scholarly journals Influence of distributary channels on sediment and organic carbon supply in event-dominated coastal margins: the Po prodelta as a study case

2010 ◽  
Vol 7 (5) ◽  
pp. 7849-7902
Author(s):  
T. Tesi ◽  
S. Miserocchi ◽  
M. A. Goñi ◽  
M. Turchetto ◽  
L. Langone ◽  
...  
Keyword(s):  
Water Column ◽  
Suspended Sediment ◽  
Surface Waters ◽  
Sediment Cores ◽  
Sediment Supply ◽  
Channel Network ◽  
The North ◽  
Depositional Processes ◽  
Suspended Sediment Concentrations ◽  
Peak Flood

Abstract. From November 2008 through May 2009, the North Italy experienced the highest precipitation period recorded over the last century. As a result, a long series of flood events occurred in the Po river (North Italy). This series of events ended with a large flood in early May 2009. An event-response sampling was carried out in the Po prodelta in April–May 2009 to characterize this latter event and to investigate the strata preservation in the stratigraphy record as a result of this series of floods. The water sampling was carried out during two periods of the flood, including early in the event under conditions of moderate river flow (~5000 m3 s−1) and 24 h later during the peak discharge (~8000 m3 s−1). At each station, profiles of conductivity, transmittance, and fluorescence were acquired whereas surface and bottom waters were sampled to collect sediments in suspension. In addition, sediment cores were collected in the Po prodelta before and after the peak flood. Biogeochemical compositions and sedimentological characteristics of suspended and sediment samples were investigated using a multi-proxy approach that included bulk and biomarkers analyses. Furthermore, 7Be down-core profiles and radiographs were used to analyze the internal stratigraphy of sediment cores. During moderate discharge, the water column did not show evidence of plume penetration. In surface waters, suspended sediment concentrations were found to be similar to low river discharge periods whereas the main OC was autochthonous. After 24 h, during the peak flood, water column properties and biogeochemical parameters exhibited marked changes indicating significant penetration of the turbid plume. However, suspended sediment concentrations and terrigenous OC content in surface waters were still less then expected based on the discharge. These results suggested that, since material enters the Adriatic as buoyancy-driven flow with a reduced transport capacity, settling and flocculation processes result in trapping a significant fraction of land-derived material prior to reaching the subaqueous prodelta. In spite numerous floods occurred from November 2008 through April 2009, sediment cores collected in late April 2009 did not exhibited significant evidence of event-strata preservation. Since these floods were ordinary (2–3 y return period), the lack of preservation indicates that most of the sediment supply during these oridinary events does not reach the subaqueous prodelta. However, it is likely that modest sediment deposition occurs during these oridinary floods but thicknesses of these event-strata are not sufficient to compete with post-depositional processes. Stations in the north and central prodelta were re-occupied after the peak of the May 2009 flood. Based on 7Be and radiographs, we estimated that 17 and 6 cm event-layers, respectively. Selective trapping of coarse material occurred in the central prodelta likely because of the geomorphologic setting of the central outlet characterized by an estuary-like mouth. Despite these settling processes, lignin-based parameters indicated that sources of the terrigenous OC were fairly homogenous throughout the channel network and between size-fractions.

scholarly journals Influence of distributary channels on sediment and organic matter supply in event-dominated coastal margins: the Po prodelta as a study case

2011 ◽  
Vol 8 (2) ◽  
pp. 365-385 ◽  
Author(s):  
T. Tesi ◽  
S. Miserocchi ◽  
M. A. Goñi ◽  
M. Turchetto ◽  
L. Langone ◽  
...  
Keyword(s):  
River Flow ◽  
Sediment Cores ◽  
Suspended Sediments ◽  
Particulate Material ◽  
Sediment Supply ◽  
Sediment Record ◽  
Po River ◽  
Depositional Processes ◽  
Before And After ◽  
Peak Flood

