Coastal Circulation and Sediment Dynamics in 

Maunalua Bay, Oahu, Hawaii

Measurements of Waves, Currents, Temperature, Salinity, and Turbidity: 

November 2008―February 2009

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

Open-File Report 2010-1217

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director 

U.S. Geological Survey, Reston, Virginia: 2010

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Suggested citation:

Storlazzi, C.D., Presto, M.K., Logan, J.B., and Field, M.E., 2010, Coastal circulation and 

sediment dynamics in Maunalua Bay, Oahu, Hawaii; measurements of waves, currents, 

temperature, salinity, and turbidity; November 2008-February 2009: U.S. Geological Survey 

Open-File Report 2010-1217, 59 p. [http://pubs.usgs.gov/of/2010/1217/].

Any use of trade, product, or firm names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report.
iii

Contents

Introduction ...........................................................................................................1

Project Objectives..............................................................................................1

Study Area .........................................................................................................1

Operations ............................................................................................................2

Equipment and Data Review .............................................................................2

Acoustic Doppler Current Profilers (ADCP) ....................................................2

Conductivity and Temperature (CT)................................................................2

Turbidity Sensors (SLOBS).............................................................................2

Weather Station (WS).....................................................................................4

Terrestrial Imaging System (TIS) ....................................................................4

Water Column Profiler (WCP).........................................................................4

Coral Imaging System (CIS) ...........................................................................4

Sediment Data ................................................................................................6

Miscellaneous Data Sources ..........................................................................6

Research Platform and Field Operations...........................................................6

Data Acquisition and Quality.................................................................................6

Results..................................................................................................................7

Oceanographic and Atmospheric Forcing..........................................................7

Stream Discharge ..............................................................................................7

Winds.................................................................................................................7

Waves................................................................................................................8

Tides..................................................................................................................8

Currents .............................................................................................................8

Temporal Variations Water Column Properties................................................11

Temperature ................................................................................................. 11

Salinity ..........................................................................................................11

Turbidity ........................................................................................................11

Spatial Variations in Water Column Properties ................................................14

Sediment Composition and Grain Size ............................................................14

Discussion ..........................................................................................................23

Distribution of Forcing Conditions ....................................................................23

Spatial and Temporal Variability in Circulation Patterns and Water Column 

Properties ........................................................................................................26

Tides.............................................................................................................24

Winds............................................................................................................24

Waves...........................................................................................................24

Kona Storm...................................................................................................28

Spatial Variability in Turbidity and Salinity .......................................................34

Sediment Dynamics.........................................................................................36

Conclusions ........................................................................................................41

Acknowledgments...............................................................................................42

References Cited ................................................................................................42

Additional Digital Information ..............................................................................43
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Direct Contact Information ..................................................................................43

Appendixes .........................................................................................................53

Appendix 1.......................................................................................................53

Appendix 2.......................................................................................................55

Appendix 3.......................................................................................................55

Appendix 4.......................................................................................................56

Appendix 5.......................................................................................................57

Appendix 6.......................................................................................................58

Appendix 7.......................................................................................................59

Figures

Figure 1. Map of Maunalua Bay, Oahu, Hawaii, and location of the 

instrument packages ....................................................................................... 3 

Figure 2. Photographs of the equipment used in the study .................................. 5 

Figure 3. Meteorologic forcing and stream data during the study period.............. 9 

Figure 4. Wave forcing during the deployment...................................................10

Figure 5. Mean near surface and near bed current speed and direction at 

the deeper sites.............................................................................................12

Figure 6. Mean near surface and near bed current speed and direction at 

the shallower sites .........................................................................................13

Figure 7. Temperature and salinity data from the deep and shallow sites. ........15

Figure 8. Turbidity data from the deep and shallow sites ...................................16

Figure 9. Variability in water temperature during the November 2008 and 

February 2009 surveys..................................................................................17

Figure 10. Variability in salinity during the November 2008 and February 

2009 surveys ................................................................................................. 18

Figure 11. Variability in turbidity during the November 2008 and February 

2009 surveys ................................................................................................. 19

Figure 12. Variability in fluorescence during the November 2008 and 

February 2009 surveys..................................................................................20

Figure 13. Variability in dissolved oxygen during the November 2008 and 

February 2009 surveys..................................................................................21

Figure 14. Grain size of sediment at the main study sites..................................22

Figure 15. Composition of sediment at the main study sites ..............................25

Figure 16. Pie chart showing the distribution of dominant forcing conditions 

in Maunalua Bay for the deployment period from November 2008 

through February 2009 ..................................................................................26

Figure 17. Principal axis ellipses for mean currents during conditions 

dominated by tidal flow at the main study sites..............................................27

Figure 18. Principal axis ellipses and mean current speeds and directions 

during trade-wind conditions at the main study sites .....................................29

Figure 19. Principal axis ellipses and mean current speed and direction 

during large wave conditions at the main study sites.....................................30
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Figure 20. Principal axis ellipses and mean current speed and direction 

during the December 11, 2008 Kona storm at the main study sites ..............31

Figure 21. Photographs of Maunalua Bay taken by the Terrestial Imaging 

System during the December 11, 2008 (2008 Year Day 346), Kona 

storm .............................................................................................................32

Figure 22. Turbidity data during the December 11, 2008 (2008 Year Day 

346), Kona storm...........................................................................................33

Figure 23. Photographs of site MP6 in Maunalua Bay taken by the Coral 

Imaging System showing the impact of the December 11, 2008 (2008 

Year Day 346), Kona storm ...........................................................................34

Figure 24. Temperature and salinity data during the December 11, 2008 

(2008 Year Day 346), Kona storm................................................................. 35

Figure 25. Mean and standard deviation of the salinity and turbidity data at 

the main study sites.......................................................................................37

Figure 26. Frequency of sediment mobility at the main study sites....................38

Figure 27. Cumulative near-bed sediment fluxes at the main study sites ..........40

Tables 

Table 1. Experiment Personnel.......................................................................44

Table 2. Instrument Package Sensors............................................................45

Table 3. Instrument Package Location Information.........................................46

Table 4. Water-Column Profiler Cast Location and Depth Information. ..........46

Table 5. Meteorological Statistics. ..................................................................47

Table 6. Wave Statistics. ................................................................................47

Table 7. Current Statistics...............................................................................48

Table 8. Temperature Statistics. .....................................................................48

Table 9. Salinity Statistics. ..............................................................................49

Table 10. Turbidity Statistics.............................................................................49

Table 11. Sediment Sample Location and Depth Information...........................49

Table 12. Sediment sample grain size Information. ..........................................50

Table 13. Sediment Sample Composition Information......................................51

Table 14. Sediment Flux Statistics....................................................................52
Coastal Circulation and Sediment Dynamics in Maunalua Bay, 

Oahu, Hawaii

Measurements of Waves, Currents, Temperature, Salinity, and Turbidity: 

November 2008―February 2009

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

Introduction 

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

turbidity were made in Maunalua Bay, southern Oahu, Hawaii, during the 2008-2009 winter to better 

understand coastal circulation, water-column properties, and sediment dynamics during a range of 

conditions (trade winds, kona storms, relaxation of trade winds, and south swells). A series of bottommounted instrument packages were deployed in water depths of 20 m or less to collect long-term, highresolution measurements of waves, currents, water levels, temperature, salinity, and turbidity. These 

data were supplemented with a series of profiles through the water column to characterize the vertical 

and spatial variability in water-column properties within the bay. These measurements support the 

ongoing process studies being done as part of the U.S. Geological Survey (USGS) Coastal and Marine 

Geology Program’s Pacific Coral Reef Project; the ultimate goal of these studies is to better understand 

the transport mechanisms of sediment, larvae, pollutants, and other particles in coral reef settings. 

