NOAA Technical Report NOS CO-OPS 022

ASSESSMENT OF THE NATIONAL OCEAN SERVICE’S

TIDAL CURRENT PROGRAM

Silver Spring, Maryland

April 1999

noaa National Oceanic and Atmospheric Administration

U.S. DEPARTMENT OF COMMERCE
National Ocean Service

Center for Operational Oceanographic Products and Services

Products and Services Division
Center for Operational Oceanographic Products and Services

National Ocean Service

National Oceanic and Atmospheric Administration

U.S. Department of Commerce

The National Ocean Service (NOS)Centerfor Operational Oceanographic Products and Services

(CO-OPS) collects and distributes observations and predictions of water levels and currents to

ensure safe, efficient and environmentally sound maritime commerce. The Center provides the set

of water level and coastal current products required to support NOS' Strategic Plan mission

requirements, and to assist in providing operational oceanographic data/products required by

NOAA's other Strategic Planthemes. For example, CO-OPS provides data and products required

by the National Weather Service to meet its flood and tsunami warning responsibilities. The

Centermanages the National Water Level Observation Network (NWLON), and a national network

of Physical Oceanographic Real-Time Systems (PORTS) in major U.S. harbors. The Center:

establishesstandardsforthe collectionand processing ofwaterlevel and current data; collects and

documents user requirements which serve as the foundation for all resulting program activities;

designs new and/or improved oceanographic observing systems;designssoftware to improveCOOPS' data processing capabilities; maintains and operates oceanographic observing systems;

performs operational data analysis/quality control; and produces/disseminates oceanographic

products.
NOAA Technical Report NOS CO-OPS 022

ASSESSMENT OF THE NATIONAL OCEAN SERVICE’S

TIDAL CURRENT PROGRAM

Silver Spring, Maryland

April 1999

noaa National Oceanic And Atmospheric Administration

U.S. DEPARTMENT National Oceanic and National Ocean Service

OF COMMERCE Atmospheric Administration W. Stanley Wilson

William Daley, Secretary D. James Baker, Under Secretary Assistant Administrator

Oceanographic Products Office of Coast Survey

and Services Division Frank W. Maloney,

Director, Richard M. Barazotto

iii

TABLE OF CONTENTS

LIST OF FIGURES ......................................................... iv

LIST OF TABLES ......................................................... iv

ACRONYMS AND ABBREVIATIONS ........................................ v

EXECUTIVE SUMMARY ................................................... 1

1. INTRODUCTION ...................................................... 3

1.1 Tidal Current Predictions ........................................... 3

1.2 NOS Responsibilities .............................................. 3

1.3 Objectives ...................................................... 4

2. REVIEW OF TIDAL CURRENT REFERENCE STATIONS ..................... 7

2.1 Geographical Coverage ............................................ 8

2.2 Characteristics of the Tidal Current Constituents ......................... 9

2.3 Age of Data ...................................................... 12

2.4 Instrumentation ................................................... 13

2.5 Duration of Measurement ........................................... 15

3. VESSEL TRAFFIC AND COMMERCIAL ACTIVITY ......................... 17

3.1 Type of Tonnage .................................................. 18

3.2 Total Tonnage .................................................... 19

4. TIDAL AND NONTIDAL DYNAMICS ..................................... 23

4.1 Classification by Nontidal/Tidal Variance Ratio ......................... 23

4.2 Classification of Currents ........................................... 24

4.3 Tidal and Nontidal Variance at Water Level Stations ..................... 25

4.4 Classification of Water Level Stations ................................. 28

5. NEW CURRENT SURVEY PRIORITIES ................................... 33

5.1 Recommendations for Updating Tidal Current Reference Stations ............ 33

5.2 Proposed Real-Time Current Monitoring at Existing Tidal Current Reference 

Stations ......................................................... 35

5.3 Recommendations for Adding New Tidal Current Reference Stations and 

Evaluation for Real-Time Current Monitoring by PORTSTM ................ 36

6. CONCLUSIONS ....................................................... 41

ACKNOWLEDGMENTS .................................................... 43

REFERENCES ............................................................ 45

APPENDIX A. List of NOS Tidal Current Survey Reports .......................... 47

APPENDIX B. Tidal Current Reference Station Summary .......................... 51

APPENDIX C. Leading U. S. Ports Ranked by Total 1995 Tonnage ................... 59

APPENDIX D. 1995 U.S. Port Tonnage Grouped by Tidal Current Reference Station ..... 65
iv

LIST OF FIGURES

Figure 1. Tidal current reference stations of the United States ...................... 8

Figure 2. Changes in vessel draft ............................................. 17

Figure 3. Total 1995 tonnage for major U.S. ports ............................... 19

Figure 4. Total 1995 tonnage associated with tidal current reference stations .......... 20

Figure 5. Total 1995 tonnage for U.S. ports without a tidal current reference station ..... 21

Figure 6. Tidal and nontidal variance at NWLON stations ......................... 28

Figure 7. Nontidal/tidal variance ratio at NWLON stations ........................ 29

Figure 8. Tidal and nontidal variance at NWLON stations associated with major ports 

without an existing tidal current reference station ........................ 37

LIST OF TABLES

Table 1. Tidal Current Constituent Properties .................................. 10

Table 2. Classification of Water Levels and Currents ............................ 24

Table 3. Nontidal/Tidal Classification of Current Stations ........................ 24

Table 4. Nontidal/Tidal Classification of NWLON Stations ....................... 25

Table 5. Comparison of Current and Water Level Classification .................... 30

Table 6. Classification of NWLON Stations Associated with Major Ports without a 

Tidal Current Reference Station ...................................... 37
v

ACRONYMS AND ABBREVIATIONS

ADCP acoustic Doppler current profiler

AK Alaska

AL Alabama

CA California

CFR Code of Federal Regulation

CO-OPS Center for Operational Oceanographic Products and Services

C&GS Coast and Geodetic Survey

D diurnal tides

DOT Department of Transportation

FL Florida

GA Georgia

HI Hawaii

HR House of Representatives

LA Louisiana

MA Massachusetts

MD Maryland

ME Maine

MEC maximum ebb current

MFC maximum flood current

MN mostly nontidal tides

MMD mixed mainly diurnal tides

MMS mixed mainly semidiurnal tides

MS Mississippi

MT mostly tidal 

NH New Hampshire

NJ New Jersey

NOAA National Oceanic and Atmospheric Administration

NOS National Ocean Service

NWLON National Water Level Observation Network

NY New York

OR Oregon

PORTSTM Physical Oceanographic Real-Time System (Trademark)

PSD Products and Services Division

RI Rhode Island

S semidiurnal

TD tidal dominated

TX Texas

US United States

USC United States Code

VNT nontidal variance

V T total tidal variance

WA Washington
vi
1

EXECUTIVE SUMMARY

In an effort to provide quality data and information on a national level, the Center for Operational

Oceanographic Products and Services is assessing the National Ocean Service’s tidal current

program. The intent of this document is to set guidelinesfor future currentsurveys in order to update

the U.S. reference stations in the Tidal Current Tables and to identify areas where real-time

monitoring of currents may be appropriate. The assessment of the Tidal Current Tables is based on

a studyofthe 1) age, instrumentation, and duration of data coverage, 2) commercial importance ofthe

region, and 3) tidal and nontidal dynamics of coastal areas. A method of using data from long term

water level stations to characterize the importance of nontidal variance at tidal current reference

stationsis developed. Based on these results, recommendations are made for updating older reference

stations and creating new reference stations. Potential locations for real-time current monitoring by

Physical Oceanographic Real-Time Systems (PORTSTM) are identified. In addition to real-time

current data, PORTSTM provides other critical navigational information such as water level, density,

and meteorological data.

In view ofthe correlation between the factors of age, instrumentation, and length of observations, the

Center for Operational Oceanographic Products and Services recommends updating thirteen of the

existing tidal current reference stations where observations were collected with poles and floats

before 1950, and updating twelve additional stations where data of short duration were collected

between 1942 and 1985. Three existing reference stations have significant nontidal variability and

are recommended for real-time monitoring of currents based on the economic importance ofthe ports

they serve. Thirteen ports without tidal current reference stations, where vessel traffic and commerce

exceed 10milliontons, are evaluated and recommended for a new tidal current reference station. The

installation of a real-time current monitoring system is recommended at seven of these ports. 
2
3

1. INTRODUCTION

TheCenterfor Operational Oceanographic Products and Services (CO-OPS) provides the public with

coastal oceanographic information necessary to support the National Oceanic and Atmospheric

Administration’s environmental assessment and predictionmission, inparticularthe strategic goal to

promote safe navigation. The Center increases the efficiency of the maritime industry and the safe

use of U.S. ports by providing tidal predictions, real-time water level and current observations, and

forecasts. Operational water level and current information are important in assisting environmental

preservation and restoration, and for monitoring, evaluating, and predicting hazardous spillresponse

needs, effects ofsea levelrise incoastalregions, and risks associated with stormsurges and tsunamis.

 

1.1 Tidal Current Predictions

Professional mariners and ship operators of all propelled vessels of 1600 gross tons or more are

required by the Code of Federal Regulation (33 CFR Chapter I, 7/1/91 Edition, U.S. Coast Guard,

DOT '164.01 and '164.33) to carrythe current editionofthe Tide Tables and the Tidal Current Tables

published by the National Ocean Service (or its equivalent) when operating their vessel in navigable

waters of the United States, except in the St. Lawrence Seaway. The Tables predict the daily

magnitude and timing of high and low waters, maximum floods, maximum ebbs, and slacks for a

limited number ofrepresentative stations knownas reference stations. Predictions at these locations

are the basis for predictions at thousands ofsubordinate stations through the use ofscaling factors and

time differences. These parameters are printed in the Tables and it is up to the user to apply them

properly to daily predictions at the appropriate reference stations. It is clearly evident that all tidal

predictions depend on the quality of the predictions at the reference stations.

 

1.2 NOS Responsibilities

The evolution of NOS began with The Organic Act of February 10, 1807 (2 Stat, 413), a

Congressional Act which established the Survey ofthe Coast(later to be known asthe Coast Survey,

the Coast and Geodetic Survey, and finally, in 1970, the National Ocean Service). The study,

collection, and dissemination ofwater level and current observations and predictions have remained

a primary focus. The first Tide Tables were published in 1867, and by 1890 tidal current predictions

were introduced for New York Harbor and vicinity. The two volumes of the Tidal Current Tables

for the Atlantic Coast and the Pacific Coast of North America were first published separately from

the Tide Tables in 1923. 

NOS is statutorily authorized to collect, analyze, and disseminate data on tides and currents pursuant

to the 33rd United States Code, Sections 883a - 883f established under the auspices of the Act of

August 6, 1947 (61, Stat, 787). Specifically, 33 USC 883a authorizes NOS to conduct hydrographic

surveys, water level and current observations, geomagnetic, seismological, gravity, and related

geophysical measurements and investigations, and observations for the determination oflatitude and

longitude. In addition, 33 USC 883b authorizes NOS to analyze and predict tides and currents, and

to process and publish data information, compilations, and reports. A bibliography of tidal current

survey technical reports published since the establishment of NOAA in 1970 has been compiled in
4

Appendix A. These reports provide detailed information about the current survey data collected and

the subsequent data analyses carried out. 

The mission of NOS’ recently-established Center for Operational Oceanographic Products and

Servicesisto provide the national infrastructure, and the scientific and technical expertise to monitor,

assess, and distribute tide, current, waterlevel, and other coastal oceanographic products and services

necessary to support NOAA’s mission. An important aspect of this mission is promoting safe

navigationand improving the efficiencyofthe maritime industryand the economic productivity ofU.S.

ports by providing real-time water level and current observations, predictions, forecasts, and other

coastal oceanographic information. 

The 105th U.S. Congress passed H.R. 3461 onMarch 12, 1998, approving a governing international

fishery agreement between the United States and the Republic of Poland. This House of

Representatives bill, which became Public Law 105-384 on November 18, 1998, authorizes

appropriations for conducting tide and current measurements under the Act of 1947 for fiscal years

1999 through2002.CO-OPS is authorized to implement and operate a national quality control system

for real-time tide and current data, and to design and install real-time tide and current data

measurement systems under section 303(b)(4).

In support of CO-OPS’ mission, tidal current reference stations are being updated by the

implementationofshorttermcurrentsurveys orthe installation of Physical OceanographicReal-Time

Systems (PORTSTM). PORTSTM is a decision support tool which improves the safety and efficiency

of maritime commerce and coastal resource management through the integration of real-time

environmental observations, forecasts, and other geospatial information. PORTSTM collects and

disseminates observations and predictions of water levels, currents, temperature, salinity, and

meteorological parameters (winds, atmospheric pressure, visibility, etc.) needed by the mariner to

navigate safely. PORTSTM has been built upon CO-OPS' real-time water level measurement

capabilities by adding incremental improvements to field systems, sensor capabilities,

communications,informationsystems, and operational proceduresto ensure thatthe full value ofNOS'

capabilities is realized by the marine transportation community and other users requiring operational

oceanographic information[NOS,1998]. Although PORTSTM has beendeveloped by NOS and a need

forreal-time current data may be identified in this document, the fundingforinstallationand operation

of a PORTSTM remains the responsibility of the local maritime community.

1.3 Objectives

In the past, NOS has relied upon input from local marine pilots associations, harbor officials,

commercial shipping companies, and state and local marine managersto assist in selecting estuaries

that require updated tidal current predictions or real-time current monitoring for increased

navigational safety. This report is intended to provide a basis for evaluating these requests by

identifying potential sites based on new current survey priorities that depend on shipping activity,

economic value of cargo, and increasing vessel traffic and tonnage. 

The objectives of this study are three-fold: 1) assess the quality of the reference station predictions

in the NOS Tidal Current Tables, 2) prioritize the NOS tidal current reference stations based on
5

economic and commercial importance of the ports they serve, and 3) characterize the tidal and

nontidal dynamics ofU.S. coastal areas. This evaluation will determine which tidal current reference

stations should be updated, suggest locations for new tidal current reference stations, and indicate

where real-time monitoring of currents would contribute to increased navigational safety. This

document does not assess the accuracy of predictions at subordinate stations referenced to the tidal

current reference stations. The assessment of the subordinate stations may be performed at a future

time.

This report begins with a thorough review of the existing tidal current reference station information

in Section 2. Shipping tonnage statistics for major U.S. coastal ports are associated with an

appropriate tidal current reference station and are discussed in Section 3. Section 4 includes the

harmonic analysis of long term water level stations in order to characterize the tidal and nontidal

dynamicsinthe vicinity oftidal currentreference stations. Recommendations for updating predictions

at existing tidal currentreference stations and creating new ones are presented in Section5, alongwith

a discussion of locations where nontidal dynamics are important and real-time current observations

may be needed.
6
7

2. REVIEW OF TIDAL CURRENT REFERENCE STATIONS

The published NOS Tidal Current Tables are presented in the same format as the NOS Tide Tables.

A limited number ofstations knownas reference stations have daily predicted times of floods, ebbs,

and slacks and maximum current at floods and ebbs printed in a section known as “Table 1". The

established tidal current constituents that are used to make these predictions should be based on the

highest quality data available. Most tidal current predictions are based on data sets that would be

considered inadequate for making tidal water level predictions. Historically, due to technological,

logistical, and resource limitations, current measurements are of a shorter duration than water level

measurements. The long term continuous operation of the National Water Level Observation Network

(NWLON) stations, results in tidal water level constituents that are better resolved and more up to

date than the tidal current constituents.

The tidal constituents are obtained by a process known as harmonic analysis. For short periods, a

Fourier harmonic analysis is carried out [Dennis and Long, 1971]. Either a 15-day or a 29-day

period of continuous data can be analyzed. The 15-day analysis results in 9 computed tidal current

constituents and 15 constituents inferred fromthe computed constituents. The 29-day analysis results

in 10 computed constituents and 14 inferred constituents. For longer sets of data, a least squares

harmonic analysis is employed. A year of observations can be used to accurately resolve 32 of the

37 standard tidal constituents used by NOS formakingpredictions, althoughgood results can often be

obtained with only six months of data [Zervas, 1999]. With smaller data sets, either a least squares

harmonic analysisforfewer constituents maybe used orresultsfromseveral 29-dayFourier harmonic

analyses may be averaged together.

For a larger group of tidal current stations called subordinate stations, predicted floods, ebbs, and

slacks are calculated by the user from the “Table 1" predictions with time differences and speed

ratios. These constants are listed in a section of the Tidal Current Tables known as “Table 2". “Table

2" also indicates to which tidal current reference station to apply these constants. The constants are

obtained by a nonharmonic analysis which compares a short period of data at the subordinate station

with observations or predictions for the same period at the reference station. The amount of

subordinate station data used is usually less than 15 days and in some cases as little as 1 day.

Deciding which reference station to use for a subordinate station is a subjective decision usually

based on proximity and similarity in the shapes of the tidal current curves. 

Data from tidal current reference stations are the source for computing accepted values of harmonic

and nonharmonic constants essential to daily tidal current predictions. Existing tidal current

predictions are presently based on limited data sets fromreference stations that date as early as 1901

(North Inian Pass). Reference station name, location, year the data were obtained, length of time

series, type of instrument used, and number of secondary stations associated with each reference

station are summarized in Appendix B. The data from these stations serve as the control for the

reduction of short time seriesfromsubordinate current stations through comparison of simultaneous

observations. Historically, reference stations require a minimum of 15 days of continuous velocity

observations for harmonic analysisfromwhichsubordinate stations predictions canbe computedwith

time differences and speed ratios. Longer time series improve predictions at reference stations by

separating similar harmonic constituent frequencies.
8

Figure 1. Tidal current reference stations of the United States categorized by duration of

observations with the year of data acquisition in brackets.

A map showing existing tidal current reference stations in the United Statesillustrates the limitations

of the predictions based on age and length of observations (Figure 1). The tidal current reference

stations outside of the United States are not evaluated in this document.

 

2.1 Geographical Coverage

There are some noticeable geographical gaps between tidal current reference stations along the U.S.

coastline. The most noticeable gaps along the Atlantic Coast are betweenChesapeake Bay Entrance

and Charleston Harbor Entrance and the Florida coast between St. Johns River Entrance and Miami

Harbor Entrance. Geographical gaps along the Gulf Coast exist between Tampa Bay Entrance and

Mobile BayEntrance and fromMobileBayEntrance to GalvestonBayEntrance. The most noticeable

gaps along the Pacific Coast are between San Diego Bay Entrance and San Francisco BayEntrance

and between San Francisco BayEntrance and Grays Harbor Entrance. There is a large geographical

gap in tidal current reference stations along the southern coast of Alaska and Hawaii has no tidal

current reference station. 
9

For “Table 2" purposes, the subordinate stationdata collected in these gaps had to be associated with

a distantreference stationwith similar tidal characteristics. The subordinate stations along the North

Carolina coast are all referenced to Charleston Harbor Entrance. The east Florida coast (with the

exception of St. Johns River) is referenced to Miami Harbor Entrance. Most of the Gulf coast of

Florida (excluding Pensacola) is referenced to Tampa BayEntrance. The Louisiana coast is divided

between Mobile Bay Entrance and Galveston Bay Entrance. 

