NOAA Technical Report NOS CO-OPS 046

Humboldt Bay Current Surveys: 

December 2002 - October 2004

Silver Spring, Maryland

September 2005

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) Center for Operational Oceanographic Products and Services

(CO-OPS) provides the National infrastructure, science, and technical expertise to collect and

distribute 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 tidal

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 Plan

themes. For example, CO-OPS provides data and products required by the National Weather

Service to meet its flood and tsunami warning responsibilities. The Center manages the National

Water Level Observation Network (NWLON), a national network of Physical Oceanographic RealTime Systems (PORTS) in major U. S. harbors, and the National Current Observation Program

consisting of current surveys in near shore and coastal areas utilizing bottom mounted platforms,

subsurface buoys, horizontal sensors and quick response real time buoys. The Center: establishes

standards for the collection and processing of water level 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; designs software to improve CO-OPS’ data

processing capabilities; maintains and operates oceanographic observing systems; performs

operational data analysis/quality control; and produces/disseminates oceanographic products.
Humboldt Bay Survey Area

NOAA Technical Report NOS CO-OPS 046

Humboldt Bay Current Surveys: 

December 2002 - October 2004

Karen Earwaker

September 2005

noaa National Oceanic and Atmospheric Administration

U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration

Carlos M. Gutierrez, Secretary Vice Admiral Conrad C. Lautenbacher, Jr., U.S. Navy (Ret.)

 Undersecretary of Commerce for Oceans and

 Atmosphere and NOAA Administrator

National Ocean Service

Charlie Challstrom, Acting Assistant Administrator for NOAA Oceans and Coasts

Center for Operational Oceanographic Products and Services

Michael Szabados, Director
ii

NOTICE

Mention of a commercial company or product does not constitute an

endorsement by NOAA. Use for publicity or advertising purposes of

information from this publication concerning proprietary products or the

tests of such products is not authorized.
iii

TABLE OF CONTENTS

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

LIST OF TABLES .......................................................... vi

LIST OF ACRONYMS AND ABBREVIATIONS ................................. vii

1.0 INTRODUCTION ...................................................... 1

2.0 2002/2003 CURRENT SURVEY .......................................... 5

2.1 Stations Occupied and Instrumentation Utilized . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.2 Data Acquired and Results ............................................ 6

2.3 Products Available .................................................. 11

3.0 2004 CURRENT SURVEY ............................................... 17

3.1 Stations Occupied and Instrumentation Utilized . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3.2 Data Acquired and Results ............................................ 18

HB0401 ........................................................... 19

HB0402 ........................................................... 20

Tidal Current Predictions ............................................. 21

4.0 PRODUCTS AVAILABLE .............................................. 27

4.1 Data at Multiple Depths at Nine Stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

4.2 New Reference Station Located in Humboldt Bay . . . . . . . . . . . . . . . . . . . . . . . . . . 27

4.3 New Secondary Stations within Humboldt Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

4.4 New Secondary Stations outside Humboldt Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

4.5 Acquisition of Data During an El Nino Event . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

4.6 Updated Predictions in Humboldt Bay ................................... 28

5.0 FUTURE WORK ....................................................... 31

6.0 ACKNOWLEDGMENTS ................................................ 33
iv

LIST OF FIGURES

Figure 1. Humboldt Bay Current Survey Study Area of 2002/2003 . . . . . . . . . . . . . . . . . . . . 1

Figure 2. Questionable current alignment in the Entrance Channel . . . . . . . . . . . . . . . . . . . . 2

Figure 3. Humboldt Bay Current Survey Study Area of 2004 . . . . . . . . . . . . . . . . . . . . . . . . 2

Figure 4. Equipment utilized during the 2002/2003 Humboldt Bay current survey . . . . . . . . 5

Figure 5. Current velocity and tilts of HB0201 data at 7.9 m . . . . . . . . . . . . . . . . . . . . . . . . . 7

Figure 6. Velocity scatter diagram for Fairhaven Terminal (HB0204) showing bins 1

through 50 (~ 200 meters from the dolphin) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 7. Velocity scatter diagram for Tosco Pier (HB0205) from 5 meters through 141

meters from the pier ................................................. 8

Figure 8. Echo intensity range of beam 1 from Tosco Pier SL-ADP during the 2002

deployment. Low signal to noise threshold is at 7 counts (solid red line) . . . . . . . 9

Figure 9. Echo intensity range of beam 1 from Fairhaven Terminal SL-ADP during the

2002 deployment. Solid red line is low signal to noise threshold at 7 counts . . . . . 9

Figure 10. Percent good pings as an indicator of range at HB0206 . . . . . . . . . . . . . . . . . . . . . 10

Figure 11. Percent good pings as an indicator of range at HB0207 . . . . . . . . . . . . . . . . . . . . . 10

Figure 12. Principal current direction (January - February, 2003) at multiple depths at station

HB0206. .......................................................... 11

Figure 13. Principal current direction (January - February, 2003) at multiple depths at station

HB0207 .......................................................... 11

Figure 14. Greenwich Intervals (hours) with depth at Humboldt Bay Entrance Channel

station, HB0202. Station depth is 14.2m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Figure 15. Greenwich intervals (hours) with depth at the entrance to North Bay Channel

station (HB0203) east of Fairhaven. Station depth is 11.7m . . . . . . . . . . . . . . . . 12

Figure 16. Greenwich intervals (hours) with distance from Fairhaven Terminal station,

HB0204. Western edge of North Bay Channel is at 41m . . . . . . . . . . . . . . . . . . . . 13

Figure 17. Greenwich intervals (hours) with distance from Tosco Pier station, HB0205. 

Eastern edge of North Bay Channel is at 25m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 18 Greenwich intervals (hours) with depth at North Bay Channel station, HB0206. 