Project Objectives 

The objective of this study was to understand the temporal variations in currents, waves, tides, 

temperature, salinity and turbidity within a coral-lined embayment that receives periodic discharges of 

freshwater and sediment from multiple terrestrial sources in the Maunalua Bay. Instrument packages 

were deployed for a three-month period during the 2008-2009 winter and a series of vertical profiles 

were collected in November 2008, and again in February 2009, to characterize water-column properties 

within the bay. Measurements of flow and water-column properties in Maunalua Bay provided insight 

into the potential fate of terrestrial sediment, nutrient, or contaminant delivered to the marine 

environment and coral larval transport within the embayment. Such data are useful for providing 

baseline information for future watershed decisions and for establishing guidelines for the U.S. Coral 

Reef Task Force’s (USCRTF) Hawaiian Local Action Strategy to address Land-Based Pollution (LASLBP) threats to coral reefs adjacent to the urbanized watersheds of Manualua Bay.

Study Area

Maunalua Bay is on the south side of Oahu, Hawaii (fig. 1), and is approximately 10 km 

long and 3 km wide. The bay is flanked by two large, dormant craters: Koko Head to the east and 

Diamond Head to the west. Rainfall in the watersheds that drain into Maunalua Bay ranges from more 

than 200 cm/year at the top of the Ko’olau Range that borders the northwestern part of the bay to less 

than 70 cm/year to the east at Koko Head. Seven major channels flow into the bay, and all but one have 

been altered by engineering structures.
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Operations

This section provides information about the personnel, equipment, and field operations used 

during the study. See table 1 for a list of personnel involved in the experiment and tables 2 through 14 

for complete listings of instrument and deployment information. 

The study consisted of three suites of instruments to provide an integrated understanding of 

circulation and sediment dynamics in Maunalua Bay’s coastal waters: terrestrial instruments, bottommounted oceanographic instruments, and spatial hydrographic surveys. The terrestrial instruments 

included a weather station and a digital-camera system. These were deployed on top of the Mt. Terrace 

Apartments in Hawaii Kai to get a wide field of view of the bay and un-obstructed meteorologic data 

(fig. 1). The bottom-mounted oceanographic instruments were deployed in two reef-parallel alongshore 

arrays along the 10 m and 20 m isobaths. In addition to these fixed, bottom-mounted, time-series 

measurements, repetitive surveys of water-column properties were made in various locations throughout 

the bay at the beginning (November 2008) and end (February 2009) of the experiment. All vessel 

operations, including mobilization and demobilization, were based out of Ala Wai marina 

approximately 5 km to the east of the bay, and all instrument packages were situated on the sandy 

seabed in water depths less than 20 m. 

Equipment and Data Review

Acoustic Doppler Current Profilers (ADCP)

Six upward-looking acoustic Doppler current profilers (ADCP) were mounted on MiniPROBEs 

(MP) packages (fig. 2A) along the 10 m and 20 m isobaths in Maunalua Bay. These ADCPs sampled 

0.5-m vertical bins from 1.0 m above the seafloor up to the surface for 180 s at 2 Hz every 10 min to 

allow calculation of tides from modulations in water level (m), mean current speeds (m/s), mean current 

directions (°True), and higher frequency motions such as internal tidal bores and non-linear internal 

waves. Directional wave data were recorded for 1,024 s at 2 Hz every two hours; these data included 

significant wave height (m), dominant wave period (s), mean wave direction (°True), and directional 

spread (°). Acoustic backscatter data (dB) collected from the ADCPs for the current measurements also 

provide information on the particulates in the water column and are used as a qualitative measurement 

of turbidity. The sensor locations are listed in tables 2 and 3; complete sensor and processing 

information is listed in appendix 1. 

Conductivity and Temperature (CT)

Seven conductivity and temperature (CT) sensors (fig. 2A) also were mounted on the MPs and 

collected and averaged 4 samples every 5 min to measure water temperature (°C) and conductivity 

(S/m), from which salinity (PSU) was calculated. The rapid sampling rate was used in an attempt to 

record any transient freshwater plumes and/or submarine groundwater discharge being advected past the 

instruments. Offshore instrument locations were selected to record the distance, mixing, and direction 

of freshwater with oceanic water and to correlate with current measurements. The sensor locations are 

listed in tables 2 and 3; complete sensor and processing information is listed in appendix 2. 

Turbidity Sensors (SLOBS)

Eight self-logging optical backscatter sensors (SLOBS; fig. 2A) averaged 8 samples every 5 min 

to measure turbidity data in Nephelometric Turbidity Units (NTU). The SLOBS were calibrated to 

suspended-sediment concentrations (SSC) in mg/L using seafloor sediment from the bay. The SLOBS 

on the MPs were mounted above the ADCPs in order for the turbidity data to be correlated with the 

along- and cross-shore velocity data from the bin closest to the seabed of the ADCPs to calculate 
3
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sediment flux. The sensor locations are listed in tables 2 and 3; complete sensor information is listed in 

appendix 2, and calibration information is listed in appendix 7. 

Weather Station (WS) 

Meteorological data were acquired by a self-contained weather station (WS) deployed on top Mt. 

Terrace Apartments (fig. 1,2B), 71 m above ground, in the northeast corner of the bay. The WS 

recorded 25 min averages of barometric pressure (mb), air temperature (°C), precipitation (mm), wind 

speed (m/s), and wind direction (°True) every half hour. The instrument’s location is listed in table 3; 

complete sensor information is listed in appendix 3.

Terrestrial Imaging System (TIS)

Imagery of Maunalua Bay was collected using the USGS Terrestrial Imaging System (TIS), 

which consists of a Nikon CoolPix 8700 8-megapixel digital camera, a control unit, and battery in a 

waterproof housing with an external solar panel (fig. 2C). The TIS was mounted on a metal pole that 

was attached to the top of the apartment building at an elevation of approximately 70 m above sea level 

to achieve an unobstructed view of the eastern half of the bay. This system was employed to collect a 

time series of images to provide information on the natural frequency and duration of processes 

impacting the Bay (stream discharge, freshwater, sediment plumes, storms and waves). The TIS took 

images approximately every two hours during daylight hours (06:00, 07:00, 08:00, 10:00, 12:00, 14:00, 

16:00, and 18:00 HST) throughout the deployments. The sensor location is listed in tables 2 and 3; 

complete sensor information is listed in appendix 3. 

Water Column Profiler (WCP)

Vessel-based surveys of water-column properties were made using a 

Conductivity/Temperature/Depth (CTD) Profiler with Optical Backscatter (OBS), PhotosyntheticallyAvailable Radiation (PAR) Sensor, Dissolved Oxygen (DO) sensor, and a fluorometer that measured

chlorophyll (chl) . This package collected vertical profiles of water temperature (°C), salinity (PSU), 

density (kg/m3), turbidity (NTU), PAR (mE), DO (%), and chl (mg/m3), as shown in figure 2D. The 

profiler data position and depth information is listed in table 4; complete sensor information and 

individual cast acquisition logs are listed in appendixes 4-7. The profile surveys were completed during 

approximately 3-hour periods between Koko Head and Diamond Head craters at the beginning and end 

of the deployment (November 2008 and February 2009). 