All the subordinate stations along the California coast north of San Diego are referenced to San

Francisco BayEntrance. Many of the subordinate stations along the Oregon coastline are referenced

to the reference station at Wrangell Narrows in Alaska, although the Columbia River stations are

referenced to Grays Harbor Entrance. The subordinate stations along the southern coast of Alaska are

referenced to the three reference stations in southeastern Alaska. The Hawaiian Islands have no

regional tidal currentreference station. All of the Hawaiian subordinate stations are referenced to San

Diego Bay Entrance. 

2.2 Characteristics of the Tidal Current Constituents

The tidal constituents for the 41 tidal current reference stations were developed at different times

based on varying lengths of data collected with a variety of current-measuring instruments. These

constituents are used to produce the daily predictions in the Tidal Current Tables every year. Table

1 is a list of properties for each of the tidal current reference stations which can be used to compare

and contrast the predicted tidal currents. 

The number of constituents used to make tidal current predictions varies between 8 for the Canadian

station, Bay of Fundy Entrance, and 33 for Charleston Harbor Entrance. Predictions for the Bay of

Fundy Entrance are provided by the Canadian Hydrographic Service and it is included in this study

because 135 U.S. subordinate stations are referenced to it. If the Fourier harmonic analysis program,

which requires 29 continuous days of data, was used to derive the tidal constituents, a maximum of

24 constituents could be obtained. (Ten constituents are calculated and 14 constituents are inferred.)

Smaller constituents were often zeroed out. For example, at a number of stations, calculated

constituentslessthan0.03 knots and inferred constituentslessthan0.01 knots were deleted (Appendix

B). When the least squares harmonic analysis program is applied to data sets longer than 29 days,

more ofthe 37 standard tidal constituents used by NOS for tidal predictions canbe obtained. The five

long-termconstituents (semimonthly, monthly,semiannual, and annual periods) are unreliable without

multiple year data sets and are usually zeroed out for tidal current stations. These five constituents,

while often important for tide predictions, are usually not significant for tidal current predictions.
10

Table 1. Tidal Current Constituent Properties

Reference Station

Name

Number of

Subordinate

Stations

Number of

Constituents

MFC

Speed

(knots)

MEC

Speed

(knots)

Permanent

Current

(knots)

Tidal

Ratio

Tidal 

Classification

Bay of Fundy Entrance

(Canada) 135 8 2.3 2.4 -0.041 0.09 S

Portsmouth Harbor

Entrance, NH 82 13 1.2 1.8 -0.300 0.11 S

Boston Harbor, MA 153 13 1.1 1.2 -0.280 0.15 S

Cape Cod Canal, MA 16 17 4.0 4.5 0.000 0.10 S

Pollock Rip Channel,

MA 115 16 2.0 1.8 0.150 0.08 S

The Race, NY 155 22 2.7 3.0 -0.105 0.09 S

Throgs Neck, NY 16 21 1.0 0.6 0.035 0.04 S

Hell Gate, NY 33 20 3.4 4.6 -0.600 0.04 S

The Narrows, New York

Harbor, NY 77 17 1.7 2.0 -0.200 0.14 S

Delaware Bay

Entrance, DE 92 28 1.4 1.3 0.000 0.16 S

Chesapeake Bay

Entrance, VA 247 32 0.8 1.2 -0.175 0.20 S

Baltimore Harbor

Approach, MD 155 12 0.8 0.8 0.000 0.46 M M S

Chesapeake &

Delaware Canal, MD 8 22 2.0 1.9 0.000 0.44 M M S

Charleston Harbor

Entrance, SC 227 33 1.7 2.0 -0.217 0.11 S

Savannah River

Entrance, GA 124 15 1.6 2.6 -0.450 0.10 S

St Johns River

Entrance, FL 17 18 1.9 2.3 -0.350 0.17 S

Miami Harbor

Entrance, FL 45 24 1.8 1.6 0.051 0.10 S

Key West, FL 18 16 1.0 1.7 -0.360 0.22 S

Tampa Bay Entrance,

FL 54 29 1.3 1.3 0.037 0.80 M M S

Sunshine Skyway

Bridge, FL 0 28 1.3 1.1 0.106 0.74 M M S

Old Tampa Bay

Entrance, FL 16 29 1.0 0.9 -0.038 0.65 M M S
Reference Station

Name

Number of

Subordinate

Stations

Number of

Constituents

MFC

Speed

(knots)

MEC

Speed

(knots)

Permanent

Current

(knots)

Tidal

Ratio

Tidal 

Classification

11

Mobile Bay Entrance,

AL 14 15 1.4 1.5 0.000 18.6 D

Galveston Bay

Entrance, TX 21 19 1.7 2.3 -0.250 1.76 M M D

Aransas Pass, TX 3 24 1.6 1.5 0.320 4.55 D

San Diego Bay

Entrance, CA 27 16 1.2 1.5 -0.090 0.36 M M S

San Francisco Bay

Entrance, CA 136 20 2.9 3.4 -0.200 0.38 M M S

Carquinez Strait, CA 57 29 2.1 2.2 -0.138 0.51 M M S

Grays Harbor Entrance,

WA 44 20 1.9 2.8 -0.300 0.30 M M S

Strait of Juan de Fuca

Entrance, WA 1 14 0.6 1.5 -0.500 0.53 M M S

Admiralty Inlet, WA 75 17 1.6 2.6 -0.500 0.53 M M S

The Narrows Puget

Sound, WA 31 20 3.2 2.8 0.000 0.44 M M S

Deception Pass, WA 4 17 5.2 6.6 -0.650 0.29 M M S

Rosario Strait, WA 46 20 1.1 1.9 -0.400 0.70 M M S

San Juan Channel, WA 13 21 2.6 2.6 -0.050 0.50 M M S

Wrangell Narrows, AK 345 21 3.7 3.4 0.000 0.16 S

Sergius Narrows, AK 62 18 5.9 5.5 0.200 0.06 S

North Inian Pass, AK 28 21 2.9 5.1 -1.400 0.17 S

Isanotski Strait, AK 11 18 3.6 2.8 0.400 0.36 M M S

Unimak Pass, AK 35 20 3.4 3.0 0.500 0.72 M M S

Akutan Pass, AK 7 21 5.8 5.3 0.200 0.56 M M S

Kvichak Bay, AK 39 17 2.5 2.5 -0.300 0.29 M M S

S = Semidiurnal, M M S = Mixed Mainly Semidiurnal, M M D = Mixed Mainly Diurnal, D = Diurnal

The maximum flood currents (MFC) and maximum ebb currents (MEC), shown in Table 1, are the

average of the greatest speeds during a flood or an ebb period. They provide an estimate of the

strength of current at the reference stations which were usually chosen to be located where the

strongest currents in a bay or estuary could be measured. The volume of water that must pass a given

point in a bay or estuary is equal to the tidal prism above that location. The tidal prism is

approximately the area of the bay multiplied by the mean tidal range of the bay. Tidal currents will

be proportional to the tidal prismand inverselyproportional to the crosssectional area through which
12

the volume of water must pass. The strongest currents (> 5 knots) occur in narrow channels or

channels through which large volumes of water must pass (Deception Pass, Sergius Narrows, and

Akutan Pass). The weakest currents (< 1 knot) occur in wide or deep channels (Chesapeake Bay

Entrance and Strait of Juan de Fuca Entrance) or at some distance from the ocean (Throgs Neck,

Baltimore Harbor Approach, and Old Tampa Bay Entrance).

The permanent current in Table 1 is a unchanging current in the flood (positive) or ebb (negative)

direction that is always assumed to be present when making tidal current predictions. It is obtained

fromthe mean current measured during the deployment of the instrument. A permanent ebb current is

commonly found in river estuaries. There are 24 reference stations which have permanent ebb

currents, with the strongest at North Inian Pass (1.4 knots); all the other permanent ebb currents are

less than 0.65 knots. Seven reference stations have zero for their permanent current. Ten reference

stations have permanent flood currents. A permanent flood current is often driven by thermohaline

circulationbetweenfreshriver water and salty ocean water. However, the strongest permanent flood

current, at Unimak Pass (0.5 knots), is due to the exchange of water between the Pacific Ocean and

the Bering Sea. 

The accuracy of the permanent currents are dependent on the length of the data sets used to obtain

them. A shorter deployment is less likely to give an accurate permanent current especially if there

were anomalous river flow conditions at the time. Permanent currents can vary substantially with

depth in the water column or with location in a channel. The presence of a strong permanent current

affects the speeds of maximum flood and maximum ebb and the timing of the slacks. The reference

stations where the permanent current is the greatest percentage ofthe average tidal current amplitude

include the Strait ofJuan de Fuca Entrance (48%) and North Inian Pass (35%). There were less than

3 days of current observations at these stations. All the other permanent currents are less than 27%

of the average tidal current amplitude.

The tidal ratio as defined by Defant [1961] is a ratio of the amplitudes of the largest diurnal

constituents (K1 + O1) to the largest semidiurnal constituents (M2 + S2), classifying tides as

semidiurnal (< 0.25), mixed mainly semidiurnal (0.25 - 1.5), mixed mainly diurnal (1.5 - 3.0), or

diurnal (> 3.0). A subordinate station should be associated with a reference station that has a similar

tidal ratio. Table 1 identifies each of the reference station’s tidal characteristics based on the tidal

ratio. All of the east coast of the U.S. is semidiurnal with the exception of Baltimore Harbor

Approach and Chesapeake & Delaware Canal, which are mixed mainly semidiurnal. In contrast, the

Gulf of Mexico coast changes from semidiurnal to mixed mainly semidiurnal to diurnal to mixed

mainly diurnal and back to diurnal, proceeding from Key West, FL to Aransas Pass, TX. All of the

reference stations in California and Washington are mixed mainly semidiurnal. In Alaska, the

southeastern stations are semidiurnal while the southwestern stations are mixed mainly semidiurnal.

 

2.3 Age of Data

Historical information for the 41 tidal current reference stations reveals the age of the observations

used to derive the tidal constituents (Figure 1 and Appendix B). Tidal current predictions based on

these observations are used to infer tidal currents at 2784 subordinate stations. Review of the NOAA

tidal current reference station records showsthat 20 ofthe 41 stations are based on data more than 50
13

years old, most of them derived from current pole or Zeskind float measurements (see section 2.4).

The mostrecently acquired data were obtained by revisiting reference stations as requested by local

pilots associations and harbor officials to update the tidal current predictions. Seven reference

stations have been updated or added in the last 11 years with acoustic Doppler current profiler

(ADCP) data. A complete summary of information for each tidal current reference station is presented

in Appendix B. 

The Atlantic Coast has 17 tidal current reference stations. The average age of the data is 38 years

ranging from 1926 to 1989. There are 1697 (61% of the total) subordinate stations referenced to the

Atlantic Coast reference stations. The most recently acquired data (1989) were used to update the

Tidal Current Tables at Throgs Neck, and The Race, Long Island Sound. The reference station at

Charleston Harbor Entrance was also recently updated with data collected in 1987 and 1988. (Since

this assessment, NOS has updated Savannah River Entrance and St. Johns River Entrance with new

tidal constituents.) 

The GulfCoast has 7 tidal current reference stations. The average age of the observations is 29 years

ranging from 1935 to 1991. There are only 126 subordinate stations (4.5% of the total) referenced

to the Gulf Coast reference stations. Predictions at four ofthe seven tidal current reference stations

have been updated in the last eight years. The Galveston Bay Entrance predictions, which are based

on data acquired in 1935, will be updated with PORTSTM data, and should appear in the year 2000

Tidal Current Tables. 

The Pacific Coast has 17 tidal current reference stations including 7 in Alaska. The average age of

the observations is 55 years ranging from1923 to 1980. There are 961 subordinate stations (34.5%

of the total) referenced to the Pacific Coast reference stations. The most recent reference station is

Carquinez Strait, first used in the 1989 Tidal Current Tables based on data from 1980. The most

recent data used for an Alaskan reference station is six days of data from1952 for Sergius Narrows.

Although the reference station at San Francisco Bay Entrance is based on data from 1923 and 1930,

the bay is monitored by PORTSTM and real-time data are available. New San Francisco Bay Entrance

predictions based on PORTSTM data will appear in the Year 2000 Tidal Current Tables.

2.4 Instrumentation

There is a direct correlation between the age of the tidal current reference station and the type of

instrument used to collect the observed data. Data collected fromthe early 1920s through muchofthe

1940s were of short duration using fixed-depth poles or Zeskind floats. Floats were used in narrow

passages where the current was too swift to anchor a boat. Floats were either dropped from shore or

upstream by boat and ranges were monitored by observers with stop watches [C&GS, 1950]. This

type of measurement did not record direction and allowed for a wide margin of error.

The current pole and log line were the simplest form of apparatus used to measure observed surface

current speed and direction. It consisted of a 15-foot pole weighted at the lower end to float upright

with the top about a foot out of the water [C&GS, 1950]. The log line was attached to the pole and

reeled out froma mounted stand. The line was graduated to reflect the velocity of the current in tenths

of knots which was indicated by the amount of line carried out by the current pole in a specified

interval oftime. A full minute of recording current speed was measured using a stop watch noting the
14

reference point (beginning mark on the log line). In strong currents, a 30-second run was used. The

longest record of current pole observations was 748 days at Stonehorse Lightship in Pollock Rip

Channel (August 6, 1934 through August 31, 1936). However, most current pole observations were

for much shorter periods with only five reference stations having enough continuous data to allow a

29-day harmonic analysis.

Roberts RadioCurrentMeters were designed byCapt. ElliottRoberts ofC&GSand usedwith success

fromthe 1940s through the mid-1960s. The advantage of the Roberts Current Meter over the pole and

log line was that it could be operated remotely from an anchored buoy and the length of data

measurement was limited only by the life of the batteries. The buoy housed a radio transmitter,

complete with batteries, electrically attached to the current meter and an above-water antenna. The

currentmeter had a rotating impeller connected to a magnetic device thatmade and broke contactwhen

actuated by the current. The devices were arranged so that when the instrument was heading south,

both contacts occurred simultaneously. When the meter headed in any other direction, the time relation

between the two sets of contacts changed with the meter heading. This time relation served as a

measure of the direction of the current. The current speed was recorded as a number of seconds

between contacts and transmitted by radio signals to a receiving station chronometer. The

corresponding velocity was taken from a rating table prepared from the calibration of the meter

[C&GS, 1950]. Instrument accuracy was plus or minus 0.1 knotfor currentspeed and plus or minus

5 degrees for direction [Long, 1978].

Instrumentation used within the last 30 years have increasingly improved measurement accuracy.

Current direction, speed, temperature, time, conductivity, and depth data were collected with the

Grundy 9021G current meters between the mid-1970s and the mid-1980s. The nearly 5-foot long

meter recorded data on an internal magnetic tape while attached to a taut line mooring secured at a

specified depth from the surface. The Roberts-type rotorspeed sensor was oriented into the current

by a 20-inch long fin. The speed was measured by the number of rotations of the rotor averaged over

a 10-minute sampling period. Current direction was measured instantaneously at the end ofthe rotor

count by comparing direction with that of magnetic north from a gimbaled magnetic compass. A

continuously running crystal oscillator ensured that the programming of sensors, sampling rate, and

tapemotorspeed were consistent throughout the deployment [Browne, 1983]. The reported accuracy

of the Grundy 9021G current meter was 2 cm/s [Klavans, 1986]. 

Currentspeed, direction, temperature, pressure, conductivity, and time data were collected during the

1970s and 1980s using the Aanderaa RCM4 current meters. The speed was calculated by averaging

the number of rotations of the rotor over a 10-minute interval and direction recorded was an

instantaneous value. The length of the current meter was nearly 4.5 feet in its entirety with a 3-foot

long vane which oriented the meterto the prevailing current direction. As with the Grundy, data were

internallyrecorded onmagnetic tape. The Aanderaa RCM4 current meters had a theoretical accuracy

of less than 1.5 cm/s.

The General Oceanics Niskin winged current meter (Model 6011 Mark II), which was deployed in

Miami Harbor in 1985, used a tilt sensor (a force balance inclinometer) to measure the angle of tilt

and three orthogonally mounted flux-gate sensors which acted as a solid state compass to measure

direction. The angle of tilt varied with the speed of the current; the greater the current the greater the

angle of tilt. The instrument was fitted with a winged stabilizer that oriented the instrument in the
15

direction of current flow. The data and time stamp were recorded on a Philips type magnetic tape

cassette. Speed could be determined directly from the angle of tilt. A calibration curve for each style

of wing showed the relation between speed and tilt angle. The current direction was derived from

readings of the three orthogonal sensors. Manufacturer-stated accuracy for instrument tilt was 0.5

degree, current directionsensors had a 2-degree accuracy, and currentspeed was plus or minus 1 cm/s

at the 1-knot range [General Oceanics, 1984].

The most recent current metersin use by NOS are ADCPs which use acoustic rather than mechanical

technology. Most of the water column can be profiled with an ADCP whether it is deployed on the

bottomor towed fromthe surface. The data can be disseminated by radio transmitter in real time. The

ADCP velocity data has a long term accuracy bias of 0.5 percent of the measured velocity, plus or

minus 0.5 cm/s [RD Instruments, 1992].

Eighteen (or 44%) ofthe 41 reference stations are based oncurrent pole or Zeskind float data. A total

of1117 subordinate stations (40% ofthe total) are referenced to tidal currentreference stations based

on current pole or Zeskind float data. PORTSTM current meters are in operation near two of those

stations, Galveston Bay Entrance and San Francisco Bay Entrance. NOS plans to update their tidal

constituents in the 2000 NOS Tidal Current Tables.

2.5 Duration of Measurement

The daily predictions published in the NOS Tidal Current Tables are based on current data which

varies in length from 2 days (North Inian Pass and Strait of Juan de Fuca) to 748 days (Pollock Rip

Channel). A tidal current reference station needs a minimum of 15 days of continuous velocity

observations in order to compute tidal current constituents by harmonic analysis. Predictions based

on longer data sets can resolve more constituents and provide a closer match to the observed

astronomical tidal curves. The more recently acquired data are of longer duration due to advances

in instrument technology.