Station depth is 14.3m ............................................... 14

Figure 19. Greenwich intervals (hours) with depth at Fields Landing Channel station,

HB0207. Station depth is 8.9 m ........................................ 14

Figure 20. Equipment utilized during the 2004 Humboldt Bay current survey . . . . . . . . . . . . 17

Figure 21. Time series of echo intensity at 9.3 m (MLLW) showing instant degradation of 

beam 2 of the ADCP deployed outside the Bar Channel . . . . . . . . . . . . . . . . . . . . . 19

Figure 22. Percent good pings of HB0401 data at 9.3 m below MLLW . . . . . . . . . . . . . . . . . . 19
v

Figure 23. Principal current direction near the bottom at subsurface buoy station, HB0401 . . 19

Figure 24. Principal current direction near the surface at subsurface buoy station, HB0401 . . 19

Figure 25. Principal current direction near the bottom at the station, HB0402 . . . . . . . . . . . . . 20

Figure 26. Principal current direction near the surface at station, HB0402 . . . . . . . . . . . . . . . 20

Figure 27. Principal current direction at multiple depths at the new Humboldt Bay reference

station, HB0402 .................................................... 21

Figure 28. Percent good pings at the Entrance Channel station, HB0402 . . . . . . . . . . . . . . . . . 22

Figure 29. Comparison of tidal current predictions and observations at HB0206 during a

neap tide .......................................................... 22

Figure 30. Comparison of tidal current predictions and observations at HB0206 during a

spring tide......................................................... 22

Figure 31. Comparison of predictions and observations at HB0205 during a neap tide . . . . . . 23

Figure 32. Comparison of predictions and observations at HB0205 during a spring tide . . . . 23

Figure 33. Comparison of observed currents and water level between the jetties of

Humboldt Bay ..................................................... 23

Figure 34. Comparison of predicted currents and water level between the jetties of

Humboldt Bay ..................................................... 23

Figure 35. Residual (non-tidal) currents at HB0402 at 4.5 meters below MLLW during a

neap tidal current ................................................... 24
vi

LIST OF TABLES

Table 1. Station summary for the 2002/2003 Humboldt Bay current survey . . . . . . . . . . . . . . 6

Table 2. Table 2 of speed ratios and time differences for Humboldt Bay stations referenced

to San Francisco Bay Entrance from the 2005 NOS Tidal Current Tables - Pacific

Coast of North America and Asia ........................................ 15

Table 3. Station summary for the 2004 Humboldt Bay current survey . . . . . . . . . . . . . . . . . . . 18

Table 4. Characteristics of observed currents at selected depths below MLLW within the

Entrance Channel: 2002-2004 ........................................... 21

Table 5. Characteristics of observed currents at selected depths below MLLW outside 

Humboldt Bay: 2002-2004 ............................................. 25

Table 6. Table 2 of speed ratios and time differences for Humboldt Bay stations referenced

to Humboldt Bay Entrance Channel from the 2006 NOS Tidal Current Tables -

Pacific Coast of North America and Asia .................................. 29
vii

LIST OF ACRONYMS AND ABBREVIATIONS

ADCP Acoustic Doppler Current Profiler

ASCII American Standard Code for Information Interchange

ATON Aids to Navigation

cm/s centimeters per second

CO-OPS Center for Operational Oceanographic Products and Services

dir direction in degrees True North

HA 29 day harmonic analysis

HBHD Humboldt Bay Harbor District

kHz kiloHertz

m meters

MEC Maximum Ebb Current

MFC Maximum Flood Current

MLLW mean lower low water

nm nautical mile

NCOP National Current Observation Program

NOAA National Oceanic and Atmospheric Administration

NOS National Ocean Service

NW northwest

NWLON National Water Level Observation Network

NWS National Weather Service

PORTS Physical Oceanographic Real-Time System

QC quality control

RDI R.D. Instruments

RMS root mean square

SL-ADP side looking acoustic Doppler profiler

SNR signal to noise ratio

SSE south southeast

TRBM trawl resistant bottom mounted

USACE United States Army Corps of Engineers

UTC Universal Time Coordinate

1

1.0 INTRODUCTION

At the request of the Humboldt Bay Harbor Recreation and Conservation District and the Humboldt

Bay Pilots Association, the National Ocean Service’s Center for Operational Oceanographic

Products and Services (CO-OPS) conducted a series of current measurements within Humboldt Bay,

California, under the auspices of the National Current Observation Program. The local user

community reported that the currents differed in strength and timing from the existing published

predictions that were referenced to San Francisco Bay Entrance and based on 7 days of 1923 pole

data acquired 0.6nm south of Pt. Diablo. Mariners noted strong cross currents at the entrance to

Humboldt Bay that tended to ‘push’ their vessel towards the north jetty during the winter. This first

current survey of Humboldt Bay met CO-OPS mission to promote safe navigation and was

conducted during the winter when conditions were expected to be most extreme, as requested by the

Humboldt Bay Chief Executive Officer. A total of seven stations were occupied during the 2002-

2003 survey: one station outside the harbor and six within the Bay (Figure 1). Prior to the 2002

survey, there were 5 stations within Humboldt Bay referenced to time and speed ratio offsets to SF

Bay Entrance. CO-OPS’ intention to make a new reference station near the entrance of Humboldt

Bay at HB0202 was thwarted when high sediment transport buried the current meter platform and

data acquisition was less than the required 30 days. Although the current direction measured at

HB0202 did not align with the expected flow between the jetties in the Entrance Channel, the

profiler did not malfunction. Current direction recorded at all levels throughout the water column

were consistent with the direction of sediment transport and flow reflected off the north jetty and

along the shoal just to the north of the profiler’s position (Figure 2).

Figure 1. Humboldt Bay Current Survey Study Area of 2002/2003.
2

Another survey was conducted during the summer of 2004 to measure currents during a relatively

quiescent meteorological period when wind and swells were expected to be less intense. Site

selection, within the Entrance Channel, was determined from a 12-hour acoustic Doppler current

profiler (ADCP) tow where currents displayed the anticipated alignment with the main ship channel

and sand movement was expected to be minimal. During this survey, two stations were occupied,

one outside the harbor at HB0401 and one between the jetties at HB0402. Development of a new

reference station at HB0402, 0.25nm SSE of the north jetty of the Entrance Channel (Figure 3),

Figure 3. Humboldt Bay Current Survey Study Area of 2004 

Figure 2. Questionable current alignment in the Entrance Channel 
3

resulted when nearly 86 days of quality data were collected in 12.8 meters of water. Forty-nine days

of data were collected outside the breakwater in 14.1 meters of water.