Coral Imaging System (CIS)

The USGS Coral Imaging System (CIS) was used to collect a time series of seabed images and 

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 all mounted on a tetrapod (fig. 2E), it was used to collect a 

time series of seabed images. The CIS was deployed in a patch of sand at the MP6 site, and the camera 

and strobe were angled to not only record images of the adjacent reef, but also of a gridded black and 

white camera-calibration reference block. 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 (0000, 0400, 0800, 1200, 1600, and 2000 HST); complete sensor 

information is listed in appendix 3. 
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Sediment Data

Sediment traps were deployed during the entire length of the experiment (November 2008-

February 2009) at all six MP sites to collect suspended sediment from the water column. Simple tube 

traps, consisting of a clear plastic tube 60 cm long with an internal diameter of 6.7 cm, were deployed 

with their openings 0.7 m above the seabed at the six main instrument sites. A baffle was placed in the 

top of each tube trap to reduce turbulence and minimize disturbance by aquatic organisms (Bothner and 

others, 2006), as shown in figure 2A. Net vertical sediment flux onto the coral reef surface was not 

measured by the sediment traps due to the energetic nature of the deployment sites on the inner shelf, 

principally because material falling into the trap has a much lower potential for resuspension than the 

same material that settles on the adjacent reef surface (Bothner and others, 2006). Coarse sediment 

particles likely were collected preferentially because of their higher settling velocity than finer particles. 

Thus finer particles with slow settling velocities relative to the circulation and exchange of water 

contained in the trap can be underrepresented in the collected samples (for example, Gardner and others, 

1983; Baker and others, 1988). The location and depth of each sediment trap is listed in table 11. In 

addition to these suspended-sediment samples, seabed-sediment samples were collected by divers at the 

MP study sites. The bulk grain sizes of the seabed and sediment-trap samples were analyzed using both 

Beckman Coulter Counter (silt and clay fractions) and 2-m settling tubes (sand fraction), and within 

each grain size fraction the percentage of carbonate was determined with a UIC Coulometer. Carbonate 

and terrigenous percentages for the sand-, silt-, and clay-size fractions were determined using the 

methodology developed by Barber (2002). 

Miscellaneous Data Sources

Discharge data (m3/s) for the H-1 storm drain at Kapiolani Avenue were provided by the 

National Water Information System’s stream-flow gauge #211722157485601 (NWIS, 2010); listed in 

table 3. Navigation equipment for deployment, recovery, and survey operations included a hand-held 

WAAS-equipped GPS unit 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. 

Research Platform and Field Operations

The instrument deployments and recoveries were done using the F/V Alyce C. Vessel operations, 

including mobilization and demobilization, were based out of the Ala Wai marina, Oahu, Hawaii. The 

port 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. 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 WCP casts were done by hand from the same vessel. The vessel wheelhouse was 

outfitted with a laptop computer and GPS-enabled navigation system to provide the vessel captain with 

a graphic display of position information, speed, heading, and distance to the next location. 

Data Acquisition and Quality

Data were acquired for 98 days during the period between November 10, 2008, and February 15, 

2009 (2008 Year Day [YD] 315-413). More than 2.6 million data points were recorded by the ADCPs, 
7

CTs, SLOBS, and WS, more than 12,000 data points were recorded by the WCP, 648 images were 

taken by the TIS, and 192 images were taken by the CIS. The raw data were archived and copies of the 

data were post-processed for analysis.

The ADCP, CT, SLOBS, TIS, and WS data generally appeared to be of high quality. The ADCP 

at site MP6 stopped recording on 2008 Year Day 388 due to an electronic malfunction. The SLOBS at 

sites MP2, MP3, and UH had issues with their anti-biofouling wipers and thus reliable data were 

recorded only for the first 11 days of the experiment (2008 Year Days 315-325). The CTs had 

intermittent anomalously low conductivity (and thus salinity) values during large wave events when 

sediment clogged the conductivity cell. 

The ADCPs’ current data were 10-28 hour band-pass filtered to investigate the contribution of 

the tides to flow patterns and 36 hour low-pass filtered to look at the influence of winds and waves 

when one or the other was the primary forcing condition (for example, weak winds and large waves or 

strong winds and small waves). In order to address sediment fluxes in the bay, we computed suspendedsediment concentrations in mg/L for the SLOBS as addressed above. The CIS imagery, although overall 

very good at the beginning of the deployment, was inoperable after a Kona storm on December 11, 

2008, damaged the camera. The WCP data were high in quality; however, as typically occurs, the OBS 

data near the surface and seabed often displayed spikes due to interaction of the optical beam with the 

vessel or the seabed, respectively. These spurious profiler data were removed during processing. 

Electronic issues with the WCP’s PAR sensor made the data unreliable and, therefore, these data are not 

presented in this report. 

Results

This section reviews the data collected by the instruments during the deployments and addresses 

the significance of the findings to better understand the oceanographic conditions in the study area. 

Oceanographic and Atmospheric Forcing

The study period from November 2008 through February 2009 covered the beginning of the wet, 

non-trade wind season in Hawaii (fig. 3). The precipitation ranged from 0.0 to 10.3 mm/30 min, with a 

mean rainfall ± one standard deviation of 0.1±0.4 mm/30 min (fig. 3e). The majority of precipitation 

occurred during storms approaching from the south, with some of the precipitation due to orographic 

effects associated with strong trade winds blowing over the Ko’olau Range. The air temperature ranged 

from 17.75 to 29.31oC with a mean temperature ± one standard deviation of 22.97±1.55oC (fig. 3b). 

Diurnal heating on the order of 1 to 2oC was observed, with a slight decrease caused by the seasonal 

trend in temperature during the course of the deployment corresponding to the onset of the northern 

hemisphere winter.

Stream Discharge

Daily stream-discharge data were acquired from the USGS stream-flow gauge in the H-1 storm 

drain at Kapiolani Avenue, Oahu, Hawaii (fig. 3F). These data provide a measure of the stream response 

to precipitation in the study area. Discharge ranged from 0 to 0.21 m3

/s, with a mean discharge ± one 

standard deviation of 0.0047±0.02 m3/s. The highest discharge coincided with the heavy precipitation 

from December 11, 2008, through December 15, 2008, (2008 YD 346-350; fig. 3E,F).

Winds

The mean wind speeds at the WS in Maunalua Bay ranged from 0.00 to 15.75 m/s, with a mean 

speed ± one standard deviation of 4.77±2.83 m/s during the deployment (fig. 3C). The mean wind 
8

direction ± one standard deviation during the deployment was 105.2±84.7° (fig. 3D). Winds 

predominantly from the east were classified as “trade winds” and were associated with dry, stable 

weather; this set of forcing conditions characterized approximately 50 percent of the study period. 

Strong, south winds were associated with drops in barometric pressure from locally generated storms 

that usually coincided with rainfall. Light, variable winds also are prevalent during this deployment and 

were associated with low amounts of rainfall and stable weather patterns. 

Waves

The waves that impacted Maunalua Bay during the course of the experiment measured by the 

directional wave gauge at the MP1 site in the central part of the bay are shown in fig. 4. Significant 

wave heights ranged from 0.48 to 4.07 m, with a mean significant height ± one standard deviation of 

1.06±0.34 m (fig. 4A,B). Dominant wave periods varied from 2.2 to 6.7 s, with a mean dominant period 

± one standard deviation of 4.4±0.6 s (fig. 4C). The mean wave direction ± one standard deviation was 

146.1±17.2°. The waves measured at the MP1 site were consistently from the southeast with wave 

heights and periods on the order of 1 m and 4 s, respectively, that were generated by the strong easterly 

trade winds. A large south swell (>4m) was measured from December 10-

15, 2008 (2008 YD 344-349), 

during the large Kona storm that impacted Maunalua Bay. This swell coincided with strong winds and a 

large amount of precipitation during a short period of time. Wave heights at the shallow sites (MP4-6, 

depth <10 m) show similar patterns but are smaller in size than the deep sites (depths ~20 m). 

Tides

The study period encompassed more than seven complete spring-neap tidal cycles (fig. 5A). 

