Physical Sciences and Mathematics Commons^™

Hydrodynamics And Equilibrium Sediment Dynamics Of Shallow, Funnel-Shaped Tidal Estuaries, Carl T. Friedrichs, Bruce A. Armbrust, H. E. Deswart

VIMS Books and Book Chapters

No abstract provided.

Effects Of Channel Geometry On Cross Sectional Variation In Along Channel Velocity In Partially Stratified Estuaries, Carl T. Friedrichs, John M. Hamrick

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Analytic solutions for along‐channel velocity through an estuarine cross‐section with laterally varying depth are compared to observations from an array of current meters deployed over a nearly triangular cross‐section of the James River estuary. Analytic results suggest that the transverse structure of along‐channel velocity at this cross‐section is primarily due to simple density‐driven circulation modified by bathymetry. Comparisons of analytic solutions for the amplitude and phase of tidal velocity to observations suggest that linear models which include realistic lateral depth variation should also incorporate across‐channel variation in eddy viscosity. Solutions for various contributions to mean velocity are then derived which …

Introduction, Carl T. Friedrichs, D. G. Aubrey

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No abstract provided.

Uniform Bottom Shear Stress And Equilibrium Hyposometry Of Intertidal Flats, Carl T. Friedrichs

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Hypsometry is the distribution of horizontal surface area with respect to elevation. Recent observations of tidal flat morphology have correlated convex hypsometry with large tide ranges, long‐term accretion and/or low wave activity. Concave hypsometry, in turn, has been correlated with small tide ranges, long‐term erosion and/or high wave activity. The present study demonstrates that this empirical variation in tidal flat hypsometry is consistent with a simple morphodynamic model which assumes tidal flats to be at equilibrium if maximum bottom shear stress (τ) is spatially uniform. Two general cases are considered: (i) dominance of τ by tidal currents, where τ is …

Resuspension Behavior In The Lower Chesapeake Bay, J.P. -Y Maa, C. -H. Lee

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Using the VIMS Sea Carousel to conduct in-situ experiments in lower Chesapeake Bay, we found significant spatial a.nd temporal difference of the critical bed shear stress for sediment resuspension, tcr- At the Wolftrap site, tcr varied from 1.1 Pa in the summer to 1.9 Pa in the winter. At the Burwell Bay site, although the bed was too soft for anchoring our research vessel against the changing tide, we identified that tcr was 0.045 Pa. At the Old Plantation site, there was a small amount of fluffy material on top of the bed. At a winter deployment at the Cherrystone …

Hydrodynamical Modeling Of A Multiple‐Inlet Estuary/Barrier System: Insight Into Tidal Inlet Formation And Stability, Carl T. Friedrichs, David G. Aubrey, Graham S. Giese, Paul E. Speer

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Two specific questions are addressed concerning the role of tidal hydrodynamics in determining the long‐term morphologic evolution of the Nauset Beach‐Monomoy Island barrier system and the Chatham Harbor‐Pleasant Bay tidal estuary, Massachusetts: (1) why do the barrier and estuary exhibit a long‐term (∼150 yr) cycle of new inlet formation, and (2) once a new inlet forms, why is the resulting multiple inlet system unstable? To address these questions, a branched 1‐d numerical model is used to recreate the basic flow patterns in the tidal estuary at ten‐year intervals during the last half century and also to recreate flow conditions shortly …

Transport Of Hypoxic Waters: An Estuary-Subestuary Exchange, A. Y. Kuo, K. Park

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Hypoxic or anoxic conditions in the subpycnocline water of Chesapeake Bay persist throughout the summer. The effect on the dissolved oxygen concentration in the deep basin of the lower Rappahannock River, a subestuary on the western side of the bay, was studied with an observational program. The data indicate that in the lower portion of the water column the subtidal (or residual) current was directed into the subestuary most of the time. The mass fluxes of salt and dissolved oxygen into the subestuary through a point near the estuarine bottom at the river mouth were calculated for tidal and subtidal …