As indicated in Appendix B, predictions at three reference stations have been inferred from water

level data. These stations are San Francisco Bay Entrance (1923), Wrangell Narrows (1925), and

North Inian Pass (1925). This was done for older stations where only limited current data were

available but a tidal current reference station was needed. The constituents of a nearby water level

stationwere adjusted in amplitude and phase to fitthe limited current data available using a procedure

known as harmonic comparison described in the Manual ofCurrent Observations [C&GS, 1950]. A

similar method was used to obtain constituents for the Strait of Juan de Fuca Entrance, by using

constituents of another tidal current station (Admiralty Inlet) that were adjusted in amplitude and

phase.

Sixothertidal current reference stations are hydraulic current stations (Appendix B) which are located

in channels with different tidal driving forces at both ends ofthe channel. The tides at both entrances

may have different ranges and/or phases. The current in the channel is based on the difference in

water levels between the entrances. A limited amount of current data collected in the channel was

then used to adjust the tidal constituents obtained from the water level difference. The six hydraulic
16

reference stations areCapeCodCanal(1956),Chesapeake and DelawareCanal(1937-38), Hell Gate

(1932), Deception Pass (1925), Sergius Narrows (1952), and Isanotski Strait (1940).

Of the tidal current reference stations, 15 (37%) are based on less than 29 days of data (Figure 1)

including all 7 Alaskan reference stations. Eight tidal current reference station predictions are based

on less than 15 days of data. Seven stations have predictions based on 15 days to 28 days of data.

Of all U.S. subordinate stations, 942 (34%) are referenced to tidal current reference station

predictions based on less than 29 days of current data. 

Improvements in instrument technology have allowed NOSto obtainlonger time series and to resolve

more harmonic constituents.Twelve tidal current reference stations(29%) are based ondata acquired

within the last 30 years with an average of 227 days of Grundy 9021G, Aanderaa RCM4, or ADCP

measurements (Figure 1). Data acquired within the last 10 years are based on an average of 211 days

of ADCP data. 
17

Figure 2. Changes in vessel draft [NOAA, 1999].

3. VESSEL TRAFFIC AND COMMERCIAL ACTIVITY

PORTSTM is designed to provide real-time currents, water levels, salinity, temperatures, and wind

conditions which are critical factors for the safe navigation ofships. At the same time, the real-time

waterlevel,salinity, and temperature informationprovided by PORTSTM allows shipping companies

to better plan the loading and lightering of vessels transiting the port. The oceanographic

measurements collected by PORTSTM are available to coastal managers to monitor salinity and

temperature conditions in the estuary and in developing plans for hazardous materials spill response.

Presently, PORTSTM are located in San Francisco Bay, Tampa Bay, New York Harbor, Galveston

Bay, and Chesapeake Bay.

Trends in vessel transit statistics show that U.S. commercial waterways are increasingly congested

with larger deep-draft vessels. As shown in Figure 2, vessel draft has dramatically increased since

the mid-nineteenth century. In conjunction with this trend, there is an increasing need for real-time

water level and current data to maximize use of channel depths, to prevent costly delays in offloading

cargo, and for hazardous spill response [NOAA, 1995]. 

If predicted currents are inaccurate due to long term changes in channel bathymetry and repeated

dredging activity, the incidence of hazardous spills may increase and impact more estuaries and

sensitive environments. Spill response and cleanup can be hindered by inadequate current

predictions. 

Recent oil spills in Texas, Delaware, Alaska, and Rhode Island indicate that the safe transportation

of crude oil is a national concern [U.S. Coast Guard, 1998]. Petroleum products and organic and

inorganic chemicalstransported as bulkcargo pose the greatest threat to the environment during a spill

situation or vessel accident. Historical data suggests that an oil tanker spill can be 5 times larger than

one from other vessel types [U.S. Coast Guard, 1998]. It is especially significant when these

hazardous spills occur in high traffic areas such as Louisiana, Texas, and Alaska. Oil tanker transits
18

in and out of the major Pacific coast ports in 1989, for example, represented about 18% of all

deep-draft cargo-carrying vessels with drafts greaterthan19 feet[U.S.Coast Guard, 1998]. The 1989

Waterborne Commerce data show that the percentage of oil tanker transits varied from 28% for San

Francisco Bay, to less than 7% for the Columbia River. 

The waterborne tonnage values presented in thisreport are based onthe 1995Waterborne Commerce

statistics of the U.S. Corps of Engineers. [U. S. Army Corps of Engineers, 1997]. Appendix C

presents the total tonnage (ranked from high to low) categorized as domestic, foreign, import and

export tonnage at all the major U.S. coastal ports. Appendix D groups the total tonnage for coastal

ports with the associated tidal current reference station (or stations) for each port. If a port does not

contain a reference station, it is associated with the reference station for the subordinate stations in

that port. Some of the tidal current reference stations have no total tonnage reported because they are

not associated with a major coastal port, although substantial vessel traffic may pass nearby en route

to a major port(e.g., Strait ofJuan de Fuca Entrance). (Note that Chesapeake Bay Entrance does not

include Baltimore tonnage and Admiralty Inlet does not include Tacoma tonnage.) The reference

stations in the Aleutian Islands are not associated with a major port but are of significant economic

importance due to the regional fishing industry.

 

3.1 Type of Tonnage

Cargo is classified as bulk (liquid and dry), container, general and breakbulk [U. S. Army Corps of

Engineers, 1997]. Some examples of bulk cargo are petroleum products (crude petroleum, oil), coal,

coke, iron, or steel scrap, and liquid bulk (organic and inorganic chemicals, vegetable oils, jet fuel).

Container cargo mayinclude agri-products, automobiles, and manufactured equipment and machinery.

Examples of breakbulk cargo are steel, fruit, lumber, meat, motor vehicles, wood products,

paper/pulp, and cocoa beans. General cargo could include anything not covered in the other

categories and varies from port to port depending upon the type of traffic (domestic or foreign).

Domestic commerce is considered coastal whena vessel transits an ocean or the Gulf of Mexico (e.g.

New Orleans to Baltimore, New York to Puerto Rico, San Francisco to Hawaii, Alaska to Hawaii).

Domestic traffic is considered internal when vessel movements take place solely on inland

waterways. An inland waterway (e.g. San Francisco Bay, Puget Sound, Delaware Bay and

Chesapeake Bay) is one geographically located within the boundaries of the contiguous 48 states or

within the boundaries of Alaska. The statistics presented in this section and in Appendices C and D

do notinclude barge ortugtonnage through the intercoastal waterways nor do theyinclude cruise liner

traffic, military cargo moved in Department of Defense vessels, cargo carried on general ferries, or

coal and petroleumproductsloaded fromshore facilities directly into bunkers ofvesselsforfuel. The

cargo does include fish landing data as internal and intraport domestic traffic. Intraport traffic is

movement within a single port whether it has one or more arms or channels. It does not include car

or generalferries. This report does not include discussion of the Great Lakes ports or the inland river

ports on the Ohio or Mississippi rivers. 
19

Figure 3. Total 1995 tonnage for major U.S. ports (with greater than 10 million tons of shipping)

based on Waterborne Commerce of the United States statistics published by the Army

Corps of Engineers.

3.2 Total Tonnage

The total tonnage statistical data in AppendixC is presented in map formin Figure 3. There are three

major ports where total 1995 tonnage exceeded 100 million tons.The PortofSouthLouisiana,LAhad

the greatest tonnage (204.5 million tons) followed byHouston, TX(135 million tons) and New York,

NY (119 million tons). Of the twelve ports with total tonnage greater than 50 million tons, nine are

on the Gulf of Mexico. The other three are New York, NY, Valdez, AK, and Long Beach, CA. The

largest port in Alaska is Valdez (81 million tons) and the largest port in Hawaii is Honolulu (11.5

million tons).

The total tonnage grouped by tidal current reference station in Appendix D is displayed as a bar chart

in Figure 4. This provides a measure of the relative importance of individual tidal current reference

station predictions for U.S. commercialshipping. Two Gulf Coast reference stations alone (Mobile

BayEntrance and GalvestonBayEntrance) account for 46% ofthe total U.S. tonnage. The GulfCoast

tonnage (997 million tons) is 52.3% ofthe total. The two major Atlantic Coast reference stations are

The Narrows (NY Harbor) and Delaware Bay Entrance. The Atlantic Coast tonnage (517 million

tons) is 27.2% ofthe total. The major Pacific Coast reference station is San Francisco Bay Entrance.

The Pacific Coast tonnage (390 million tons) accounts for 20.5% of the total. 
20

1.91

2.46

2.50

10.26

13.37

14.40

15.37

15.69

15.90

17.94

19.38

23.04

24.84

26.20

30.74

30.98

44.76

55.44

58.85

70.46

73.22

121.23

125.14

137.09

347.62

0.26

81.88

521.26

0.14

0 100 200 300 400 500 600

Key West, FL

North Inian Pass, AK

Race Rocks, B.C.

Carquinez Strait, CA

Bay of Fundy Entr, ME

Pollock Rip Channel, MA

Wrangell Narrows, AK

Rosario Strait, WA

Portsmouth Harbor Entr, NH

St. Johns River Entr, FL

The Race, LIS, NY

Boston Harbor, MA

Savannah River Entr, GA

The Narrows, Puget Snd, WA

Charleston Harbor Entr, SC

San Diego Bay Entr, CA

Miami Harbor Entr, CA

Admiralty Inlet, WA

Baltimore Harbor Appr, MD

Tampa Bay Entr, FL

Grays Harbor Entr, WA

Aransas Pass, TX

Chesapeake Bay Entr, VA

Sergius Narrows, AK

Delaware Bay Entr, DE

The Narrows, NY Harbor, NY

San Francisco Bay Entr, CA

Galveston Bay Entr, TX

Mobile Bay Entr, AL

millions of tons Figure 4. Total 1995 tonnage associated with tidal current reference stations. 

The distribution of subordinate tidal current stations does not reflect the distribution of tonnage by

coast. As stated in Section 2.3, 61% of the subordinate stations are on the Atlantic Coast, 34.5% are

on the Pacific Coast, and only 4.5% are on the Gulf Coast. More current information for GulfCoast

locations may be needed to assist vessel operators with the safe transport of cargo.

Examination of the statistics in Appendix D shows that for some tidal current reference stations, the

tonnage from a distant port is greater than the tonnage of the port in which the reference station is

located. These reference stations and ports in parenthesis are: Portsmouth Harbor Entrance (Portland,

ME),Miami Harbor Entrance (Port Everglades), Mobile BayEntrance (the MississippiRiver ports),

San Diego Bay Entrance (Honolulu), San Francisco Bay Entrance (Long Beach and Los Angeles),

Grays Harbor Entrance (the Columbia River ports), Wrangell Narrows (Nikishka, Coos Bay, and

Anchorage), and Sergius Narrows (Valdez). Figure 5 shows U.S. coastal ports with more than 1

million tons of shipping which do not contain a tidal current reference station. Tidal Current Table

predictions for these busy ports could be improved if they had a “Table 1" reference station instead

of only “Table 2" subordinate stations.
21

Figure 5. Total 1995 tonnage for U.S. ports without an existing tidal current reference station and

greater than 1 million tons of shipping.
22
23

4. TIDAL AND NONTIDAL DYNAMICS

With the advent of ADCPs for measuring currents, there are new opportunities for improving

navigational safety and aiding commercial shipping. The deployment of an ADCP enables the

collection of more accurate data over longer periods of time in locations previously difficult to

monitor such as busy shipping channels. The data collected can be used to calculate new, more

accurate, tidal current constituents to update the Tidal Current Tables. With the development and

deployment ofreal-time data delivery systems (PORTSTM), an ADCP can continue to collect current

data and distribute information operationally to users on demand. 

Significant nontidal variability at a location important for safe navigation can justify real-time

monitoring of currents to help identify dangeroussituations. The decision whether to deploy an ADCP

for a limited time to update tidal current predictions or to install an ADCP to measure currents in real

time as part of a new PORTSTM will depend in part on the relative importance of nontidal currents.

Nontidal currents are seasonally-dependent with generally larger amplitudes in the winter due to

storms. Therefore, a long current record from both summer and winter months is necessary to obtain

a statistically accurate representation of the nontidal current variance. Long term time series from

recent ADCP deployments provide a means of deriving the nontidal current variance at The Race,

Throgs Neck, Bayonne Bridge, Charleston, Sunshine Skyway, Bolivar Roads, Golden Gate, and

Benicia. 

Nontidal and tidal variances resulting fromleast-squares harmonic analyses are used to characterize

currents at several locations of navigational importance in Section 4.1 and 4.2. All tidal current

reference stations are then associated with nearby National Water Level Observation Network

(NWLON) stations in an effort to characterize tidal and nontidal current dynamics in each area

(Section 4.3). The nontidal/tidal variance ratio plays a key role in classifying the NWLON stations

in order to rank the relative importance of nontidal currents at the tidal current reference stations

(Section 4.4).

 

4.1 Classification by Nontidal/Tidal Variance Ratio

A water level record measured at a single location can be a good representation of water levels for

a large surrounding area, with a variable time lag as tidal and nontidal signals reach different

locations. Unlike water level fluctuations, currents in bays and estuaries often vary by an order of

magnitude at different locations and at different depths. Current records can show large variations in

speed depending on the local bathymetry. Currents are generally slower near the sea floor due to

bottomfriction and, consequently, are also slower in shallower waters near shorelines. Currents are

faster near the surface in deep water areas. Currents are also faster near the entrance to a bay or

estuary where large volumes of water must be transported, compared with locations further fromthe

ocean. 

Owing to the spatial variability of current speeds, it is more useful to categorize currents by the

nontidal to tidal variance ratio. The variances can be obtained in the course of performing a least

squares harmonic analysis on a current time series. The least squares harmonic analysis program

calculates the amplitudes and phases of the tidal constituents. The sum of all the resolvable tidal
24

constituent variances is the total tidal variance, VT. The remaining variance is the nontidal variance,

VNT. A water level or a current can be classified according to the ratio of the nontidal variance to the

tidal variance, as proposed in Table 2.

Table 2. Classification of Water Levels and Currents

Tidally Dominated (T D) VNT/VT < 0.1

Mostly Tidal (M T) 0.1 < VNT/VT < 1.0

Mostly Nontidal (M N) 1.0 < VNT/VT < 10.0

Nontidally Dominated (N D) 10.0 < VNT/VT

4.2 Classification of Currents

There are presently five PORTSTM in operation in the United States. Four of them have ADCPs

deployed to measure currents; San Francisco has five ADCPs, while New York/New Jersey,

Houston/Galveston, and TampaBayeachhave two. Least squares harmonic analyses were performed

on 6-minute real-time observations at the following five ADCP stations: Bayonne Bridge, Sunshine

Skyway, Bolivar Roads, Golden Gate (outbound), and Benicia. Two of these stations were recently

established as new reference stations in the Tidal Current Tables: Sunshine Skyway in 1994 and

Bayonne Bridge in 1998. Although Bolivar Roads, Golden Gate, and Benicia were not exactly colocated with an existing tidal current reference station, they are in close proximity to the reference

stations at Galveston Bay Entrance, San Francisco BayEntrance, and Carquinez Strait, respectively,

and are expected to have a similar tidal classification. 

Least squares harmonic analyses were carried out for the five PORTSTM stations. In addition, least

squares harmonic analyses were performed on 10-minute ADCP data from The Race, Throgs Neck,

and Charleston Harbor Entrance. All stations had at least half a year of data with data from both

summer and winter months. All of the standard NOS tidal constituents were obtained except for the

five long termconstituents (Sa, Ssa, Mm, Mf, and Msf). The nontidal/tidal variance ratios (Table 3)

ranged between 0.034 for Golden Gate and 0.224 for Bolivar Roads. Based on the classification

proposed in Table 2, all the current stations are classified as tidally dominated except for Bolivar

Roads which is classified as mostly tidal.

In harbors without a PORTSTM, the historical current data could be re-analyzed in the same manner,

but in most cases the data are very old and far less than a year in length. Substantial changes have

occurred to the bathymetry of the bays and estuaries since the measurements were made and nontidal

variances obtained from the old current data are likely to be inadequate. Therefore, in order to make

comparisons between tidal current stations, the tidal and nontidal variances at nearby water level

stations will be examined.
25

Table 3. Nontidal/Tidal Classification of Current Stations

Observed Nontidal Tidal Nontidal/Tidal Classifi- Days

Station Name Variance Variance Variance Variance cation of

(m/s)2(m/s)2(m/s)2 Ratio Code Data

The Race, NY 0.345 0.015 0.330 0.045 T D 178.3

Throgs Neck, NY 0.075 0.004 0.071 0.056 T D 483.0

Bayonne Bridge, NY 0.388 0.019 0.369 0.051 T D 227.2

Charleston, SC 0.476 0.016 0.460 0.035 T D 315.1

Sunshine Skyway, FL 0.193 0.015 0.178 0.084 T D 305.8

Bolivar Roads, TX 0.266 0.060 0.217 0.224 M T 241.9

Golden Gate, CA 0.764 ERR 0.739 ?? T D 248.3

Benicia, CA 0.376 0.013 0.369 0.036 T D 243.6

T D = Tidally Dominated, M T = Mostly Tidal, M N = Mostly Nontidal, N D = Nontidally Dominated

 

4.3 Tidal and Nontidal Variance at Water Level Stations

The NWLON operated by the National OceanService is composed of primary and secondary control

water level stations along the coasts of the United States [Hicks, 1989]. This network provides the

basic tidal datums for coastal and marine boundaries and the chart datum for NOS nautical charts.

Observations at a secondary control or tertiary water level station are reduced to equivalent l9-year

tidal datums throughthe comparison ofsimultaneous observations with a primary control water level

station. Water level data in close proximity to tidal current reference stations will be used to examine

the relative importance of nontidal dynamics near the reference stations listed in the published Tidal

Current Tables. 

Table 4 lists the NWLON station chosen for each tidal current reference station. In some cases, two

tidal currentreference stations are associated with the same NWLONstation. St. Petersburg represents

the tidal current reference stations at Old Port Tampa and Sunshine Skyway. Cherry Point represents

the tidal current reference stations at Deception Pass and Rosario Strait. Sand Point represents the

tidal current reference stations at Isanotski Strait and Kvichak Bay. Unalaska represents the tidal

current reference stations at Unimak Pass and Akutan Pass. 

An effort was made to chose a NWLON station as close as possible to the tidal current reference

station, preferably in the same waterway, but this was not always possible especially in Alaska.

Isanotski Strait, KvichakBay, North InianPass, UnimakPass, and WrangellNarrows are all more than

a degree of longitude fromtheir associated NWLON station, and the following analysis may be less

applicable for the Alaskan stations than for the other stations. 