Tides in Maunalua Bay are typical for the Hawaiian Islands: microtidal, mixed, semi-diurnal with two 

uneven high tides and two uneven low tides per day, thus the tides change approximately every 6 hours. 

The mean daily tidal range was approximately 0.6 m, while the minimum and maximum daily tidal 

ranges were 0.4 m and 1.0 m, during neap and spring tides, respectively.

Currents

The mean current speed at the three shallow (depth <10 m) sites was 0.21±0.12 m/s close to the 

surface and 0.05±0.03 m/s close to the seabed (fig. 5). The near-surface currents at MP4 and MP5 

showed a strong, net offshore flow and were influenced more by wind speed and direction (fig. 5C,D) 

than those near the surface at the MP6 site (fig. 5E). The near-bottom currents at all three shallow (depth 

<10 m) sites also were influenced by the winds but were smaller in magnitude. 

The mean current speed at the three offshore deep (depth ~20 m) sites ± one standard deviation 

was 0.33±0.17 m/s close to the surface and 0.21±0.12 m/s close to the seabed (fig. 6), approximately 50 

percent greater than mean speeds close to the surface at the shallower sites and four times greater than 

those near to the bed at the shallower sites. Both the near surface and near bed currents at all the deep 

sites did not correlate well with wind speed or direction. It appears that bathymetry, tides, and the 

influence of larger-scale, open-ocean flow exert greater influence on the magnitude and direction of the 

currents than do the winds. 
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Temporal Variations Water Column Properties

The water-column properties that were measured by the deployed CTs and SLOBS included 

variations in temperature (oC), salinity (PSU), and optical backscatter (NTU). The measurements were 

done to address the temporal variability in water-column properties over a range of forcing conditions. 

Temperature

Water temperatures in the bay ranged from 23.65 to 26.36°C, with a mean temperature ± one 

standard deviation of 25.10±0.4°C (table 8). The inshore and offshore sites showed similar seasonal 

patterns in decreasing temperature during the deployment (fig. 7A,C). The diurnal temperature 

variations did not appear to be coherent across water depths. In some instances, the offshore sites 

showed greater day-to-day variations, while at other times the inshore sites showed greater diurnal 

variability. The non-coherence of water temperatures may be the result of tidally-driven interactions 

between deeper, cooler oceanic water and warmer nearshore waters.

Salinity

Salinity measurements in the bay ranged from 19.64 to 35.21 PSU, with a mean salinity ± one 

standard deviation of 34.83±0.31 PSU (table 9). The salinity measurements at the offshore and inshore 

sites display different trends and variability during the deployment (fig. 7B,D). Salinity at the offshore 

sites was fairly constant around 35 PSU but showed greater variability during times of heavy 

precipitation, suggesting that these sites may be influenced by freshwater discharge from streams or 

submarine groundwater discharge. The inshore sites also were relatively constant, with salinity values 

generally between 34 and 35 PSU, until the large precipitation from the December 11, 2008 (2008 Year 

Day 346), Kona storm. Salinity values at all the sites dropped significantly, with the largest decreases at 

the shallow MP6, MP5, and MP4 sites. The periods where Salinity values were low and variability was 

almost absent following the Kona storm at sites MP4 and MP5 are likely spurious data resulting from 

wave-driven sediment blocking the conductivity sensors.

Turbidity

Concurrent, reliable turbidity data were recorded for only 10 days (2008 YD 315-325) by all five 

of the SLOBS instruments; only the SLOBS at the MP4, MP5, and MP6 sites recorded data for the 

duration of the experiment (fig. 8). During the short time period with complete data coverage, the 

turbidity in the study area ranged between 0.00 and 31.94 NTU, with a mean turbidity ± one standard 

deviation of 0.87±1.09 NTU (table 10). The turbidity data for the longer time period (2008 YD 315-

396) ranged between 0.16 and 136.57 NTU, with a mean turbidity ± one standard deviation of 

2.68±4.35 NTU (table 10). Overall the turbidity in the bay is relatively low compared to previous 

measurements made elsewhere in the Main Hawaiian Islands except at the inshore sites MP4 and MP5, 

which consistently showed elevated turbidity values. The greatest turbidity values were measured 

during and shortly after the Kona storm from December 10-12, 2008 (2008 Year Day 345-347), that 

introduced large quantities of terrigenous sediment into the system. During this event, turbidity values 

exceeded 35 NTU for hours at the inshore (<10 m) sites, as discussed in greater detail in a later section 

of this report. Other periods of elevated turbidity occurred during periods when larger-than-normal 

waves impacted the bay (2008 Year Days 330, 370-390). 

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”, as defined on page 54-30 of that report 

(Department of Health, 2004), sets the maximum allowable wet season mean turbidity level at 0.50 

NTU. The mean turbidity values for the period of study at sites MP4, MP5, and MP6 exceeded this 

threshold, and the mean turbidity value at the UH site (0.46 NTU) was barely below that threshold. 
12
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The mean turbidity value at the MP5 site exceeded the maximum acceptable mean level by almost half 

an order of magnitude (table 5). 

Spatial Variations in Water Column Properties

Spatial variations in water-column properties were measured in November 2008 and February 

2009 at a greater number of locations within Maunalua Bay than the MPs using a vessel. The properties 

that were measured by the water column profiler included variations in temperature (oC), salinity (PSU), 

turbidity (NTU), chl (mg/m3), and DO (%) with depth. The surveys were done to address both alongand cross-shore variability in water-column properties in Maunalua Bay and to put the high temporal 

resolution but spatially-limited measurements made by the CTs and SLOBSs in the context of larger 

patterns throughout the bay. The greater density of sample locations near the coastline and in the Hawaii 

Kai Harbor channel was established to identify areas where terrestrial sediment or submarine 

groundwater discharge might be entering the bay. The profiles extended offshore to the 30 m isobath to 

examine the extent of mixing with oceanic waters.

In November 2008 (fig. 9A), depth-averaged water temperatures generally were lower and less 

variable closer to shore, except in the Hawaii Kai Harbor channel and off the paleostream channel at 

Kahala. During February 2009 (fig. 9B), however, the variability in water temperature was greatest 

close to shore, possibly due to cooler fluvial or submarine groundwater inputs. Overall, the water 

temperature throughout the bay was approximately 2°C cooler during the February 2009 survey than 

during the November 2008 survey. In November 2008 (fig. 10A), depth-averaged salinity values 

generally were higher and less variable closer to shore, except in the northeastern portion of the bay, 

including the Hawaii Kai Harbor channel. During February 2009 (fig. 10B), however, the variability in 

salinity was greatest close to shore in the western portion of the bay, possibly due to fluvial or 

submarine groundwater inputs. Overall, the salinity values throughout the bay were approximately 0.05 

PSU greater during February 2009 than during November 2008. 

In November 2008 (fig. 11A), depth-averaged turbidity values generally were greater and more 

variable closer to shore, especially in the Hawaii Kai Harbor channel. During February 2009 (fig. 11B), 

the turbidity were greatest in Hawaii Kai Harbor channel. Overall, the turbidity values throughout the 

bay were approximately 20 NTU lower during the February 2009 survey than during the November 

2008 survey, suggesting the large inputs of sediment observed during the December 2008 Kona storm 

did not linger long in the bay under the environmental forcing conditions (winds and waves) that 

occurred between the December 2008 storm and the February 2009 survey. In both November 2008 

(fig. 12A) and February 2009 (fig. 12B), depth-averaged chl values generally were greater in the 

northeastern portion of the bay, the Hawaii Kai Harbor channel, and offshore of Diamond Head in the 

southwestern portion of the bay. Overall, the chl values throughout the bay were approximately 0.3 

mg/m3

 greater during the February 2009 than during the November 2008 survey, possibly due to the 

introduction of nutrients either through fluvial or submarine groundwater sources following the heavy 

rainfall that occurred during the December 2008 Kona storm. The spatial patterns of DO in Maunalua 

Bay during both the November 2008 (fig. 13A) and February 2009 (fig. 13B) were not consistent except 

for lower values in the Hawaii Kai Harbor channel. 

