Friedrichs, Carl T.

Kraatz, L. M.

English

College of William & Mary: W&M Publish

W&M ScholarWorks Presentations 4-20-2011 The assessment of sediment bed properties within the York River estuary as a function of spring and neap tidal cycle L. M. Kraatz Virginia Institute of Marine Science Carl T. Friedrichs Virginia Institute of Marine Science Follow this and additional works at: https://scholarworks.wm.edu/presentations  Part of the Environmental Sciences Commons Recommended Citation Kraatz, L. M. and Friedrichs, Carl T.. "The assessment of sediment bed properties within the York River estuary as a function of spring and neap tidal cycle". 4-20-2011. York River Research Symposium, Gloucester Point, VA. This Presentation is brought to you for free and open access by W&M ScholarWorks. It has been accepted for inclusion in Presentations by an authorized administrator of W&M ScholarWorks. For more information, please contact scholarworks@wm.edu. Lindsey Kraatz and Carl FriedrichsYork River Research SymposiumApril 20, 2011The assessment of sediment bed properties within the York River estuary as a function of spring and neap tidal cycles MotivationMotivationBackgroundStudy AreaSample CollectionWater ContentMud:SandRatioErodibilitySummaryManagement ImplicationsNSF MUDBED Project (Multi-disciplinary Benthic Exchange Dynamics)Understanding fine sediment transport is critical to managing coastal water quality and ecological health, and to understanding coastal ecology, chemical fluxes and the geological record.Erodibility and settling velocity are difficult to predict because physicaland biological effects fundamentally impact them over short scales and physical and feedback on each other• Erodibility- Stress to initiate movement of particles- Mass eroded at a given stress• Erodibility of sediment beds is a function of:– Grain size– Water content– Mineralogical composition– Biological activity– Salinity– Temperature– Etc• Fine sediment erosion difficult to predict– Number of techniques have been developed • Laboratory flume tests (Parchure and Mehta, 1985)• In situ measurements using submersible flumes (Maa, 1998)• Cores (McNeil et al, 1996)BackgroundMotivationBackgroundStudy AreaSample CollectionWater ContentMud:SandRatioErodibilitySummaryManagement Implications• Erodibility- Stress to initiate movement of particles- Mass eroded at a given stress• Erodibility of sediment beds is a function of:– Grain size– Water content– Mineralogical composition– Biological activity– Salinity– Temperature– Etc• Fine sediment erosion difficult to predict– Number of techniques have been developed • Laboratory flume tests (Parchure and Mehta, 1985)• In situ measurements using submersible flumes (Maa, 1998)• Cores (McNeil et al, 1996)BackgroundMotivationBackgroundStudy AreaSample CollectionWater ContentMud:SandRatioErodibilitySummaryManagement ImplicationsYork River River Flow(Lin and Kuo, 2001), (Schaffner et al., 2001) (Lin and Kuo, 2003),(Scully and Friedrichs, 2003), (Dickhudt et al. 2008), , (Cartwright et al., 2009), and (Friedrichs, 2009)MotivationBackgroundStudy AreaSample CollectionWater ContentMud:SandRatioErodibilitySummaryManagement ImplicationsYork River•Microtidal system ~ 0.8m range•Studies show deep physical mixing of the seabed up to 100 cm on spring-neap and longer time cycles•Mixing can occur by:•Physical processes•Bioturbation•Strong tidal currents • - ~1 m s-1 near surface•Severely fetch limited• - Weak local wind waves•ETM located at West Point•STM found seasonally at Clay BankMotivationBackgroundStudy AreaSample CollectionWater ContentMud:SandRatioErodibilitySummaryManagement Implications• Sediments were collected with a Gomex box core during the spring of 2010• Collection occurred:– weekly – during slack tides – analyzed differences of spring and neap sediment properties and erodibility• Each week, cores were sub-sampled for:– Water content– Grain size– Organic content– Digital X-radiography– Erodibility– Be7 Isotope ~ Sediment datingSample CollectionP. DickhudtMotivationBackgroundStudy AreaSample CollectionWater ContentMud:SandRatioErodibilitySummaryManagement Implications• Sediments were collected with a Gomex box core during the spring of 2010• Collection occurred:– weekly – during slack tides – analyzed differences of spring and neap sediment properties and erodibility• Each week, cores were sub-sampled for:– Water content– Grain size– Organic content– Digital X-radiography– Erodibility– Be7 Isotope ~ Sediment datingSample CollectionP. DickhudtMotivationBackgroundStudy AreaSample CollectionWater ContentMud:SandRatioErodibilitySummaryManagement Implications024681012141655 60 65 70 75 80 85Depth down core (cm)Percent MoistureMay 5 - NeapMay 11 - SpringMay 20 - NeapMay 27 - SpringWater ContentMotivationBackgroundStudy AreaSample CollectionWater ContentMud:SandRatioErodibilitySummaryManagement ImplicationsMud:Sand RatioDepth down core (cm)• Dual core Gust Microcosm• 2 cores collected in situ• Simulates tidal resuspension• Profiles of critical shear stress and erosion rate constantErodibilityMotivationBackgroundStudy AreaSample CollectionWater ContentMud:SandRatioErodibilitySummaryManagement Implications(Dickhudt et al., 2009)Erodibility0 0.1 0.2 0.3 0.4 0.5 0.600.511.522.5  49084907490048994883487748750 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.4500.10.20.30.40.50.60.7c , [Pa]Eroded Mass, [kg .  