Upon completion of the summer project, data products were generated and new predictions are now

available for all stations occupied during the 2002/2003 and 2004 surveys. New reference station

daily predictions are available for the remainder of 2005 and will appear in the NOS Tidal Current

Tables beginning with the 2006 edition. Due to the limited number of pages in the Tidal Current

Tables, the Humboldt Bay stations are listed as secondary stations rather than stand-alone reference

stations. All existing stations within Humboldt Bay will be referenced to the new Entrance Channel

station. Time differences and speed ratios have been computed and will appear in Table 2 of the

2006 NOS Tidal Current Tables - Pacific Coast of North America and Asia. Raw and quality control

(QC) data are available upon request. In addition, harmonic constituents and harmonic-based

predictions are available upon request for all stations. 

5

2.0 2002/2003 CURRENT SURVEY

An investigation was conducted by CO-OPS to address the Humboldt Bay Harbor District’s

(HBHD) concern that time differences from the predicted flood and ebb were experienced by the

local marine community. As a result, a current survey to update predictions within the harbor and

improve safe navigation began in December 2002. Normally CO-OPS conducts current surveys

during ‘normal’ sea conditions to adequately measure the tidal currents in an area of concern to the

maritime community. The users requested that this survey be conducted in the winter during the

extreme conditions of storms and high sediment transport. Storms, El Nino, and hurricanes are not

considered ‘normal’ sea conditions, therefore CO-OPS current surveys are not normally conducted

during those times. Sometimes the passage of storms or other anomalies during a survey result in

valuable oceanographic measurements.

2.1 Stations Occupied and Instrumentation Utilized

Seven locations were identified by the HBHD, the Humboldt Bay Bar Pilots, and CO-OPS as being

critical to safe navigation. The seven stations spanned the breadth of the bay from just outside the

breakwater at the entrance, north to Tosco Pier in North Bay Channel (Figure 1). Trawl resistant

bottom mounted (TRBM) platforms designed and manufactured by Flotation Technologies were

utilized at each of the four stations within the harbor at HB0202, HB0203, HB0206 and HB0207.

(Refer to Table 1 for precise information on each station). The ADCP deployed in the Entrance

Channel was housed in a concrete-based TRBM platform (Figure 4e) capable of withstanding

Figure 4. Equipment utilized during the 2002/2003 Humboldt Bay current survey

consisted of (a) RDI WorkHorse ADCP in a subsurface buoy, (b) Sontek side

looking profiler (SL-ADP), (c) mounted to the dolphin at Fairhaven Terminal, (d)

bottom mounted ADCP housed in an aluminum base and (e) concrete base.
6

currents over 3 knots. The other three platforms had the standard aluminum base (Figure 4d). Two

stations utilized side looking acoustic Doppler profilers (SL-ADP) mounted to the face of the pier

at Tosco Pier and a stand-alone dolphin at Fairhaven Terminal (Figure 4b and 4c). One station

deployed outside the jetties, utilized an ADCP housed in a subsurface buoy (Figure 4a). 

Two separate deployments occurred during the winter survey; the first in December 2002 (Entrance

Channel and North Bay Channel), and the second in late January 2003 (Fields Landing Channel and

North Bay Channel near channel marker #9 close to the US Coast Guard Station at Samoa, CA).

Table 1 provides station details of instruments utilized, deployment period, and days of quality data

acquired. 

 Table 1. Station Summary for the 2002/2003 Humboldt Bay Current Survey

STATION PROFILER DEPLOYMENT

PERIOD

GOOD

QUALITY

DATA

ID

Position depth (m)

below

MLLW

s/n Freq

kHz Days

HB0201 40o

 45.973' N 124o 14.815' W 12.4 238 1200 12/09/02 - 03/01/03 5.68

subsurface buoy deployed ~8.5 meters east of ATON Bell Buoy 2, outside Bar Channel

HB0202 40o

 45.475' N 124o 13.967' W 14.2 2203 600 12/11/02 - 04/09/03 20.93

~25.5 meters northwest of ATON Bell Buoy 5, inside Entrance Channel

HB0203 40o

 47.226' N 124o 11.552' W 11.7 1062 1200 12/11/02 - 01/24/03 43.69

North Bay Channel opposite Fairhaven Terminal

HB0204 40o

 47.266' N 124o 11.700' W 4.6 C465 250 12/11/02 - 02/25/03 74.97

Fairhaven Terminal. Station depth is 10.8 meters. Multiple distances out to 201meters

HB0205 40o

 47.771' N 124o 11.237' W 4.6 C410 500 12/12/02 - 02/27/03 76.75

TOSCO Eureka Terminal Pier. Station depth is 9.1 meters. Multiple distances out to 161meters

HB0206 40o

 45.465' N 124o 13.367' W 14.3 3096 600 01/24/03 - 02/28/03 34.3

near marker #9, inside Entrance Channel on north side at the confluence with North Bay Channel

HB0207 40o

 44.871' N 124o 13.446' W 8.9 1062 1200 01/24/03 - 2/27/03 33.9

near marker #2, at the entrance to Fields Landing Channel

NOTE: Sensor depth is given at stations, HB0204 and HB0205 instead of station depth.

Deployment of the SL-ADP at the Tosco pier and on the stand-alone dolphin at Fairhaven Terminal

utilized the HBHD pontoon boat, while the heavier bottom mounted platforms were deployed with

the Humboldt State University’s RV Coral Sea.

2.2 Data Acquired and Results

One of the challenges associated with this survey was the extreme sediment transport through the

Entrance Channel complicated by longshore currents that mix with jetty-produced eddies outside
7

the harbor. Site selection was determined by talking to numerous local marine experts, all of whom

helped to identify areas where current predictions were inadequate. CO-OPS mission to promote

safe navigation and update tidal current predictions played a key role in selecting the sites within

the harbor. 