Sediment Composition and Grain Size

The grain size of the seabed at the instrument sites primarily was sand (mean for all sites = 

95.0%) with a small amount of gravel (mean = 4.6%; fig 14A). The largest grain sizes of the seabed 

were found at MP3, approximately 80% sand and 20% gravel, likely a result of the strong currents and 

large waves winnowing out any finer-grained material delivered to the area (tables 11-12). The grain 

size of the sediment collected in the traps shows a very different distribution than the grain size of the 
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seabed samples. The grain size in the traps primarily was sand (mean = 88.7%), with a larger 

component of mud than in the seabed samples (mean = 11.1% versus 0.4% for seabed samples; fig 

14B). This demonstrates that there was fine-grained muddy sediment transported through the system 

but, given the wave energy and current speeds, it was not able to settle and remain on the seabed for 

long durations. This difference in grain size between the seabed and what accumulates in sediment traps 

is not uncommon. Finer-grained, lighter particles can be resuspended more easily and carried higher up 

into the water column and thus to the height of the trap’s opening, than can coarser particles. Once these 

fine-grained particles settle into the trap, they cannot be resuspended and advected away as could the 

same-sized material on the adjacent seabed (e.g., Bothner et al., 2006). 

The composition of the sediment on the seabed primarily was bioclastic reef-derived calcium 

carbonate (mean = 94.6%) at all of the instrument sites (fig. 15A; table 13). All sites had a minor (mean 

= 11.4%) component of total inorganic carbon and an even smaller percentage (mean = 5.4%) of 

terrigenous material. The composition of sediment collected by the sediment traps at all of the 

instrument sites was also primarily reef-derived calcium carbonate (mean = 86.2%), but all traps had a 

larger component of terrigenous sediment (mean = 13.8%) than the seabed samples (fig. 15B). Sediment 

traps often are better indicators of the type of sediment being transported through the system than 

indicators of net deposition on the seabed (e.g., Bothner et al., 2006). Sites MP3, MP5, and MP6 had the 

largest components of terrigenous sediment, indicating these areas may be where the terrigenous 

sediment is introduced into the bay. More than twice as much terrigenous sediment was collected in the 

traps than was observed on the seabed, suggesting that very little terrigenous sediment was deposited on 

the bay’s seabed, and that it primarily was advected through the system because of the predominantly 

small grain size. Overall, the trap collection rates at the shallow (<10 m depth) sites exceeded 70 

mg/cm2

/day and were greater off the northwestern portion of the bay’s (off Kahala) reef flats than off 

the northeastern portion of the bay’s reef flats (Paiko Lagoon; table 11). These high trap accumulation 

rates (>70 mg/cm2/day) potentially can result in mortality of adult corals (Phillip and Fabricius, 2003); 

however, as shown by the geochemistry, much of this material was carbonate in origin and thus likely 

due to resuspension of the surrounding seabed material rather than to the net influx of terrestrial 

sediment.

Discussion

Distribution of Forcing Conditions 

The deployment in Maunalua Bay took place during the months of November – February, at the 

transition from steady, dry, trade-wind season to the winter, which is characterized by rain and 

inconsistent trade winds (fig. 3). During the deployment four dominant conditions were observed and 

quantified: trade wind, variable winds, Kona storm, and south swell (fig. 16). 

Trade wind conditions were defined as wind speeds greater than 4 m/s and wind directions 

between 45° and 135°T. This condition occurred during approximately 50% of the deployment period, 

which is consistent with analyses of observations made elsewhere in the Hawaiian Islands (Presto et al, 

2006). The second most prevalent condition (40%) of the deployment period was variable/low winds, 

which are characterized by wind speeds less than 4 m/s and waves smaller than 1 m. During these times 

tidal currents and/or large-scale oceanographic forcing conditions (for example, eddies) are the primary 

mechanisms driving nearshore circulation. South swell, the third most prevalent condition (7% of the 

deployment), was characterized by waves from directions greater than 170°T, with significant wave 

heights greater than 1 m. These swells often are generated far away from the Hawaiian Islands and are 

not often associated with locally strong winds or precipitation. The least prevalent condition (3% of the 
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deployment period) was Kona storms. Kona storms are episodic, locally generated low-pressure systems 

that often move from the south to north during the winter months and are associated with high rainfall 

and strong south winds. Kona storms were defined as those periods with wind speeds greater than 4 m/s 

and wind directions between 135 and 225°T. 

Spatial and Temporal Variability in Circulation Patterns and Water Column Properties

Tides, trade winds, and waves occurred on different time scales during the experiment and 

contributed to the overall circulation in the bay and the resulting flux of fresh water and sediment. The 

resulting circulation patterns are described below for each of the oceanographic conditions and their 

implications for the delivery of sediment to different portions of the bay. 

Tides

Tides drive most of the daily variability in current speed and direction in Maunalua Bay. During 

flood (rising) tide, the near-surface currents are predominantly to the west and offshore at most of the 

instrument sites (fig. 17A). The near-surface currents at the MP2 site are to the west and onshore, while 

at site MP3 the near-surface currents are to the east and offshore, resulting in a counter-clockwise 

circulation in the bay. During the ebb (falling) tide, the near-surface currents are to the east and slightly 

onshore at most of the instrument sites (fig. 17B). The near-surface currents are to the east and offshore 

at MP2 and to the west and onshore at MP3. During the ebb tide, the near-surface currents create a 

clockwise circulation cell in the bay. The near-surface currents during the flood tide appear to be 

slightly stronger than during the ebb tide at all instrument sites. The principal axes of flow are oriented 

primarily along the bathymetry. The near-bed tidal currents mimic the near-surface currents in 

direction, but are smaller in magnitude.

Winds

Near-surface currents during trade-wind conditions show a circulation pattern influenced by 

wind speed and direction. The near-surface currents at all of the sites are affected by the strong, 

consistent, easterly trade winds (fig 18A). Currents are oriented primarily offshore and slightly to the 

west, suggesting that the bay is flushed of water under this kind of forcing. An exception to this general 

offshore flow pattern was observed at site MP6, where the currents flowed into the wind, toward the 

east, suggesting that there must be some sort of recirculation feature bringing water onshore and up into 

the northeast corner of the bay that was not captured by one of the instruments due to the large distance 

between sites. Near-bed currents (fig. 18B) also mimic the direction of the near-surface currents, but are 

smaller in magnitude. Near-bed turbidity during trade-wind conditions was minimal (<10 NTU) at all 

of the instrument sites, suggesting that very little seabed sediment was resuspended and transported by 

trade-wind forcing. 

Waves

The deployment period coincided with periods of large waves from the south that typically are 

associated with summer conditions, thus providing information on circulation during those periods. 

Near-surface currents during large wave events are shown in figure 19a. At most of the sites in the bay, 

the near-surface current direction was primarily offshore, and at site MP1 and MP6 the currents were 

alongshore. The diversion of water to the west at sites MP1 and MP4 and to the east at sites MP 2 and 

MP6 suggests that there must be a recirculation feature bringing water onshore and up into the northeast 

corner of the bay that was not captured by one of the instrument due to the large distance between the 

sites. Near-bed currents were similar to the near-surface currents in direction but were much smaller in 

magnitude (fig. 19b). The offshore direction of currents during large wave events may be a mechanism 
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for transporting sediment out of the bay during the summer months after sediment is delivered to the 

bay from winter precipitation and stream discharge. 