Abstract. From November 2008 through May 2009, the Po river (Italy) experienced several floods exceeding 5000 m3 s−1. This long series of events ended with a large flood in early May 2009 (~8000 m3 s−1). An event-response sampling was carried out in the Po prodelta in April–May 2009 to characterize the preservation of this series of floods in the sediment record and to describe the event-supply and deposition of riverborne particulate material during the May 2009 flood. The water sampling was carried out early in the event under conditions of moderate river flow (~5000 m3 s−1) and 24 h later during the peak discharge (~8000 m3 s−1). Sediment cores were collected in the prodelta before and after the peak flood. At each station, profiles of conductivity, transmittance, and fluorescence were acquired. Surface and bottom waters were sampled to collect sediments in suspension. In addition, a few days before the May 2009 event, suspended sediments were collected at Pontelagoscuro gauging station, ~90 km upstream from the coast. Biogeochemical compositions and sedimentological characteristics of suspended and sediment samples were investigated using bulk and biomarker analyses. Furthermore, 7Be and radiographs were used to analyze the internal stratigraphy of sediment cores. During moderate flow, the water column did not show evidence of plume penetration. Stations re-occupied 24 h later exhibited marked physical and biogeochemical changes during the peak flood. However, the concentration of terrestrially-derived material in surface waters was still less than expected. These results suggested that, since material enters the Adriatic as buoyancy-driven flow with a reduced transport capacity, settling and flocculation processes result in trapping a significant fraction of land-derived material in shallow sediments and/or within distributary channels. Although numerous discharge peaks occurred from November 2008 through April 2009 (4000–6000 m3 s−1), sediment cores collected in late April 2009 showed lack of event-strata preservation and reduced 7Be penetrations. This suggested that only a small fraction of the sediment supply during ordinary events reaches the deepest region of the prodelta (12–20 m water depth). As a result, these event-strata have a thickness not sufficient to be preserved in the sediment record because of post-depositional processes that destroy the flood signal. Stations in the northern and central prodelta were re-occupied after the peak of the May 2009 flood. Based on 7Be and radiographs, we estimated event layers of 17 and 6 cm thickness, respectively. Selective trapping of coarse material occurred in the central prodelta likely because of the geomorphologic setting of the central outlet characterized by an estuary-like mouth. Despite these settling processes, lignin-based parameters indicated that the composition of the terrigenous OC was fairly homogenous throughout the network of channels and between size-fractions.

scholarly journals THE BRANCHING CHANNEL NETWORK IN THE YANGTZE ESTUARY

2012 ◽  
Vol 1 (33) ◽  
pp. 69
Author(s):  
Zheng Bing Wang ◽  
Pingxing Ding
Keyword(s):  
Yangtze Estuary ◽  
River Delta ◽  
Sediment Supply ◽  
Channel Structure ◽  
The South ◽  
Channel Network ◽  
The Yangtze Estuary ◽  
The North ◽  
Navigation Channel ◽  
The Impact

The channels in the Yangtze Estuary have an ordered-branching structure: The estuary is first divided by the Chongming Island into the North Branch and the South Branch. Then the South Branch is divided into the North Channel and South Channel by the Islands Changxing and Hengsha. The South Channel is again divided into the North and South Passage by the Jiuduansha Shoal. This three-level bifurcation and four-outlet configuration appears to be a natural character of the estuary, also in the past (Chen et al., 1982), although the whole system has been extending into the East China Sea in the southeast direction due to the abundant sediment supply from the Yangtze River. Recently, the natural development of the system seems to be substantially disturbed by human interferences, especially the Deep Navigation Channel Project. For the understanding of the behaviour of the bifurcating channel system in the estuary we present analysis on two aspects: (1) the equilibrium configuration of river delta distributary networks, and (2) influence of tidal flow on the morphological equilibrium of rivers. Based on the analyses we conclude that the branching channel structure of the Yangtze Estuary can be classified as tide-influenced river delta distributary networks. Its basic structure is the same as in case of river dominated delta. The empirical relations describing the basic features of the river-dominated distributary delta networks can be explained by theoretical analysis, although they are not fully satisfied by the Yangtze Estuary because of the influence of the tide. Two major influences of the tide are identified, viz. increasing the resistance to the river flow into the sea and increasing the sediment transport capacity. As consequence of these two influences the cross-sectional area of the river/estuary increases in the seawards direction and the bed slope decreases. The insights from the analyses are helpful for the understanding of the impact of the Deep Navigation Channel Project on the large scale morphological development of the estuary.

