Coastal Circulation and Sediment

Dynamics in Hanalei Bay, Kauai

PART I:

Measurements of waves, currents, temperature, salinity and

turbidity: June – August, 2005

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2006-1085

QuickBird satellite image of Hanalei Bay

Coastal Circulation and Sediment

Dynamics in Hanalei Bay, Kauai

PART I:

Measurements of waves, currents, temperature, salinity and

turbidity: June – August, 2005

Curt D. Storlazzi, M. Kathy Presto, Joshua B. Logan and Michael E. Field

U.S. Geological Survey, Pacific Science Center, Santa Cruz, CA

U.S. GEOLOGICAL SURVEY

Open-File Report 2006-1085

2006
LIST OF TABLES

TABLE 1. Experiment personnel.

TABLE 2. Instrument package sensors.

TABLE 3. CTD/OBS/PAR profiler log.

TABLE 4. Salinity and Temperature statistics.

TABLE 5. Turbidity statistics.

LIST OF FIGURES

FIGURE 1. Map of the study area location in relation to the main Hawaiian Island chain.

FIGURE 2. Location of spatial measurements and the bottom-mounted instrument packages.

FIGURE 3. Photographs of the equipment used in the study.

FIGURE 4. Oceanographic and meteorologic forcing during the study period.

FIGURE 5. Hanalei River discharge during the study period.

FIGURE 6. Tide and wave data from the Offshore Wall Site.

FIGURE 7. Tide and wave data from the CRAMP Site.

FIGURE 8. Tide and current data from the CRAMP and Offshore Wall Sites.

FIGURE 9. Mean and principal axes of flow at the CRAMP and Offshore Wall Sites.

FIGURE 10. Phasing between tides and flow at the CRAMP and Offshore Wall Sites.

FIGURE 11. Water temperature and salinity at the CRAMP and Wall Sites.

FIGURE 12. Phasing between tides, temperature and salinity at the CRAMP and Wall Sites.

FIGURE 13. Variation in salinity as a function of temperature at the CRAMP and Wall Sites.

FIGURE 14. Mean variation in water temperature, salinity, density, turbidity and PAR with depth.

FIGURE 15. Images of the seafloor at different times from the Coral Imaging System.

LIST OF APPENDICES

APPENDIX 1. ADCP Information.

APPENDIX 2. Dobie, Microcat and SCOBS Sensor Information.

APPENDIX 3. CTD Profiler with OBS and PAR Sensor Information.
ADDITIONAL DIGITAL INFORMATION

For additional information on the instrument deployments, please see:

http://walrus.wr.usgs.gov/infobank/a/a105ka/html/a-1-05-ka.meta.html

http://walrus.wr.usgs.gov/infobank/s/s105ka/html/s-1-05-ka.meta.html

For an online PDF version of this report, please see:

http:// pubs.usgs.gov/of/2006/1085/

For more information on the U.S. Geological Survey Western Region’s Coastal and

Marine Geology Team, please see:

http://walrus.wr.usgs.gov/

For more information on the U.S. Geological Survey’s Coral Reef Project,

please see:

http://coralreefs.wr.usgs.gov/

DIRECT CONTACT INFORMATION

General Project Information

Dr. Michael E. Field (Project Chief): mfield@usgs.gov

Regarding this Report:

Dr. Curt D. Storlazzi (Lead Oceanographer): cstorlazzi@usgs.gov

REPORT REFERENCE

Storlazzi, C.D., Presto, M.K., Logan, J.B. and Field, M.E., 2006. “Coastal Circulation

and Sediment Dynamics in Hanalei Bay, Kauai. PART I: Measurements of waves,

currents, temperature, salinity and turbidity: June – August, 2005.” U.S. Geological

Survey Open-File Report 2006-1085, 35 p.
INTRODUCTION

High-resolution measurements of waves, currents, water levels, temperature,

salinity and turbidity were made in Hanalei Bay, northern Kauai, Hawaii, during the

summer of 2005 to better understand coastal circulation and sediment dynamics in coral

reef habitats. A series of bottom-mounted instrument packages were deployed in water

depths of 10 m or less to collect long-term, high-resolution measurements of waves,

currents, water levels, temperature, salinity and turbidity. These data were

supplemented with a series of vertical instrument casts to characterize the vertical and

spatial variability in water column properties within the bay. The purpose of these

measurements was to collect hydrographic data to learn how waves, currents and water

column properties vary spatially and temporally in an embayment that hosts a

nearshore coral reef ecosystem adjacent to a major river drainage. These

measurements support the ongoing process studies being conducted as part of the U.S.

Geological Survey (USGS) Coastal and Marine Geology Program’s Coral Reef Project;

the ultimate goal is to better understand the transport mechanisms of sediment, larvae,

pollutants and other particles in coral reef settings. This report, the first part in a series,

describes data acquisition, processing and analysis.

Project Objectives:

The objective of these deployments was to understand how currents, waves,

tides, temperature, salinity and turbidity vary spatially and temporally in Hanalei Bay. To

meet the objectives of the Coral Reef Project, flow and water column properties in

Hanalei Bay were investigated. These data will provide insight into the impact of

terrestrial sediment, nutrient or contaminant delivery and coral larval transport on

nearshore coral reefs. The instrument packages were deployed over a 3-month period

during the summer of 2005. A series of vertical profiles were collected during the

instruments deployments in June, 2005, to characterize the vertical and spatial

variability in water column properties within the bay. Data collected during these

instrument deployments provide baseline information for future watershed restoration

projects proposed by the U.S. Coral Reef Task Force’s (USCRTF) Hawaiian Local

Action Strategy (LAS) to address Land-Based Pollution (LBP) threats to coral reefs in

the Hanalei ahupua’a (linked watershed-reef system).