There are 37 NWLON stations thatwere linked to tidal current reference stations. The NWLON data

analyzed in this study were verified hourly observed water levels referenced to mean lower low

water. For 30 of the stations, 366 days of observed 1996 data were analyzed. Three stations (Sandy

Hook, Dauphin Island, and Cherry Point) were analyzed with 332, 362, and 358 days of 1996 data,

respectively. Three other stations (Cape Cod Canal, Seavey Island, and Key West) were analyzed
26

with 365 days of data from1975, 1985, and 1995, respectively. Chesapeake City was analyzed with

319 days of data from 1982-1983, the most recent long term data set available. 

Table 4 lists the variances of the long term water level stations linked to the published NOS tidal

current reference stations. Figure 6 presents a plot of the tidal and nontidal variance, color coded by

symbol for each coast. The range in tidal variance among the stations is more than two orders of

magnitude whereas the range in nontidal variance is only one order of magnitude. It is apparent that

the classification of the water level stations is more dependent on the level of tidal variance rather

than the nontidal variance.

Two California stations, San Diego Bay Entrance and San Francisco Bay Entrance, have the lowest

nontidal variances. Although nontidal variance appears to be roughly equivalent for all the other

waterlevelstations, theyare due to different combinations oftwodriving forces atdifferent locations.

The first is the effect of winterstorms overthe continentalshelf. The strength of this effect is strongest

in the higher latitudes and weakest in the lower latitudes. It is especially weak in California where

the continentalshelfis narrow. The second effect is due to annual meteorological cycles in wind and

ocean temperature. Routine water level predictions incorporate this effect in the tidal constituents,

Sa and Ssa [Hicks, 1989]. The harmonic analyses performed on the water level data in this report did

not include Sa and Ssa and as a result the annual cycle becomes a part of the nontidal variance. On

the east coast, the annual cycle is very small for northern stations and gradually increases toward the

south to a maximum in Florida. On the Pacific coast, the annual cycle is small in California, and is

larger for the Pacific coast of Washington and for Alaska.

Table 4. Nontidal/Tidal Classification of NWLON Stations

Associated Tidal Total Nontidal Tidal ClassifiNWLON Station Current Reference Variance Variance Variance Variance cation

Station(s) m2 m2 m2 Ratio Code

ATLANTIC COAST

Eastport, ME Bay of Fundy Entrance,

CANADA 3.960 0.016 3.944 0.004 T D

Seavey Island, ME Portsmouth Harbor Entrance,

NH 0.788 0.014 0.774 0.019 T D

Boston, MA Boston Harbor, MA 1.102 0.022 1.080 0.020 T D

Cape Cod Canal, MA Cape Cod Canal, MA 0.908 0.017 0.891 0.019 T D

Nantucket, MA Pollock Rip Channel, MA 0.133 0.019 0.114 0.166 M T

New London, CT The Race, NY 0.104 0.024 0.080 0.295 M T

Willets Point, NY Throgs Neck, NY 0.791 0.046 0.745 0.062 T D

The Battery, NY Hell Gate, NY 0.294 0.034 0.260 0.130 M T

Sandy Hook, NJ The Narrows, New York

Harbor, NY 0.309 0.029 0.280 0.105 M T

Lewes, DE Delaware Bay Entrance, DE 0.248 0.033 0.215 0.155 M T

Chesapeake City, MD Chesapeake and Delaware

Canal, MD 0.139 0.041 0.098 0.422 M T

Annapolis, MD Baltimore Harbor Approach,

MD 0.049 0.036 0.013 2.839 M N
Associated Tidal Total Nontidal Tidal ClassifiNWLON Station Current Reference Variance Variance Variance Variance cation

Station(s) m2 m2 m2 Ratio Code

27

Chesapeake Bay

Bridge Tunnel, VA

Chesapeake Bay Entrance,

VA 0.113 0.028 0.085 0.325 M T

Charleston, SC Charleston Harbor Entrance,

SC 0.380 0.031 0.349 0.089 T D

Ft Pulaski, GA Savannah River Entrance, GA 0.644 0.038 0.606 0.062 T D

Mayport, FL St. Johns River Entrance, FL 0.274 0.029 0.245 0.119 M T

Virginia Key, FL Miami Harbor Entrance, FL 0.060 0.011 0.049 0.224 M T

GULF COAST

Key West, FL Key West, FL 0.038 0.013 0.025 0.521 M T

St Petersburg, FL Sunshine Skyway Bridge and

Old Tampa Bay Entrance, FL 0.058 0.023 0.035 0.666 M T

Clearwater, FL Tampa Bay Entrance, FL 0.077 0.022 0.055 0.401 M T

Dauphin Island, AL Mobile Bay Entrance, AL 0.033 0.020 0.013 1.568 M N

Port Bolivar, TX Galveston Bay Entrance, TX 0.044 0.027 0.017 1.588 M N

Corpus Christi, TX Aransas Pass, TX 0.052 0.030 0.022 1.364 M N

PACIFIC COAST

San Diego, CA San Diego Bay Entrance, CA 0.270 0.005 0.265 0.018 T D

Golden Gate, CA San Francisco Bay Entrance,

CA 0.281 0.008 0.273 0.030 T D

Port Chicago, CA Carquinez Strait, CA 0.225 0.015 0.210 0.072 T D

Toke Point, WA Grays Harbor Entrance, WA 0.694 0.055 0.639 0.086 T D

Neah Bay, WA Strait of Juan de Fuca

Entrance, WA 0.546 0.034 0.512 0.066 T D

Port Townsend, WA Admiralty Inlet, WA 0.627 0.023 0.604 0.037 T D

Seattle, WA The Narrows, Puget Sound,

WA 1.076 0.022 1.054 0.021 T D

Cherry Point, WA Deception Pass and Rosario

Strait, WA 0.694 0.019 0.675 0.029 T D

Friday Harbor, WA San Juan Channel, WA 0.525 0.021 0.504 0.041 T D

Ketchikan, AK Wrangell Narrows, AK 2.351 0.021 2.330 0.009 T D

Sitka, AK Sergius Narrows, AK 0.898 0.022 0.876 0.025 T D

Juneau, AK North Inian Pass, AK 2.622 0.022 2.600 0.009 T D

Sand Point, AK Isanotski Strait and Kvichak

Bay, AK 0.466 0.028 0.438 0.063 T D

Unalaska, AK Unimak Pass and Akutan

Pass, AK 0.133 0.019 0.114 0.165 M T

T D = Tidally Dominated, M T = Mostly Tidal, M N = Mostly Nontidal, N D = Nontidally Dominated
28

0.000

0.001

0.010

0.100

1.000

10.000

0.000 0.001 0.010 0.100 1.000 10.000

Nontidal (m2)

Tidal (m

2

)

ATLANTIC COAST

GULF COAST

PACIFIC COAST

Tidally

Dominated

Nontidally

Dominated

Mostly

Nontidal

Mostly

Tidal

Figure 6. Tidal and nontidal variance at National Water Level Observation Network stations. The

diagonal lines separating the categories correspond to the ratios presented in Table 2.

4.4 Classification of Water Level Stations

The next step in assessing the dynamics of the tidal current reference stations is to classify the

appropriate NWLON stations. The tidal and nontidal variances are shown for each NWLON station

inTable 4 and Figure 6. These values identify the NWLON stations as tidally dominated, mostly tidal,

mostly nontidal, or nontidally dominated. The lines separating the categories in Figure 6 correspond

to the classification presented in Table 2. The nontidal/tidal variance ratios are displayed as a bar

chart in Figure 7. 
29

0.165

0.063

0.009

0.025

0.009

0.041

0.029

0.021

0.037

0.066

0.086

0.072

0.030

0.018

1.364

1.588

1.568

0.401

0.666

0.521

0.224

0.119

0.062

0.089

0.325

2.839

0.422

0.155

0.105

0.130

0.062

0.295

0.166

0.019

0.020

0.019

0.004

0.000 0.500 1.000 1.500 2.000 2.500 3.000

Unalaska, AK

Sand Point, AK

Juneau, AK

Sitka, AK

Ketchikan, AK

Friday Harbor, WA

Cherry Point, WA

Seattle, WA

Port Townsend, WA

Neah Bay, WA

Toke Point, WA

Port Chicago, CA

Golden Gate, CA

San Diego, CA

Corpus Christi, TX

Port Bolivar, TX

Dauphin Island, AL

Clearwater, FL

St Petersburg, FL

Key West, FL

Virginia Key, FL

Mayport, FL

Ft Pulaski, GA

Charleston, SC

Ches Bay Bridge, VA

Annapolis, MD

Chesapeake City, MD

Lewes, DE

Sandy Hook, NJ

The Battery, NY

Willets Point, NY

New London, CT

Nantucket, MA

Cape Cod Canal, MA

Boston, MA

Seavey Island, ME

Eastport, ME

Ratio of Nontidal to Tidal Variance

Figure 7. Nontidal/tidal variance ratio at NWLON stations.
30

The variance ratios of the Atlantic Coast NWLON stations range from 0.004 at Eastport to 2.839 at

Annapolis. Based on Table 2, seven of the Atlantic Coast stations are classified as tidally dominated,

nine Atlantic Coast stations are classified as mostly tidal, and Annapolis is classified as mostly

nontidal. The variance ratios of the Gulf Coast NWLON stations range from 0.401 at Clearwater to

1.588 at Port Bolivar. The three Gulf Coast stations in Florida have variances that classify them as

mostly tidal while the other GulfCoaststations are classified as mostly nontidal. The variance ratios

ofthe Pacific Coast NWLON stations range from0.009 atJuneau and Ketchikanto 0.165 atUnalaska.

All the Pacific Coast NWLON stations are tidally dominated with the exception of Unalaska in the

Aleutian Islands, which is classified as mostly tidal. 

Since the nontidal to tidal variance ratio of an NWLON station will be used to infer the classification

of a nearby tidal current reference station, the variance ratios given in Table 3 for currents should be

compared to the variance ratios of an appropriate NWLON station. It can be seen from Table 5, that

the nontidal/tidal variance ratio is generally lower for current stations than for corresponding water

level stations. This indicates that currents tend to be more tidal than nearby water levels. The current

stations fall into a more tidal category than the associated water level station. Mostly tidal (M T)

water level stations have tidally dominated (T D) currents in the vicinity. Mostly nontidal (M N)

water level stations have mostly tidal currents (M T) in the vicinity. Of course, tidally dominated (T

D) water levels are associated with tidally dominated (T D) currents.

Table 5. Comparison of Current and Water Level Classification

Current Water Level

Station Variance

Ratio

Classification

Code Station VarianceRatio

Classification

Code

Golden Gate, CA 0.034 T D Golden Gate, CA 0.030 T D

Throgs Neck, NY 0.056 T D Willets Point, NY 0.062 T D

Benicia, CA 0.036 T D Port Chicago, CA 0.072 T D

Charleston, SC 0.035 T D Charleston, SC 0.089 T D

Bayonne Bridge, NY 0.051 T D The Battery, NY 0.130 M T

The Race, NY 0.045 T D New London, CT 0.295 M T

Sunshine Skyway, FL 0.084 T D St. Petersburg, FL 0.666 M T

Bolivar Roads, TX 0.224 M T Port Bolivar, TX 1.588 M N

T D = Tidally Dominated, M T = Mostly Tidal, M N = Mostly Nontidal, N D = Nontidally Dominated

Although attempts were made, a reliable quantitative relationship betweenthe nontidal/tidal variance

ratio of water level and current stations could not be found. There were no significant correlations

between nontidal water levels and currents when the variance ratios were low. There are significant

correlations (up to 0.6) between nontidal water levels and currents when the variance ratios were

higher (i.e., at Bolivar Roads, Sunshine Skyway, and Bayonne Bridge), but these correlations are

dependent on varying amounts of smoothing applied to the nontidal water levels. 
31

The clearest result ofthese comparisons is that a higher water level variance ratio corresponds to a

higher current variance ratio and currents fall into a more tidal category thanwater levels in the same

area. In the next section, it will be assumed that the classification of water level stations can be used

as a guide in drawing up a priority list for the real-time monitoring of currents by a PORTSTM.
32
33

5. NEW CURRENT SURVEY PRIORITIES

The previous sections of this report have reviewed the reference stations where tidal current

constituents may be inadequate due to age, instrumentation, or data length, evaluated the nations ports

based on vessel traffic and shipping tonnage, and categorized the water levels and currents based on

the nontidal/tidal variance ratio. Based on these results, recommendations for future current surveys

are presented in this section. 

A limited current meter deployment is required to update old tidal current constituents or collect data

for establishing a new tidal currentreference station. When the tidal constituents have been accurately

resolved, tidal currents will be predictable until there are significant changesin channel bathymetry

or harbor configuration. Short term current surveys are recommended for areas where reference

stationpredictions are based on data more than 30 years old (Section5.1). The waterborne commerce

of the region defines the priority for updating existing reference stations. 

The installation of a PORTSTM to disseminate real-time current measurements is preferred for

locations where nontidalsignals comprise a significant partofthe total current variance (Section5.2).

Major ports which do not presently containa tidal currentreference stationare recommended for new

tidal current predictions and are individually evaluated for real-time current monitoring by a new

PORTSTM (Section 5.3).

 

5.1 Recommendations for Updating Tidal Current Reference Stations

In Section 2, 41 tidal current reference stations for which daily predictions are published in the NOS

Tidal Current Tables were evaluated on the basis of age, instrumentation, and the length of

observations used to obtain the tidal constituents. There is a general correlation between these three

factors, with older current data collected by current pole or floatfor periods shorter than 29 days and

newer current data collected by ADCPs for periods longer than 29 days. Adequate tidal current

constituents are obtained from a 29-day Fourier harmonic analysis. More accurate constituents are

obtained with longer data sets. In view of the correlations between the three factors of age,

instrumentation, and length of observations, recommendations for updating reference stations will be

summarized for three groups of stations based on type of instrumentation.

The current pole or Zeskind float were used to collect data for 18 tidal current reference stations

before 1946. As stated in Section 2.4, the longest current pole measurement was 2 years of

observations fromStonehorseLightship in PollockRip Channel. It is unlikely that this location needs

to be revisited. It is recommended that all the 17 other pole or float stations be updated based on age,

instrumentation, and length of data. These stations will be called Group 1. 

Recently, NOS has obtained new current data for four ofthe stations in Group 1. Two current survey

projects were completed in 1998 at Savannah River Entrance and St. Johns River Entrance and new

tidal predictions for SavannahRiver Entrance appear in the 1999 NOS Tidal Current Tables. The St.

Johns River Entrance reference station was updated in a January 1999 Notice to Mariners and will

appear in the 2000 Tidal Current Tables along with seven new subordinate stations. A large set of

PORTSTM current data are available for locations near Galveston Bay Entrance and San Francisco
34

Bay Entrance and predictions based on new constituents are planned for the 2000 Tidal Current

Tables. 

It is recommended that new current data be obtained for the remaining 13 tidal current reference

stations in Group 1. In order to prioritize the reference stations that need to be updated, the tonnage

statistics discussed in Section 3 are used. The reference stations that need updating are ranked based

on their associated tonnages as displayed in Figure 4. The ranking in Group 1 from most urgent to

least urgent is as follows:

1. Mobile Bay Entrance, AL

2. The Narrows, New York Harbor, NY

3. San Diego Bay Entrance, CA

4. Portsmouth Harbor Entrance, NH

5. Wrangell Narrows, AK

6. North Inian Pass, AK

7. Hell Gate, NY

8. Chesapeake and Delaware Canal, MD

9. Strait of Juan de Fuca Entrance, WA

10. Deception Pass, WA

11. Isanotski Strait, AK

12. Unimak Pass, AK

13. Kvichak Bay, AK

A second group ofstations are based onmore recently acquired data obtained with better technology

than the stations in Group 1. The Roberts Current Meter was used to collect data for 9 tidal current

reference stations between 1942 and 1964. In 1965, a Geodyne current meter was used to collect 29

days ofdata atRosario Strait. In addition, data were collected by the Canadian Hydrographic Service

in 1960 for the Bay of Fundy Entrance with an unknown instrument. The station at Miami Harbor

Entrance was updated in 1985 based on an analysis of 29 days of data using a Niskin winged current

meter [General Oceanics, Inc., 1984]. These stations will be called Group 2. It is recommended that

all 12 ofthese stations be updated based on age, instrumentation, and limited data sets. Based on the

tonnage statistics in Figure 4, the ranking in Group 2 from most urgent to least urgent is as follows:

1. Sergius Narrows, AK

2. Grays Harbor Entrance, WA

3. Baltimore Harbor Approach, MD 

4. Admiralty Inlet, WA

5. Miami Harbor Entrance, FL

6. The Narrows, Puget Sound, WA

7. Rosario Strait, WA

8. Bay of Fundy Entrance, ME

9. Key West, FL

10. Cape Cod Canal, MA 

11. San Juan Channel, WA

12. Akutan Pass, AK
35

The remaining reference stations are placed in Group 3. Between 1971 and 1984, long term data sets

were collected for updating 4 tidal current reference stations with the AanderaaRCM4 orthe Grundy

9021G current meters. Between 1987 and 1991, the ADCP was used to collect current data for

updating 7 tidal current reference stations. Only the station at Aransas Pass was based on a short 29-

day harmonic analysis. Since the data from all 11 ofthese reference stations are relatively recent, it

is not recommended that new data be collected at this time.

 

5.2 Proposed Real-Time Current Monitoring at Existing Tidal Current Reference

Stations

The nontidal/tidal variance ratios discussed in Section 4 canprovide a methodto evaluate a reference

station for real-time current monitoring by a PORTSTM, although other navigational safety

requirements can be factored into the decision. For locations where a long term current time series

is not available, a NWLON water level station in the vicinity was harmonically analyzed and its

nontidal/tidal variance ratio was calculated. All the NWLON stations that were classified as mostly

nontidal are considered to have a large enoughnontidal/tidal variance ratio requiring continuousrealtime monitoring of currents by a PORTSTM (Table 4). These stations are in Chesapeake Bay or the

GulfofMexico. One of these locations is already part of a PORTSTM (GalvestonBayEntrance). The

three other tidal current reference stations listed below are associated with significant vessel traffic

and have strong enough nontidal variance to be candidates for a new PORTSTM. 