Near-bed turbidity during wave conditions out of the south was greater (20-50 NTU) than during 

trade-wind conditions at all of the instrument sites, suggesting that the shear stresses generated from the 

large waves were sufficient to have caused the resuspension of seabed sediment. When large waves 

coincided or followed sediment and freshwater input from local streams, the largest turbidity values 

(>100 NTU) of the experiment were observed at the inshore sites (MP4 and MP5). The quick return of 

turbidity to pre-event levels indicates that the sediment in suspension predominantly was sand, as 

indicated by the sediment trap and seabed sample data. 

Kona Storm

A large Kona storm brought strong south winds, large waves, and more than 95 mm of rainfall to 

the Maunalua Bay region during a 3-day period from December 11-13, 2008 (2008 Year Day 346-348). 

The large amount of rainfall during the short period of time resulted in large amounts of terrestrial 

sediment being transported into the bay. Near-surface currents in the bay show a pattern of alongshore 

flow toward the middle of the bay and offshore flow to the east (fig. 20A). Near-bed currents show 

alongshore flow to the east and slightly offshore at the deep sites and variable directions at the inshore 

sites (fig. 20B).

A sequence of photos from the TIS shows the progression of the storm, with initially strong 

onshore (southerly) winds (fig. 21A) followed by large waves and heavy precipitation (fig. 21B). The 

waves are shown breaking in the outer part of the bay, indicating their large size (waves break in water 

depths relative to their height, so larger waves break in deeper water); these large waves appear to have 

generated near-bed shear stresses sufficient to resuspend carbonate material on the seabed as inferred 

from the anomalous light color of the water offshore. Just before noon on December 11 (2008 Year Day 

346), the terrestrial sediment-laden plume exited the lagoon east of Hawaii Kai and entered the bay off 

the western slope of Koko Head (fig. 21C). By mid-afternoon, the surface plume had been advected 

west past the Paiko Lagoon along the fore reef (fig. 21D). 

An increase in turbidity due to either wave resuspension of seabed material or the injection of 

terrestrial material into the bay was recorded by all of the operational SLOBS in the bay. The turbidity 

levels increased first at site MP5, followed by site MP4, site MP6, and site MP2. The largest increase 

and duration in turbidity was observed at site MP5, with values exceeding 120 NTU (fig. 22) and 

greater than 35 NTU for more than 1,065 min (~17.8 hours); the turbidity values exceeded 35 NTU for 

50 min at site MP6 and 310 min (~5.2 hours) at site MP4. The turbidity at MP6 also was imaged by the 

CIS (fig. 23). Before the storm, the coral head and calibration block can be seen clearly in the imagery 

(fig. 23A,B). By noon, the turbidity had exceeded 35 NTU, resulting in a complete “brown-out” at the 

MP6 site (fig. 23C), resulting in no sunlight reaching the seabed and thus a complete shut-down of 

photosynthesis. The imagery from the day following the storm on December 13, 2008 (2008 YD 348) 

showed much lighter (whiter) material in suspension (fig. 23D), suggesting the sediment imaged was 

carbonate seabed material resuspended by waves, and that the terrestrial sediment imaged during the 

storm was no longer the dominant material in the water column and had been advected away. This rapid 

advection of the material away from site MP6 also is supported by the SLOBS data, which showed 

greater (>40 NTU) turbidity values during the storm, but only for a relatively short duration (50 min; 

fig. 22). 

The salinity and temperature values at the offshore and inshore sites during the Kona storm show 

a significant freshwater signal in the bay (fig. 24). The temperature signal at the offshore sites showed a 

minor decrease during the period of heavy precipitation. The salinity also showed a slight decrease at 

sites MP2 and MP3 and little change at site MP1, indicating a significant freshwater signal was not 
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present at that part of the bay. The inshore sites also showed little change in temperature during this 

time period (fig. 24C). Conversely the salinity signal at sites MP4, MP5, and MP6 showed large 

decreases in salinity during this period. The salinity values were lower than 25 PSU (as discussed 

above, mean for bay ~35 PSU) for 70 min at site MP4 and 85 min at site MP6, indicating the presence 

of freshwater either from surface runoff in the form of a freshwater plume being mixed down close to 

the seabed by the large waves or submarine groundwater discharge (SGD).

Spatial Variability in Turbidity and Salinity

The spatial variability for salinity shows the mean and the standard deviation at each site (fig. 

25a). The highest salinity values were measured in the eastern portion of the bay and the lowest values 

in the west, loosely mirroring the terrestrial east-west gradient in rainfall and groundwater recharge, 

with the Ko’olau Range bordering the northwestern part of the bay receiving more than twice the 
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36

precipitation than at Koko Head in the east. The areas of lower salinity values and higher variability 

were in the western part of the bay near sites MP4 and MP5. These locations may have a greater 

influence of freshwater surface flow and SGD. Site MP2 near Koko Head on the eastern edge of the bay 

also had lower salinity values that suggest the possible influence of SGD. 

The spatial variability for turbidity shows the mean and the standard deviation at each site (fig. 

25b). The highest mean and standard deviation of turbidity values were measured at sites MP4 and 

MP5; the eastern portion of the bay showed low mean turbidity values with very little variation. The 

highest turbidity values were measured closer to shore and were greater in the western portion of the 

bay, either indicating a westward transport of sediment along the bay’s fringing reef and/or greater 

inputs of sediment to the bay by the streams in the Kahala region due to higher rainfall upslope in the 

Ko’olau Range.

Overall, the data from the time-series measurements at the instrument sites and the water-column 

surveys suggest that the Hawaii Kai Harbor channel and northeastern portion of the bay is much 

different in nature compared to the rest of Maunalua Bay. This is likely due to three reasons. First, the 

Hawaii Kai Harbor channel is relatively confined, being incised 3-5 m deep in the 0.5-1.5 m deep reef 

flat that dominates the northeastern portion of the bay between Paiko Lagoon and Koko Head. Second, 

the northeastern portion of the bay is in the lee of Koko Crater and Koko Head, and thus is subjected to 

relatively lower trade-wind speeds as compared to the western portion of the bay. Lastly, the channel 

drains the marina, which has different water properties than the bay. As a result of the confined nature 

of the channel and relatively limited trade-wind forcing in the area (wind-driven currents and trade-wind 

waves), it appears that the Hawaii Kai Harbor channel incised into the reef-flat and the northeastern 

portion of the bay is mixed relatively poorly and therefore characterized by water-column properties 

unlike those that dominate the majority of the fore reef and deeper waters through the rest of the bay. 

Sediment Dynamics

By comparing the critical shear stress (amount of stress, or force applied per unit area) for the 

sediment on the seabed and the sediment collected in the sediment traps at each site to the shear stress 

applied to the seabed by waves and currents at each site, an understanding of the frequency that the 

material at a given site is mobilized and resuspended can be determined. When the critical shear stress 

for sediment is less than wave- and current-induced shear stresses, the sediment is in motion; 

conversely, when the critical shear stress is greater than the applied wave and current shear stresses, the 

sediment either falls out of suspension and settles (sedimentation) or is not mobilized from the seabed. 

During this study, the finer material collected in the sediment traps at all of the main study sites (fig. 26) 

was more frequently (51.8%) in motion than the coarser material on the seabed (36.4%). The high 

current speeds at the deeper (~20 m depth) sites off Koko Head and Diamond Head result in greater 

percentages of time the seabed (72.4±5.9%) and sediment trap (87.2±12.0%) material was in motion 

compared to the percentages determined for sediment at the shallower (<10 m depth) sites (12.5±11.8% 

and 28.2±7.9%, respectively). The lower frequency of motion at the shallower sites in the bay suggest a 

greater probability of greater temporary sedimentation of similar-sized material at these sites compared 

to those further offshore along the 20 m isobath. 

