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• 1. [Article] Tidal Asymmetry in an Estuarine Pycnocline 2. Transport

  Flood currents in shallow estuaries are driven by an along-channel barotropic and baroclinic pressure gradient that increases monotonically toward the bottom, while friction retards near-bottom currents. ...

  Citation × Citation Citation Abstract Copy Title: Tidal Asymmetry in an Estuarine Pycnocline 2. Transport Author: Jay, David A., Cudaback, Cynthia N. Year: 2001 Flood currents in shallow estuaries are driven by an along-channel barotropic and baroclinic pressure gradient that increases monotonically toward the bottom, while friction retards near-bottom currents. Therefore, in many estuaries there is a middepth maximum in flood currents. We explore this phenomenon using a simple three-layer model in which each layer has vertically uniform currents and constant density. In this model the middle layer is of intermediate density and grows by shear-induced entrainment from the other two layers. This very simple model produces a middepth maximum in flood currents and simulates observed currents in the Columbia River entrance channel within about 10%. There is good qualitative agreement between model salinity transport and observed transport. The model pycnocline rises and falls tidally, in phase with the observed pycnocline, although pycnocline depth and thickness are better simulated using results from a two-layer model Title: Tidal Asymmetry in an Estuarine Pycnocline 2. Transport Author: Jay, David A., Cudaback, Cynthia N. Year: 2001 Flood currents in shallow estuaries are driven by an along-channel barotropic and baroclinic pressure gradient that increases monotonically toward the bottom, while friction retards near-bottom currents. Therefore, in many estuaries there is a middepth maximum in flood currents. We explore this phenomenon using a simple three-layer model in which each layer has vertically uniform currents and constant density. In this model the middle layer is of intermediate density and grows by shear-induced entrainment from the other two layers. This very simple model produces a middepth maximum in flood currents and simulates observed currents in the Columbia River entrance channel within about 10%. There is good qualitative agreement between model salinity transport and observed transport. The model pycnocline rises and falls tidally, in phase with the observed pycnocline, although pycnocline depth and thickness are better simulated using results from a two-layer model Close

• 2. [Article] Residual Circulation in Shallow Estuaries 1. Highly Stratified, Narrow Estuaries

  Long-wave theory and simple turbulence closures have been used to show that three distinct types of circulation (highly stratified, weakly stratified, and partially mixed) arise in narrow, shallow estuaries ...

  Citation × Citation Citation Abstract Copy Title: Residual Circulation in Shallow Estuaries 1. Highly Stratified, Narrow Estuaries Author: Jay, David A., Smith, J. Dungan Year: 1990 Long-wave theory and simple turbulence closures have been used to show that three distinct types of circulation (highly stratified, weakly stratified, and partially mixed) arise in narrow, shallow estuaries from the finite amplitude of the tide and the interaction of stratification with vertical mixing. Each type has a different dominant process causing the vertical exchange of salt and fresh water on the flood, and each gives rise to a characteristic residual circulation. The tidal circulation in highly stratified shallow estuaries, described herein, is the result of a finite amplitude internal motion driven by the barotropic tide; shear instabilities at the interface are the major vertical exchange mechanism. The residual circulation is caused primarily by ebb-flood asymmetry in interface position and thickness. A model based on our theoretical analysis shows that the interface thickness on flood is much less than the depth of flow up to a critical tidal amplitude at which the two-layer flow is destroyed, and correctly predicts the tidal amplitude of the neap-spring transition in the Columbia River Estuary. Tidal frequency internal wave motion is not found in weakly stratified and partially mixed estuaries. Because of the reduced tidal shear, shear instabilities are weak or absent, and the residual circulation assumes a very different character, as described in part 2. Title: Residual Circulation in Shallow Estuaries 1. Highly Stratified, Narrow Estuaries Author: Jay, David A., Smith, J. Dungan Year: 1990 Long-wave theory and simple turbulence closures have been used to show that three distinct types of circulation (highly stratified, weakly stratified, and partially mixed) arise in narrow, shallow estuaries from the finite amplitude of the tide and the interaction of stratification with vertical mixing. Each type has a different dominant process causing the vertical exchange of salt and fresh water on the flood, and each gives rise to a characteristic residual circulation. The tidal circulation in highly stratified shallow estuaries, described herein, is the result of a finite amplitude internal motion driven by the barotropic tide; shear instabilities at the interface are the major vertical exchange mechanism. The residual circulation is caused primarily by ebb-flood asymmetry in interface position and thickness. A model based on our theoretical analysis shows that the interface thickness on flood is much less than the depth of flow up to a critical tidal amplitude at which the two-layer flow is destroyed, and correctly predicts the tidal amplitude of the neap-spring transition in the Columbia River Estuary. Tidal frequency internal wave motion is not found in weakly stratified and partially mixed estuaries. Because of the reduced tidal shear, shear instabilities are weak or absent, and the residual circulation assumes a very different character, as described in part 2. Close

