Mid to late Holocene geomorphological and sedimentological evolution of the fluvial–tidal zone

Prokocki, E.; Best, James L.; Ashworth, Philip; Parsons, Daniel R.; Smith, Gregory H. Sambrook; Nicholas, A. P.; Simpson, Christopher J.; Wang, H.; Sandbach, S. D.; Keevil, C.

doi:10.1016/b978-0-444-63529-7.00022-5

Cited by 8 publications

(20 citation statements)

References 34 publications

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“…Note, however, that the image displayed was taken when water-levels were below the Mean Lower Low Water (MLLW) mark, and that the normal condition is for almost all barforms displayed to be submerged when the water surface is higher than MLLW (see fig. 6.1, Prokocki et al, 2015). The largest wind-waves (pink arrows) are generated over the longest fetch length between January to April and in October and November, and are oriented from the west/south-west to east/north-east, whilst smaller wind-waves (white arrows) are produced from May to September, and are oriented from north/northwest to south/south-east.…”

Section: Modern Lower Columbia River Sediment Supplymentioning

confidence: 97%

“…This classification scheme does, however, exclude the effects of oceanic-waves within lower FTTs and intrabasinal wind-waves in mid to upper-FTTs, which can be important hydraulic constituents in particular settings (cf. Chaumillon et al, 2008;Peterson et al, 2014;Prokocki et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

“…Moreton & Carter, 2015). Modern FTT barforms have thus received a lot of recent attention (Smith, , 1989Smith et al, 2009;Choi, 2010;Sisulak & Dashtgard, 2012;Choi et al, 2013;Johnson & Dashtgard, 2014;Carling et al, 2015;Prokocki et al, 2015;Leuven et al, 2016) in order to establish how fluvial-tidal processes alter their morphology and alluvial architecture. Most sedimentological observations from modern FTTs, however, are restricted to bed-scale trenches and cores (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Most sedimentological observations from modern FTTs, however, are restricted to bed-scale trenches and cores (e.g. Dalrymple & Rhodes, 1995;Choi et al, 2004;van den Berg et al, 2007;Baker et al, 2010;Martinius & Van den Berg, 2011;Sisulak & Dashtgard, 2012;Peterson et al, 2014;Carling et al, 2015;Prokocki et al, 2015;Ghinassi et al, 2018), whilst seismic data of bar-scale architecture is scarce, limited in its spatial resolution and confined to individual sandbanks, or -tidal transition as tidal-processes increase in magnitude and frequency in the downstreamdirection. This model assumes that the increased deposition of relatively thick silt/mud horizons within point-bar accretion-sets is primarily the product of suspension-fallout of fine-grained sediment during tidal slackwater periods, and enhanced flocculation and deposition of fines within the turbidity-maximum zone.…”

Section: Introductionmentioning

confidence: 99%

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Alluvial architecture of mid‐channel fluvial–tidal barforms: The mesotidal Lower Columbia River, Oregon/Washington, USA

et al. 2020

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Barforms of mesotidal to macrotidal fluvial-tidal transitions, regardless of fluvial-discharge, are currently thought to display a sedimentary architecture dominated by tidal signatures. Due to the scarcity of observations from modern mesotidal fluvial-tidal transitions, especially those of multi-channelled large-rivers (mean annual discharge ≥7000 m 3 s À1 and peak discharges ≥15 000 m 3 s À1) with mid-channel bars, this concept remains unproven. The present study analyses data produced by a combination of high-resolution ground penetrating radar and coupled shallow vibracores (<5 m depth), collected from modern fluvial-tidal mid-channel bars of the mesotidal multichannelled Lower Columbia River, Washington/Oregon, USA, which can experience peak discharges ≥18 000 m 3 s À1. These data were used alongside time-sequenced aerial imagery to characterize the spatio-temporal sedimentological evolution of these barforms in singular flows or combined flows consisting of river, tidal and/or wind-wave oscillatory, current components operating in unique fluvial-tidal transition regimes. Results indicate that ca 75% of the Lower Columbia River fluvial-tidal transition produces braidbars with basal to bar-top sedimentological architectures that are indistinguishable from fluvial-only braid-bars recorded in the literature. Barform stratal characteristics within the fluvial-tidal transitions of mesotidal largerivers are therefore more likely to be dominated by downstream-oriented currents. Furthermore, a new style of low-angle (<5°) inclined heterolithic stratification found in bar-top accretion-sets within upper-mixed tidal-fluvial

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Section: Modern Lower Columbia River Sediment Supplymentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Alluvial architecture of mid‐channel fluvial–tidal barforms: The mesotidal Lower Columbia River, Oregon/Washington, USA

et al. 2020

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“…The FMTZ also experiences temporal variations in extension, location and depositional processes, which are driven by changes in fluvial (for example, seasonal), tidal (for example, ebb-flood or neap-spring) and wave processes (Dalrymple et al, 2015;La Croix & Dashtgard, 2015;Gugliotta et al, 2016Gugliotta et al, , 2017Jablonski & Dalrymple, 2016). Although the FMTZ is a fundamental feature of modern and ancient coastal rivers, this zone has been described in detail from only a few modern examples (La Croix & Dashtgard, 2015;Prokocki et al, 2015;Gugliotta et al, 2017) and rarely from the ancient rock record (van den Berg et al, 2007;Martinius et al, 2015;Gugliotta et al, 2016). This paper aims to improve the understanding of sediment distribution and depositional processes along the FMTZ using a comprehensive dataset of channel bed sediment samples collected from the Vietnamese part of the modern Mekong River delta (Fig.…”