Study Area:

Spatial and temporal measurements were made in Hanalei Bay, on the north

side of Kauai, Hawaii, USA (FIGURE 1). All instrument packages were situated on the

sandy seabed in water depths less than 10 m. All vessel operations, including

mobilization and demobilization, were based out of Hanalei Bay.
160o W 159o W 158o W 157o W 156o W 155o W

19o N 20o N 21o N 22o N

HAWAIIAN ISLANDS

Niihau Kauai

Oahu

Molokai

Lanai

Maui

Kahoolawe

Hawaii

160o W 159o W 158o W

isobath interval: 200m

157o W 156o W 155o W

19o N 20o N 21o N 22o N

FIGURE 1. Map of the study area location in relation to the main Hawaiian Island chain. Hanalei Bay is exposed to 

the large North Pacific swell during the winter but is relatively protected form the Northeast Trade winds during the summer.
OPERATIONS

This section provides information about the personnel, equipment and vessel

used during the deployments. See TABLE 1 for a list of personnel involved in the

experiment.

Scientific Party:

Three USGS scientists deployed the bottom-mounted instrument deployments.

The team for instrument deployment and recovery operations included the vessel

captain as well. Vertical profiles were collected by a scientist aboard the boat

concurrently with the instrument deployments.

Equipment and Data Review:

FIGURE 2 shows the location where instrument packages were deployed for

extended periods (large orange circles) and where vertical profile casts were made

(small white circles). Up to four different instruments, measuring waves, currents,

temperature and salinity, were employed at each long-term sampling site. In some

instances, more than one of the same instruments was used at a give site to measure

the parameters at various depths. A summary of instrument packages and depths at

which they were deployed is provided in TABLE 2. The instruments included selfcontained RD Instrument 600 kHz upward-looking Acoustic Doppler Current Profilers

(ADCPs), NIWA Dobie-A wave/tide gauges, Aquatec/Seapoint 200-TY and 210-TYT

self-contained optical backscatter sensors (SCOBSs), and Seabird SBE-37SM Microcat

conductivity-temperature sensors (FIGURE 3). The ADCPs collected vertical profiles of

current speed and direction, which, in conjunction with the recorded pressure data, can

be used to calculate wave height, wave period and wave direction. The Dobies,

SCOBS, and Microcats collected single-point measurements of waves and tides,

turbidity, and temperature and salinity, respectively.

The oceanographic instruments were deployed for a 76-day period. The sensors

made measurements using three sampling schemes. The ADCP (FIGURE 3a) collected

water depth and current information for 512 sec bursts at 2 Hz every 2 hours to provide

directional wave and tide information. The Dobies (FIGURE 3b) collected 512 sec

bursts at 2 Hz every hour to provide non-directional wave and tide information; the

ADCP, SCOBS and Microcat (FIGURE 3c) recorded current profiles, turbidity,

temperature and salinity data, respectively, every 5 min. Instrument specifics and

sampling schemes are listed in APPENDICES 1-2.

The second type of instrument utilized was a Conductivity/Temperature/Depth

(CTD) Profiler with Optical Backscatter (OBS) and Photosynthetically-Available

Radiation (PAR) sensors to collect vertical profiles of water temperature, salinity,

density, turbidity and PAR. The CTD/OBS/PAR data acquisition log is presented in

TABLE 3. The instrument specifics and sampling schemes are listed APPENDIX 3.

The third type of instrument deployed during the study was the USGS Coral

Imaging System (CIS), which consists of a Canon D60 6.3-megapixel digital camera

with a 24-mm lens, an external Canon Speedlight 550EX TTL strobe, control unit and

batteries on a tetrapod; this system was employed to collect a time series of sea floor

images (FIGURE 3d). The CIS was deployed in a patch of sand at Site 2 (FIGURE 2)
Northwest Reef (1)

Wave/Tide

Turbidity @ 10m

Temperature @ 10m

South-central Reef (4)

Wave/Tide

Turbidity @ 10m

Temperature @ 10m

CRAMP Site (5)

Current Profiler

Directional Wave/Tide

Turbidity @ 10m

Salinity @ 10m

Temperature @ 10m

Offshore Wall (2)

Current Profiler

Directional Wave/Tide

Camera

Turbidity @ 10m

Turbidity @ 6m

Turbidity @ 3m

Salinity @ 10m

Salinity @ 3m

Temperature @ 10m

Temperature @ 3m

Inshore Wall (3)

Turbidity @ 6m

Turbidity @ 3m

Salinity @ 3m

Temperature @ 3m

1

2

3

4

5

6

7 8 9 10

11 12

13

14

= Instrument package = CTD/OBS/PAR profiler cast

159o31'0"W

159o31'0"W

159o30'0"W

159o30'0"W

22o12'0"N

22o12'0"N

22o13'0"N

22o13'0"N

5 m

10 m

15 m

20 m

25 m

30 m

FIGURE 2. Locations of the bottom-mounted instrument packages employed for long-term sampling and vertical profile casts 

used in the study. The numbers following the parameters denote the depths of the measurements below the sea surface. The CRAMP 

site refers to a permanent monitoring site of the Coral Reef Assessment and Monitoring Program by the University of Hawaii.
a) c)

b)

d)

FIGURE 3. Photographs of the equipment used in the study. a) ADCP, SCOBS and Microcat 

along the 10m isobath at the Offshore Wall site. b) Dobie and SCOBS at the Northwest Reef site. c) 

Microcat and SCOBS 3m below the surface at the Offshore Wall site. d) CIS along the 10m isobath at 

the Offshore Wall site. All of the instrument packages and moorings were deployed in patches of sand.
and the camera and strobe were angled to not only image the seafloor and the black

and white camera calibration reference block, but also a colony of the coral Pocillapora

meandrina that had been detached from the adjacent reef, likely during a storm the

previous winter. The CIS provided data on the natural frequency and duration of

sediment deposition and resuspension on an actual coral surface. The CIS took images

every four hours throughout the deployment (00:00, 04:00, 08:00, 12:00, 16:00 and

20:00).

Far-field oceanographic and meteorologic forcing for the study period was

compiled by NOAA’s National Data Buoy Center (NDBC, 2005) NW Kauai buoy. The

NW Kauai Buoy, station identification #510001, is deployed in 3 km of water

approximately 280 km west-northwest of Kauai. It makes hourly measurements of wind

speed (m/sec), wind direction (°True), wave height (m), wave period (sec), mean wave

direction (°True), sea-level barometric pressure (mBar), and air and sea-surface

temperature (°C).