1. Mobile Bay Entrance, AL

2. Aransas Pass, TX

3. Baltimore Harbor Approach, MD

Another group of NWLON stations have nontidal/tidal variance ratios that are classified as mostly

tidal (Table 4). The associated tidal current reference stations in the vicinity can be considered for

real-time current monitoring by a PORTSTM, but are not assigned as high a priority as the stations

listed above. The stations at Sunshine Skyway and Old Port Tampa Entrance are already being

monitored in real time as part ofthe Tampa PORTSTM. The other tidal current reference stations that

are associated with major ports (greater than 10 million tons) are ranked below according to the

tonnage statistics shown in Figure 4:

1. The Narrows, New York Harbor, NY

2. Delaware Bay Entrance, DE

3. Chesapeake Bay Entrance, VA

4. Tampa Bay Entrance, FL

5. Miami Harbor Entrance, FL

6. The Race, NY

7. St. Johns River Entrance, FL
36

5.3 Recommendations for Adding New Tidal Current Reference Stations and

Evaluation for Real-Time Current Monitoring by PORTSTM

There are long stretches ofthe U.S. coastline without tidal current reference stations as discussed in

Section 2.1. Over the years, major ports have developed in these geographical gaps. The subordinate

stations in these ports are linked to a distant reference station. In some cases, discussed in Section

3.2, the tonnage at these subordinate station ports is greater than the tonnage of the port where the

reference station is located. The major U.S. ports (greater than 1 million tons) without a tidal current

reference station are shown in Figure 5. Consideration should be given to establishing new tidal

currentreference stations in some ofthese portsto assistmariners handling the increased vessel traffic

at these locations. 

Thirteen U.S. ports with more than 10 million tons of shipping are recommended for a new tidal

current reference station and are evaluated forreal-time current monitoring by a new PORTSTM. The

Tidal Current Tables were examined to determine how many subordinate stations are in these ports.

The maximum flood and maximum ebb currents at these subordinate stations were examined to

determine if strong currents exist in these ports (e.g., if both maximum flood and maximum ebb

currents are greater than or equal to 1 knot). They are discussed in the following order based on

tonnage, with the nearest NWLON station in parentheses:

1. Port of South Louisiana, BatonRouge, New Orleans, Port of Plaquemine,

LA (South Pass, LA)

2. Long Beach, Los Angeles, CA (Los Angeles, CA)

3. Valdez, AK (Valdez, AK)

4. Port Arthur, Beaumont, TX (Sabine Pass, North, TX)

5. Portland, OR / Kalama, Vancouver, Longview, WA (Astoria, OR)

6. Lake Charles, LA (Sabine Pass, North, TX)

7. Pascagoula, MS (Dauphin Island, AL)

8. Freeport, TX (Freeport, TX)

9. Port Everglades, FL (Virginia Key, FL)

10. Matagorda Ship Channel, Victoria, TX (Freeport, TX)

11. Honolulu, HI (Honolulu, HI)

12. Portland, ME (Portland, ME)

13. Providence, RI / Fall River, MA (Newport, RI)

Harmonic analysis and evaluation of a nearby NWLON station gives the expected tidal regime of the

port with the results presented in Table 6. The tidal and nontidal variances are plotted in Figure 8,

showing the classificationofthe stations according to the variance ratio. If water levels are classified

as mostly nontidal, currents are likely to fall in the mostly tidal category and a PORTSTM installation

for monitoring currents is strongly recommended (indicated by an asterisk). The ports with mostly

tidal NWLON stations (Port Everglades, Honolulu, and Providence/Fall River) can also be

considered for currentmonitoring byPORTSTM but are not assigned as high a priority. The ports with

NWLON stations classified as tidally dominated are not recommended for current monitoring by

PORTSTM. (Although the NWLON station at Astoria, OR is classified as tidally dominated, the

Columbia River is recommended for current monitoring for reasons discussed below.) 
37

Table 6. Classification of NWLON Stations Associated with Major Ports without a Tidal

Current Reference Station

Observed Nontidal Tidal Variance ClassifiStation Name Variance Variance Variance Ratio cation

m2 m2 m2 Code

South Pass, LA * 0.035 0.020 0.015 1.333 M N

Los Angeles, CA 0.246 0.004 0.242 0.017 T D

Valdez, AK 1.387 0.032 1.355 0.024 T D

Sabine Pass, North, TX * 0.057 0.039 0.018 2.167 M N

Astoria, OR * 0.653 0.047 0.606 0.078 T D

Dauphin Island, AL * 0.033 0.020 0.013 1.538 M N

Freeport, TX * 0.051 0.027 0.024 1.125 M N

Virginia Key, FL 0.060 0.011 0.049 0.224 M T

Honolulu, HI 0.035 0.004 0.031 0.129 M T

Portland, ME 1.100 0.018 1.082 0.017 T D

Newport, RI 0.177 0.021 0.156 0.135 M T

T D = Tidally Dominated, M T = Mostly Tidal, M N = Mostly Nontidal, N D = Nontidally

Dominated

*Installation of a real-time current measuring system is recommended for ports near this NWLON station.
38

Dauphin Island

Honolulu

Portland Valdez

Astoria

Newport

Virginia Key

Los Angeles

South Pass

Sabine Pass

Freeport

0.000

0.001

0.010

0.100

1.000

10.000

0.000 0.001 0.010 0.100 1.000 10.000

Nontidal (m2)

Tidal (m2

)

Nontidally

Dominated

Tidally 

Dominated

Mostly

Tidal

Mostly

Nontidal

Figure 8. Tidal and nontidal variance at NWLON stations associated with major ports, without an

existing tidal current reference station.

1. Port of South Louisiana, Baton Rouge, New Orleans, Port of Plaquemine, LA (Nearest NWLON

station, South Pass, LA, is mostly nontidal) These four ports on the Mississippi River together

account for 438 million tons ofshipping which is 23% ofthe total U.S. tonnage. The vessels entering

or leaving these ports pass through the mouth of the Mississippi. There are no subordinate current

stations near the mouth ofthe Mississippi or on the river itself. There is only one subordinate current

station at SeabrookBridge in New Orleans whichis ona waterwaybetweenthe Mississippi and Lake

Pontchartrain. This station has flood and ebb currents greater than 1 knot.

There is evidence that tidal currents may be important in some stretches of the Mississippi River

itself. There are six subordinate water level stations at the mouth of the Mississippi which have tidal

ranges from 0.9 to 1.4 feet. A subordinate water level station at Paris Road Bridge on a waterway

in New Orleans has a tidal range of 1.1 feet. There is the following endnote about New Orleans in

the Tide Tables:

“At New Orleans the diurnal range of the tide during low river stages averages 0.8 foot.

There is no periodic tide at high river stages.”

Due to the importance of the Mississippi River to U.S. shipping and the complicated, frequently

changing geography due to natural and man-made causes, it is recommended that a new tidal current

reference station be established in the mouth ofthe Mississippi. Due to the important nontidal effects

from the Gulf of Mexico and fromthe variability ofriver flow, installation of a PORTSTM should be
39

considered. There are likely to be challenges associated with working in such a waterway with a

large volumetric flowrate and deposition of sediment not seen at previous PORTSTM projects.

2. LongBeach, Los Angeles, CA (Nearest NWLON station, Los Angeles, CA, is tidally dominated)

 There is one subordinate station in this harbor with the following associated endnote:

“In Los Angeles and Long Beach Harbors, the tidal current is weak. Currents can exceed

1 knotin the outer harbor at San Pedro, understrong wind conditions. Also, it is reported

that three minute surge waves are responsible for major ship movements and damage.”

It appears from the small enclosed area and geometry of these harbors that tidal currents are not

important here. It should be investigated whether changes to the harbor since the endnote was written

have increased tidal currents at any location. A PORTSTM maybe justified to monitorthe threeminute

surge waves.

3. Valdez, AK (Nearest NWLON station, Valdez, AK, is tidally dominated) There are 43

subordinate stations in Prince WilliamSound and Orca Bay. Tidal currents are very weak with four

rotary tidal current stations in the center of the bay. The only strong tidal currents are in narrow

passages nearthe edges ofthe bay(ElringtonPassage,Bainbridge Passage, and between Hinchinbrook

and Hawkins Islands) which are far from the main shipping channels. The main entrance to Prince

WilliamSound should be evaluated for locations with currents strong enough for a new tidal current

reference station. Despite the significant tonnage for this port, it is not recommended for real-time

current monitoring by a PORTSTM.

4. Port Arthur, Beaumont, TX (Nearest NWLON station, Sabine Pass North, TX, is mostly nontidal)

There are 4 subordinate stations in this waterway, with strong flood and ebb currents (greater than 1

knot) at Texas Point, Sabine, and Mesquite Point. This port is recommended for a tidal current

reference station. Due to the importance of the nontidal signal in the Gulf of Mexico, real-time current

monitoring by a PORTSTM is recommended.

5. Portland, OR / Kalama, Vancouver, Longview, WA (Nearest NWLON station, Astoria, OR, is

tidally dominated) There are 34 subordinate stations in the Columbia River. Both the tidal current

and the river flow are large from the entrance up to the last subordinate current station at Kalama

Upper Range. Both the flood and ebb currents are greater than 2 knots at the subordinate current

stations near Sand Island Tower, Clatsop Spit, and Chinook Point. They are greater than 1 knot at a

number of other locations. The tide is known to progress further upriver, with subordinate water

level stations at Vancouver, WA with a diurnal range of 1.8 feet and into the Willamette River at

Portland, OR with a diurnal range of 2.4 feet. The Tidal Current Table has the following endnote

about the Columbia River:

“The Columbia River bar can be very dangerous because of sudden and unpredictable

current changes accompanied bybreakers. It is reported that ebb currents on the north side

ofthe bar attain speeds of 6 to 8 knots and thatstrongNWwindssometimes cause currents

thatset north in the area outside the jetties. In the entrance, the currents are variable and

may reach a speed of over 5 knots on the ebb while the flood speed seldom exceeds 4
40

knots. The tidal current in the river is always modified by the river discharge, sometimes

to the extent that the flood current is indiscernible and the current ebbs continuously.”

Due to the rapid currents and the volume of shipping, it is recommended that a new tidal current

reference station be established in the Columbia River. Because of the importance of river flow

variability, and repeated requests for information by mariners, a PORTSTM installation is also

recommended. As at the mouth of the Mississippi, there are significant challenges to establishing a

PORTSTM at the mouth ofthe Columbia River, but there are also strong tidal currents upriver where

instruments could be located.

6. Lake Charles, LA (Nearest NWLON station, Sabine Pass North, TX, is mostly nontidal) There

is one subordinate station in Calcasieu Pass which is the waterway leading to Lake Charles. Both

flood and ebb currents are greater than 1 knot. This port isrecommended for the establishment of a

new tidal current reference station because of the ship tonnage, and for real-time current monitoring

by a PORTSTM because of the importance of nontidal effects from the Gulf of Mexico.

7. Pascagoula, MS (Nearest NWLON station, Dauphin Island, AL, is mostly nontidal) There is one

subordinate station at the Pascagoula River highway bridge with both flood and ebb currents greater

than 1 knot. Due to the ship tonnage and the nontidal effects of the Gulf of Mexico, this location is

recommended for a new tidal current reference station and for real-time current monitoring by a

PORTSTM.

8. Freeport, TX(NearestNWLONstation, Freeport, TX is mostly nontidal) There are no subordinate

stations and therefore no current predictions at this port. Due to the ship tonnage and the nontidal

effects of the Gulf of Mexico, this location is recommended for a new tidal current reference station

and for real-time current monitoring by a PORTSTM.

9. Port Everglades, FL (Nearest NWLON station, Virginia Key, FL, is mostly tidal) There are six

subordinate stations in this port. The stations at the entrance and at the 17th Street Bridge have flood

and ebb currents greater than 1 knot. This port is recommended for the establishment of a new tidal

current reference station.

10. Matagorda Ship Channel, Victoria, TX (Nearest NWLON station, Freeport, TX, is mostly

nontidal) Together these two ports have more than 10 million tons of shipping. There is one

subordinate station at Matagorda Channel(entrance jetty) whichhasflood and ebb speeds greaterthan

1 knot. Due to the ship tonnage and the nontidal effects of the Gulf of Mexico, this location is

recommended for a new tidal current reference station and for real-time current monitoring by a

PORTSTM.

11. Honolulu, HI (Nearest NWLON station, Honolulu, HI, is mostly tidal) There are no subordinate

current stations for the island of Oahu. The diurnal tide range at Honolulu is 2 feet. Based on the

geometry ofPearl Harbor, tidal currents maybemeasurable atthe entrance to Pearl Harbor. Although,

the port of Honolulu is reached by dredged channels directly accessible fromthe ocean, the entrance

to Pearl Harbor may be considered for the establishment of a new tidal current reference station for

the state of Hawaii.
41

12. Portland, ME (Nearest NWLON station, Portland, ME, is tidally dominated) There are 11

subordinate stations for this port, with flood and ebb speeds greater than 1 knot at Portland Harbor

Entrance. This port is recommended for the establishment of a new tidal current reference station but

not for real-time current monitoring. 

13. Providence, RI / Fall River, MA (Nearest NWLON station, Newport, RI, is mostly tidal)

Together these two ports have more than 10 million tons of shipping. There are 39 subordinate

stations for Narragansett Bay. The stations at Tiverton, Bull Point, Mount Hope Bridge, Kickamuit

River, DutchIsland, and India Point have flood and ebb speeds greaterthan1 knot. It is recommended

that a new tidal current reference station be established in Narragansett Bay. 

If these new reference stations are added, the priority rankings for updating existing tidal current

reference stations as discussed in Section 5.1 may change slightly. The only significant changes are

the top two stations in Group 2. If a new tidal current reference station is created for Valdez, AK, the

station at Sergius Narrows, AK loses priority. If a new tidal current reference stations is created for

the Columbia River, the station at Grays Harbor Entrance loses priority.
42

6. CONCLUSIONS

In this report, a thorough review was conducted of the data which forms the basis for predictions at

41 NOS tidal current reference stations. The geographic distribution, number of subordinate stations,

and characteristics ofthe tidal current constituents were described and compared. Almost half of the

reference stations were based on data sets more than 50 years old. Most of these stations are based

on data collected using current poles or floats. Over a third of the tidal current reference stations are

based on less than 29 days of data, with tidal current constituents developed from various types of

nonharmonic analysis. There is a clear correlation between age of data, type of instrument used, and

duration of measurement.

Shipping tonnage statistics forleadingU.S. coastal ports, as compiled bythe U.S. Corps of Engineers,

were examined as an indicator ofthe relative importance ofthe tidal current reference stations. Two

Gulf Coast reference stations (Mobile Bay Entrance and Galveston Bay Entrance) were associated

with tidal predictions for nearly half of the U.S. shipping tonnage. Despite the fact that over half of

the U.S. shipping tonnage is associated with Gulf Coast ports, less than 5% of the subordinate tidal

current stations are in the Gulf of Mexico. Six of the twelve ports with the greatest tonnages do not

contain a tidal current reference station. 

Inorderto determine the relative importance ofnontidal currents atthe tidal currentreference stations,

a method of classification was devised based on the nontidal to tidal variance ratio calculated from

harmonic analysis results. Four categories were defined by the variance ratio: tidally dominated,

mostly tidal, mostly nontidal, and nontidally dominated. The nontidal/tidal variance ratio was

obtained for recent long term time series recorded at or near the location of eight reference stations.

All ofthe stations were in the tidally dominated category, exceptfor Bolivar Roads which was in the

mostly tidal category. In order to infer the importance of nontidal currents at the other reference

stations, the closest NWLON stations were chosen and the nontidal/tidal variance ratios were

calculated. It was found that mostly nontidal water levels are associated with mostly tidal currents.

Mostly tidal water levels are associated with tidally dominated currents. 

Based on the findings summarized above, a number of recommendations concerning current survey

priorities can be made. An update of the tidal current constituents is recommended for the reference

stations that are based on older data oflimited duration. A group of 13 reference stations are based

on data collected before 1950 with current poles or floats. A second group of 12 reference stations

are based onlimited data sets collected bymechanical currentmeters between 1942 and 1985. Based

onananalysis of nontidal/tidal variance ratios, four ofthe existing tidal current reference stations are

most likely to have strong nontidal currents. Currents at one of them (Galveston Bay Entrance) are

presently being monitored by a PORTSTM. The three other locations (Mobile BayEntrance, Aransas

Pass, and Baltimore Harbor Approach) are associated with significant vessel traffic, and therefore

are also recommended for real-time current monitoring.

A new tidal currentreference stationisrecommended for 13major ports(greaterthan10 million tons)

inorderto provide improved tidal current predictions forthese ports, whichpresentlyare represented

by a limited number of subordinate stations. Six of these ports are expected to have significant

nontidal currents, based on the nontidal/tidal variance ratio, and are recommended for real-time

currentmonitoring. They are the mouth of the Mississippi River, Port Arthur/Beaumont, Lake Charles,
43

Pascagoula, Freeport, and Matagorda Ship Channel/Victoria. The mouth of the Columbia River is

also recommended for real-time current monitoring based on the expected importance of river flow

variability. 
44

ACKNOWLEDGMENTS

StephenGill provided guidance in using variance as a means of comparing NWLON stations to tidal

current reference stations. Dale Deitemyer and Janet Culp of the Products and Services Division

(PSD) provided assistance in acquiring data from long term water level control stations not readily

available on the Internet. 

TomKendrick, Richard Sillcox, and WilliamWatsonprovided keyinformationaboutthe tidal current

reference stationcards, officialformC&GS-444, and background informationon the instruments used

to obtain the current data. Information about the type of instrumentation and inferred values were

obtained fromdocumentationcompiled byTomKendrick. Joseph Welch provided memoranda about

the tidal current survey cards from former oceanographers in NOS. Darren Wright created the

templates for the thematic maps with data provided by the authors. 

Constructive comments and direction were provided by Kathryn Bosley and StephenGill. The draft

technicalreport was reviewed by Kathryn Bosley, Stephen Gill, Tom Kendrick, and William Stoney.

BrendaVia critiqued, edited, and finalized the figures and provided desktop publishing forthisreport.
45

REFERENCES

Browne, D. R. and Gary Dingle, 1983. New York Harbor Circulation Survey: 1980-81, NOS

Oceanographic Circulation Survey Report No. 5.

C&GS, 1950. Manual of Current Observations, Special Publication No 215, Washington, DC, US

Govt Printing Office.

Defant, A., 1961. Physical Oceanography, Vol. II Pergamon Press, New York, NY, 598 pp.

Dennis, R. E., and E. E. Long, 1971. A User’s Guide to a Computer Programfor Harmonic Analysis

of Data at Tidal Frequencies, NOAA Technical Report NOS 41, Office of Oceanography and

Marine Assessment, NOS, NOAA, Rockville, MD, 31 pp.

General Oceanics, Inc., 1984. Technical Proposal andResponse to Statement of Work, Circulation

Survey, Port of Miami, Volume II, 55 pp.

Hicks, Steacy D., 1989. NOS Tide and Current Glossary.