Normally, subsurface buoys are deployed at depths in excess of 30.5 meters and in areas where

sediment loading is high [NOAA, 2003]. The depth near ATON Bell Buoy #2 was about 14 meters

and migrating sand movement was known to occur in the vicinity of the mooring. Performance of

the subsurface buoy was compromised by the short mooring chain, shallow station depth, and

excessive tilts. The mooring broke from its chain early in the deployment and only 5.7 days of

quality data were recovered from the subsurface buoy after it was found and returned to CO-OPS

in May 2003, almost 5 months after it was deployed. Figure 5 shows that both pitch and roll were

approaching excessive levels (greater than 20 degrees). The data showed that north velocity was

in excess of 4.5 knots at 7.9 meters below mean lower low water (MLLW). CO-OPS present suite

of instrumentation had known limitations in high surge conditions which are prevalent in this area

of the Bay especially during an El Nino year. After the subsurface buoy broke from its mooring, it

was carried north along the coast until it beached on the coast near McKinleyville, CA. 

Side looking profilers were utilized in Humboldt Bay to characterize the currents in the North Bay

Channel. CO-OPS has successfully acquired quality data with horizontal current meters in areas

near berthing and piers where a bottom mounted system could be compromised by deep draft vessels

offloading their products [Earwaker, 2002]. Figure 6 shows the principal current direction from the

Figure 5. Current velocity and tilts of HB0201 data at 7.9 m.
8

western side of North Bay Channel at HB0204 (Bin 1) to the eastern side at HB0205 (Figure 7). The

Fairhaven Terminal SL-ADP, deployed at a depth of 15 feet, measured currents that were aligned

with the main ship channel for the entire profiling range of 200 meters (Figure 6). The profiler at

Tosco Pier also measured currents from the eastern side of the channel to a distance of 161 meters;

it also showed alignment with the North Bay Channel flow (Figure 7). Figure 7 shows about a 15

to 20 degree shift in direction between the farthest and nearest range, although all measurements

align with the main ship channel. 

Installation of the mounting hardware was accomplished by divers in 10.79 meters of water with the

sensor mounted at 4.5 meters below MLLW. Only one 250 kHz H-ADCP was available for this

survey and the sensor was deployed at Fairhaven Terminal. Maximum profiling range of the SLADPs were attained owing to adequate scatterers and their placement in the water column.

Examples of range in 2002 are shown in Figure 8 at Tosco Pier and Figure 9 at Fairhaven Terminal.

The low signal to noise (SNR) threshold at 7 counts is the cutoff for quality data. The largest echo

intensities are closest to the profiler at bin 1 at a range of 5 meters and become progressively less

as the distance increases out to Bin 40 at 161 meters (Figure 8). Echo intensities from the 250 kHz

Sontek SL-ADP at Fairhaven Terminal exceeded maximum profiling range (120 to 180 meters) in

Figure 6. Velocity scatter diagram for Fairhaven

Terminal (HB0204) showing bins 1 through 50 (~ 200

meters from the dolphin).

Figure 7. Velocity scatter diagram for Tosco Pier

(HB0205) from 5 meters through 141 meters from the

pier.
9

Figure 9. Echo intensity range of beam 1 from Fairhaven Terminal SL-ADP

during the 2002 deployment. Solid red line is low signal to noise threshold at 7

counts.

Figure 8. Echo intensity range of beam 1 from Tosco Pier SL-ADP during the

2002 deployment. Low signal to noise threshold is at 7 counts (solid red line).

December 2002 without coming close to the SNR threshold (or cutoff). Measured echo intensities

during 2003 were occasionally below the SNR threshold. 
10

Figure 10. Percent good pings as an indicator of

range at HB0206. Bin 12 at 2 feet (below MLLW) is

at the air/water interface.

Figure 11. Percent good pings as an indicator of

range at HB0207. Bin 7 at 2.3 feet (below MLLW)

is the last good bin (near the surface).

Data quality (as percent good pings) at two stations (HB0206 and HB0207) are shown in Figures

10 and 11, respectively. Last good bin range is the depth where “percent 4 beam solution” is very

close to 100% (greater than 75%). Last good bin at HB0206 (Figure 10) is Bin 11 at 1.6 m below

MLLW. Last good bin at HB0207 (Figure 11) is Bin 7 at 0.7 m below MLLW. 

Principal current direction changes from top to bottom during the deployment at station HB0206

(Figure 12), where the surface depth is represented by green and the bottom depth by black/red

symbols. The current mostly aligns with the main ship channel with higher speeds toward the

entrance of Humboldt Bay. The flood direction is almost due east near channel marker #9 (station

HB0206) where Figure 12 shows flood currents are deflected off the south jetty and flow toward

North Bay Channel. The principal current direction, at station HB0207 during the January to

February deployment, shows good alignment along the north/south orientation of Fields Landing

Channel (Figure 13). This station also had higher speeds toward the entrance of Humboldt Bay at

all depths (Figure 13). The principal flood direction is southeast near channel marker #2, (station

HB0207) as expected in a narrow channel opening such as at the entrance to Fields Landing

Channel. 
11

2.3 Products Available 

Loss of data from the proposed reference station posed a challenge to CO-OPS since a full update

to the Humboldt Bay predictions was not possible. As an interim measure, CO-OPS published

special 2004 “Daily Predictions” for the five stations, but left them referenced to the existing station

at San Francisco Bay Entrance. The entrance station of Humboldt Bay was re-occupied during the

summer survey to acquire at least 30 days of data to perform harmonic analysis and develop a new

reference station for Humboldt Bay. 

Special 2004 “Daily Predictions” for five of the seven stations occupied were made available to the

Humboldt Bay Harbor Safety Committee at their September 2003 meeting. Other copies were

distributed to individuals who expressed an interest. Table 2 time differences and speed ratios as

referenced to San Francisco Bay Entrance were also generated and were disseminated in the 2005

edition of the Tidal Current Tables released in January 2005. Results of Greenwich interval

analysis, showing hours of each phase of the tidal current versus depth, are shown in Figures 14-19.