Navigation equipment included two hand-held WAAS-equipped GPS units and a

computer with positioning and mapping software. The positioning and mapping

software enabled real-time GPS position data to be combined with images of previously

collected high-resolution SHOALS color-coded LiDAR, shaded-relief bathymetry, 5 m

isobaths and aerial photographs of terrestrial portions of the maps. See FIGURE 2 for

the location of instruments and profile casts.

Research Platform:

The instrument deployments and recoveries were conducted using the F/V Sea

Cat. The starboard quarterdeck was adapted for instrument deployment and recovery

operations, which included the use of an electric winch and an overhead davit. The

instruments were deployed by attaching a removable bridle to the instrument package

with a connecting line through the davit and down to the winch. The instruments were

lowered to within a few meters of the seafloor where scuba divers attached a lift bag

and detached the lifting line. The divers then moved the instrument package into

position for anchoring. After determining the package’s location, the divers emplaced

sand anchors into the seafloor and attached them to the instrument package using

cables and turnbuckles. Surficial seafloor sediment samples were collected, and the

heights of the sensors above the seafloor were measured and recorded. Recovery

operations employed the same techniques. The CTD/OBS/PAR profiler casts were

conducted from the same vessel via hand. The driver’s station was outfitted with a LCD

display and GPS-enabled navigation system to provide the vessel captain with a

graphic display of position information, speed, heading and distance to the next cast

location.

DATA ACQUISITION AND QUALITY

Data were acquired for 76 days during the period between 06/08/2005 and

08/22/2005. More than 23200 5-minute samples were recovered from each of the

ADCPs, SCOBS and Microcats; less than 300 hourly data points were recovered from

the Dobies due to battery failure. The ADCP and Dobie data quality was generally very
high except towards the end of the deployment, when biofouling of the pressure sensor

caused the data quality to decrease. The raw pressure data were archived and copies

of the data were post-processed to calculate water depth, tidal height, significant wave

height and dominant wave period; this data, in conjunction with the ADCP’s 2 Hz current

data, was used to calculate wave direction.

The Microcat data appeared to be of high quality. The SCOBS data problems

were primarily due to biofouling of the optical sensor, which interrupts the SCOBS

optical path and results in false elevated readings. Due to this growth, which started

very shortly after the instruments’ deployments, high quality concurrent data from all of

the SCOBS is limited (<7 days).

The CTD/OBS/PAR profile data near the bed often displayed spikes in the OBS

data due to interaction of the optical beam with the bed. The raw CTD/OBS/PAR data

were archived and copies of the data were post-processed by calculating the average

over 0.5 m depth windows to reduce high-frequency system noise. These 0.5 m binaveraged data were then used for visualization and analysis. The CTD/OBS/PAR data

were very high in quality, with features such as low-salinity (freshwater) surface plumes

visible in the salinity data, multi-layered structures (water masses) identified by density

contrasts, and turbid layers identifiable in the OBS data.

RESULTS AND DISCUSSION

This section reviews the data collected by the instruments during the

deployments and addresses the significance of the findings to better understand the

local oceanographic conditions in the study area.

Oceanographic and Meteorologic Forcing

The summer study period was relatively quiescent, with relatively stable waves,

and winds (FIGURE 4). The waves were small (2 m), short period (7-9 sec) and

typically out of the northeast, likely driven by the Northeast Trade winds. These Trade

wind waves were replaced by longer period (12-16 sec) swell out of the Northwest

Pacific when the Trade Winds slackened. This generally occurs when regions of lower

than average barometric pressure move through the island chain and cause the North

Pacific anticyclone, which drives the Trade Winds, to weaken.

River Discharge

The US Geological Survey’s Pacific Islands Water Science Center in Honolulu,

Hawaii (http://hi.water.usgs.gov/), maintains a water and sediment gauging station on

the Hanalei River approximately 9.2 km upstream from the river mouth. This gauge

provides daily mean values of water discharge (m3

/sec), suspended sediment

concentration (mg/l) and total suspended sediment load (kg/day). The study period was

marked by very low water and sediment discharges compared to the entire 2004-2005

record; only one event on June 19 (Year-Day 170) had above-average suspended

sediment concentrations and total sediment loads (FIGURE 5).
160 170 180 190 200 210 220 230

1014

1016

1018

1020

1022

1024

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−2

0

2

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5

10

15

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10

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24

26

28

ATM pressure

[mBar]

Wave Height

[m]

Wave Period

[sec]

Wind

[m/sec]

Blue = Water Red = Air

Temperature

[deg C]

Year Day 2005

FIGURE 4. Oceanographic and meteorologic forcing during the study period. The 

waves were predominantly due to the Northeast Trade winds throughout most of the study. 

The study area was not impacted by any substantial storms during the course of the experi-
160 170 180 190 200 210 220 230

0

5

10

15

20

25

160 170 180 190 200 210 220 230

0

10

20

30

40

50

60

70

80

160 170 180 190 200 210 220 230

0

x 105

River Discharge

[m/sec]

Suspended Sediment Concentration

[mg/l]

Suspended Sediment Load

[kg/day]

Year Day 2005

0.5

1.0

1.5

2.0

FIGURE 5. Water and suspended sediment discharged from the Hanalei River during the study period from the USGS 

Pacific Islands Water Science Center. The daily mean data are in blue; the mean values for the entire 2004-2005 period are 

shown in red. The study period was marked by very low water and sediment discharges compared to the entire 2004-2005 
Tides

The study period encompassed more than five complete spring-neap tidal cycles.

The tides in Hanalei Bay are mixed, semi-diurnal with two uneven high tides and two

uneven low tides per day; thus the tides change just over every 6 hours (FIGURES 6-7).

The mean daily tidal range is roughly 0.6 m, while the minimum and maximum daily tidal

ranges are 0.4 m and 0.9 m, respectively.

Waves

The waves that impacted Hanalei Bay during the course of the experiment are

shown in FIGURES 6-7 and, while substantially smaller and shorter period than those

observed further offshore (FIGURE 4), their temporal variations are in general

agreement with the deep-water NDBC data. In the eastern side of the bay at the

Offshore Wall site (Site 2, FIGURE 6), significant wave heights (Hsig) ranged from 0.12

m to 0.30 m, with a mean significant height ± one standard deviation of 0.19 ± 0.03 m.