Section: Introductionmentioning

confidence: 99%

Sediment distribution and depositional processes along the fluvial to marine transition zone of the Mekong River delta, Vietnam

Gugliotta

Saito

Nguyen³

et al. 2018

Sedimentology

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The area of coastal rivers with a combination of fluvial, tidal and wave processes is defined as the fluvial to marine transition zone and can extend up to several hundreds of kilometres upstream of the river mouth. The aim of this study is to improve the understanding of sediment distribution and depositional processes along the fluvial to marine transition zone using a comprehensive dataset of channel bed sediment samples collected from the Mekong River delta. Six sediment types were identified and were interpreted to reflect the combined action of fluvial and marine processes. Based on sediment‐type associations, the Mekong fluvial to marine transition zone could be subdivided into an upstream tract and a downstream tract; the boundary between these two tracts is identified 80 to 100 km upstream of the river mouth. The upstream tract is characterized by gravelly sand and sand and occasional heterolithic rhythmites, suggesting bed‐load supply and deposition mainly controlled by fluvial processes with subordinate tidal influence. The downstream tract is characterized by heterolithic rhythmites with subordinate sand and mud, suggesting suspended‐load supply and deposition mainly controlled by tidal processes with subordinate fluvial influence. Sediment distributions during wet and dry seasons suggest significant seasonal changes in sediment dynamic and depositional processes along the fluvial to marine transition zone. The upstream tract shows strong fluvial depositional processes with subordinate tidal influence during the wet season and no deposition with weak fluvial and tidal processes during the dry season. The downstream tract shows strong coexisting fluvial and tidal depositional processes during the wet season and strong tidal depositional processes with negligible fluvial influence during the dry season. Turbidity maxima are present along the downstream tract of the fluvial to marine transition zone during both wet and dry seasons and are driven by a combination of fluvial, tidal and wave processes.

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The morphology of fluvial‐tidal dunes: Lower Columbia River, Oregon/Washington, USA

Prokocki

Best

Perillo

et al. 2022

Earth Surf Processes Landf

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This article quantifies changes in primary dune morphology of the mesotidal Lower Columbia River (LCR), USA, through ~90 river kilometres of its fluvial‐tidal transition at low‐river stage. Measurements were derived from a multibeam echo sounder dataset that captured bedform dimensions within the thalweg (≥ 9 m depth; H/Hmax ≥ 0.7) of the LCR main channel. Measurements revealed two categories of dunes: (i) fine to medium sand ‘fluvial‐tidal to tidal’ (upstream‐oriented, simple, and two‐dimensional) low‐angle dunes (heights ≈ 0.3–0.8 m; wavelengths ≈ 10–25 m; mean lee‐angles ≈ 7°–11°), and (ii) medium to coarse sand ‘fluvial’ (downstream‐oriented, compound, and 2.5‐dimensional to three‐dimensional) low‐angle dunes (heights ≈ 1.5–3 m; wavelengths ≈ 60–110 m; mean lee‐angles ≈ 11°–18°). At low‐river stage, where H/Hmax ≥ 0.7, approximately 86% of the fluvial‐tidal transition is populated by ‘fluvial’ dunes, whilst ~ 14% possesses ‘fluvial‐tidal to tidal’ dunes that form in the downstream‐most reaches. Thus, throughout the majority of the deepest channel segments of the fluvial‐tidal transition, seaward‐oriented river and ebb‐tidal currents govern dune morphology, whilst strong bidirectional tidal‐current influence is restricted to the downstream most reaches of the transition zone. Two mechanisms are reasoned to explain dune low‐angle character: (1) high‐suspended sediment transport near peak tidal‐currents that lowers the leeside‐angles of ‘fluvial‐tidal to tidal’ dunes, and (2) superimposed bedforms that erode the crests, leesides, and stoss‐sides, of ‘fluvial’ dunes, which results in the reduction of leeside‐angles. Fluctuations in river discharge create a ‘dynamic morphology reach’ at depths where H/Hmax ≥ 0.7, which spans river kilometres 12–40 and displays the greatest variation in dune morphology. Similar channel reaches likely exist in fluvial‐tidal transitions with analogous physical characteristics as the LCR and may provide a distinct signature for the fluvial‐tidal transition zone.

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Mid to late Holocene geomorphological and sedimentological evolution of the fluvial–tidal zone

Cited by 8 publications

References 34 publications

Alluvial architecture of mid‐channel fluvial–tidal barforms: The mesotidal Lower Columbia River, Oregon/Washington, USA

Alluvial architecture of mid‐channel fluvial–tidal barforms: The mesotidal Lower Columbia River, Oregon/Washington, USA

Sediment distribution and depositional processes along the fluvial to marine transition zone of the Mekong River delta, Vietnam

The morphology of fluvial‐tidal dunes: Lower Columbia River, Oregon/Washington, USA

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