storms (Ritter, 1972;Crockett and Nittrouer, 2004). Fluvial mud bypasses the inner shelf and reaches the middle shelf via surface plumes and, more important, near-bottom suspensions maintained by turbulence in the wave-boundary layer.…”

Section: Regional Setting and Previous Workmentioning

confidence: 99%

Late Holocene sediment accumulation on the northern California shelf: Oceanic, fluvial, and anthropogenic influences

Sommerfield

Wheatcroft

2007

Geological Society of America Bulletin

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The late Holocene sedimentary record of the northern California continental shelf archives the combined infl uences of fl uvial and oceanic mechanisms of land to ocean sediment fl ux, and provides perspective on the cumulative impacts of major fl oods and land-use change in the drainage basin during historical time. Piston cores collected on the shelf (50−150 m water depths) off the Eel and Klamath Rivers were analyzed to identify lithologies indicative of depositional processes over the past 5 k.y., and dated using 137 Cs and 14 C methods to resolve spatial patterns in sediment accumulation rates. Sediment accumulation rates averaged over the past several millennia display along-and across-shelf gradients that refl ect interactions between the shelf fl ow fi eld and antecedent tectonically produced topography. The highest rates (3−6 mm/yr; 0.4−0.8 g/cm 2 /yr) are associated with structural lows on the middle shelf, whereas the lowest rates (0.2−0.6 mm/yr; 0.03−0.05 g/cm 2 /yr) occur at structural highs and at the shelf edge. This accumulation pattern is spatially coincident with postglacial sediment thicknesses on the shelf, and with depocenters that form on shorter time scales in response to oceanic fl ood events. The sediment column exhibits an upward-fi ning sequence consistent with increased bypass of river silt and clay as delta plains progressively fi lled during the Holocene transgression. Sedimentary event beds indicative of major river fl oods, including two probable hyperpycnal discharges of the Eel River within the past 1 k.y., are preserved. Stratigraphic evidence of accelerated sediment delivery to the shelf during historical time, in the form of increased burial of fl uvial mud relative to fi ne-grained sand, is superimposed on this natural record. This change is concordant with the regional history of forest clearing and related land-use practices in the watershed after the early 1800s, and appears to record the combined impacts of timber harvesting and several extreme fl oods after ca. A.D. 1950.

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Sand transport by the Eel River and its effect on nearby beaches

Abstract: Introduction 7 2 Previous investigations 4 Sand transport by the Eel River near its mouth 4 Deposition of sand transported by the Eel River 9 References 16 si N, X vs

Cited by 9 publications

References 4 publications

Formation and Removal of a Coastal Flood Deposit

Formation and Removal of a Coastal Flood Deposit

Spatio-temporal geomorphological and ecological evolution of a transgressive dunefield system, Northern California, USA

Late Holocene sediment accumulation on the northern California shelf: Oceanic, fluvial, and anthropogenic influences

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