• 3. [Article] Increasing Storm Tides in New York Harbor, 1844–2013

  Three of the nine highest recorded water levels in the New York Harbor region have occurred since 2010 (March 2010, August 2011, and October 2012), and eight of the largest twenty have occurred since 1990. ...

  Citation × Citation Citation Abstract Copy Title: Increasing Storm Tides in New York Harbor, 1844–2013 Author: Talke, Stefan A., Orton, Philip M., Jay, David A. Year: 2014 Three of the nine highest recorded water levels in the New York Harbor region have occurred since 2010 (March 2010, August 2011, and October 2012), and eight of the largest twenty have occurred since 1990. To investigate whether this cluster of high waters is a random occurrence or indicative of intensified storm tides, we recover archival tide gauge data back to 1844 and evaluate the trajectory of the annual maximum storm tide. Approximately half of long-term variance is anticorrelated with decadal-scale variations in the North Atlantic Oscillation, while long-term trends explain the remainder. The 10 year storm tide has increased by 0.28 m. Combined with a 0.44 m increase in local sea level since 1856, the 10 year flood level has increased by approximately 0.72 ± 0.25 m, and magnified the annual probability of overtopping the typical Manhattan seawall from less than 1% to about 20–25%. Title: Increasing Storm Tides in New York Harbor, 1844–2013 Author: Talke, Stefan A., Orton, Philip M., Jay, David A. Year: 2014 Three of the nine highest recorded water levels in the New York Harbor region have occurred since 2010 (March 2010, August 2011, and October 2012), and eight of the largest twenty have occurred since 1990. To investigate whether this cluster of high waters is a random occurrence or indicative of intensified storm tides, we recover archival tide gauge data back to 1844 and evaluate the trajectory of the annual maximum storm tide. Approximately half of long-term variance is anticorrelated with decadal-scale variations in the North Atlantic Oscillation, while long-term trends explain the remainder. The 10 year storm tide has increased by 0.28 m. Combined with a 0.44 m increase in local sea level since 1856, the 10 year flood level has increased by approximately 0.72 ± 0.25 m, and magnified the annual probability of overtopping the typical Manhattan seawall from less than 1% to about 20–25%. Close

• 4. [Article] Interfacial Mixing in a Highly Stratified Estuary: 1. Characteristics of Mixing

  This article is Part I of a set of papers addressing mixing in a highly stratified estuary. Measurements of interfacial turbulence were made in Columbia River estuary under conditions of moderate river ...