Greenwich intervals are the periods between the moon’s transit over the Greenwich meridian and

the arrival of each tidal phase at a station [Zervas, 2000]. Generally, multiple depths from a single

station will have Greenwich intervals close to the adjacent depth as shown in Figures 14, 15, 18 and

19. 

Figure 13. Principal current direction (January -

February, 2003) at multiple depths at station

HB0207.

Figure 12. Principal current direction (JanuaryFebruary, 2003) at multiple depths at station HB0206.
12

Figure 14. Greenwich intervals (hours) with depth at

Humboldt Bay Entrance Channel station, HB0202. 

Station depth is 14.2m.

Figure 15. Greenwich intervals (hours) withdepth at

North Bay Channel station, HB0203 east of

Fairhaven. Station depth is 11.7m.
13

Figures 16 and 17 show results from the horizontal profiler where distances are from the mount out

toward the main ship channel, rather than vertical depth measured in meters below MLLW. Note

that timing of the maximum flood current at station HB0204 (Figure 16, 200m) should occur before

the maximum flood at HB0205 (Figure 17, 161m). One would expect the Greenwich intervals from

station HB0203 (Figure 15, 4.5m) to be quite close in time to the 200 meter distance at station

HB0204 (Figure 16) since they are measuring nearly the same water. However, this is not the case.

It appears that the timing of maximum flood current at HB0203 occurs about 50 minutes after the

maximum flood current at HB0204. This means that the profilers are not measuring the same

volume of water and the west side of the channel floods faster than the east side. The horizontal

profiler samples nearly the entire water column at locations farthest from the sensor so some errors

may be introduced from side lobe interference that could contribute to the difference in Greenwich

interval hours between the two stations.

Figure 16. Greenwich intervals (hours) with distance

from Fairhaven Terminal station, HB0204. Western

edge of North Bay Channel is at 41m and middle of

the channel is near 200m.

Figure 17. Greenwich intervals (hours) withdistance

from Tosco Pier station, HB0205. Eastern edge of

North Bay Channel is at 25m.
14

Figure 19. Greenwich intervals (hours) with depth at

Fields Landing Channel station, HB0207. Station

depth is 8.9m.

Figure 18. Greenwich intervals (hours) with depth at

North Bay Channel station, HB0206. Station depth is

14.3m.
15

Speed ratios and time differences for the Humboldt Bay stations that appeared in Table 2 of the 2005

NOS Tidal Current Tables are presented in Table 2 below.

Table 2. Table 2 of speed ratios and time differences for Humboldt Bay stations referenced

to San Francisco Bay Entrance from the 2005 NOS Tidal Current Tables - Pacific Coast of

North America and Asia.

CO-OPS is developing web-based access to the data.

17

3.0 2004 CURRENT SURVEY

CO-OPS was unable to compute tidal current predictions in the Entrance Channel and outside the

harbor during the 2002/2003 survey due to the series of storms that hit the coast of northern

California in December and January. There was a failure to acquire at least 30 days of data because

of the loss of the subsurface ADCP at HB0201 and burial of the bottom platform at HB0202.

Because of this, a second attempt to acquire data at the entrance to the harbor (utilizing a subsurface

buoy and open type bottom platform) was performed in July 2004. Cross sectional current

measurements at the entrance area (utilizing a vessel mounted ADCP system) (Figure 20a) helped

to identify an area where currents were representative of the main ship channel. CO-OPS was

concerned about sediment transport through the harbor and potential burial of the bottom platform,

but several sources assured the team that the north side of the main ship channel was less likely to

develop sand shoals or be affected by migration of sand through the harbor during the summer.

Breakers appeared to come in straight through the jetties and weren’t deflected from the north jetty

as observed during the winter season of 2002. The station outside of the harbor (HB0401) was

positioned in deeper water and farther away from the previous site deployed at the ATON Bell Buoy

2, thus assuring it wouldn’t be clipped by any passing deep draft vessels transiting the entrance or

within the watch circle of the ATON Bell Buoy 2 buoy.

Figure 20. Equipment utilized during the 2004 Humboldt Bay current survey

consisted of: (a) vessel mounted ADCP attached to a 15 foot pole, (b) bottom

mounted ADCP, and (c) subsurface buoy with Argos beacon and dual acoustic

releases. 
18

3.1 Stations Occupied and Instrumentation Utilized

The station outside the breakwater (HB0401) utilized a 1200 kHz RD Instruments WorkHorse

ADCP housed in a subsurface buoy, with a 3.5 meter long mooring line, attached to a railroad wheel

anchor (Figure 20c). The subsurface buoy, equipped with an ARGOS beacon, was deployed in 14

meters of water about 0.4 nautical miles west northwest of the south jetty, on the edge of the Bar

Channel. The current profiler measured currents every six minutes (from near bottom (9.3 meters)

to the surface) from July 21 to September 8, 2004. 

The station inside the jetties (HB0402) housed an ADCP inside an open-sided bottom platform

(Figure 20b) where currents less than 3 knots were expected. A 1200 kHz RD Instruments ADCP

was configured to sample and record currents, tilts, heading, pressure, and water temperature every

six minutes. The profiler was deployed in 12.7 meters of water near the north jetty rock marker

(labeled “58") from July 21 to October 15, 2004.

Some complications were encountered at the Entrance Channel station when the pop-up release

(float) attached to the platform was cut on September 17. All physical reference to the location of

the bottom platform was lost at that time. Divers, using the last known GPS fix of the platform from

the deployment log, searched for the platform and profiler on three separate occasions. The profiler

was finally recovered by the divers on October 14 after NOAA’s Navigation Response Team #6

pinpointed its location with their side scan sonar. The platform was buried under about 2 feet of sand

and was left at the site after attempts to release it using a hydraulic pump were unsuccessful. The

body of the ADCP was completely encrusted with growth and marine fouling although this did not

affect data quality.

3.2 Data Acquired and Results

Nearly forty-nine days of quality data from the station outside the breakwater and about 86 days of

data from the Entrance Channel site were acquired during the summer survey. Data and station

information are summarized in Table 3. Data from the 4.5 meter depth at station HB0402 in the

Entrance Channel will be used as a new reference station for all Humboldt Bay stations, including

additional depths at HB0402 and 2 depths at HB0401.