The Dynamics Of Long-Term Mass Transport In Estuaries, John M. Hamrick

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The dynamics of long-term mass transport in estuaries having weakly nonlinear long wave dynamics are investigated. Low pass filtered long-term mass transport equations are derived for conditions of weak and strong vertical stratification. The dynamics of the residual mass transport velocity, or lowest order approximation to the Lagrangian residual velocity, are investigated by perturbation analyses of the hydrodynamics equations. For weak vertical stratification conditions, analytical results showing the influence of topography, the earth's rotation, and channel curvature on the distribution of the residual mass transport velocity field are presented. The calculation of the residual mass transport velocity field from field …

Quaternary Geology Of The Chesapeake Bay, Jeffrey P. Halka, Steven M. Colman, Carl H. Hobbs Iii

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The Chesapeake Bay, which is a classic coastal plain estuary, is located on a trailing edge continental margin. It has a surface area of nearly 6,000 km2 and ranges in width from 8 to 48 km. The morphology of the bay clearly reflects its formation as a response to fluctuating sea level during and following the last major continental glaciation. The shoreline is highly irregular, the tributaries form an intricate dendritic drainage pattern, and a deep axial channel occurs along much of its length (fig. 1). Water depths commonly exceed 30m in this deep channel, which is flanked by broad …

Persistence Of Residual Currents In The James River Estuary And Its Implication To Mass Transport, Albert Y. Kuo, John M. Hamrick, Gamble M. Sisson

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The distribution and persistence of Eulerian and Lagrangian residual velocity in a cross sectional transect of the James River estuary, Virginia are analyzed. The Eulerian residual velocity has the characteristic two-layered estuarine circulation in the northern half of the transect, however, the net flow is directed downriver at all depths in the shallower southern half of the transect. In the deep channel, the two-layered Eulerian residual circulation is highly persistent over the six month study duration, with disruptions occurring less than 10% of the time when meteorological forcings are intense. No spring-neap tidal cycle variation is apparent. The magnitude of …

The Response Of Estuarine Circulation To Local Wind Events, K. P. Kiley, C. S. Welch

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An analysis of non-tidal estuarine circulation and local wind events was conducted employing wind and current records taken along the York River. Three distinct response conditions of non-tidal circulation to wind were observed. These conditions exhibited significant temporal and spatial variability. The first was typified by a positive two layer flow response to wind that was significant in the middle section of the York during the first six days of the study. The second exhibited a positive one layer flow response to wind that was significant in the upper section of the York during the last three days of the …

Interaction Between Circulation Of The Estuary Of The James River And Transport Of Oyster Larvae, Evon P. Ruzecki, William J. Hargis Jr.

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Hydraulic model dye test results are examined to provide estimates of nontidal horizontal circulation and movement/retention of oyster larvae in the James River Estuary. Test conditions maintained a constant mean tide and average summer low freshwater discharge. It was assumed that movement of dye in the model would approximate movement of the planktonic (larval) stages of oysters (Crassostroa virginica) in the prototype. Test results were used to rank six dye release points (candidate brood stock locations) with respect to relative quantities of dye retained in areas of the model representing commercially important seed oyster beds during the period 20-40 tidal …

Storage Efficiency Of Estuaries, Maynard M. Nichols

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Estuaries or the U.S. Atlantic coast exhibit a range or storage efficiencies from complete storage to partial by-passing through the system. Efficiency, I.e. the ratio or sediment accumulation to river Input rate, ranges 0.7 in the Altamaha River, Ga. to 7.6 In the Choptank River, Md. Northern estuaries trap and store the bulk or their river input In addition to large amounts or sediment supplied from other sources. Southern estuaries accumulate major sediment loads in marshes and allow partial escape through channels to the sea.

The storage efficiency or difrerent estuaries is compared with respect to key factors that can …

Temporal And Spatial Variations Of The Chesapeake Bay Plume, Evon P. Ruzecki

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Historical records and data obtained during the Superflux experiments are used to describe the temporal and spatial variations of the effluent waters of Chesapeake Bay. The alongshore extent of the plume resulting from variations of fresh water discharge into the Bay and the effects of wind are illustrated. Variations of the cross-sectional configuration of the plume over portions of a tidal cycle and results of a rapid-underway water sampling system are discussed.

Chesapeake Bay Plume Dynamics From Landsat, John C. Munday Jr., Michael S. Fedosh

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Examination of 81 dates of Landsat images with enhancement and density slicing has shown that the Chesapeake Bay plume usually frequents the Virginia coast south of the Bay mouth. Southwestern (compared to northern) winds spread the plume easterly over a large area. Ebb tide images (compared to flood tide images) show a more dispersed plume. Flooding waters produce high turbidity levels over the shallow northern portion of the Bay mouth.