Cumulative sediment flux is the mass of sediment moving through an area during a particular 

time period, and it shows in which locations the most (or least) sediment is transported through the area 

due to the mean current velocities and suspended-sediment concentrations (SSC). Instantaneous 

sediment fluxes were calculated using the SSCs calculated from the SLOBS turbidity data (appendix 7) 

and the near-bed velocity data collected from the ADCP’s lowest bin; these instantaneous fluxes were 
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then summed for the period of calculation. Due to instrument problems, SSC data were collected only 

for 2008 Year Days 315-325 (November 10-20, 2008) at all of the instrument sites (table 14). For this 

time period, the largest mass of sediment (52.48 kg/cm2

) in the bay was transported offshore to the 

southeast at site MP5 off Kahala (fig. 27a) due to a combination of moderate near-bed current velocities 

and relatively high SSCs. The orientation to the southeast is in contrast to the dominant westward flow 

pattern under trade-wind forcing (fig. 18) and suggests that there is strong coupling between tides and 

SSCs, with higher SSCs occuring during falling tides when flow is predominantly to the southeast (fig. 

17). Similar patterns of higher SSCs during falling tides have been observed along fringing reefs off 

south Molokai (Storlazzi et al., 2004) and west Maui (Storlazzi and Jaffe, 2008), where terrestrial 

sediment deposited on the reef flat was resuspended by larger waves and stronger currents at high tide 

and advected off the reef flat and over the fore reef as the falling tides drained the sediment-laden water 

off the reef flats. While characterized by vigorous near-bed current velocities, relatively little sediment 

was transported offshore at the deeper (~20 m depth) sites in the bay due to the very low SSCs. Overall, 

the predominant direction of near-bed sediment flux through the bay was offshore toward the southeast 

and the sites closer to shore (MP4, MP5, and MP6) exhibited the greatest near-bed sediment fluxes in 

the bay, with decreasing quantities from west to east. 

Although not all of the SLOBS were operational for the entire study period, the inshore 

instruments collected data during 2008 Year Days 315-396 (November 10, 2008 – January 30, 2009) 

and provide a picture of the amount of sediment moving through the bay during the experiment. As 

during the period when all the instruments were functioning properly (2008 Year Days 315-325), the 

greatest near-bed sediment flux (2680.05 kg/cm2) occurred at site MP5 off Kahala; the sediment flux 

decreased toward the east, with 519.03 kg/cm2

 of sediment flux at site MP6 off Paiko Lagoon (fig 27b). 

Similar to the predominant direction of near-bed sediment flux during the limited time when all of the 

instruments were working, the sediment flux at all of the shallow (<10 m depth) sites for the entire 

experiment was offshore toward the southeast, and the coupling between high SSCs and falling tides is 

apparent. These values were two orders of magnitude greater than the fluxes measured during the first 

10 days of the experiment. This can be attributed partially to the large storm waves, precipitation, and 

fluvial discharge during the December 10-12, 2008 (2008 Year Day 345-347), Kona storm that 

delivered large quanties of sediment to the bay. 

These calculations, together with the large quanity of in place and remotely-sensed data from 

this experiment, suggest that most of the terrestrial sediment that enters the bay from the northern 

shoreline is driven westward on the reef flats along the northern part of the bay. Any sediment that is 

carried offshore of the reef flats by larger plumes likely is advected rapidly offshore to the southeast due 

to the high current velocities in the deeper portions of the bay. As the sediment-laden water on the reef 

flat is advected off the reef flat due to combinations of winds, waves, and falling tides, temporary 

depostion on the shallow fore reef in the northern portion of the bay likely occurs due to the low shear 

stresses. There is little to no long-term accumulation of this terrestrial sediment, and it is advected 

quickly offshore and dispersed. Thus, the inner bay’s reef flats and shallow fore reefs likely are 

subjected to high turbidity values following input events and possibly temporary, short-duration 

sediment deposition but not long-term accumulation of sediment. Due to their more energetic nature, the 

outer portions of the bay are subjected to neither these high turbidity nor temporary depostion events. 

Overall, although significant volumes of terrigenous sediment may be delivered to Maunalua Bay, these 

particles likely are advected through the bay’s waters relatively quickly and do not reside on the seabed 

for long durations. Although this fine-grained terrestrial sediment was not observed on the seabed 

during this study or incorporated in large amounts into the geologic record, it was advected over the 
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bay’s fringing reefs, and has the potential consequence of decreasing photosynthetically available 

radiation (PAR) and desorbing nutrients and/or contributing toxicants. Some researchers (e.g., 

Marszalek, 1981) suggest that prolonged turbidity and the resulting decreased photosynthetically 

available radiation (PAR) are more detrimental to corals than short-term accumulation of sediment.

Conclusions

More than 2.6 million measurements of meteorologic and oceanographic forcing and the 

resulting water-column properties were made. Key findings from these measurements and analyses 

include the following. 

1. Due to the wide range of conditions observed during this experiment, we were able to 

sufficiently characterize the different combination of atmospheric and oceanographic forcing 

conditions typically observed in the Hawaiian Islands. Circulation in the bay was primarily to 

the west due to the prevalent trade-wind forcing. Tidal circulation was to the west (counterclockwise) during flood tide and to east (clockwise) during ebb tide. Large south swell events 

that impacted the bay appear to flush the bay by driving flow primarily offshore. 

2. Overall, turbidity was relatively low in the bay during the entire study. The most turbid periods 

occurred after heavy precipitation and run-off and/or resuspension from large waves. The 

turbidity decreased quickly to pre-event levels upon the cessation of forcing (fluvial discharge or 

large waves), likely due either to the fast current speeds that advected finer material out of the 

bay or the rapid settling of the sand-sized particles (carbonate material that dominates the seabed 

in the bay). 

3. In comparison with areas elsewhere in the bay, the shallow, north-central (off Wailupe) and

northwestern (off Kahala) portions of the bay generally are lower in salinity and more turbid and 

appear to be areas where fresher, sediment-laden water enters the bay. The shallow, northeastern 

(off Hawaii Kai) portion of the bay generally has lower turbidity values and higher salinity 

values than are observed in areas to the west. The salinity and turbidity data suggest one of the 

following: (1) sediment and freshwater inputs are greatest in the central and western portions of 

the bay, causing the fore reef in these regions to be most directly impacted by depressed salinity 

values and elevated turbidity values; or (2) while sediment may be introduced at many points 

along the bay’s northern shoreline, including the Hawaii Kai region, westward transport along 

the northern bay’s reef flat by the northeast trade winds results in depressed salinity values and 

elevated turbidity values along the fore reef coral habitats along the central and western portions 

of the bay. Furthermore, the data from the in place time-series measurements at the instrument 

sites and the water-column surveys suggest that the Hawaii Kai region and northeastern portion 

of the Maunalua Bay is characterized by water-column properties unlike those that dominate the 

majority of the fore reef and deeper waters through the rest of the bay. 

4. The December 10-12, 2008, Kona storm introduced large quantities of freshwater and 

terrigenous sediment into Maunalua Bay that resulted in high (>35 NTU) turbidity values and 

significantly depressed (<25 PSU) salinity values for hours at the inner bay sites. Although 

turbidity levels were elevated, it is evident from the sediment traps and seabed samples that this 

terrigenous sediment did not reside in the bay and apparently was advected away from the sites 

where measurements were made.
42

5. The lower frequency of sediment motion at the shallower (<10 m depth) sites in the bay suggests 

a greater probability of temporary deposition compared to deeper areas (20 m). Overall, the 

dominant direction of near-bed sediment flux through the bay was offshore toward the southeast. 