Dominant wave periods (Tdom) varied from 2.5 sec to 4.3 sec, with a mean dominant

period ± one standard deviation of 3.2 ± 0.3 sec. Mean wave direction ± one standard

deviation was 235.1° ± 70.3°. The mean wave direction out of the southwest is likely

the result of two processes: wave refraction and wave energy dissipation. As the waves

propagate into the bay, they refract around the large reef in the eastern half of the bay;

the instrument package at Site 2 was situated along the south side of this reef and thus

the waves had to refract around the west side of the reef and propagate onshore, which,

at this location, would correspond to a direction out of the southwest, as the edge of the

reef is oriented northwest-southeast. Second, the shorter period waves, which refract

less and can propagate over the reef from the northwest, dissipate much of their energy

by breaking over the top of the reef. Thus, by the time they make it over the reef and to

the instrument site on the sheltered south side of the reef, they are quite small. It is

very difficult for the ADCPs to resolve wave direction for very small, short-period waves,

and thus much of the variability in direction may be due to poor analytical solutions in

the wave direction calculations, especially for the smaller, shorter-period waves.

In the eastern side of the bay at the CRAMP site (Site 5, FIGURE 7), significant

wave heights (Hsig) ranged from 0.22 m to 0.82 m, with a mean significant height ± one

standard deviation of 0.54 ± 0.10 m. Dominant wave periods (Tdom) varied from

between 3.1 sec and 5.9 sec, with a mean dominant period ± one standard deviation of

4.4 ± 0.1 sec. Mean wave direction ± one standard deviation was 26.3° ± 39.8°. The

waves were primarily out of the north-northeast and appear to be due to the Trade

winds. The wave heights are greater and their directions are more consistent at the

CRAMP site than the Offshore Wall, as the CRAMP site is directly exposed to the

northeast Trade wind waves while the Offshore Wall site is shadowed by the reef, as

discussed above. Because of this greater exposure, the wave data from the CRAMP

site provides a much better picture of the general wave parameters in the bay during

these summer months.

Currents

Mean current speeds ± one standard deviation at the Offshore Wall site (Site 2)

were 0.02 ± 0.02 m/sec close to the surface and 0.01 ± 0.01 m/sec close to the sea

floor (FIGURE 8). At the CRAMP site (Site 5), mean current speeds ± one standard
160 170 180 190 200 210 220 230

160 170 180 190 200 210 220 230

160 170 180 190 200 210 220 230

160 170 180 190 200 210 220 230

-0. 6

-0. 4

-0. 2

0

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1

2

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5

6

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-0. 6

-0. 4

-0. 2

0

0.2

Tide [m] Wave Height [m] Wave Period [sec] Wave Height and Direction [m]

Year Day 2005

FIGURE 6. Tide and wave data from the Offshore Wall Site. The vectors denote the height and direction 

of the waves. The wave heights and periods were very small here, as the Trade wind waves underwent substantial breaking and refraction over the adjacent reef to the north that sheltered this area from direct wave impact.
160 170 180 190 200 210 220 230

-0. 6

-0. 4

-0. 2

0

0.2

0.4

0.6

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0.2

0.4

0.6

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1

160 170 180 190 200 210 220 230 2

3

4

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6

160 170 180 190 200 210 220 230 -0. 8

-0. 6

-0. 4

-0. 2

0

0.2

Tide [m] Wave Height [m] Wave Period [sec] Wave Height and Direction [m]

Year Day 2005

FIGURE 7. Tide and wave data from the CRAMP Site. The vectors denote the height and direction of the waves. 

The wave heights and periods were much larger at this site, as it is directly exposed to the Northeast Trade wind waves.
160 170 180 190 200 210 220 230

-0.5

0

0.5

160 170 180 190 200 210 220 230

-0.10

-0.05

0

0.05

0.10

160 170 180 190 200 210 220 230

-0.10

-0.05

0

0.05

0.10

160 170 180 190 200 210 220 230

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-0.05

0

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160 170 180 190 200 210 220 230

-0.10

-0.05

0

0.05

0.10

Year Day 2005

depth = 8.5 m

depth = 8.5 m

depth = 1.5 m

depth = 1.5 m

Tide [m] Current [m/sec] Current [m/sec] Current [m/sec] Current [m/sec]

Offshore Wall site CRAMP site

FIGURE 8. Tide and current data from the CRAMP and Offshore Wall Sites. The vectors denote 

the speed and direction of the currents at the different depths. In general the currents were stronger 

near the surface and in the western part of the bay, likely due to its greater exposure to the open ocean.
deviation were more than 50% higher both close to the surface (0.05 ± 0.03 m/sec) and

close to the sea floor (0.02 ± 0.01 m/sec) than along the Offshore Wall site. Overall, net

flow near the surface at the Offshore Wall site was to the southeast into the bay and to

the northwest out of the bay at the CRAMP site (FIGURE 9). Close to the bed,

however, the net flow at both sites were in the opposite directions- to the northwest out

of the bay at the Offshore Wall site and to the southeast into the bay at the CRAMP site.

The orientation of maximum flow variability varied vertically at each site, implying

bathymetric steering. At the Offshore Wall site, the flow close to the surface oriented

west-northwest by east-southeast, along the general trend of the top of the adjacent

wall, while close to the seafloor the flows are oriented more northwest by southeast,

along the general trend of the 10 m isobath (see FIGURE 2). Similar vertical variation in

the orientation of maximum flow variability is seen at the CRAMP site, with the flow

close to the surface oriented northwest by southeast, along the general trend of the top

of the adjacent reef, while close to the seafloor the flows are oriented more northnorthwest by south-southeast, along the general trend of the 10 m isobath (see FIGURE

2). These vertical variations in flow speed and direction at each site result not only in

different magnitudes and directions of net transport at different depths, but also vertical

velocity shear, which, in turn, likely increases turbulence and vertical mixing.