Marsh Processes and Their Response to Climate Change and Sea-Level Rise

2019 ◽  
Vol 47 (1) ◽  
pp. 481-517 ◽  
Author(s):  
Duncan M. FitzGerald ◽  
Zoe Hughes
Keyword(s):  
Climate Change ◽  
Carbon Dioxide ◽  
Sea Level Rise ◽  
Suspended Sediment ◽  
Sea Level ◽  
Salt Marshes ◽  
Biomass Productivity ◽  
Sediment Supply ◽  
Marsh Vegetation ◽  
Suspended Sediment Concentrations

In addition to their being vital components of mid- to high-latitude coastal ecosystems, salt marshes contain 0.1% of global sequestered terrestrial carbon. Their sustainability is now threatened by accelerating sea-level rise (SLR) that has reached a rate that is many times greater than the rate at which they formed and evolved. Modeling studies have been instrumental in predicting how marsh systems will respond to greater frequencies and durations of tidal inundation and in quantifying thresholds when marshes will succumb and begin to disintegrate due to accelerating SLR. Over the short term, some researchers believe that biogeomorphic feedbacks will improve marsh survival through greater biomass productivity enhanced by warmer temperatures and higher carbon dioxide concentrations. Increased sedimentation rates are less likely due to lower-than-expected suspended sediment concentrations. The majority of marsh loss today is through wave-induced edge erosion that beneficially adds sediment to the system. Edge erosion is partly offset by upland marsh migration during SLR. ▪ Despite positive biogeomorphic feedbacks, many salt marshes will succumb to accelerating sea-level rise due to insufficient mineral sediment. ▪ The latest multivariate marsh modeling is producing predictions of marsh evolution under various sea-level rise scenarios. ▪ The least well-known variables in projecting changes to salt marshes are suspended sediment concentrations and net sediment influx to the marsh. ▪ We are in the infancy of understanding the importance and processes of marsh edge erosion and the overall dynamicism of marshes. ▪ This review defines the latest breakthroughs in understanding the response of salt marshes to accelerating sea-level rise and decreasing sediment supply. ▪ Climate change is accelerating sea-level rise, warming temperatures, and increasing carbon dioxide, all of which are impacting marsh vegetation and vertical accretion.

Mixed sediment transport in a stratified estuary: first insights from a field study

2021 ◽  
Author(s):  
Iris Niesten ◽  
Ton Hoitink ◽  
Bart Vermeulen ◽  
Ymkje Huismans
Keyword(s):  
Sediment Transport ◽  
Water Column ◽  
Suspended Sediment ◽  
Lower Layer ◽  
Sediment Type ◽  
Sediment Characteristics ◽  
Channel Network ◽  
Flow Measurements ◽  
Gravitational Circulation ◽  
Port Area

<p>Many estuaries are characterized by a mixture of clay, silt and sand. The erosion, (re-)suspension and transport of these sediments determine the bathymetry and stability of an estuary. Net estuarine sediment transport is the result of multiple processes. In stratified estuaries, gravitational circulation may lead to an inland near-bed sediment transport, which is directed opposite to the net sediment transport higher in the water column. Considering that coarse material is often transported near the bed, while suspended sediment usually consists of finer particles, gravitational circulation may cause a seaward flux of fine sediment and a landward flux of coarse sediment. The New Waterway in the Rotterdam Port area (The Netherlands) is such a stratified channel. Repeated channel deepening has intensified stratification, resulting in a strong salt-wedge type of flow. The channel is continuously dredged for navigation purposes, while the channel would naturally be gaining sediment (Cox et al., 2020). The amount of sediment entering the channel from sea and upstream, and the contribution of different sediment fractions however remain unclear. In this research, we combine  data analysis with numerical modelling to better understand and quantify sediment transport in stratified estuarine channels.</p><p>As a first step, we set up a field campaign which combines flow measurements with determination of suspended sediment characteristics. A measurement frame is equipped with a Sequoia LISST-200x and an YSI EXO Turbidity meter. Suspended sediment characteristics are determined every hour at three depths, next to water temperature, salinity and turbidity. Water samples are taken simultaneously to determine suspended sediment concentration, and flow is monitored continuously using a vessel-mounted ADCP. The full campaign includes two 13-hour measurements and covers two locations in the New Waterway.</p><p>The flow in the upper layer of the water column shows to be decoupled from the saline layer below. Before the flood acceleration phase, the upper and lower layer show an opposite flow direction, corresponding to the findings of De Nijs et al. (2010). The LISST-measurements confirm that suspended sediment in the upper water layer contains a high amount of clay and silt, while the material close to the bed is predominantly sand. This suggests a correlation between grain size and net transport direction. It should be noted that a major part of suspended sediment seems to be transported in the saline bottom layer, and that near-bed processes and local sediment availability could play an important role in the net sediment transport. Continued measurements and the modelling study will further reveal the sensitivity of the net sediment transport to sediment type, and provide insight in the effect of channel deepening.</p><p> </p><p>Cox, J.R., Y. Huismans, J.F.R.W. Leuven, N.E. Vellinga, M. Van der Vegt, A.J.F. Hoitink, and M.G. Kleinhans (2020). “Anthropogenic effects on the Contemporary Sediment Budget of the Lower Rhine-Meuse Delta Channel Network.” Manuscript submitted to Earths Future.</p><p>Nijs, Michel A. J. de, Johan C. Winterwerp, and Julie D. Pietrzak (2010). “The Effects of the Internal Flow Structure on SPM Entrapment in the Rotterdam Waterway.” Journal of Physical Oceanography 40, no. 11: 2357–80.</p>