  Citation × Citation Citation Abstract Copy Title: Interfacial Mixing in a Highly Stratified Estuary: 1. Characteristics of Mixing Author: Kay, David J., Jay, David A. Year: 2003 This article is Part I of a set of papers addressing mixing in a highly stratified estuary. Measurements of interfacial turbulence were made in Columbia River estuary under conditions of moderate river flow and neap tides. A flux correlation method was used to determine buoyancy fluxes, and fits to theoretical velocity and temperature variance spectra were used to measure turbulent kinetic and potential energy dissipation rates. At the measurement site in the interior of the estuary, mixing along the top of the salt wedge is found to occur only on ebb, during periods when the internal Froude number is supercritical. The wedge cannot, therefore, be in a quasiequilibrium state, and vertical mixing plays a dominant role in its ebb retreat. The turbulent Froude number FrT, which represents the ratio of effects of shear and stratification on the mixing, was found to be close to FrTap 1 during mixing episodes. This suggests an interplay between shear and buoyancy effects that corresponds to a condition of maximum mixing efficiency Gamma. Gamma is measured using both direct calculations of the buoyancy and dissipation terms in the turbulent kinetic energy (TKE) balance (this estimate of Gamma is referred to as Gammad), and by estimating the buoyancy term B by its relationship to chiT, the dissipation of temperature variance (this estimate of Gamma is referred to as Gammad). Averages over several mixing events give Gamma0ap 0.22 and Gammadap 0.36. Sources of bias in these measurements result from (1) approximations to the full TKE and available potential energy (APE) balances, (2) empirical constants used in fits of measured spectra in inertial subranges, (3) frame motion, and (4) high-pass filtering. The sign of the biases suggest that 0.22 < Gamma < 0.36. Flood-ebb asymmetry in mixing also results in a time dependent force balance (discussed further by Kay and Jay, 2003). This asymmetry is analyzed using a new method to determine profiles of the momentum balance during ebb mixing events. Title: Interfacial Mixing in a Highly Stratified Estuary: 1. Characteristics of Mixing Author: Kay, David J., Jay, David A. Year: 2003 This article is Part I of a set of papers addressing mixing in a highly stratified estuary. Measurements of interfacial turbulence were made in Columbia River estuary under conditions of moderate river flow and neap tides. A flux correlation method was used to determine buoyancy fluxes, and fits to theoretical velocity and temperature variance spectra were used to measure turbulent kinetic and potential energy dissipation rates. At the measurement site in the interior of the estuary, mixing along the top of the salt wedge is found to occur only on ebb, during periods when the internal Froude number is supercritical. The wedge cannot, therefore, be in a quasiequilibrium state, and vertical mixing plays a dominant role in its ebb retreat. The turbulent Froude number FrT, which represents the ratio of effects of shear and stratification on the mixing, was found to be close to FrTap 1 during mixing episodes. This suggests an interplay between shear and buoyancy effects that corresponds to a condition of maximum mixing efficiency Gamma. Gamma is measured using both direct calculations of the buoyancy and dissipation terms in the turbulent kinetic energy (TKE) balance (this estimate of Gamma is referred to as Gammad), and by estimating the buoyancy term B by its relationship to chiT, the dissipation of temperature variance (this estimate of Gamma is referred to as Gammad). Averages over several mixing events give Gamma0ap 0.22 and Gammadap 0.36. Sources of bias in these measurements result from (1) approximations to the full TKE and available potential energy (APE) balances, (2) empirical constants used in fits of measured spectra in inertial subranges, (3) frame motion, and (4) high-pass filtering. The sign of the biases suggest that 0.22 < Gamma < 0.36. Flood-ebb asymmetry in mixing also results in a time dependent force balance (discussed further by Kay and Jay, 2003). This asymmetry is analyzed using a new method to determine profiles of the momentum balance during ebb mixing events. Close

• 5. [Article] Impacts of Columbia River Discharge on Salmonid Habitat: 2. Changes in Shallow-Water Habitat

  This is the second part of an investigation that analyzes human alteration of shallow-water habitat (SWH) available to juvenile salmonids in the tidal Lower Columbia River. Part 2 develops a one-dimensional, ...