Most of the daily variability in current speed and direction at the study sites are

due to the tides. As the tide rises (floods), tidal currents close to the surface at the

Offshore Wall site flow to the southeast (~110o); these tidal current speeds are greater

than those observed when the tide falls (ebbs) and tidal currents are to the northwest

(~290o). The flow close to the seafloor at this location appears to be in the opposite

direction (FIGURE 10). The flood tidal currents close to the surface at the CRAMP site

flow to the southeast (~150o); these tidal current speeds are slower than those observed

when the tide falls (ebbs) and tidal currents are to the northwest (~330o). The flow close

to the seafloor at this location appears to be in the opposite direction. This pattern is set

by the local tidal node (amphidrome) to the west of the Hawaiian Island chain and the

counter-clockwise sweep of the tidal bulge around the amphidromic point. The

magnitude of the tidal currents is driven by the lunar tidal cycle, with the highest tidal

current speeds occurring during the spring tides (new and full moons) and the weakest

during the neap tides (quarter moons). Overall, the tidal currents are faster but less

consistent in the alongshore direction at the CRAMP site (Site 5) than along the

Offshore Wall site (Site 2).

Due to the lack of co-located wind measurements and the high topographic

complexity of the north shore of Kauai, it is unwise to try to interpret the local wind field

from the offshore NDBC buoy’s anemometer data. At this time we are unable to resolve

the magnitude of the influence of local winds on driving currents in the bay.

Water Column Properties

The water column properties that were measured by the bottom-mounted

Microcats and SCOBS included variations in temperature (oC), salinity (PSU) and

optical backscatter (NTU). The water column properties that were measured by the

CTD/OBS/PAR profiler included variations in temperature (oC), salinity (PSU), optical

backscatter (NTU) and PAR (mE) with depth; from these data we were able to compute

the density of seawater (sigma-theta).
Northward Current Velocity (m/sec)

Eastward Current Velocity (m/sec)

CRAMP Site

-0.05 0 0.05

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depth = 1.5 m

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depth = 8.5 m

Northward Current Velocity (m/sec)

Eastward Current Velocity (m/sec)

Offshore Wall Site

-0.05 0 0.05

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0.05

depth = 1.5 m

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depth = 5.5 m

-0.05 0 0.05

-0.05

0

0.05

depth = 7.0 m

- 0.05 0 0.05 - 0.05

0

0.05

depth = 8.5 m

FIGURE 9. Mean and principal axes of flow at the CRAMP and Offshore Wall Sites at different water depths. 

Blue vectors show the orientation and magnitude of net flow; red ellipses show the variability of flow. Mean flow is 

primarily along-isobath at all depths; net flow is onshore at the Offshore Wall site and offshore at the CRAMP site.
170 170.5 171 171.5 172 172.5 173

170 17 0.5 171 171.5 172 172.5 173

170.5 171 171.5 172 172.5 173

170 170.5 171 171.5 172 172.5 173

170.5 171 171.5 172 172.5 173

170

170

-0.5

0

0.5

-0.10

-0.05

0

0.05

0.10

-0.10

-0.05

0

0.05

0.10

-0.10

-0.05

0

0.05

0.10

-0.10

-0.05

0

0.05

0.10

Year Day 2005

depth = 8.5 m

depth = 8.5 m

depth = 1.5 m

depth = 1.5 m

Tide [m] Current [m/sec] Current [m/sec] Current [m/sec] Current [m/sec]

Offshore Wall site CRAMP site

FIGURE 10. Phasing between tides and flow at the CRAMP and Offshore Wall Sites. The vectors denote the 

speed and direction of the currents at the different depths. As the tide rises (floods), tidal currents at the Offshore 

Wall and CRAMP sites flow to the southeast; as the tide falls (ebbs), the tidal currents are to the northwest.
Spatial and Temporal Variability in Temperature:

Water temperatures ranged between 24.22 °C and 27.03 °C, with a mean

temperature ± one standard deviation of 25.97 ± 0.45 °C (TABLE 4). The water

typically warmed 0.1°C during the day, likely due to insolation (FIGURE 11). In general,

temperatures at the sites along the wall in the eastern part of the bay (Sites 2-3) were

less variable than that at the CRAMP site (Site 5). Water temperatures increased

slightly as the tide fell, likely because of water warmed by the air and/or sun in the

shallows was being advected out past the sensors (FIGURE 12). Without co-located

meteorologic data we are not sure what the cause was for the low frequency variations

in water temperature (see next section for further detail).

Spatial and Temporal Variability in Salinity:

Salinity in the bay ranged between 33.78 PSU and 35.24 PSU, with a mean

temperature ± one standard deviation of 34.80 ± 0.17 PSU (TABLE 4). The salinities

generally varied on the order of 0.01 PSU (FIGURE 11) and mirrored the tides,

increasing slightly during flood tides and decreasing slightly during ebb tides (FIGURE

12). The increases are likely due to the advection of more saline waters onshore during

the rising tide and the advection of fresh submarine groundwater or fluvial discharge

offshore during the falling tide. In general, salinities at the Offshore Wall site (Site 2)

were higher and less variable than at the Inshore Wall site (Site 3) and at the CRAMP

site (Site 5). The higher variability and lower salinities at the Inshore Wall and CRAMP

sites is likely due to the greater proximity to freshwater being discharged by the Hanalei

River and Waipa and Waioli Streams. The low frequency variations in salinity mirror

those in water temperature (see above), suggesting some large-scale variations in

water mass composition in the bay, with possibly a slow introduction of a more oceanic

(cooler, more saline) water mass in the bay starting around June 29 (Year-Day 180) and

it slowly being mixed out starting around July 14 (Year-Day 195).

The variability in salinity as a function of temperature is shown in FIGURE 13.

The near-surface and near-bed measurements at the Offshore Wall site (Site 2) show

increasing salinity with decreasing temperature that are indicative of oceanic water

being transported into the eastern part of the bay at this location. Data from the Inshore

Wall site (Site 3) show a pattern similar to the Offshore Wall site; in addition, they show

the influence of fresh water being discharged from the Hanalei River that is not

concurrently seen at the Offshore Wall site. This freshwater is identifiable as a vertical

trend in the temperature-salinity plot of a variation in more than 1.5 PSU in salinity

around 25.5°C. The pattern at the CRAMP site (Site 5) shows the inverse temperaturesalinity relationship seen along the wall overprinted by a decrease in temperature with a

decrease in salinity that indicates freshwater being transported into the area, likely from

the Waipa and Waioli Streams that discharge into the west side of Hanalei Bay.