Table 3. Station Summary for the 2004 Humboldt Bay Current Survey

STATION

PROFILER DEPLOYMENT

PERIOD

GOOD

QUALITY

DATA

ID Position depth s/n Freq Days

(m)

MLLW

kHz

HB0401 40o

 46.013' N 124o 15.179' W 14.1 238 1200 07/21/04 - 09/08/04 48.86

subs buoy; 0.4 nm WNW of south jetty outside Bar Channel

HB0402 40o

 45.906' N 124o 14.252' W 12.7 604 1200 07/21/04 - 10/15/04 85.9

0.25nm SSE of north jetty in the Entrance Channel
19

Figure 21. Time series of echo intensity at 9.3 m (MLLW) showing instant

degradation of beam 2 of the ADCP deployed outside the Bar Channel. 

Figure 24. Principal current direction near the

surface at subsurface buoy station, HB0401.

Figure 23. Principal current direction near the

bottom at subsurface buoy station, HB0401.

Figure 22. Percent good pings of HB0401 data at 9.3 m below MLLW.

HB0401

Although beam 2 at HB0401 was degraded (Figure 21) and the ADCP returned to RDI for repair,

the data are considered good for analysis as shown in the percent good ping plot of Bin 1(Figure 22).

Analysis using 3 beam solution was performed on all ten of the 1-meter bins.
20

Principal current direction at two depths (near surface and near bottom) from station HB0401 are

shown in Figures 23 and 24. The tidal signal is weak, currents are dominated by alongshore drift.

HB0402

Speed histograms (at the new reference station, HB0402) are shown in Figures 25-26. Flood current

direction is about 142 degrees true North. As expected, the flood currents are stronger than the ebb

currents near the bottom (Figure 25). Near-surface currents show about the same strength for flood

and ebb (Figure 26). 

Mean flood current is slightly stronger than mean

ebb at all depths at HB0402. Mean ebb current is

stronger than mean flood at HB0202, HB0206, and

HB0207 (all depths) which agrees with the

permanent current directions (Table 3). These

differences may be due to location of the good

quality measurement and not seasonal influences.

Principal current direction aligns with the Entrance

Channel along 140 degrees true North at all depths

below MLLW from 10.5 meters to 1.5 meters

(surface) at HB0402 (Figure 27). The reference

station, at depth 4.5 meters below MLLW, is

shown as the gray filled triangle in Figure 27 and

is highlighted in bold font in Table 4.

Figure 27. Principal current direction at multiple

depths at the new Humboldt Bay reference station,

HB0402.

Figure 26. Principal current direction near 

the surface at station HB0402.

Figure 25. Principal current direction near 

the bottom at station, HB0402.
21

Table 4. Characteristics of observed currents at selected depths below MLLW within the

Entrance Channel: 2002-2004

STATION

Mean

MFC

MAX

MFC

Mean

MEC

MAX

MEC

Permanent

Current

Principal

Current 

ID Location / Description Depth Spd Dir Spd Dir Spd Dir Spd Dir Spd Dir Direction

(m) kt o

 T kt o T kt o T kt o T kt o T o T

HB0402

40o

 45.906'N 

124o 14.252'W

 10.5 1.31 141 2.65 152 1.06 323 2.02 326 0.171 136 143

4.5 1.74 140 3.20 140 1.59 322 2.95 322 0.148 129 142

1.5 1.64 140 3.22 137 1.53 323 3.3 322 0.093 123 142

0.25nm SSE of north jetty in the Entrance Channel

HB0202

40o

 45.475'N 

124o

 13.967'W 

12.2 1.25 172 2.13 169 1.77 347 3.0 338 0.257 344 169

9.2 1.5 171 2.23 175 2.06 346 3.3 339 0.271 343 168

4.2 1.61 168 2.76 176 2.19 341 3.48 343 0.287 336 165

1.2 1.46 168 2.45 175 2.06 340 3.59 344 0.337 338 164

25.5 meters NW of ATON Bell Buoy #5, inside Entrance Channel

HB0206

40o

 45.465'N 

124o

 13.367'W

9.6 0.60 070 2.02 086 1.27 257 2.25 250 0.331 258 077

4.6 0.63 073 1.85 116 1.63 243 2.81 244 0.483 239 065

1.6 0.65 071 1.58 081 1.88 237 3.17 239 0.537 233 060

entrance to North Bay Channel & inside Entrance Channel near channel marker #9

HB0207

40o

 44.871'N 

124o 13.446'W

5.7 0.78 181 1.56 170 1.16 001 2.33 004 0.138 004 001

4.7 0.80 178 1.62 166 1.24 002 2.42 004 0.16 013 001

1.7 0.78 169 1.71 160 1.41 004 2.61 004 0.241 024 178

entrance to Fields Landing Channel near channel marker #2

NOTES: MAX MFC & MAX MEC refers to the maximum observed current during the deployment.

The new reference station at HB0402 at 4.5 meters below MLLW is highlighted in bold font.

Data quality of the new reference station at HB0402 shows good “percent 4-beam solution” up to

the surface at Bin 10 (Figure 28). Some of the deployment showed very low “percent 4-beam

solutions”, which may be the result of times when the platform and sensor were affected by

migrating sand shoals.

Tidal Current Predictions

Comparison of predictions for the new reference station versus the existing reference station at the

Entrance to San Francisco Bay show that the Humboldt Bay Entrance Channel station (HB0402)

matches observations at two stations within the harbor better than the old reference station. Figures

29-32 show the comparisons during both a neap and spring tide at stations HB0206 and HB0205.

The predictions are expected to be better at HB0206 due to its proximity to the new reference

station, length of the time series, and age of the observations (Table 4). Note that ebb current

amplitudes at HB0206 are under-predicted during neap conditions, but timing of the flood current

amplitudes are better than when referenced to San Francisco Bay Entrance (Figure 29). Timing of

slacks is slightly better when referenced to the Humboldt Bay Entrance station. The predictions,

when referenced to the Humboldt Bay Entrance station, are better during an average spring tide at

HB0206 
22

Figure 28. Percent good pings at the Entrance Channel station, HB0402. 