  Citation × Citation Citation Abstract Copy Title: Impacts of Columbia River Discharge on Salmonid Habitat: 2. Changes in Shallow-Water Habitat Author: Jay, David A., Kukulka, Tobias Year: 2003 This is the second part of an investigation that analyzes human alteration of shallow-water habitat (SWH) available to juvenile salmonids in the tidal Lower Columbia River. Part 2 develops a one-dimensional, subtidal river stage model that explains ~90% of the stage variance in the tidal river. This model and the tidal model developed in part 1 (Kukulka and Jay, 2003) uncouple the nonlinear interaction of river tides and river stage by referring both to external forcing by river discharge, ocean tides, and atmospheric pressure. Applying the two models, daily high-water levels were predicted for a reach from rkm-50 to rkm-90 during 1974 to 1998, the period of contemporary management. Predicted water levels were related to the bathymetry and topography to determine the changes in shallow-water habitat area (SWHA) caused by flood control dikes and altered flow management. Model results suggest that diking and a >40% reduction of peak flows have reduced SWHA by ~62% during the crucial spring freshet period during which juvenile salmon use of SWHA is maximal. Taken individually, diking and flow cycle alteration reduced spring freshet SWHA by 52% and 29%, respectively. SWHA has been both displaced to lower elevations and modified in its character because tidal range has increased. Our models of these processes are economical for the very long simulations (seasons to centuries) needed to understand historic changes and climate impacts on SWH. Through analysis of the nonlinear processes controlling surface elevation in a tidal river, we have identified some of the mechanisms that link freshwater discharge to SWH and salmonid survival. Title: Impacts of Columbia River Discharge on Salmonid Habitat: 2. Changes in Shallow-Water Habitat Author: Jay, David A., Kukulka, Tobias Year: 2003 This is the second part of an investigation that analyzes human alteration of shallow-water habitat (SWH) available to juvenile salmonids in the tidal Lower Columbia River. Part 2 develops a one-dimensional, subtidal river stage model that explains ~90% of the stage variance in the tidal river. This model and the tidal model developed in part 1 (Kukulka and Jay, 2003) uncouple the nonlinear interaction of river tides and river stage by referring both to external forcing by river discharge, ocean tides, and atmospheric pressure. Applying the two models, daily high-water levels were predicted for a reach from rkm-50 to rkm-90 during 1974 to 1998, the period of contemporary management. Predicted water levels were related to the bathymetry and topography to determine the changes in shallow-water habitat area (SWHA) caused by flood control dikes and altered flow management. Model results suggest that diking and a >40% reduction of peak flows have reduced SWHA by ~62% during the crucial spring freshet period during which juvenile salmon use of SWHA is maximal. Taken individually, diking and flow cycle alteration reduced spring freshet SWHA by 52% and 29%, respectively. SWHA has been both displaced to lower elevations and modified in its character because tidal range has increased. Our models of these processes are economical for the very long simulations (seasons to centuries) needed to understand historic changes and climate impacts on SWH. Through analysis of the nonlinear processes controlling surface elevation in a tidal river, we have identified some of the mechanisms that link freshwater discharge to SWH and salmonid survival. Close

• 6. [Article] Particle Trapping in Stratified Estuaries - Definition of a Parameter Space

  Estuarine turbidity maxima (ETM) retain suspended particulate matter (SPM) through advection, settling, aggregation and non-linearities in bed processes. This contribution defines for the first time a ...