Spatial Variability in Turbidity:

 Due to the very short length of concurrent, high-quality data from all of the

SCOBS, we cannot at this time present an accurate picture of the temporal variability of

turbidity in the study area. Concurrent, reliable data were recorded only during the first

5 days (June 8-13). During that time period, the turbidity in the study area ranged
160 170 180 190 200 210 220 230

-0.5

0

0.5

160 170 180 190 200 210 220 230 24

25

26

27

160 170 180 190 200 210 220 230

34.0

34.5

35.0

Green = Offshore Wall @ 3 m

Yellow = Inshore Wall @ 2 m

Blue = Offshore Wall @ 10 m

Red = CRAMP Site @ 10 m

Tide [m] Temperature [oC] Salinity [PSU]

Year Day 2005

FIGURE 11. Water temperature and salinity at the CRAMP and Wall Sites. The higher variability and lower salinities at the 

Inshore Wall and CRAMP sites is likely due to the greater proximity to terrestrial freshwater discharge. The low frequency variations 

in salinity mirror those in water temperature, suggesting some large-scale variations in water mass composition in the bay.
220 220.5 221 221.5 222 222.5 223

6

4

2

0

2

4

6

220 220.5 221 221.5 222 222.5 223

2

4

6

8

220 220.5 221 221.5 222 222.5 223

2

4

6

8

Tide [m] Temperature [oC] Salinity [PSU]

Year Day 2005

-0.

-0.

-0.

0.

0.

0.

26.0

26.

26.

26.

26.

27.0

34.0

34.

34.

34.

34.

35.0

Green = Offshore Wall @ 3 m

Yellow = Inshore Wall @ 2 m

Blue = Offshore Wall @ 10 m

Red = CRAMP Site @ 10 m

FIGURE 12. Phasing between tides, temperature and salinity at the CRAMP and Wall Sites. The temperatures 

decrease and the salinities increase slightly during flood tides; temperatures increase and the salinities decrease 

slightly during ebb tides. These variations are likely due to the advection of cooler, more saline waters onshore during 

the rising tide and the advection of fresh submarine groundwater or fluvial discharge offshore during the falling tide.
24.0 24.5 25.0 25.5 26.0 26.5 27.0

33.5

34.0

34.5

35.0

35.5

Temperature [oC]

Salinity [PSU]

Offshore Wall, depth = 10m CRAMP Site, depth = 10m

Offshore Wall, depth = 3m Inshore Wall, depth = 3m

24.0 24.5 25.0 25.5 26.0 26.5 27.0

33.5

34.0

34.5

35.0

35.5

Temperature [oC]

Salinity [PSU]

24.0 24.5 25.0 25.5 26.0 26.5 27.0

33.5

34.0

34.5

35.0

35.5

Temperature [oC]

Salinity [PSU]

24.0 24.5 25.0 25.5 26.0 26.5 27.0

33.5

34.0

34.5

35.0

35.5

Temperature [oC]

Salinity [PSU]

FIGURE 13. Variation in salinity as a function of temperature at the CRAMP and Wall Sites. The general trend 

of increasing salinity with decreasing temperature are indicative of oceanic waters. This inverse temperature-salinity 

relationship seen throughout most of the bay is overprinted by a decrease in temperature with a decrease in salinity 

that indicates freshwater being transported into the area, likely from the adjacent river and streams.
between 0.0 NTU and 12.2 NTU, with a mean turbidity ± one standard deviation of 1.2 ±

0.7 NTU (TABLE 5). In general the waters were more turbid inside the bay, especially

close to shore and close to the seafloor. The highest turbidity levels were close to the

bed at the Inshore Wall site (Site 3), closest to the Hanalei River mouth. The turbidity

was slightly higher in the western part of the bay at the CRAMP site (Site 5) than in the

middle of the bay (Site 4), likely due to discharge from the Waipa and Waioli Streams.

All of the mean turbidity values recorded during this dry summer period exceed

the State of Hawaii Department of Health’s Administrative Rules, Title 11, Chapter 54,

Water Quality Standards for “open ocean out to 600 foot depth” (defined on page 54-30

of that report). The maximum allowable wet season mean turbidity level (which are

roughly twice those of dry season levels) is 0.50 NTU; the mean turbidity near the

seafloor at the Inshore Wall site exceeds the maximum acceptable mean level by 7

times (TABLE 5).

Variability in Temperature, Salinity, Turbidity and PAR with Depth:

 The overall trends for the variation in water column properties with depth during

the June survey displays a very thin turbid buoyant freshwater surface plume overlying

a stable water column (FIGURE 14); these data reflect the influence of rainfall that

started ~12 hours before the start of the survey and continued through the survey. In

general, temperature and PAR decreased with depth while salinity and density

increased with depth. The higher turbidity but lower temperature, salinity and density at

the surface are indicative of the influence of a turbid, buoyant lower-salinity surface

plume, likely due to runoff from Hanalei River and the streams that drain into Hanalei

Bay. The temperature typically rose to its maximum just below the surface, below which

it decreased slowly towards the bed. Turbidity generally decreased towards the bed,

typically reaching base levels 3 m below the water’s surface; this suggests the slow

settling of material (likely fine-grained terrestrial sediment and/or biogenic material) from

the surface plume. The turbidity then increased towards the bed, likely due to

resuspension of the fine sediment and organics that typically cover the sea floor.

Spatially, the water in Hanalei Bay is generally more saline and cooler further offshore

and with increasing depth.

Short-term Sediment Deposition and Resuspension

The CIS was placed roughly 5 m south of the Offshore Wall site (Site 2) to

provide visual documentation of sedimentation on coral surfaces that will be correlated

with measurements of waves, currents, rainfall, and stream discharge (FIGURE 15).