NAPTRAM - Plastiktransportmechanismen, Senken und Interaktionen mit Biota im Nordatlantik / NAPTRAM - North Atlantic plastic transport mechanisms, sinks, and interactions with biota, Cruise No. SO279, Emden (Germany) – Emden (Germany), 04.12.2020 – 05.01.2021

2021 ◽  
Author(s):  
Aaron Beck
Keyword(s):  
Water Column ◽  
North Atlantic ◽  
Surface Waters ◽  
Open Ocean ◽  
Transport Pathways ◽  
The North ◽  
The North Atlantic ◽  
Vertical Export ◽  
Core Questions ◽  
Ocean Gyre

The coastal and open oceans represent a major, but yet unconstrained, sink for plastics. It is likely that plastic-biota interactions are a key driver for the fragmentation, aggregation, and vertical transport of plastic litter from surface waters to sedimentary sinks. Cruise SO279 conducted sampling to address core questions of microplastic distribution in the open ocean water column, biota, and sediments. Seven stations were sampled between the outer Bay of Biscay and the primary working area south of the Azores. Additional samples were collected from surface waters along the cruise track to link European coastal and shelf waters with the open ocean gyre. Microplastic samples coupled with geochemical tracer analyses will build a mechanistic understanding of MP transport and its biological impact reaching from coastal seas to the central gyre water column and sinks at the seabed. Furthermore, floating plastics were sampled for microbial community and genetic analyses to investigate potential enzymatic degradation pathways. Cruise SO279 served as the third cruise of a number of connected research cruises to build an understanding of the transport pathways of plastic and microplastic debris in the North Atlantic from the input through rivers and air across coastal seas into the accumulation spots in the North Atlantic gyre and the vertical export to its sink at the seabed. The cruise was an international effort as part of the JPI Oceans project HOTMIC (“HOrizontal and vertical oceanic distribution, Transport, and impact of MICroplastics”) and the BMBF funded project PLASTISEA (‘Harvesting the marine Plastisphere for novel cleaning concepts’), and formed a joint effort of HOTMIC and PLASTISEA researchers from a range of countries and institutes.

scholarly journals Scale-breaks of suspended sediment rating in large rivers in Germany induced by organic matter

2020 ◽  
Author(s):  
Thomas O. Hoffmann ◽  
Yannik Baulig ◽  
Helmut Fischer ◽  
Jan Blöthe
Keyword(s):  
Organic Matter ◽  
Suspended Sediment ◽  
Suspended Matter ◽  
Monitoring Network ◽  
Suspended Sediments ◽  
Sediment Supply ◽  
Organic Fraction ◽  
Sediment Rating Curve ◽  
Suspended Sediment Concentrations ◽  
Rating Model

Abstract. Understanding the dynamics of suspended sediment and associated nutrients is of major relevance for sustainable sediment management aiming to achieve healthy river systems. Sediment rating curves are frequently used to analyze the dynamics of suspended sediments and their potential sources and sinks. Here we are using more than 750 000 measurements of the suspended sediment concentrations (SSC) and discharge at 62 gauging stations along 19 waterways in Germany based on the suspended sediment monitoring network of the German water and shipping authority, which started in the 1960ties. Furthermore, we analyse more than 2000 measurements of the loss on ignition (LOI) of suspended matter at two stations along the rivers Moselle and Rhine to asses the mineral and organic fraction of the suspended matter. SSC and LOI are analysed in terms of the power law rating to identify discharge depended process regimes of suspended matter. Our results indicate that for most studied gauging stations, rating coefficients are not constant over the full discharge range, but there is a distinct break in the sediment rating curve, with specific SSC-Q domains above and below this break. The transition of the rating exponent is likely to be a result of a change of controlling factors of the suspended sediment from intrinsic organic matter formation at low flows to extrinsic sediment supply (including mineral and organic fractions) due to hillslope erosion at high flows. Based on these findings we developed a conceptual rating model separating the mineral and organic fraction of the suspended matter in the Germany waterways. This model allows evaluating the sources of the mineral and organic fraction of the suspended matter and gain new insights into the first order control of discharge dynamics of suspended sediments.