Bacterial Biomass And Heterotrophic Potential In The Waters Of The Chesapeake Bay Plume And Contiguous Continental Shelf, Howard I. Kator, Paul L. Zubkoff

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Bacterial populations in Chesapeake Bay and contiguous shelf waters are significant to such essential processes as mineralization, nutrient recycling, degradation of pollutants and biomass production. However, our understanding of such dynamic relationships of physical and chemical factors to bacterial biomass and activities in Chesapeake Bay plume waters is limited. The availability of synoptic hydrographic (and remotely sensed physical-chemical) data obtained simultaneously with measurement of of microbial biomass and activity presented an opportunity to examine such relationships.

A Benchmark Multi-Disciplinary Study Of The Interaction Between The Chesapeake Bay And Adjacent Waters Of The Virginian Sea, William J. Hargis Jr.

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No abstract provided.

Response And Recovery To Sediment Influx In The Rappahannock Estuary: A Summary, Maynard M. Nichols, Galen Thompson, Bruce Nelson

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Flooding from Tropical Stonn Agnes produced unique hydrographic conditions for transport and dispersal of sediment in the Rappahannock and .James estuaries. Analyses indicate two cycles of response and recovery to the shock of extreme freshwater and sediment influx; one cycle in response to Rappahannock inflow; the other to intense mixing within the estuary. Important stages in the sequence consist of: (1) an initial response and seaward surge of river water and sediment; (2) shock with downstream translation of the salt intrusion head with a near-bottom salinity front and high turbidity in surface and in bottom water; (3) rebound with intense …

The Effect Of Tropical Storm Agnes On Heavy Metal And Pesticide Residues In The Eastern Oyster From Southern Chesapeake Bay, M. E. Bender, R. J. Huggett

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The concentrations of cadmium, copper, and zinc in the eastern oyster, Crassostrea virginica, are compared for samples collected before and after Tropical Storm Agnes. The "before" samples consisted of 475 animals from 95 stations collected in January 1971 and the "after" samples of 285 animals from 57 stations collected in January 1973. Shifts in the areal concentrations distributions were observed, apparently due to Agnes. Analyses of hard clams, blue crabs and oysters for chlorinated hydrocarbon pesticides showed influx of these compounds to be minimal as reflected by the residue levels observed. Comparison of residue levels in oysters to pre-Agnes conditions …

Changes In Salinity Structure Of The James, York And Rappahannock Estuaries Resulting From The Effects Of Tropical Storm Agnes, Paul V. Hyer, Evon P. Ruzecki

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The peak effect of the flood waters produced by Tropical Storm Agnes was seen on June 25 in the James, June 26 in the Rappahannock, and June 30 in the York. Recovery toward normal salinity conditions after the high runoffs proceeded discontinuously, with alternating periods of vertical stratification and destratification. During strongly stratified stages, saline water advanced upstream along the bottom. In the York and James Rivers, the most dramatic stratification occurred about July 20- 25. This event resulted in bottom salinity values exceeding normal ambient values and, at the river mouths, reaching values hitherto unobserved. This event was apparently …

The Effects Of The Agnes Flood On The Salinity Structure Of The Lower Chesapeake Bay And Contiguous Waters, A. Y. Kuo, E. P. Ruzecki, C. S. Fang

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The transient response of salinity distribution in lower Chesapeake Bay to flood waters from Tropical Storm Agnes is studied in terms of a two-layered, partially mixed estuary. Prior to 30 June 1972, surface salinities were well depressed throughout the Bay while those at the bottom near the Bay mouth were not depressed by 5 July. This resulted in a highly stratified situation normally found in the spring of the year. Stratification decreased when bottom waters were flushed down-bay by the flood (on 5 to 10 July for the region south of New Point Comfort). The "rebound" of salinity structure started …

The Effects Of Tropical Storm Agnes On The Copper And Zinc Budgets Of The Rappahannock River, Robert J. Huggett, Michael E. Bender