The CIS’s images show whether the particles actually settled on the bottom or were

transported through the region. The gridded concrete block is used as a proxy for an

irregular coral surface so that estimates of levels of sediment accumulation - and

erosion - can be correlated with other measurements and improve understanding of the

conditions that affect sedimentation on corals. A small coral, broken off from a previous

storm, was also placed under the camera as a reference. Images from the CIS show a

relatively rapid initial accumulation (estimated to be up to 0.5 cm thick) of fine-grained

sediment on the gridded block over the first 3 weeks of the deployment, followed by low

levels of gradual removal and re-accumulation of fine-grained sediment over the rest of

the deployment. The small piece of coral that was placed adjacent to the concrete
25.2 25.4 25.6 25.8 26.0 26.2 26.4

0

2

4

6

8

10

12

Depth [m]

33.5 34.0 34.5 35.0

22.0 22.2 22.4 22.6 22.8 23.0 23.2 23.4 23.6

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

0 500 1000 1500

Temperature [oC]

Salinity [PSU]

Density [sigma-theta]

Turbidity [NTU]

PAR [mE]

FIGURE 14. Mean variation in water temperature, salinity, density, turbidity and PAR with depth complied from 

14 casts made throughout the bay in June, 2005. The overall trends for the variation in water column properties with 

depth during the June survey displays a turbid buoyant freshwater surface plume overlying a stable water column. 

Spatially, the water in Hanalei Bay is generally more saline and cooler further offshore and with increasing depth.
a)

c)

b)

d)

FIGURE 15. Images of the seafloor at different times from the Coral Imaging System. a) Photograph of 

the CIS, block and coral head at the time of deployment. b) CIS image 8 hours after deployment. c) CIS 

image 1 week after deployment. d) CIS image 3 weeks after deployment. The CIS imagery revealed a 

relatively rapid initial accumulation of fine-grained sediment that occurred over the first 3 weeks of the 

deployment, followed by low levels of gradual removal and re-accumulation of sediment over the rest of the 
block during deployment and is visible in the first images was moved out of the

camera's view by unknown forces during the first week of the experiment. Further

analysis of the CIS data and its comparison to oceanographic forcing will be discussed

in further detail in a subsequent report.

CONCLUSIONS

In all, more than 24000 measurements of currents, waves, tides, temperature,

salinity, turbidity and PAR were made in Hanalei Bay, Kauai, during the 3-month period

between 06/08/2005 and 08/22/2005. Key findings from these measurements and

analyses include:

1) Flow was relatively weak and circulation was sluggish in Hanalei Bay during the 2005

summer study period. Flows were generally oriented parallel to shore but varied

vertically, with the near-surface flows often heading in the opposite direction of the nearbed flows, causing vertical velocity shear. Net near-surface flow was into the eastern

portion of the bay and out of the western portion of the bay, net near-bed flows had an

opposite pattern. The waves were relatively small during the deployments and primarily

driven by the Northeast Trade Winds. Both waves and currents were more energetic in

the western portion of the bay that was more directly exposed to the Trade Winds.

2) Lower salinities and higher turbidities were observed closer to shore, especially near

the mouths of the Hanalei River and the Waipa and Waioli Streams.

3) The water in Hanalei Bay is generally more saline and cooler farther offshore and

with increasing depth. These general trends, however, are greatly influenced by the

presence of freshwater either from river/stream discharge or groundwater effluence.

4) A relatively rapid initial accumulation of fine-grained sediment occurred at the

Offshore Wall site over the first 3 weeks of the deployment, followed by low levels of

gradual removal and re-accumulation of fine-grained sediment over the rest of the

deployment.

These data provide information on the nature and controls on flow and water column

properties in Hanalei Bay during the summer months. A number of interesting

phenomena were observed that indicate the complexity of coastal circulation in Hanalei

Bay and may help to better understand the implications of the processes on coral reef

health.

ACKNOWLEDGEMENTS

This work was carried out as part of the USGS’s Coral Reef Project as part of an

effort in the U.S. and its trust territories to better understand the affect of geologic

processes on coral reef systems. We would like to thank Hanalei residents Charlie
Bass and Garret Santos of the F/V Sea Cat, who graciously donated their time, effort

and aloha during our numerous instrument deployment and recovery operations. Carl

Berg (Hanalei Watershed Hui) overextended himself by helping us with every aspect of

the fieldwork and coordinating our efforts with the numerous other institutions working in

the Hanalei watershed-reef system, and for that we owe him much thanks. We would

also like to thank Li Erikson and Katie Farnsworth (USGS), who contributed numerous

excellent suggestions and a timely review of our work.

REFERENCES

National Data Buoy Center, NW Kauai Buoy, 2005. Online digital data.

http://www.ndbc.noaa.gov/station_page.php?station=51001

TABLE 1. Experiment personnel

Person Affiliation Responsibilities

Mike Field USGS Chief scientist, diver

Curt Storlazzi USGS Co-chief scientist, diver

Joshua Logan USGS Information specialist, diver

Kathy Presto USGS Instrument specialist

Amy Draut USGS Geologist, diver

Tom Reiss USGS Dive safety officer

Dave Gonzales USGS Instrument specialist

Hank Chezar USGS Instrument specialist

Carl Berg HWH Hanalei Watershed Hui science coordinator

Charlie Bass F/V Sea Cat Vessel captain

Garret Santos F/V Sea Cat First mate
TABLE 2. Instrument package sensors

Site Name Depth

[m]

Sensors

Northwest Reef [1] 10 NIWA Dobie-A wave/tide gauge

10 Aquatec/Seapoint 200-TYT optical backscatter sensor with temperature sensor

Offshore Wall [2] 10 RD Instruments 600 kHz Workhorse Monitor acoustic Doppler current profiler

10 Aquatec/Seapoint 200-TY optical backscatter sensor

10 Seabird SBE-37SI Microcat conductivity-temperature sensor

10 Coral Imaging System time-series camera

6 Aquatec/Seapoint 200-TY optical backscatter sensor

3 Seabird SBE-37SI Microcat conductivity-temperature sensor

3 Aquatec/Seapoint 200-TY optical backscatter sensor

Inshore Wall [3] 5 Aquatec/Seapoint 200-TY optical backscatter sensor

3 Seabird SBE-37SI Microcat conductivity-temperature sensor

3 Aquatec/Seapoint 200-TY optical backscatter sensor

South-central Reef [4] 10 NIWA Dobie-A wave/tide gauge

10 Aquatec/Seapoint 200-TYT optical backscatter sensor with temperature sensor

CRAMP Site [5] 10 RD Instruments 600 kHz Workhorse Monitor acoustic Doppler current profiler

10 Aquatec/Seapoint 200-TY optical backscatter sensor

10 Seabird SBE-37SI Microcat conductivity-temperature sensor

Numbers in brackets refer to locations on FIGURE 2.