Klavans, Alan, Peter Stone, Gina Stoney, 1986. Delaware River and BayCirculation Survey: 1984-

1985, NOS Oceanographic Survey Report No 9.

Long, E.E., 1978.Tide and TidalCurrentObservationsfrom1965 through1967 in Long Island Sound,

Block Island Sound and Tributaries, NOS Oceanographic Circulatory Survey Report No. 1.

NOAA, 1999. NOS, OPSD, National PORTSTM Program Plan.

NOAA, 1998. NOS, CO-OPS, Strategic Plan for the National Ocean Service Center for Operational

Oceanographic Products and Services.

NOAA, 1995. NOAA Stratigic Plan: A Vision for 2005.

RD Instruments, 1992. Self-Contained Acoustic Doppler Current Profiler Technical Manual,

Firmware Version 17.10.

U. S. Army Corps of Engineers, 1997. Waterborne Commerce of the United States, Navigational

Data Center, Waterborne Commerce State Center.

U.S. Coast Guard, 1998. Evaluation of Oil Tanker Routing per Section 4111(b)(7) Oil Pollution Act

of 1990. Part 1: Pacific Coast, Part 2: Atlantic Coast.

Zervas, C. E., 1999. Tidal Current Analysis Procedures and Associated Computer Programs, NOAA

Technical Report NOS CO-OPS 021, Center for Operational Oceanographic Products and

Services, NOS, NOAA, Silver Spring, MD, 101 pp.
46
47

APPENDIX A

List of NOS Tidal Current Survey Reports

Since the formation of NOAAin1970, a numberofin-house publications have beenproduced byNOS

giving informationaboutthe data collected during circulation surveys and the resulting analysis ofthe

data. These reports were written by the staff ofthe Coastal and Estuarine Oceanography Branch and

its predecessors, the Estuarine and Ocean Physics Branch and the Circulatory Surveys Branch. The

publications are a part of several numbered series.

The NOS Oceanographic Circulation SurveyReportseries were published in order to give detailed

informationaboutthe data collected during a circulationsurvey. In general, data analysis results were

not included in the Circulation Survey Reports.

#1. Tide and tidal current observations from 1965 through 1967 in Long Island Sound, Block

Island Sound, and tributaries, Elmo E. Long, 1978.

#2. Tampa Bay circulatory survey, 1963, Demetrio A. Dinardi, 1978.

#3. Puget Sound approaches circulatory survey, Bruce B. Parker and James T. Bruce, 1980.

#4. CookInletcirculatorysurvey, 1973-1975,RichardC. Patchen,JamesT.Bruce, and Michael

J. Connolly, 1981.

#5. New York Harbor circulation survey, 1980-81, David R. Browne and Gary Dingle, 1983.

#6. SoutheastAtlantic coast estuaries: Sapelo Sound to St. Simons Sound, Georgia Circulation

Survey, 1980, William A. Watson, 1990.

#7. San Francisco Bay area circulation survey : 1979-1980, Joseph M. Welch, Jeffrey W.

Gartner, and Stephen K. Gill, 1985.

#8. Chesapeake Bay circulation survey, 1981-1983, David R. Browne and Carl W. Fisher,

1986.

#9. Delaware River and Bay circulation survey, 1984-1985, Alan S. Klavans, Peter J. Stone,

and Gina A. Stoney, 1986.

#10. Long Island Sound Oceanography Project : 1988-1990, editor: Karen L. Earwaker,

contributors: Gerald F. Appell et al., 1990.

#11. TampaBayOceanography Project : 1990-1991, Fran Nowadly, contributors: Gerald Appell

et al., 1992.

Data analysis results were published in a series of NOAA Technical Reports. The earlier ones were

published in the series NOAA Technical Report NOS.
48

#69. Tidal hydrodynamics in the Strait of Juan de Fuca - Strait of Georgia, Bruce B. Parker,

1977.

#80. Circulation and hydrodynamics ofthe lower Cape Fear River, North Carolina, Joseph M.

Welch and Bruce B. Parker, 1979.

#100. Tidal hydrodynamics and sediment transport in Beaufort Inlet, North Carolina, Alan S.

Klavans, 1983.

They were followed by the series NOAA Technical Report NOS OMA,

#3. Tide and tidal currentsin the Chesapeake Bay, David R. Browne and Carl W. Fisher, 1988.

and by the series NOAA Technical Report NOS OES.

#2. Tampa Bay Oceanography Project: physical oceanographic synthesis, editor: Chris E.

Zervas, contributors: Kathryn T. Bosley et al., 1993.

#3. Long Island Sound Oceanography Project: summary report, Richard A. Schmaltz, Jr., 1994.

The results of data analysisfor more limited projects (some knownas miniprojects) were published

as NOAA Technical Memorandums. The earlier publications were in the series NOAA Technical

Memorandum NOS OMA.

#50. Tampa Bay current prediction quality assurance miniproject, Robert G. Williams, Thomas

D. Bethem, and Henry R. Frey, 1989.

#53. Houston Ship Channel/Galveston Bay current prediction quality assurance miniproject,

Robert G. Williams, Henry R. Frey, and Thomas D. Bethem, 1990.

#60. Corpus Christi Bay current prediction quality assurance miniproject, Robert G. Williams

et al., 1991.

The following publications were in the series NOAA Technical Memorandum NOS OES.

#2. Quality assurance of Tampa Bay PORTSTM: current measurementes atthe Sunshine Skyway

Bridge, C. Reid Nichols, Robert G. Williams, and Gerald F. Appell, 1992.

#3. San Francisco Bay current prediction quality assurance miniproject, Robert G. Williams,

Wayne L. Wilmot, and Henry R. Frey, 1993.

#8. Special 1994 tidal current predictions for Aransas Pass, Corpus Christi, Texas, C. Reid

Nichols, 1994.

#9. TampaPORTSTM voice data response systemdescription and access statistics, May1993 -

May 1995, Thomas D. Bethem, 1995.
49

#10. National Ocean Service partnership: real-time environmental monitoring in upper San

Francisco Bay: final report, Kurt W. Hess et al., 1996.

#14. Special 1995 tidal current predictions for Galveston Bay, Texas, Karen L. Earwaker, C.

Reid Nichols, and William T. Ehret, 1995.

APPENDIX B

Tidal Current Reference Station Summary. Comments include information from Form C&GS-444, type of instrument, and number

of secondary stations (based on the 1998 NOS Tidal Current Tables). National Water Level Observation Network Stations and long

term control tide stations associated with the Tidal Current Reference Stations are listed in italics. Footnotes from Official Form 696

denoted by “<x>” are listed at the end of this table. 

Station Name

Location Year Data 

Obtained Duration Comments

Latitude N Longitude W

Admiralty Inlet (off Bush

Point),

WA <5>

Port Townsend

48o01.8'

48o06.9'

122o38.22'

122o45'

1908, 1942 &

1943

means of 29d(2),

32d, 26d & 36d

2 ebbs+flood=3 consecutive ebbs; short period comps inc

10%; M4, M6, M8 not used because of lg var in kappas

from diff analyses. 

Pole (1908) and Roberts CM (1942&1943), 

75 sub sta ref to Admiralty Inlet

Akutan Pass, Aleutian Islands,

AK

 

Unalaska

54o01'

53o52.8'

166o03'

166o32.3'

1950 24 day series

7/31/50 - 

compared to

tides; S2 kappas

from 15-day HA

1 yr pred (1952) gives tropic ebb 8.0kts. T.M officially

changed 10/30/83. Predicted speeds > or = 7.5 knots must

be modified according to a scale on C&GS 444. Slack int &

avg vel from 1952 pred; Fld & Ebb int & tropic vel from

Form 180. Harmonic const from 24 day. 

Roberts Current Meter at 15ft depth,

 7 sub sta ref to Akutan Pass

Aransas Pass (btw jetties), TX

Corpus Christi

27o50.03'

27o34.8'

97o02.65'

97o13.0'

1990 4/9-5/7 NOS Analysis for 15ft bel MLLW. 

ADCP, 3 sub sta ref to Aransas Pass

Baltimore Harbor Approach

(off Sandy Point), MD

Annapolis

39o00.78'

38o59'

76o22.10'

76o28.8'

1963 8/14 (29days) C&GS 29d HA; short period components inc 7%; used anal

values > or = 0.030; Used inferred values >or=0.010;

published vel < 0.3 knot as “weak and variable”. 

Roberts Current Meter, 

155 sub sta ref to Baltimore Harbor Approach

Bay of Fundy Entrance (Grand

Manan Channel)

 Eastport, ME

44o45.0'

44o54.0'

66o56.0'

66o59.0'

1960 June -July, 1960

29d(2)

Data received from Canada; slack intervals obtained from 4

months reduction of 1964 Canadian predictions. Ratio =

Spring vel/mean = 1.13 Time Meridian = 60o. 

?instr, 135 sub sta ref to Bay of Fundy

51
Station Name

Location Year Data 

Obtained Duration Comments

Latitude N Longitude W

52

Boston Harbor (off Deer Isl

Light), MA (north component)

Boston

42o20.267'

42o21.3'

70o57.317'

71o03'

1971 NOS lsqha

5/10-10/26

Supercedes rev cur pred beg w/1976 ACCT; rotary current;

use both n&e component sheets for predictions. 

Aanderaa RCM4, 153 sub sta ref to Boston Harbor

Boston Harbor (off Deer Isl

Light), MA (east component)

42o20.267' 70o57.317' 1971 lsqha

5/10-10/26

Rotary current; use both n&e component sheets for

predictions

Cape Cod Canal (R.R.Bridge),

MA

Cape Cod Canal, Buzzards Bay

 Entrance (1975)

41o44.5'

 

41o44'

70o36.8'

70o37'

1956 15day cur & 29d

(2) tide series

Hydraulic cur sta; two 29d tide obs (8/55) at @ end of

canal land cut & 15 d cur (10/56); Col A includes time lag

of 0.55hr & 15% inc in Col B; kappas derived from orig

values of kappa primes from analysis. 

Roberts Current Meter, 

16 sub sta ref to Cape Cod Canal

Carquinez Strait, w end

bridge, CA 

Port Chicago

38o03.68'

 

38o03.4'

120o13.1'

 

120o02.3'

1980 4/3/80 -11/12/80

(224 days)

NOS 224d lsqha at 39ft bel MLLW; first used in 1989

PCCT; 2MN2 used in place of L2; 

Aanderaa RCM4, 57 sub sta ref to Carquinez Strait

Charleston Harbor Entr (off

Fort Sumter), SC 

Charleston

32o45.36'

32o46.9'

79o52.22'

79o55.5'

1987-1988 5/26/87-7/28/88 NOS lsqha first used in 1997 ACCT; 

superceded 1962 C&GS 29dHA, 

ADCP, 227 sub sta ref to Charleston Hbr

Chesapeake Bay Entrance,

VA Chesapeake Bay Bridge

Tunnel

36o58.78'

36o58.1'

75o59.93'

76o06.8'

1982 330 days

beginning

3/30/82 

NOS analysis at 27 ft bel MLLW; 1st used in 1988 ACCT

Grundy current meter,

247 sub sta ref to Ches Bay Entr

Chesapeake and Delaware

Canal (Chesapeake City), MD

Chesapeake City (1972-1983)

39o32'

39o32.023'

75o49'

75o49.014'

1938 51⁄2 days obs at

Ches City

Bridge; June 7 -

July 14, 1938

Hydraulic cur sta; Series by US Engineers; constant “C”

factor = 1.85; Col A time lag correction = 0.86 hr; Orig

form 444 gave values of kappa from which these kappas

were computed; Constants rep diff in H2O levels btw

Cthouse Pt (369 days) & Reedy Pt (369 days), the fld or

possitve flow taken as eastward. 

Pole, 8 sub sta ref to Ches & DE Canal
Station Name

Location Year Data 

Obtained Duration Comments

Latitude N Longitude W

53

Deception Pass (Narrows),

WA <6>

Cherry Pt

48o24'

48o51.8'

122o38'

122o44.9'

1925 29 day series

9/9/25 - 10/9/25

Hydraulic current sta; M2 inc 5%, K1 adv 10o; constant

“C” factor = 18.4, Col A time lag = 0.87 hr. Epochs

modified by 180o so that east going stream may be

considered as positive. Constants rep diff in elev btw

Yokeko Pt. & Reservation Bay; the elev of YP above RB

being taken as positive. 

Zeskind float, 4 sub sta ref to Deception Pass

Delaware Bay Entrance, DE 

Lewes 

38o46.85'

38o46.9'

75o02.58'

75o07.2'

1984 221 days; 

4/25/84 -12/1/84

NOS analysis at 22ft bel MLLW; 1st used in 1987 ACCT

Grundy current meter,

92 sub sta ref to DE Bay Entr

Galveston Bay Entrance

(between jetties), TX 

Port Bolivar

29o20.8'

29o21.8'

94o42.3'

94o46.7'

1935 two 29day series

beginning 

4/5/35 &

4/10/35

Two 29-day series corrected by comparison w/Gal tides;

short period comp inc by 5%; may be tabulated as 3

consecutive ebbs where spd <0.3kt is “weak & variable”. 

Pole, 21 sub sta ref to Galv Bay Entr

Grays Harbor Entrance, WA

 

Toke Point

46o55.0'

46o42.4'

124o07.5'

123o57.9'

1950 29 day (half

hourly obs)

beginning

3/25/50

Analysis of half hourly obs; short period comps inc by 1%. 

Roberts current meter, 

44 sub sta ref to Grays Harbor

Hell Gate (off Mill Rock) East

River, NY <1>

 

The Battery

40o46.7'

40o42'

73o56.3'

74o00.9'

1932 35 days of time

from stations 2,5,6

and 11 days of vel

from station 6,

which is in the

center of the

channel.

Hydraulic cur sta; Diff in elev btw Willets Pt and Gov Isl

(GI above WP taken as positive); Constant “C” factor =

3.520, Col A includes time lag of 0.64 hr, Col D values for

M4 and M6 are revised to agree w/mean from tidal and

current constants from Station #6; 

Pole, 33 sub sta ref to Hell Gate

Isanotski Strait (False Pass

Cannery), AK

 

Sand Point

54o52'

55o20.2'

163o24'

160o30.1'

1940

1925 (water

levels)

6 days obs in

May 1940

Hydraulic current station. Constants represent diff in ht of

tide at King Cove & False Pass. Time zone officially

changed from 165oW to 135oW on 10/30/83; New time

reflected 1st in 1985 PCCT. Constant “C” factor = 6.0, Col

A time lag = 1.1hr. Constants 1st used in 1973 PCCT. 

Pole, 11 sub sta ref to Isanotski Strait
Station Name

Location Year Data 

Obtained Duration Comments

Latitude N Longitude W

Key West, FL

Key West

24o32.9'

24o33.2'

81o49.0'

81o48.5'

1954 29 days of half

hourly speeds

beginning

1/22/54

C&GS analysis of half hrly obs. New obs in 1965 indicated

a need to revise orig const. Dredging of channels caused a

diff. Orig ampl were inc 26.6%. Times were adjusted to

0.2hr earlier via Col A. New perm current = -0.3kts.

Constants 1st used in 1967 ACCT. 

Roberts current meter, 18 sub sta ref to Key West

Kvichak Bay (off Naknek River

Entrance), AK 

Sand Point

58o42.2'

55o20.2'

157o15.0'

160o30.1'

1946 14 days

beginning

9/16/46

Short period comps inc 12%. Time zone officially changed

from 150o W to 135oW on 10/30/83. New time 1st reflected

in 1985 PCCT. 

Pole, 39 sub sta ref to Kvichak Bay

Miami Harbor Entrance

(Government Cut), FL 

Virginia Key

25o45.9'

25o43.9'

80o08.2'

80o09.7'

1985 29 days 

beginning

1/18/85

NOS analysis first used in 1987 ACCT

GONiskin winged CM (Model 6011 MK2), 

45 sec sta ref to Miami Harbor Entrance

Mobile Bay Entrance, AL

 

Dauphin Island

30o14'

30o15'

88o02'

88o04.5'

1935 29 day

beginning

5/24/35

29 day series in 1935 w/amplitudes inc 10% except M2 &

S2 which are from 15 days in 1918 (weight 1) and 29 days

in 1935 (weight 2). Inferred values > or = 0.01 except for

M4 & M6, published speeds < 0.3 kts = “weak and

variable” 

Pole, 14 sub sta ref to Mobile Bay Entrance

North Inian Pass, Cross Sound,

AK

 

Juneau

58o17'

58o17.9'

136o23'

134o24.7'

1925

1901 (104

days water

levels)

21⁄2 days Harmonic tidal constants at Hoonak. Time zone changed

from 120oW to 135oW on 10/30/83. New times reflected 1st

in 1985 PCCT. Published spd < 0.3kts = “weak &

variable”Tropic inequalities for flood & ebb as derived

from pred for 1932 are flood=1.2 and ebb = 2.06. 

Zeskind Float, 28 sub sta ref to North Inian Pass

Old Port Tampa, Old Tampa

Bay, FL

St Petersburg

27o51.9'

27o46.012'

82o33.2'

 

82o37.016'

1990-91 6/25/90 -

9/11/91 (457

days)

NOS LSQHA, major axis only; minor axis insignificant.

First used in 1994 ACCT. 

ADCP, 16 sub sta ref to Old Tampa Bay

54
Station Name

Location Year Data 

Obtained Duration Comments

Latitude N Longitude W

Pollock Rip (Butler Hole)

Channel, MA <2>

Nantucket

41o32.8'

41o17.2'

69o59.1'

70o05.7'

1934, 1935,

1936

748 days 

8/6/34-8/31/36

Used analyzed values > or = 0.030 and inferred values >

or= 0.010

 from Narragansett Bay & Nantucket Sound, 

Pole, 115 sub sta ref to Pollack Rip

Portsmouth Harbor

Entrance, (off Wood Isl), NH

<3>

Seavey Island, ME

43o04'

43o04.9'

70o42'

 

70o44.7'

1926 15 days; pole &

Price Current

Meters from 1926;

Roberts in 1953

wasn’t used in

tables

From HA of 3 short series of obs corrected by comparison

w/constants from simultaneous tidal obs at Portland ME.

Short period comp inc 20%. When times of max flood scan

backwards, change them to make them progressive. 

Pole & Price (1926); Roberts (1953), 

82 sub sta ref to Portsmouth

Rosario Strait, WA

Cherry Point 

48o27.53'

48o51.8'

122o46.75'

122o44.9'

1965 29 days

beginning

3/10/65

C&GS 29day HA first used in 1967 PCCT. Ampl inc 11%. 