scholarly journals Effects of River-Ice Breakup on Sediment Transport and Implications to Stream Environments: A Review

Water ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 2541
Author(s):  
Spyros Beltaos ◽  
Brian C. Burrell
Keyword(s):  
Suspended Sediment ◽  
Sediment Supply ◽  
River Ice ◽  
Sediment Erosion ◽  
Ice Jams ◽  
Form And Function ◽  
Ice Breakup ◽  
Sharp Waves ◽  
Suspended Sediment Concentrations ◽  
And Function

During the breakup of river ice covers, a greater potential for erosion occurs due to rising discharge and moving ice and the highly dynamic waves that form upon ice-jam release. Consequently, suspended-sediment concentrations can increase sharply and peak before the arrival of the peak flow. Large spikes in sediment concentrations occasionally occur during the passage of sharp waves resulting from releases of upstream ice jams and the ensuing ice runs. This is important, as river form and function (both geomorphologic and ecological) depend upon sediment erosion and deposition. Yet, sediment monitoring programs often overlook the higher suspended-sediment concentrations and loads that occur during the breakup period owing to data-collection difficulties in the presence of moving ice and ice jams. In this review paper, we introduce basics of river sediment erosion and transport and of relevant phenomena that occur during the breakup of river ice. Datasets of varying volume and detail on measured and inferred suspended-sediment concentrations during the breakup period on different rivers are reviewed and compared. Possible effects of river characteristics on seasonal sediment supply are discussed, and the implications of increased sediment supply are reviewed based on seasonal comparisons. The paper also reviews the environmental significance of increased sediment supply both on water quality and ecosystem functionality.

scholarly journals High resolution paleo-environmental changes during the Sapropel 1 in the North Ionian Sea, central Mediterranean

The Holocene ◽  
2020 ◽  
Vol 30 (11) ◽  
pp. 1504-1515 ◽  
Author(s):  
Helena Checa ◽  
Giulia Margaritelli ◽  
Leopoldo D Pena ◽  
Jaime Frigola ◽  
Isabel Cacho ◽  
...  
Keyword(s):  
High Resolution ◽  
Water Column ◽  
Surface Waters ◽  
Environmental Changes ◽  
Nutrient Content ◽  
Ionian Sea ◽  
Central Mediterranean ◽  
White Variety ◽  
The North ◽  
Geochemical Analyses

High-resolution paleoceanographic reconstruction of surface water properties during the most recent Sapropel event (S1) has been carried out by means of quantitative analyses of planktonic foraminiferal assemblages, planktonic foraminiferal oxygen isotopes (δ18O) and XRF elemental data from a 655 m depth core recovered in the North Ionian Sea. The results show that the S1 interval presents two distinctive warm phases (S1a and S1b), separated by a cold interruption event (S1i). High resolution faunal and geochemical analyses allow to identify two sub-phases within S1a interval, the oldest one has similar characteristics to S1b interval while the youngest sub-phase has less stratified surface waters with relatively lower nutrient content. The high abundance of Globigerinoides ruber white variety opposite to the low percentages of Neogloboquadrina pachyderma during the pre-S1 phase suggests that the onset of surface waters stratification occurred prior to the beginning of Sapropel deposition, acting as a pre-conditioning phase. Paleo-productivity proxies indicate that the deposition of S1 initiated after an increase in nutrient content, potentially related to increased fluvial inputs. Based on the integrated ecological interpretation of our records we argue that S1a and S1b are characterized as warm, stratified and nutrient rich surface waters in the Ionian Sea, while proxies related to oxygen content indicate dysoxic deep waters linked to a combination of the high nutrient content and stratified water column. The S1 interruption phase is characterized by the entrance of colder waters that caused mixing of the stratified water column and re-ventilation of the deep dysoxic waters.

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