Figure 30. Comparison of tidal current predictions

and observations at HB0206 during a spring tide. 

Each tick mark is 36 minutes.

Figure 29. Comparison of tidal current predictions

and observations at HB0206 during a neap tide.
23

Figure 33. Comparison of observed currents and

water level between the jetties of Humboldt Bay.

(see February 1, 2003 in Figure 30). Predictions referenced to SF Bay Entrance and Humboldt Bay

Entrance Channel are shown in Figures 31 and 32 for a typical neap and spring tide at the Tosco Pier

site located in the northern reach of North Bay Channel. The new reference station appears to do a

better job of predicting currents during both neap and spring tides at Tosco Pier ( Figures 31 and 32).

Figure 32. Comparison of predictions and

observations at HB0205 during a spring tide. 

Each tick mark is 36 minutes.

Figure 31. Comparison of predictions and

observations at HB0205 during a neap tide. Each

tick mark is 36 minutes.

Figure 34. Comparison of predicted currents and

water level between the jetties of Humboldt Bay.
24

In addition, Figure 33 shows the relationship between the nearby National Water Level Observation

Network (NWLON) station at North Spit to tidal current observations at the new reference station

at HB0402. Note that slack currents (blue line) occur during high water or low water phases of the

tide (magenta line) as opposed to being out of phase (brown dashed lines) when compared to SF Bay

Entrance (Figure 34). Phase lag difference can be up to 2.4 hours. 

Another comparison of predictions to observations is shown in Figure 35 where the non-tidal

(residual) current during a neap tide is reported as a root mean square (RMS) of 10.752 cm/s at the

reference station (HB0402). Residual current is the difference between self-predicted and observed

current where the small RMS indicates that most of the energy is tidal. Other statistics of the

proportion of tidal and non-tidal energy are produced when data are detided as in Figure 35 [Zervas,

1999].

Station comparison outside the harbor are summarized in Table 5 where principal current direction

indicates the direction along which the main current flow is aligned. Mean maximum currents are

the average of all observed maximum current at the selected depth. The maximum observed ebb

current speeds were greater at HB0201 than at station HB0401 probably owing to the series of

storms that hit the northern coast of California in December 2002. Also, since only 5 days of data

were acquired at HB0201 while almost 49 days of data were acquired at HB0401, there’s a

possibility that data are biased by the small sample size. Currents are normally faster near the

surface where bottom friction has less effect. 

Figure 35. Residual (non-tidal) currents at HB0402 at 4.5 meters below

MLLW during a neap tidal current.
25

Table 5. Characteristics of observed currents at selected depths below MLLW outside

Humboldt Bay: 2002-2004

STATION

Princpal

Current

Mean

MFC

MAX

MFC

Mean

MEC

MAX

MEC

Permanent

Current

ID Location / Description depth

MLLW

dir spd dir spd dir spd dir spd dir speed dir

(m) o

 T kt o T kt o T kt o T kt o T kt o T

HB0401

40o

 46.013' N 

124o 15.179' W

 9.3 47 0.32 036 0.72 041 0.47 234 1.15 256 0.045 021

4.3 50 0.37 045 1.33 052 0.53 235 1.41 260 0.031 015

2.3 51 0.38 046 1.34 051 0.53 236 1.45 262 0.024 351

1.3 49 0.40 052 1.32 048 0.48 234 1.52 262 0.009 327

2004 sub-surface buoy; 0.4 nm WNW of south jetty outside Bar Channel

HB0201

40o

 45.973' N 

124o 14.815' W

7.9 175 na na 0.41 194 1.70 001 5.02 355 1.365 004

4.9 176 na na 0.33 197 1.71 001 4.39 359 1.457 000

0.9 166 na na 0.15 200 1.79 356 4.65 341 1.579 353

2002 sub-surface buoy; ~8.5 meters east of ATON Bell Buoy 2, outside Bar Channel

The permanent current represents a current that runs continuously and is independent of tides or

other temporary causes. Permanent current includes the general surface circulation of the oceans

[Zervas, 2000]. The station near ATON Bell Buoy #2, HB0201, occupied during the winter, has a

higher permanent current compared to the station occupied in the summer at HB0401 (Table 5) and

may be due to the series of coastal storms that passed through Humboldt Bay in December 2002 and

January 2003. Note that the permanent current direction for both stations at all depths is to the

north. 

27

4.0 PRODUCTS AVAILABLE 

User requests for data and products listed in this report are available through the CO-OPS home

page and by email at the addresses provided below.

4.1 Data at Multiple Depths at Nine Stations

American Standard Code for Information Interchange (ASCII) data from the seven stations occupied

during the 2002/2003 survey and both stations occupied during the 2004 survey are available via

data requests through the Predictions Team at: Tide.Predictions@noaa.gov. In the near future, data

may be available via the CO-OPS home page at: http://tidesandcurrents.noaa.gov/. Quality control

was performed on all velocity data. Harmonic constituents from least squares analysis are available

for the stations listed in this report except HB0201 and HB0202, where data were insufficient to run

29 day harmonic analysis. Metadata associated with the data, sensors, and stations are also

available. Raw and QC data are available for the following stations:

- HB0402 - Entrance Channel, 0.25 nm SSE of North Jetty at 34 feet below MLLW

- HB0202 - Entrance Channel, 1.0 nm NE of South Spit Light at 14 feet and 30 feet below MLLW

- HB0206 - North Spit, 0.15 nm SW of at 15 feet and 32 feet below MLLW

- HB0207 - South Spit, 0.1 nm NE of (Entrance to Fields Landing Channel) at 15 feet below MLLW

- HB0203 - North Bay Channel, west of Eureka at 15 feet and 28 feet below MLLW

- HB0204 - North Bay Channel at Fairhaven Terminal at 13 feet below MLLW

- HB0205 - North Bay Channel at Samoa Channel (Tosco Pier) at 15 feet below MLLW

- HB0401 - Humboldt Bay Bar Channel, 0.4nmi WNW of s jetty at 14 feet and 31 feet below MLLW

- HB0201 - Humboldt Bay Bar Channel, near ATON Bell Buoy #2 (just 5 days at multiple depths)

4.2 New Reference Station Located in Humboldt Bay

The new reference station is located in the Entrance Channel, 0.25nm SSE of north jetty, at 4.5

meters below mean lower low water (MLLW). Daily predictions of this station in the Entrance

Channel to Humboldt Bay will appear in the 2006 Tidal Current Tables - Pacific Coast of North

America and Asia. This station replaces the existing reference station, San Francisco Bay Entrance,

for those stations located within Humboldt Bay that were occupied during the 2004 survey. The

station located outside the harbor (HB0401) is also referenced to this new station. 