Geodyne current meter, 

46 sub sta ref to Rosario Strait

San Diego Bay Entrance (off

Ballast Point), CA

San Diego

32o40.9'

32o42.9'

117o13.8'

117o10.4'

1934 29 days

beginning

8/24/34

Used analyzed $ 0.03kts and inferred $ 0.010kts. Mean of

Pole & meter, 

27 sub sta ref to San Diego Bay Entr 

(20 in CA&7 in HI)

San Francisco Bay Entrance

(Golden Gate), CA <7>

 

Golden Gate

37o48.63'

37o48.4'

122o30.13'

122o27.9'

1923

&

1930

(3 days)

7 days

beginning

10/19/23

These constants are inferred from an analysis of hourly speedsfor 7

days compared w/ a simultaneoustidal analysis at Presidio and best

determined values for Presidio. M2, M4, M6 obtained by

combining orig constants from above method w/ constants from an

analysis of diff btw predicted & obs speeds for the same series.

Empirical corrections for K1, O1, and P1 obtained through

comparison w/obs Pole; 136 sub sta ref to SF Bay Entr

San Juan Channel(south

entrance), WA

Friday Harbor

48o28'

48o32.7'

122o57'

123o00.7'

1964 29 days

beginning

5/21/64

C&GS analysis where short period components are

increased 6% and published speeds < 0.3kts are “weak and

variable”. Roberts Current Meter, 

13 sub sta ref to San Juan Channel

55
Station Name

Location Year Data 

Obtained Duration Comments

Latitude N Longitude W

Savannah River Entrance

(between jetties), GA

Ft Pulaski

32o02.2'

32o02'

80o51.5'

80o54.1'

1934 two 15-day

series beginning

5/1/34

Means of two 15-day series of hourly speeds beginning

5/1/34 corrected by comparison w/Tybee Light, GA tides.

Correction of 0.15 hr to speeds of each component to make

predicted times later.

Pole, 124 sub sta ref to Savannah River Entr

Sergius Narrows, Peril Strait,

AK

 

Sitka

57o24.4'

 

57o03.1'

135o37.6'

135o20.5'

1952 6 days

beginning

5/25/52

Hydraulic cur sta. Kappa prime is mean of values derived

from 6 days of obs analysis & derived from tidal constants

from Sitka and Sergius Narrows. Time zone officially

changed from 120oW to 135oW on 10/30/83. New TM 1st

appear in 1985 PCCT. “C” factor = 5.0. (Oldest sec sta 1895).

Roberts Current Meter, 62 sub sta ref to Sergius Narrows

St. Johns River Entrance, FL

Mayport

30o24.0'

30o23.6'

81o23.0'

81o25.9'

1934 means of two 

15-day series

beginning

1/4/34

Corrected by comparison w/Mayport tides. Series are half

hourly where M2, M4, & M6 were inc 3%. 

Pole, 17 sub sta ref to St Johns River Entrance

Strait of Juan de Fuca

Entrance, WA <8>

Neah Bay

48o27'

48o22.1'

124o35'

124o37'

1931 (2 days

obs direction)

7/23/31 -

7/25/31 (2 days)

& 1 mo pred

(1945) at

Admiralty Inlet

Inferred from Admiralty Inlet such that constants in Col B =

1⁄2 those at Admiralty Inlet and kappa prime values = 30

min earlier. Short period components inc 10% Pub speeds

may be tabulated as 3 consecutive ebbs +/or “weak and

variable”.

Pole, 1 sub sta to Strait of Juan de Fuca

Sunshine Skyway Bridge,

Tampa Bay, FL

St Petersburg

27o37.2'

27o46.012'

82o39.3'

82o37.016'

1990 - 1991 292 days; 

8/22/90 -

6/10/91

NOS LSQHA at 15 ft below MLLW first used in 1994

ACCT. Minor axis insignificant. 

ADCP, no subordinate stations

Tampa Bay Entrance (Egmont

Channel), FL

Clearwater

27o36.3'

27o58.6'

82o45.6'

82o49.9'

1990 - 1991 401 days; 

8/20/90 -

9/25/91

NOS LSQHA at 15 ft below MLLW 1st used in 1994

ACCT. Minor axis insig.

ADCP, 54 sub sta ref to Egmont

56
Station Name

Location Year Data 

Obtained Duration Comments

Latitude N Longitude W

The Narrows (north end), Puget

Sound, WA

 

Seattle

47o18'

47o36.2'

122o33'

122o20.2'

1944 28 day series

beginning

1/19/44

Based on 28-day series at station 26 & compared w/tides at

Seattle. Short period comp inc 5%. Values for N2 spec

determined from 2 short series. Pred are for midstream. W

side currents flood most of the time; 

east side ebbs most of the time. 

Roberts Current Meter,

 31 sub sta ref to The Narrows Puget Snd

The Narrows, New York

Harbor, NY <4>

Sandy Hook, NJ

40o36.6'

 

 40o28.0'

74o02.8'

 

 74o00.6'

1932 29 days; 

8/18/32 -

9/16/32

C&GS analysis of US Engineers’ obs. Short period

components inc 9%. 

Pole, 77 sub sta ref to The Narrows New York Harbor

The Race, Long Island Sound,

NY

New London, CT

41o14.0'

41o21.3'

72o03.6'

72o05.2'

1989 72 days 

(1/1/89 -

3/13/89)

NOS average of 2 29-day HA’s at 38 ft below MLLW. First

used in 1994 ACCT. Minor axis negligible.

 ADCP (89); 155 sub sta ref to The Race

Throgs Neck, Long Island Sound,

NY

Willets Point

40o48.6'

 

40o48'

73o47.1'

 

73o47'

1989 483 days; 

3/30/88 -

10/3/89

NOS average of 16 29-day HA’s at 15 ft below MLLW.

First used in 1994 ACCT. Minor axis negligible 

ADCP (89), 16 sub sta ref to Throgs Neck

Unimak Pass (off Scotch Cap),

Aleutian Islands, AK 

 

Unalaska

54o21.9'

53o52.8'

164o48'

 

166o32.3'

1938 and

1950

11 1⁄4 days

(1938) and 33

broken days

(1950)

Combination of constants from 3 series of pole obs in 6/38

& 7/38 of 4 1⁄4, 4 & 3 days w/33 days of broken series

w/meter beg 6/14/50. Short period components inc 3%.

Station exhibits a min flood (0kt). Time zone officially

changed from 165o to 135oW on 10/30/83.

 New times reflected 1st in 1985 PCCT. 

Pole, 35 sub sta ref to Unimak Pass

Wrangell Narrows (off

Petersburg), AK

Ketchikan

56o49'

55o20'

132o58'

131o37.5'

1925 16 days in Aug Derived from tidal constants for Petersburg, AK. Corrected

by using channel dir & inc speeds by10%(25). Short period

comps inc 6%. Time zone officially changed from 120o

 to

135oW on 10/30/83; new TM appeared in 1985 PCCT

Zeskind Float, 345 sub sta ref to Wrangell Narrows

57
58

Footnotes:

<1> Hell Gate (off Mill Rock) East River, NY: Observations by US Engineers 1932. Greenwich interval times are from mean of results from stations 2, 5, &

6 totaling about 35 days. Velocities are from Station 6 (11 days) which is in the center of the channel. Predictions are made w/harmonic constants derived

from tidal constants at Willets Pt. (2 yrs, 1891&1894) and Governors Island (3 yrs., 1876-1878), the constants giving the diff in elev of tide at WP and

GI. Predictions for 1934 obtained from revised constants using lag of 0.64 hr, ebb set of 0.6kt, M4 kappa prime = 106.6, M6 kappa prime = 111.0. Using

these constants, predictions for May 1932 are: Gr SBF=9:03, Gr MFC=11:59 3.26kt, Gr SBE=2:33, Gr MEC =5:35 4.53kts. Spring vel = 3.8kts (flood)

and 5.0kts (ebb) where Spring (Sg) vel = avg vel * sqrt (1.2) where 1.2 = Sg/Mean at The Battery and Willets Point.

<2> Pollock Rip Channel (Butler Hole) MA: One year of observations at Stonehorse Lightship (9/1/34 - 8/31/35) w/15 ft pole. Two years “plus” (748 days)

8/6/34 - 8/31/36 w/15 ft pole. First used as reference station in 1937. Sg vel = Av vel * [(M2 + S2)÷M2]where [(M2 + S2)÷M2] = 1.15. From predictions

for Jan 1937: Greenwich Intervals and corrected velocities are: SBF 7:55, MFC 11:17, MFC vel 1.92 (kt), SBE 1:59, MEC 4:48, MEC vel 1.69 (kt).

Notified by Englebrecht that Lightship was removed. Form 696 has (Butler Hole, MA). Flood differences = 6 hr 32 min; Ebb differences = 5 hr 53 min.

Velocities at strength MFC = 2.0 kts, MEC = 1.8 kts; Spring tide MFC = 2.3 kts and MEC = 2.1 kts.

<3> Portsmouth Harbor Entrance (off Wood Island) NH: Data from pole and meter (9ft and 22ft) copied from “Standard Station Summary” sheet. Radio

current meter at Sta 7 9/16/53 - 10/1/53 at 15 ft depth may have questionable directions, particularly flood. Channel is almost N-S (dated 4/26/55) and

directions for MFC = 40o and MEC = 170o. Maximum obs vel = 2.2kts, 142o (1953). Data first used in 1934. Remarks: flood diff = 5hr 47min and [(M2

+ S2)÷M2] where [(M2 + S2)÷M2] = 1.16. Average flood vel = 1.2kts, ebb = 1.8kts; mean spring tide = 1.7kts.

<4> The Narrows, New York Harbor, NY: 28 days of data (8/18/32 - 9/16/32) collected by US Engineers - Sta 1 (meter at 16.8 ft) Directions are from 11 days

in 1922 at Sta 9. Amplitudes are multiplied by 1.09 to make predictions agree with observations. This station was first used as a reference station

beginning with 1976 Current Tables. It is predicted with north and east components as a rotary current. Average flood vel = 1.7 knots, ebb = 2.0 knots,

mean spring tide = 2.2 knots.

<5> Admiralty Inlet, WA: Mean of the results from following series: 26 days 1908 (Derickson), 32 days 1942 (EB Roberts), 26 days 1943 (Sta 14) (EB

Roberts) and 36 days 1943 (Sta 1) using EB Roberts. Using constants from obs in those 4 years give predictions for 1946 as FL vel 1.6 knots and EB

vel 2.6 knots. Remarks: Total current vel from Form 180 - Constants used for predictions. Predictions for years 1945 and 1946 give total current flood

2.6 knots and total current ebb 3.2 knots.Mean GI(from 4 years): SBF=8.06hr, MFC=10.32hr, SBE=0.29hr, MEC=4.11hr. There are 26 secondary stations

referenced to Admiralty Inlet. Most surveyed in 1946 and 1965 with Roberts Current Meters.

<6> Deception Pass, WA: Based on float (Zeskind) observations from 9/9/25 - 10/9/25. Slacks (9/9/25 - 10/9/25) and strengths (9/13 - 9/17/25). Slacks

averaged 3 min later than the full time series so strengths were decreased by 3 min to obtain the GI: SBF=5hr20min, MFC=8hr16min, SBE=11hr14min,

MEC=1hr31min. Avg flood vel 5.2 & ebb 6.6 knots.
59

<7> San Francisco Bay Entrance (Golden Gate): Weighted mean of 7 days, Oct 19-26, 1923 (Shoppe Sta No 10 - Weight 2). Pole only. Weight 1 = 3 days

May 1-2, 27-29, 1930 by US Eng Sec. R, Sta 3 at 10 foot depth. Velocities are from Shoppe’s observations. Tropic velocities are from 1 year predictions

in 1935. 22 Secondary stations are referenced to San Francisco Bay Entrance. In 1990 ref sta changed from Alcatraz to SFB Entr.

<8> Strait of Juan de Fuca: One month prediction (July 1945) using new Admiralty Inlet constants; less 30 min and amplitudes times 0.5. Directions are from

2 days observations by K.T. Adams, July 22-25, 1931, Station #1. Observations five flood velocity 0.5 knots, ebb velocity 1.4 knots.
60