m-2]  4908490749004899488348774875Erodibility vs. Dickhudt et al., 2009Τ crit (Pa)Eroded mass (kg m-2)MotivationBackgroundStudy AreaSample CollectionWater ContentMud:SandRatioErodibilitySummaryManagement Implications• Sediment dynamics is one of the most important factors affecting coastal, estuarine, and riverine systems• Little is known about the transport and dynamics of fine-grained sediment, despite the importance of particle dispersal• High quantities of suspended sediment can result in negative impacts within the estuary, including:– enhanced light attenuation– disruption and change of benthic community structure and distribution– modified transport of organic carbon– changes in the location and duration of eutrophication and hypoxia – pollutant contaminationhttp://diffusesources.com/files/estuarydiagram.jpgManagement Implicationshttp://www.waterwise.com/images/waterwisdom/thinkbeforeyoudrinkpict.jpgMotivationBackgroundStudy AreaSample CollectionWater ContentMud:SandRatioErodibilityManagement ImplicationsSummary• Seafloor sediments exhibited a higher erodibility during spring tides than neap tides• More muds were present and a higher water content was found during neap tides.• This is thought to be due to a higher abundance of flocculated sediments present during neap tides than spring tides.• Sediment transport greatly affects all aspects of estuarine ecosystem health, ranging from light limitation to pollutant contamination.SummaryMotivationBackgroundStudy AreaSample CollectionWater ContentMud:SandRatioErodibilityManagement ImplicationsSummaryAcknowledgementsCommitteeJesse McNinchCourtney HarrisSteve KuehlLinda SchaffnerArt TrembanisGrace CartwrightPat DickhudtKelsey FallCarissa WilkersonPayal DhariaTara KniskernAaron BeverBob GammischWayne ReisnerTim GassSam LakeRachel CorriganCielomar RodriguezJulia MoriartyThanks to:Funding SourcesNSF Co-Op ~ OCE-0536572 NSK GK-12 ~ DGE-0840804Chirp RecordsApril 0720 m500 m20 m500 mOctober 07Erodibility vs. Dickhudt, 2009MotivationBackgroundStudy AreaSample CollectionWater ContentMud:SandRatioErodibilityX-raysSummaryManagement ImplicationsX-Rays• 12 cm wide x 2.5 cm thick x 10-20cm in length• Grayscale indicative of relative density• X-ray negatives– Light shade = high density– Dark shade = lower densityX-RaysMotivationBackgroundStudy AreaSample CollectionWater ContentMud:SandRatioErodibilityX-raysSummaryManagement Implications4878 4878_perpendicular48754876_perpen4876April 29, 2010 ~ Clay Bank4884 A 4884 B4885 A4885 BMay 5, 2010 ~ Clay BankMay 11, 2010 ~ Clay Bank4891 A 4891 B4892 A 4892 B4898 A 4898 B48974901 A 4901 BMay 20, 2010 ~ Clay Bank4905 A 4905 BMay 27, 2010 ~ Clay Bank4906 A4906 Bhttp://pubs.usgs.gov/circ/circ1133/images/fig51.jpeghttp://diffusesources.com/files/estuarydiagram.jpgFresh water and sediment transportLin and Kuo (2001)• Persistent ETM - West Point- near limit of salt• Ephemeral STM - Clay Bank-first stratification downstream of ETM      -elevated river flow - sediment trapping- high TSS- low river flow- no trapping- low TSSHigh Flow Low Flow(from Lin and Kuo, 2001)http://www.waterwise.com/images/waterwisdom/thinkbeforeyoudrinkpict.jpghttp://www.sccwrp.org/images/ResearchAreas/Contaminants/MeasurementFateAndBioavailability/PassiveSamplingApplications/EstimatingLoadingsAndFluxes/EstimatingLoadingsAndFluxes_Figure1.jpgInfluences on cohesion and erodibility• Salinity• Temperature• Mineralogy• Grain size• Consolidation (water content, solids fraction, bulk density, etc.)Biostabilization• Organic content• Colloidal carbohydrates• Extracellular polymeric substances (EPS)• Pelletization (?)Biodestabilization• Bioturbation• Pelletization (?)Physical BiologicalErodibility-Stress to initiate movement of particles- Mass eroded at a given stressConsolidation and Erodibility• Bulk density    w/depth into sediment• As bulk density - critical stress (c)and- erodibility   0.5Parchure and Mehta (1985)Depth (cm)00 0.2 0.41.0Shear Stress (Pa)0 100 200 300 40023451Depth (cm)Density (g l-1)0Amos et al. (1997)ErodibilityInfluence of Tides vs Waves• Microtidal- 0.8 m range• Strong tidal currents - ~1 m s-1 near surface• Severely fetch limited- Weak local wind waves- Period < 5 sec- Height < 0.5 m-largest wave stresses      average tidal stresses• Suspended sed. stratification limits resuspension (Friedrichs et al (2000)Tidal current stress at Clay BankErnestow = 0.3 PaFresh Water and Sediment SupplyResidence Time• 70 - 200 years -Dellapenna et al. (1998; 2003)• Supply small relative to active in systemFresh Water Supply• High in winter• Low in summer• EpisodicSediment Sources• Riverine   ~ 55%• Shoreline erosion~ 12%• Chesapeake main stem~ 33%(Nichols (1991))http://waterdata.usgs.gov/nwis Summer SummerWinter

The assessment of sediment bed properties within the York River estuary as a function of spring and neap tidal cycle

https://scholarworks.wm.edu/cgi/viewcontent.cgi?article=1176&context=presentations

The assessment of sediment bed properties within the York River estuary as a function of spring and neap tidal cycle

Abstract

Similar works

Full text

Available Versions

College of William & Mary: W&M Publish