TABLE 3: CTD/OBS/PAR profiler log.

Cast

Number

Time

[HST]

Latitude

[decimal degrees]

Longitude

[decimal degrees]

Depth

[m]

1 10:21 22.212117 -159.501450 14.5

2 11:36 22.207917 -159.503800 8.5

3 11:43 22.206800 -159.508900 10.0

4 11:52 22.208183 -159.507117 10.0

5 12:05 22.208967 -159.509850 4.5

6 13:23 22.210983 -159.511483 11.5

7 13:28 22.214467 -159.513633 7.5

8 13:35 22.214150 -159.510200 13.5

9 13:39 22.213733 -159.507300 13.0

10 13:45 22.212967 -159.504383 12.5

11 13:59 22.214917 -159.503117 13.5

12 14:38 22.214067 -159.501717 13.5

13 14:42 22.213400 -159.500267 7.5

14 14:45 22.212717 -159.499333 7.5

Cast numbers refer to locations on FIGURE 2.
TABLE 4: Salinity and temperature statistics.

Site Name Depth

[m]

Salinity

[P.S.U.]

Temperature

[

o

C]

Northwest Reef [1] 10 N.D. 25.91 ± 0.47

Offshore Wall [2] 3 34.87 ± 0.12 26.02 ± 0.44

Offshore Wall [2] 6 N.D. N.D.

Offshore Wall [2] 10 34.87 ± 0.13 25.90 ± 0.46

Inshore Wall [3] 3 34.91 ± 0.21 26.04 ± 0.43

Inshore Wall [3] 5 N.D. N.D.

South-central Reef [4] 10 N.D. 25.98 ± 0.45

CRAMP Site [5] 10 34.54 ± 0.25 25.91 ± 0.48

All values are mean ± one standard deviation.

N.D. = No data.

Numbers in brackets refer to locations on FIGURE 2.

TABLE 5: Turbidity statistics.

Site Name Depth

[m]

Turbidity

[N.T.U.]

Northwest Reef [1] 10 0.67 ± 0.18

Offshore Wall [2] 3 1.06 ± 0.43

Offshore Wall [2] 6 0.78 ± 0.77

Offshore Wall [2] 10 1.74 ± 0.82

Inshore Wall [3] 3 1.16 ± 0.69

Inshore Wall [3] 5 3.40 ± 2.92

South-central Reef [4] 10 1.01 ± 0.73

CRAMP Site [5] 10 1.47 ± 1.05

All values are mean ± one standard deviation.

Numbers in brackets refer to locations on FIGURE 2.

These data are from the time period from June 8-13 when concurrent, reliable data were recorded.
APPENDIX 1

ADCP Information

RD Instruments 600 kHz Workhorse Monitor; s/n: 2074 and 2432

Transmitting Frequency: 614 kHz

Depth of Transducer: 10 m

Blanking Distance: 0.25 m

Height of First Bin above Bed: 0.73 m

Bin Size: 0.5 m

Number of Bins: 24

Operating Mode: High-resolution, broad bandwidth

Sampling Frequency: 2 Hz

Beam Angle: 20 deg

Time per Ping: 00:00:00.30

Pings per Ensemble: 120

Profile Ensemble Interval: 0:05:00.00

Wave Ensemble Interval: 2:00:00.00

Sound Speed Calculation: Set salinity, updating temperature

via sensor

Data Processing:

The data were averaged over 36-bin (1 hour) ensembles, all of the

spurious data above the water surface were removed and all of the data in

bins where the beam correlation dropped below 70% were removed for

visualization and analysis.

Position Information:

Garmin GPS-76 GPS; s/n: 80207465; USGS/CRP unit#1

RDI internal compass/gyroscope, set to –10 deg magnetic offset
APPENDIX 2

Dobie, Microcat and SCOBS Sensor Information

NIWA Dobie-A Wave/tide Gauge; s/n: 2000-18 and 2000-21

Depth of Transducer: 10 m

Operating Mode: Water level time series

Sampling Frequency: 2 Hz

Measurements per Burst: 1024

Time Between Bursts: 01:00:00.00

Seabird Microcat SBE-39SM CT; s/n: 1161, 2792, 3800 and 3801

Sampling Frequency: 2 Hz

Measurements per Burst: 8

Time Between Bursts: 00:05:00.00

Aquatec/Seapoint 200-TY SCOBS; s/n: 371-013, 371-014, 371-015, 371-025 and

371-026

Aquatec/Seapoint 210-TYT SCOBS; s/n: 024-002, 024-005, 024-006 and 024-007

Sampling Frequency: 2 Hz

Measurements per Burst: 30

Time Between Bursts: 00:05:00.00

Data Processing:

The Dobie water level data were averaged over the entire 20 min burst to

compute tidal height while hourly significant wave height and dominant

wave period data were computed spectrally using the USACE

SUPERDUCK method. The SCOBS and CT data were post-processed

for visualization and analysis by removing all instantaneous (only one data

point in time) data spikes that exceeded the deployment mean + 3

standard deviations.

Position Information:

Garmin GPS-76 GPS; s/n: 80207465; USGS/CRP unit#1
APPENDIX 3

Conductivity/Temperature/Depth (CTD) Profiler with Optical Backscatter (OBS) and

Photosynthetically-Available Radiation (PAR) Sensor Information

Instruments:

Seabird 19plus CTD; s/n: 4299

D&A Instruments OBS-3; s/n: 1983

Li-Cor SPQA-3562; s/n: 825

Sampling Frequency: 4 Hz

Position Information:

Garmin GPS-76 GPS; s/n: 80207465; USGS/CRP unit#1

Data Processing:

The data were averaged into 0.5 m vertical bins and all of the spurious data

marked by a flag in the raw data were removed for visualization and analysis.

Stratification were measured as the difference between the mean of the top

three bins (0.5-1.5 m below the surface) and the bottom three bins (0.5-1.5 m

above the bed).