APPENDIX C

Leading U. S. Ports Ranked by Total 1995 Tonnage

PORT_NAME TOTAL DOMESTIC FOREIGN IMPORTS EXPORTS

South Louisiana, LA, Port of 204,482,591 106972579 97510012 28867399 68642613

Houston, TX 135,231,322 63694434 71536888 42859905 28676983

New York, NY and NJ 119,341,574 71281214 48060360 38728644 9331716

Baton Rouge, LA 83,612,788 45384087 38228701 26564120 11664581

Valdez, AK 80,955,084 80881706 73378 0 73378

New Orleans, LA 76,984,036 37962557 39021479 18770926 20250553

Plaquemine, LA, Port of 72,897,301 48466434 24430867 7854328 16576539

Corpus Christi, TX 70,456,033 25885340 44570693 38624945 5945748

Long Beach, CA 53,227,490 19738999 33488491 15994553 17493938

Tampa, FL 51,911,335 31812115 20099220 6069656 14029564

Mobile, AL 50,972,223 25083220 25889003 11711441 14177562

Texas City, TX 50,402,938 19213208 31189730 29980279 1209451

Port Arthur, TX 49,799,977 6763743 43036234 36864423 6171811

Pittsburgh, PA 48,849,508 48849508 0 0 0

Norfolk Harbor, VA 47,658,182 10283351 37374831 5543382 31831449

Lake Charles, LA 46,569,641 19740706 26828935 21615421 5213514

Los Angeles, CA 46,478,586 19063467 27415119 13550393 13864726

Duluth-Superior, MN and WI 45,049,184 34932890 10116294 1425472 8690822

Baltimore, MD 44,695,812 13098369 31597443 14359323 17238120

Philadelphia, PA 40,634,284 12763551 27870733 27151633 719100

Portland, OR 31,255,509 13616851 17638658 2714802 14923856

Marcus Hook, PA 30,818,134 14549103 16269031 16222985 46046

St. Louis, MO and IL 30,137,632 30137632 0 0 0

Huntington, WV 28,265,731 28265731 0 0 0

Pascagoula, MS 26,926,582 9481727 17444855 14735302 2709553

Seattle, WA 26,179,838 6041194 20138644 7567122 12571522

Chicago, IL 25,329,030 22082501 3246529 2206262 1040267

Paulsboro, NJ 24,780,664 11645610 13135054 12984722 150332

Newport News, VA 23,365,005 5170196 18194809 1794695 16400114

Beaumont, TX 20,937,132 14922961 6014171 4026335 1987836

Tacoma, WA 20,878,751 7026469 13852282 4009359 9842923

Richmond, CA 20,839,258 15034485 5804773 3649403 2155370

Freeport, TX 19,661,621 5475882 14185739 12271130 1914609

Detroit, MI 18,660,925 15002672 3658253 3051172 607081

Port Everglades, FL 18,367,389 10238202 8129187 6254011 1875176

Savannah, GA 17,379,724 3566640 13813084 6437974 7375110

Boston, MA 16,744,386 9637706 7106680 6363958 742722

Memphis, TN 15,944,945 15944945 0 0 0

Indiana Harbor, IN 15,700,153 15019457 680696 640254 40442
PORT_NAME TOTAL DOMESTIC FOREIGN IMPORTS EXPORTS

61

Jacksonville, FL 15,692,999 8740054 6952945 5062499 1890446

San Juan, PR 15,477,965 10900245 4577720 3775480 802240

Cleveland, OH 15,393,496 12323290 3070206 2655471 414735

Lorain, OH 14,964,284 14839878 124406 124406 0

Toledo, OH 14,074,499 7240352 6834147 1376781 5457366

Oakland, CA 13,224,118 2523900 10700218 4330630 6369588

Anacortes, WA 13,109,828 11120181 1989647 538040 1451607

Cincinnati, OH 13,068,362 13068362 0 0 0

New Castle, DE 12,455,809 4874803 7581006 7540893 40113

Honolulu, HI 11,545,102 9374582 2170520 1923739 246781

Portland, ME 11,456,007 2015780 9440227 9295191 145036

Kalama, WA 11,346,546 660579 10685967 15754 10670213

Charleston, SC 11,171,597 3818269 7353328 3326472 4026856

Galveston, TX 10,465,119 3815125 6649994 1986010 4663984

Burns Waterway Harbor, IN 10,275,176 7603119 2672057 2206600 465457

Presque Isle, MI 10,099,422 8307672 1791750 30173 1761577

Ashtabula, OH 10,010,229 6172507 3837722 1074963 2762759

Gary, IN 9,978,301 9626559 351742 181175 170567

Taconite, MN 9,247,361 9247361 0 0 0

Matagorda Ship Channel, TX 9,237,437 2689155 6548282 5771996 776286

Louisville, KY 8,999,282 8999282 0 0 0

New Haven, CT 8,812,648 6402487 2410161 2218489 191672

Escanaba, MI 8,479,428 8479428 0 0 0

Stoneport, MI 8,467,755 7413215 1054540 33215 1021325

Calcite, MI 8,380,892 6520896 1859996 0 1859996

Two Harbors, MN 8,265,384 8265384 0 0 0

Barbers Point, Oahu, HI 8,232,732 3507894 4724838 3974002 750836

Mount Vernon, IN 8,225,907 8225907 0 0 0

Wilmington, NC 7,860,740 3969329 3891411 2717451 1173960

Vancouver, WA 7,534,764 2173470 5361294 893875 4467419

Providence, RI 6,932,109 4821471 2110638 1613395 497243

Miami, FL 6,578,860 1235938 5342922 2483652 2859270

Longview, WA 6,166,724 1172181 4994543 674806 4319737

Camden-Gloucester, NJ 5,919,077 2747343 3171734 2457449 714285

Albany, NY 5,802,920 4348716 1454204 870288 583916

Conneaut, OH 5,611,533 2986146 2625387 29123 2596264

Vicksburg, MS 5,127,950 5127950 0 0 0

Port Inland, MI 5,050,272 4630101 420171 31144 389027

St. Clair, MI 5,028,413 5026826 1587 1587 0

St. Paul, MN 4,769,608 4769608 0 0 0

Nikishka, AK 4,699,710 3376826 1322884 3 1322881

Victoria, TX 4,624,192 4624192 0 0 0

Morehead City, NC 4,577,242 1815307 2761935 732469 2029466
PORT_NAME TOTAL DOMESTIC FOREIGN IMPORTS EXPORTS

62

Everett, WA 4,440,858 3017536 1423322 384659 1038663

Silver Bay, MN 4,348,458 4348458 0 0 0

Wilmington, DE 4,272,719 782514 3490205 3051774 438431

Portsmouth, NH 3,913,882 813055 3100827 2770435 330392

Marine City, MI 3,850,333 3850333 0 0 0

Nashville, TN 3,748,978 3748978 0 0 0

Coos Bay, OR 3,628,036 151748 3476288 52140 3424148

Sandusky, OH 3,536,000 888431 2647569 3500 2644069

Marblehead, OH 3,517,954 2990864 527090 4 527086

Bridgeport, CT 3,447,062 3001601 445461 433546 11915

Fall River, MA 3,279,988 2542609 737379 720330 17049

Milwaukee, WI 3,262,288 1632597 1629691 868474 761217

Port Dolomite, MI 3,261,858 2975002 286856 13635 273221

Anchorage, AK 3,221,587 2269546 952041 251338 700703

Palm Beach, FL 2,972,159 2154336 817823 315169 502654

Fairport Harbor, OH 2,941,343 2376289 565054 47576 517478

Panama City, FL 2,890,579 2395807 494772 68266 426506

Port Canaveral, FL 2,816,904 1218140 1598764 1245094 353670

Alpena, MI 2,766,717 2604507 162210 31833 130377

Guntersville, AL 2,754,096 2754096 0 0 0

Brownsville, TX 2,656,193 1043221 1612972 497062 1115910

Kahului, Maui, HI 2,586,230 2510919 75311 74941 370

Chattanooga, TN 2,525,377 2525377 0 0 0

Kansas City, MO 2,371,609 2371609 0 0 0

Olympia, WA 2,165,575 1998723 166852 4858 161994

Green Bay, WI 2,122,138 1899193 222945 190486 32459

Gulfport, MS 2,023,084 86089 1936995 1231432 705563

Port Jefferson, NY 2,018,078 1855389 162689 162689 0

Brunswick, GA 2,002,489 232582 1769907 996787 773120

Helena, AR 1,964,582 1964582 0 0 0

Monroe, MI 1,919,912 1867024 52888 6578 46310

Port Angeles, WA 1,910,512 1010344 900168 305137 595031

Greenville, MS 1,873,694 1873694 0 0 0

Buffalo, NY 1,872,534 1324335 548199 487459 60740

Muskegon, MI 1,824,617 1648715 175902 175902 0

Ketchikan, AK 1,821,127 1473285 347842 108889 238953

Biloxi, MS 1,739,456 1739456 0 0 0

Pensacola, FL 1,622,528 1143417 479111 123584 355527

Drummond Island, MI 1,606,078 1402869 203209 0 203209

Charlevoix, MI 1,584,187 1521893 62294 0 62294

Grays Harbor, WA 1,565,708 101185 1464523 130 1464393

Tulsa, Port of Catoosa, OK 1,473,584 1473584 0 0 0

Buffington, IN 1,447,039 1416589 30450 0 30450
PORT_NAME TOTAL DOMESTIC FOREIGN IMPORTS EXPORTS

63

Chester, PA 1,388,968 271641 1117327 885718 231609

Hilo, HI 1,354,365 1303890 50475 49986 489

San Diego, CA 1,351,482 616598 734884 258589 476295

San Francisco, CA 1,330,066 517591 812475 324458 488017

Stockton, CA 1,320,462 129887 1190575 724516 466059

Minneapolis, MN 1,299,922 1299922 0 0 0

Bellingham, WA 1,291,373 530812 760561 400547 360014

Searsport, ME 1,262,712 417246 845466 808638 36828

Bucksport, ME 1,237,542 379639 857903 856294 1609

Georgetown, SC 1,233,580 69198 1164382 1072812 91570

Humboldt, CA 1,220,383 599221 621162 59016 562146

Salem, MA 1,197,416 395561 801855 801732 123

Ludington, MI 1,149,952 1107581 42371 8311 34060

Sacramento, CA 1,137,456 199390 938066 58379 879687

Richmond, VA 1,135,106 581063 554043 300572 253471

Ponce, PR 1,134,115 231 1133884 959193 174691

Nawiliwili, Kauai, HI 1,129,612 1113657 15955 15955 0

Erie, PA 1,056,727 936901 119826 108534 11292

Stamford, CT 994,083 994083 0 0 0

Astoria, OR 985,471 160976 824495 101747 722748

Trenton, NJ 963,860 963860 0 0 0

Grand Haven, MI 961,189 769042 192147 68016 124131

Hopewell, VA 934,835 634493 300342 9891 290451

Seward, AK 927,669 28210 899459 4975 894484

Marquette, MI 835,761 835761 0 0 0

Redwood City, CA 753,912 383784 370128 217211 152917

Orange, TX 692,720 619158 73562 0 73562

Charlotte, FL 637,175 637175 0 0 0

New London, CT 623,313 571372 51941 51941 0

Port Huron, MI 487,905 361332 126573 110171 16402

Oswego, NY 435,065 25623 409442 409433 9

Manistee, MI 431,966 426402 5564 5564 0

Dunkirk, NY 373,946 373946 0 0 0

Port Townsend, WA 362,406 339272 23134 7061 16073

Lake Providence, LA 314,957 314957 0 0 0

Christiansted, St Croix, VI 286,710 144250 142460 79825 62635

Skagway, AK 264,519 24113 240406 93182 147224

Traverse City, MI 226,187 226187 0 0 0

Rochester, NY 169,563 0 169563 155879 13684

Key West, FL 140,676 140344 332 24 308

Cape Charles, VA 126,195 126195 0 0 0

Ashland, WI 100,051 100051 0 0 0

Harbor Beach, MI 87,642 87642 0 0 0
PORT_NAME TOTAL DOMESTIC FOREIGN IMPORTS EXPORTS

64

Sturgeon Bay, WI 71,250 71250 0 0 0

Alexandria, VA 62,137 0 62137 62023 114

Newport, RI 47,629 0 47629 47629 0

Ventura, CA 22,082 22082 0 0 0

Mackinac, MI 10,944 10944 0 0 0

Monterey Harbor, CA 9,330 9330 0 0 0

Cambridge, MD 5,081 5081 0 0 0

Morro Bay, CA 3,083 3083 0 0 0

Santa Monica, CA 193 193 0 0 0

Sackets Harbor, NY 12 12 0 0 0
65
66

APPENDIX D

1995 U.S. Port Tonnage Grouped by Tidal Current Reference Station

STATION NAME TOTAL DOMESTIC FOREIGN IMPORTS EXPORTS

Bay of Fundy Entrance, ME 2,500,254 796,885 1,703,369 1,664,932 38,437

Searsport, ME 1,262,712 417,246 845,466 808,638 36,828

Bucksport, ME 1,237,542 379,639 857,903 856,294 1,609

Portsmouth Harbor Entr., NH 15,369,889 2,828,835 12,541,054 12,065,626 475,428

Portsmouth, NH 3,913,882 813,055 3,100,827 2,770,435 330,392

Portland, ME 11,456,007 2,015,780 9,440,227 9,295,191 145,036

Boston Harbor, MA 17,941,802 10,033,267 7,908,535 7,165,690 742,845

Boston, MA 16,744,386 9,637,706 7,106,680 6,363,958 742,722

Salem, MA 1,197,416 395,561 801,855 801,732 123

Cape Cod Canal, MA 0

Pollock Rip Channel, MA 10,259,726 7,364,080 2,895,646 2,381,354 514,292

Newport, RI 47,629 0 47,629 47,629 0

Fall River, MA 3,279,988 2,542,609 737,379 720,330 17,049

Providence, RI 6,932,109 4,821,471 2,110,638 1,613,395 497,243

The Race, NY 15,895,184 12,824,932 3,070,252 2,866,665 203,587

Port Jefferson, NY 2,018,078 1,855,389 162,689 162,689 0

Stamford, CT 994,083 994,083 0 0 0

Bridgeport, CT 3,447,062 3,001,601 445,461 433,546 11,915

New Haven, CT 8,812,648 6,402,487 2,410,161 2,218,489 191,672

New London, CT 623,313 571,372 51,941 51,941 0

The Narrows, N.Y. Harbor, 125,144,494 75,629,930 49,514,564 39,598,932 9,915,632

Hell Gate and Throgs Neck, NY

New York, NY and NJ 119,341,574 71,281,214 48,060,360 38,728,644 9,331,716

Albany, NY 5,802,920 4,348,716 1,454,204 870,288 583,916

Delaware Bay Entrance, DE 121,233,515 48,598,425 72,635,090 70,295,174 2,339,916

New Castle, DE 12,455,809 4,874,803 7,581,006 7,540,893 40,113

Wilmington, DE 4,272,719 782,514 3,490,205 3,051,774 438,431

Marcus Hook, PA 30,818,134 14,549,103 16,269,031 16,222,985 46,046

Paulsboro, NJ 24,780,664 11,645,610 13,135,054 12,984,722 150,332

Chester, PA 1,388,968 271,641 1,117,327 885,718 231,609

Philadelphia, PA 40,634,284 12,763,551 27,870,733 27,151,633 719,100
STATION NAME TOTAL DOMESTIC FOREIGN IMPORTS EXPORTS

67

Camden-Gloucester, NJ 5,919,077 2,747,343 3,171,734 2,457,449 714,285

Trenton, NJ 963,860 963,860 0 0 0

Chesapeake & Delaware

Canal,MD 0

Baltimore Harbor Approach, MD 44,763,030 13,103,450 31,659,580 14,421,346 17,238,234

Cambridge, MD 5,081 5,081 0 0 0

Alexandria, VA 62,137 0 62,137 62,023 114

Baltimore, MD 44,695,812 13,098,369 31,597,443 14,359,323 17,238,120

Chesapeake Bay Entrance, VA 73,219,323 16,795,298 56,424,025 7,648,540 48,775,485

Norfolk Harbor, VA 47,658,182 10,283,351 37,374,831 5,543,382 31,831,449

Newport News, VA 23,365,005 5,170,196 18,194,809 1,794,695 16,400,114

Cape Charles, VA 126,195 126,195 0 0 0

Hopewell, VA 934,835 634,493 300,342 9,891 290,451

Richmond, VA 1,135,106 581,063 554,043 300,572 253,471

Charleston Harbor Entr., SC 24,843,159 9,672,103 15,171,056 7,849,204 7,321,852

Charleston, SC 11,171,597 3,818,269 7,353,328 3,326,472 4,026,856

Georgetown, SC 1,233,580 69,198 1,164,382 1,072,812 91,570

Wilmington, NC 7,860,740 3,969,329 3,891,411 2,717,451 1,173,960

Morehead City, NC 4,577,242 1,815,307 2,761,935 732,469 2,029,466

Savannah River Entrance, GA 19,382,213 3,799,222 15,582,991 7,434,761 8,148,230

Brunswick, GA 2,002,489 232,582 1,769,907 996,787 773,120

Savannah, GA 17,379,724 3,566,640 13,813,084 6,437,974 7,375,110

St. Johns River Entrance, FL 15,692,999 8,740,054 6,952,945 5,062,499 1,890,446

Jacksonville, FL 15,692,999 8,740,054 6,952,945 5,062,499 1,890,446

Miami Harbor, FL 30,735,312 14,846,616 15,888,696 10,297,926 5,590,770

Miami, FL 6,578,860 1,235,938 5,342,922 2,483,652 2,859,270

Port Everglades, FL 18,367,389 10,238,202 8,129,187 6,254,011 1,875,176

Palm Beach, FL 2,972,159 2,154,336 817,823 315,169 502,654

Port Canaveral, FL 2,816,904 1,218,140 1,598,764 1,245,094 353,670

Key West, FL 140,676 140,344 332 24 308

Key West, FL 140,676 140,344 332 24 308
STATION NAME TOTAL DOMESTIC FOREIGN IMPORTS EXPORTS

68

Tampa Bay Entrance, 55,439,089 34,845,097 20,593,992 6,137,922 14,456,070

Sunshine Skyway, 

and Old Port Tampa, FL

Charlotte, FL 637,175 637,175 0 0 0

Tampa, FL 51,911,335 31,812,115 20,099,220 6,069,656 14,029,564

Panama City, FL 2,890,579 2,395,807 494,772 68,266 426,506

Mobile Bay Entrance, AL 521,260,589 276,319,566 244,941,023 109,858,532 135,082,491

South Louisiana, LA, Port of 204,482,591 106,972,579 97,510,012 28,867,399 68,642,613

Baton Rouge, LA 83,612,788 45,384,087 38,228,701 26,564,120 11,664,581

New Orleans, LA 76,984,036 37,962,557 39,021,479 18,770,926 20,250,553

Plaquemine, LA, Port of 72,897,301 48,466,434 24,430,867 7,854,328 16,576,539

Mobile, AL 50,972,223 25,083,220 25,889,003 11,711,441 14,177,562

Pascagoula, MS 26,926,582 9,481,727 17,444,855 14,735,302 2,709,553

Gulfport, MS 2,023,084 86,089 1,936,995 1,231,432 705,563

Biloxi, MS 1,739,456 1,739,456 0 0 0

Pensacola, FL 1,622,528 1,143,417 479,111 123,584 355,527

Galveston Bay Entrance, TX 347,622,099 141,558,564 206,063,535 155,375,499 50,688,036

Matagorda Ship Channel, TX 9,237,437 2,689,155 6,548,282 5,771,996 776,286

Victoria, TX 4,624,192 4,624,192 0 0 0

Freeport, TX 19,661,621 5,475,882 14,185,739 12,271,130 1,914,609

Galveston, TX 10,465,119 3,815,125 6,649,994 1,986,010 4,663,984

Texas City, TX 50,402,938 19,213,208 31,189,730 29,980,279 1,209,451

Houston, TX 135,231,322 63,694,434 71,536,888 42,859,905 28,676,983

Port Arthur, TX 49,799,977 6,763,743 43,036,234 36,864,423 6,171,811

Beaumont, TX 20,937,132 14,922,961 6,014,171 4,026,335 1,987,836

Orange, TX 692,720 619,158 73,562 0 73,562

Lake Charles, LA 46,569,641 19,740,706 26,828,935 21,615,421 5,213,514

Aransas Pass, TX 70,456,033 25,885,340 44,570,693 38,624,945 5,945,748

Corpus Christi, TX 70,456,033 25,885,340 44,570,693 38,624,945 5,945,748

San Diego Bay Entrance, CA 26,199,523 1,842,754 7,771,983 6,297,212 1,474,771

San Diego, CA 1,351,482 616,598 734,884 258,589 476,295

Nawiliwili, Kauai, HI 1,129,612 1,113,657 15,955 15,955 0

Barbers Point, Oahu, HI 8,232,732 3,507,894 4,724,838 3,974,002 750,836

Honolulu, HI 11,545,102 9,374,582 2,170,520 1,923,739 246,781

Kahului, Maui, HI 2,586,230 2,510,919 75,311 74,941 370

Hilo, HI 1,354,365 1,303,890 50,475 49,986 489
STATION NAME TOTAL DOMESTIC FOREIGN IMPORTS EXPORTS

69

San Francisco Bay Entr., CA 137,086,419 57,874,053 79,212,366 38,125,664 41,086,702

Long Beach, CA 53,227,490 19,738,999 33,488,491 15,994,553 17,493,938

Los Angeles, CA 46,478,586 19,063,467 27,415,119 13,550,393 13,864,726

Santa Monica, CA 193 193 0 0 0

Morro Bay, CA 3,083 3,083 0 0 0

Monterey Harbor, CA 9,330 9,330 0 0 0

Redwood City, CA 753,912 383,784 370,128 217,211 152,917

San Francisco, CA 1,330,066 517,591 812,475 324,458 488,017

Oakland, CA 13,224,118 2,523,900 10,700,218 4,330,630 6,369,588

Richmond, CA 20,839,258 15,034,485 5,804,773 3,649,403 2,155,370

Humboldt, CA 1,220,383 599,221 621,162 59,016 562,146

Carquinez Strait, CA 2,457,918 329,277 2,128,641 782,895 1,345,746

Stockton, CA 1,320,462 129,887 1,190,575 724,516 466,059

Sacramento, CA 1,137,456 199,390 938,066 58,379 879,687

Grays Harbor Entrance, WA 58,854,722 17,885,242 40,969,480 4,401,114 36,568,366

Kalama, WA 11,346,546 660,579 10,685,967 15,754 10,670,213

Longview, WA 6,166,724 1,172,181 4,994,543 674,806 4,319,737

Astoria, OR 985,471 160,976 824,495 101,747 722,748

Grays Harbor, WA 1,565,708 101,185 1,464,523 130 1,464,393

Vancouver, WA 7,534,764 2,173,470 5,361,294 893,875 4,467,419

Portland, OR 31,255,509 13,616,851 17,638,658 2,714,802 14,923,856

Strait of Juan de Fuca Entr., WA 0

Admiralty Inlet, WA 30,983,102 9,398,002 21,585,100 7,958,842 13,626,258

Seattle, WA 26,179,838 6,041,194 20,138,644 7,567,122 12,571,522

Everett, WA 4,440,858 3,017,536 1,423,322 384,659 1,038,663

Port Townsend, WA 362,406 339,272 23,134 7,061 16,073

The Narrows, Puget Sound, WA 23,044,326 9,025,192 14,019,134 4,014,217 10,004,917

Olympia, WA 2,165,575 1,998,723 166,852 4,858 161,994

Tacoma, WA 20,878,751 7,026,469 13,852,282 4,009,359 9,842,923

Deception Pass, WA 0

Rosario Strait, WA 14,401,201 11,650,993 2,750,208 938,587 1,811,621

Anacortes, WA 13,109,828 11,120,181 1,989,647 538,040 1,451,607
STATION NAME TOTAL DOMESTIC FOREIGN IMPORTS EXPORTS

70

Bellingham, WA 1,291,373 530,812 760,561 400,547 360,014

San Juan Channel, WA 0

Wrangell Narrows, AK 13,370,460 7,271,405 6,099,055 412,370 5,686,685

Coos Bay, OR 3,628,036 151,748 3,476,288 52,140 3,424,148

Ketchikan, AK 1,821,127 1,473,285 347,842 108,889 238,953

Nikishka, AK 4,699,710 3,376,826 1,322,884 3 1,322,881

Anchorage, AK 3,221,587 2,269,546 952,041 251,338 700,703

Sergius Narrows, AK 81,882,753 80,909,916 972,837 4,975 967,862

Seward, AK 927,669 28,210 899,459 4,975 894,484

Valdez, AK 80,955,084 80,881,706 73,378 0 73,378

North Inian Pass, AK 264,519 24,113 240,406 93,182 147,224

Skagway, AK 264,519 24,113 240,406 93,182 147,224

Isanotski Strait, AK 0

Unimak Pass, AK 0

Akutan Pass, AK 0

Kvichak Bay, AK 0

NOTE: No port is associated with the Tidal Current Reference Station when total tonnage is zero.
71