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The metals copper and zinc were analyzed in bottom sediments (top 1 cm) from the Rappahannock River before and after Tropical Storm Agnes. By extracting the sediments with various techniques (HN03, HCl) the nature of the metal speciation can be estimated. Data show that the inorganic copper was increased by a factor of 2 to 3 in the normally saline portion of the river as a result of Agnes but returned to before-Agnes levels within one year. Metal analyses of suspended sediments collected during the Agnes flooding allows an estimate of sedimentation indicating at least 7.5 mm of new sediments …

Flood Wave-Tide Wave Interaction On The James River During The Agnes Flood, John P. Jacobson, C. S. Fang

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During the Agnes flood hourly tidal height data were collected at seven locations along the tidal James River and currents were measured at two transects in the lower James. A comparison between actual tides and currents and the predicted tidal features as given by the tide and tidal current tables of NOAA was made. Results of this comparison show that Agnes did significantly affect water levels in the upper portion of the tidal James, especially near Richmond. However in the lower portion of the James no discernible rise was evident due to the passage of the flood crest. A small …

Effects Of Tropical Storm Agnes On Nutrient Flux And Distribution In Lower Chesapeake Bay, C. L. Smith, W. G. Macintyre, C. A. Lake, J. G. Windsor Jr.

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Nutrient concentrations measured in lower Chesapeake Bay in the summer of 1972 immediately following the flooding associated with Tropical Storm Agnes are compared with those in the summer of 1973, a season of more normal rainfall. The large amount of land runoff produced unseasonably high concentrations of dissolved inorganic nitrogen in the Bay near the mouth of the Potomac River. Phosphate concentrations were essentially unaffected by the flooding. Fluxes of total nitrogen and total phosphorus nutrients through the mouth of Chesapeake Bay were calculated for both summers. The calculated net export of nutrients from the Bay in both August 1972, …

Observations On Dissolved Oxygen Conditions In Three Virginia Estuaries After Tropical Storm Agnes (Summer 1972), R.A. Jordan

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Dissolved oxygen (DO) and salinity levels in the James, York, and Rappahannock estuaries were monitored for approximately two months (June 24-August 31, 1972) following Tropical Storm Agnes. DO depressions developed more rapidly and were more severe in the deep waters of the York and Rappahannock than in the James. Depressions that developed immediately after the storm were followed by recoveries and subsequent, more severe depressions. In late July, bottom water DO concentrations below 1 mg/1 were found at stations covering 15 miles of the York and 25 miles of the Rappahannock. Comparison of river data with Chesapeake Bay data suggests …

The Effect Of Tropical Storm Agnes As Reflected In Chlorophyll A And Heterotrophic Potential Of The Lower Chesapeake Bay, Paul L. Zubkoff, J. Ernest Warriner Iii

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A hydrographic station (Station Y) at the mouth of the York River (37°14.6'N, 76°23.4'W) was under biological surveillance for one year prior to the arrival of Tropical Storm Agnes. For one full year following this storm, these measurements were continued. In addition, the chlorophyll a and heterotrophic potential measurements were incorporated into an ongoing zooplankton sampling program of the lower Chesapeake Bay below 37°40'N latitude.

Effect Of Increasing Depth On Salinity In The James River Estuary, Maynard M. Nichols

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The effects of channel deepening on the salinity and density flow in the James River estuary, Virginia, were studied to predict changes that might affect oyster production. A hydraulic model with 1: 1,000 horizontal and l: 100 vertical scales was employed to integrate three-dimensional changes in salinity and velocity through reaches of variable bottom geometry. After natural characteristics of the tide, current, and salinity were reproduced in the model, tests were run at three levels of steady river inflow, before and after a 3-meter channel deepening. Results were combined with corollary field observations to evaluate changes in present-day ecological conditions. …

Sediments Of The James River Estuary, Virginia, Maynard M. Nichols

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The James River estuary of the Chesapeake Bay region follows the course of a former river valley drowned within the last 9,000 years by the most recent rise of sea level. The floor is shaped into a central channel bordered by submerged shoals. Observations show suspended sediment is transported mainly by alternating tidal currents and secondarily by the net nontidal estuarine circulation. Transport results in a sequence of grain size distributions reflecting the mixing of two textural end members, clay and sand.

Silty clay is deposited in the river and upper estuary, whereas sand occurs near the mouth. Transitional types, …