4.3 New Secondary Stations within Humboldt Bay

Since more than 30 days of data were acquired at each of the 2002/2003 stations, these secondary

station designations apply to only the Tidal Current Tables. Harmonic constituents were generated

and users can request “special” harmonic predictions for all of the stations to the Prediction Team

at: Tide.Predictions@noaa.gov. Five new secondary stations were acquired during the 2002/2003
28

survey in addition to two stations in 2004. The five secondary stations appeared in Table 2 of the

2004 Tidal Current Tables. The Entrance Channel station from the 2002 survey, HB0202, was

deemed acceptable as a secondary station after data comparison to newly acquired data from a

nearby station, HB0402. The following two new secondary stations are to appear in Table 2 of the

2006 Tidal Current Tables - Pacific Coast of North America and Asia.

- HB0402 - Entrance Channel, 0.25nm SSE of North Jetty at 34 feet below MLLW

- HB0202 - Entrance Channel, 1nm NE of South Spit Light at 14 feet and 30 feet below MLLW

4.4 New Secondary Stations outside Humboldt Bay

Only one new secondary station outside the harbor will appear in the 2006 Tidal Current Tables -

Pacific Coast of North America and Asia. Two depths will be reported in the Tidal Current Tables.

- HB0401 - Humboldt Bay Bar Channel, 0.4nmi WNW of s jetty at 14 feet and 31 feet below MLLW

4.5 Acquisition of Data During an El Nino Event

Storm data during The El Nino, 2002/2003, are available for one station outside the harbor and one

station within the harbor. As noted in Table 1 of this report, the data were compromised at HB0201

due to the storm and excessive tilts. In addition, the subsurface buoy departed its mooring shortly

after deployment. The station within the harbor, HB0202, acquired about 21 days of good data and

was also buried by sediment transport through the Entrance Channel. Data from these two stations

exhibit the extremes encountered when a series of storms hit the northern coast of California during

the winter of 2002/2003.

4.6 Updated Predictions in Humboldt Bay

Predictions from the five stations mentioned in Section 4.3 have been updated with new time

differences and speed ratios in Table 2 of the 2006 Tidal Current Tables and are summarized in

Table 6. A new reference station within Humboldt Bay replaces the existing station at San Francisco

Bay Entrance and all newly occupied stations within Humboldt Bay are referenced to this new

station at Humboldt Bay Entrance Channel, 0.25nm SSE of north jetty, at 4.5 meters MLLW.
29

Table 6. Table 2 of speed ratios and time differences for Humboldt Bay stations referenced

to Humboldt Bay Entrance Channel from the 2006 NOS Tidal Current Tables - Pacific Coast

of North America and Asia.

References

[1] NOAA’s current program field operations manual, Spring 2003

[2] K. Earwaker, D. McNally, E. Shih, A field study of horizontal current profilers, MTS/IEEE 2002

Conference presentation, October 2002.

[3] C. Zervas, NOS tide and current glossary, NOS CO-OPS report, 2000.

[4] C. Zervas, Tidal current analysis procedures and associated computer programs, March 1999.
31

5.0 FUTURE WORK

The Humboldt Bay Harbor District expressed an interest in a real time system that would

disseminate data every six minutes from multiple sites to promote safe navigation in the harbor. A

decision about implementing a Physical Oceanographic Real Time System (PORTS®) in the harbor

may occur after the mariners have sufficient time to use and evaluate the updated predictions. An

example of graphical images displayed to the public are shown at this PORTS link,

[http://tidesandcurrents.noaa.gov/ports.html] and accessed from the CO-OPS web page at:

http://tidesandcurrents.noaa.gov. The Entrance Channel is dredged by the U.S. Army Corps of

Engineers (USACE) every fall and spring when warranted, which may require periodic updating of

the predictions due to changes in controlling channel depths and bathymetric contours. Humboldt

Bay is a dynamic area where a real time system of sensors may benefit the marine community and

promote safe navigation through the harbor.

33

6.0 ACKNOWLEDGMENTS

The current surveys were conducted at the request of the Humboldt Bay Harbor District by a team

of CO-OPS scientists and engineers including Jennifer Ewald, James Sprenke, Eddie Shih, Rich

Bourgerie, Carl Kammerer, Chuck Payton, Steve Hudziak, and Steven Basset. Valuable assistance

from David Hull and Matt Wardinsky of Humboldt Bay Harbor District, Troy Nicolini and Nancy

Dean of NOAA’s NWS, Kees Ploeg and crew of Humboldt State University’s RV Coral Sea, Ken

Bates and the Ironic, Phil Glenn and the Shellback, US Coast Guard, John Corbett of Corbett

Diving, Charlie Notthoff of Notthoff Underwater Services, and Kurt Brown, Edmund Wernicke and

Julia Uhlendorf of NOAA’s Navigation Response Team #6 all helped to ensure the success of both

surveys. Project oversight was provided by Karen Earwaker.

Data analysis by Karen Earwaker and Allison Stolz utilized standard harmonic analysis routines

adopted by CO-OPS and the National Current Observation Program.

Much thanks to oceanographers Peter Stone, Chris Zervas, Rich Bourgerie, Stephen Gill, and

Kathryn Bosley, all of whom reviewed this report and provided valuable guidance.