  Citation × Citation Citation Abstract Copy Title: Particle Trapping in Stratified Estuaries - Definition of a Parameter Space Author: Jay, David A., Orton, Philip M., Chisholm, Thomas A., Wilson, Douglas J., Fain, Annika M., McGinity, John Year: 2003 Estuarine turbidity maxima (ETM) retain suspended particulate matter (SPM) through advection, settling, aggregation and non-linearities in bed processes. This contribution defines for the first time a parameter space descriptive of ETM water-column particle trapping processes through a scaling analysis of the local and integral SPM balances. In the absence of long-term deposition, there are five primary parameters for the large particles or aggregates that are typically trapped. Rouse number P, the ratio of settling velocity WS of the SPM relative to the shear velocity U*, describes the material trapped in the ETM in terms of the local vertical balance between vertical mixing and aggregate settling. Advection number A= P ΔU/UT scales the landward transport of SPM by tidal and mean flow processes in terms of flood-ebb velocity difference (ΔU) and maximum tidal current (UT). Supply number SR = P UR/UT defines SPM supply and removal (UR is river flow). Changes in the estuarine inventory of SPM are described in terms of a Trapping Efficiency E, a ratio of peak ETM concentration to fluvial or marine supply concentration. The effects of aggregation in the integral dynamic balance are quantified by a Floc number F that describes the tendency of aggregates to form through shear-driven collisions. This study uses observations from two strongly advective systems (the Columbia and Fraser Rivers) plus literature values from 13 other estuaries to illustrate the applicability of the above scaling. The primary question investigated is the relationship of trapping efficiency E and Floc number F to other parameters, especially river flow (expressed in terms of supply number SR). The strongest SPM trapping (high E) occurs in mid-ETM, where A ~0. The extreme high flows observed in the Fraser River estuary show how ETM trapping becomes ineffective as the estuary length contracts to one tidal excursion or less (limit of high SR). Use of data from all 15 estuaries shows that there is a strong trend toward more efficient trapping for low SR. E and F are positively correlated, so that aggregation becomes more prominent in systems with weak to moderate river flow. Examination of tidal monthly and seasonal particle properties at four closely-spaced moorings in the Columbia emphasize the importance of strong ETM gradients – particle properties are diverse even when the hydrodynamic regime is apparently similar. Finally, scaling variables and data are combined to express ETM properties in terms of U*, UR and UT.. Title: Particle Trapping in Stratified Estuaries - Definition of a Parameter Space Author: Jay, David A., Orton, Philip M., Chisholm, Thomas A., Wilson, Douglas J., Fain, Annika M., McGinity, John Year: 2003 Estuarine turbidity maxima (ETM) retain suspended particulate matter (SPM) through advection, settling, aggregation and non-linearities in bed processes. This contribution defines for the first time a parameter space descriptive of ETM water-column particle trapping processes through a scaling analysis of the local and integral SPM balances. In the absence of long-term deposition, there are five primary parameters for the large particles or aggregates that are typically trapped. Rouse number P, the ratio of settling velocity WS of the SPM relative to the shear velocity U*, describes the material trapped in the ETM in terms of the local vertical balance between vertical mixing and aggregate settling. Advection number A= P ΔU/UT scales the landward transport of SPM by tidal and mean flow processes in terms of flood-ebb velocity difference (ΔU) and maximum tidal current (UT). Supply number SR = P UR/UT defines SPM supply and removal (UR is river flow). Changes in the estuarine inventory of SPM are described in terms of a Trapping Efficiency E, a ratio of peak ETM concentration to fluvial or marine supply concentration. The effects of aggregation in the integral dynamic balance are quantified by a Floc number F that describes the tendency of aggregates to form through shear-driven collisions. This study uses observations from two strongly advective systems (the Columbia and Fraser Rivers) plus literature values from 13 other estuaries to illustrate the applicability of the above scaling. The primary question investigated is the relationship of trapping efficiency E and Floc number F to other parameters, especially river flow (expressed in terms of supply number SR). The strongest SPM trapping (high E) occurs in mid-ETM, where A ~0. The extreme high flows observed in the Fraser River estuary show how ETM trapping becomes ineffective as the estuary length contracts to one tidal excursion or less (limit of high SR). Use of data from all 15 estuaries shows that there is a strong trend toward more efficient trapping for low SR. E and F are positively correlated, so that aggregation becomes more prominent in systems with weak to moderate river flow. Examination of tidal monthly and seasonal particle properties at four closely-spaced moorings in the Columbia emphasize the importance of strong ETM gradients – particle properties are diverse even when the hydrodynamic regime is apparently similar. Finally, scaling variables and data are combined to express ETM properties in terms of U*, UR and UT.. Close