The shallower sites (<10 m) exhibited the greatest near-bed sediment fluxes in the bay, with 

decreasing quantities from west to east. Although significant volumes of terrigenous sediment 

may be delivered to Maunalua Bay, these particles likely are advected through the bay’s waters 

relatively quickly and probably do not reside on the seabed for long durations. Although finegrained terrestrial sediment was not observed on the seabed during this study, it was advected 

over the bay’s fringing coral reefs where it had the potential for decreasing photosyntheticallyavailable radiation (PAR) and for desorbing nutrients and/or contributing toxicants. 

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

Maunalua Bay, Oahu, during winter conditions. A number of interesting phenomena were observed that 

indicate the complexity of coastal circulation and sediment dynamics in the bay and may help to better 

understand the implications of the processes on coral reef health. 

Acknowledgments

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

United States and its trust territories to better understand the affect of geologic processes on coral reef 

systems. Robert Richmond (UH), Jonathan Martinez (UH), and the staff at the University of Hawaii’s 

Kewalo Marine Laboratory helped with project planning and provided significant logistical help and 

facilities to support our field operations. Alyssa Miller (Malama Maunalua) and others at Malama 

Maunalua helped with local project coordination and outreach. Gordon Tribble and Ron Rickman 

(USGS-WRD) provided field support and scientific insight while also helping with project coordination. 

Richard Boyd, the manager at Mt. Terrace Condominiums, provided us with access and security that 

made it possible to deploy our Terrestrial Imaging System and weather station atop his facility. Mike 

Torresan (USGS) and Angela Lam (USGS) processed the sediment samples described in this report. We 

would also like to thank Bruce Richmond (USGS) and Jeff Hansen (USGS) who contributed numerous 

excellent suggestions and a timely review of our work. 

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[http://waterdata.usgs.gov/usa/nwis/uv?211722157485601] (last accessed February, 15, 2010).

Phillip, E., and Fabricius, K.E., 2003, Photophysiological stress in scleractinian corals in response to 

short-term sedimentation: Journal of Experimental Marine Biology and Ecology, v. 287, p. 57-

78. 

Presto, M.K., Ogston, A.O., Storlazzi, C.D., and Field, M.E., 2006, Temporal and spatial variability in 

the flow and dispersal of suspended-sediment on a fringing reef flat, Moloka‘i, Hawai‘i: 

Estuarine Coastal and Shelf Science, v. 67, p. 67-81. 

Storlazzi, C.D. and Jaffe, B.E., 2008, The relative contribution of processes driving variability in flow, 

shear, and turbidity over a fringing coral reef--West Maui, Hawaii: Estuarine Coastal and Shelf 

Science, v. 77, no. 4, p. 549-564. 

Storlazzi, C.D., Ogston, A.S., Bothner, M.H., Field, M.E., and Presto M.K., 2004, Wave- and tidallydriven flow and sediment flux across a fringing coral reef--South-central Molokai, Hawaii: 

Continental Shelf Research, v. 24, no. 12, p. 1397-1419. 

Additional Digital Information

For additional information on the instrument deployments, please see: 

http://walrus.wr.usgs.gov/infobank/a/a1108oa/html/a-11-08-oa.meta.html

http://walrus.wr.usgs.gov/infobank/a/a209oa/html/a-2-09-oa.meta.html

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

http://pubs.usgs.gov/of/2010/1217/

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

Michael E. Field (USGS Coral Reef Project chief): mfield@usgs.gov

Regarding this Report: 

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

 
44

Table 1. Experiment Personnel.

Person Affiliation Responsibilities

Mike Field USGS Chief Scientist, diver

Curt Storlazzi USGS Co-chief scientist, diver

Kathy Presto USGS Oceanographer, Instrument specialist

Joshua Logan USGS Information specialist, diver

Tom Reiss USGS Dive safety officer

Henry Chezar USGS Imaging technician

Randy Russell USGS Field and IT support technician

Joe Reich F/V Alyce C Vessel captain
45

Table 2. Instrument Package Sensors.

Site Name Depth

[m]

Sensors

MP1 22 Nortek 600 kHz AWAC acoustic Doppler current profiler

22 Seabird SBE-37SI Microcat conductivity-temperature sensor

MP2 20 RD Instruments 600 kHz Workhorse Monitor acoustic Doppler current profiler

20 Aquatec/Seapoint 200-TY optical backscatter sensor

20 Seabird SBE-37SI Microcat conductivity-temperature sensor

20 Sediment tube trap

MP3 20 RD Instruments 600 kHz Workhorse Monitor acoustic Doppler current profiler

20 Aquatec/Seapoint 200-TY optical backscatter sensor

20 Seabird SBE-37SI Microcat conductivity-temperature sensor

20 Sediment tube trap

MP4 9 Nortek 2000 kHz Aquadopp acoustic Doppler current profiler

9 Aquatec/Seapoint 210-TYT optical backscatter sensor

9 Seabird SBE-37SI Microcat conductivity-temperature sensor

9 Sediment tube trap

MP5 9 Nortek 2000 kHz Aquadopp acoustic Doppler current profiler

9 Aquatec/Seapoint 210-TYT optical backscatter sensor

9 Seabird SBE-37SI Microcat conductivity-temperature sensor

9 Sediment tube trap

MP6 8 RD Instruments 600 kHz Workhorse Monitor acoustic Doppler current profiler

8 Aquatec/Seapoint 210-TYT optical backscatter sensor

8 Seabird SBE-37SI Microcat conductivity-temperature sensor

8 Sediment tube trap

8 USGS Coral Imaging System (CIS)

UH 5 Aquatec/Seapoint 210-TYT optical backscatter sensor

5 Seabird SBE-37SI Microcat conductivity-temperature sensor

Weather Station (WS) [10] [71]* NovaLynx WS-16N-A weather station

Terrestial Imaging System (TIS) [12] [71]* USGS Terrestrial Imaging System

*Height, in meters
46

Table 3. Instrument Package Location Information.

Site Name Latitude

[decimal degrees]

Longitude

[decimal degrees] 

MP1 21.25416 -157.72467

MP2 21.25989 -157.71616

MP3 21.24471 -157.79857

MP4 21.27082 -157.74967 

MP5 21.26383 -157.77490

MP6 21.27194 -157.72472

UH 21.26658 -157.71772

Weather Station (WS) 21.28777 -157.71938

Terrestial Imaging System (TIS) 21.28758 -157.71944

USGS stream gauge 21.28944 -157.81555

 

 

Table 4. Water-Column Profiler Cast Location and Depth Information.

Cast Number/Site Latitude

[decimal degrees]

Longitude

[decimal degrees]

Depth

[m]

1 -157.79820 21.24400 19.9

2 -157.80016 21.24809 12.2

3 -157.79985 21.25112 9.5

4 -157.77017 21.25021 21.3

5 -157.74876 21.25558 19.5

6 -157.73181 21.25807 18.6

7 -157.71502 21.25971 19.8

8 -157.71805 21.26598 7.9

9 -157.71607 21.27085 4.9

10 -157.71440 21.27455 0.9

11 -157.71360 21.27632 4.6

12 -157.71305 21.27774 4.3

13 -157.71338 21.27884 3.7

14 -157.71180 21.28114 1.7

15 -157.72521 21.27286 5.5

16 -157.73001 21.26533 14.0

17 -157.73428 21.27334 7.3

18 -157.74930 21.27100 6.1

19 -157.75042 21.26298 14.9

20 -157.76071 21.26722 8.2

21 -157.77315 21.25671 14.3

22 -157.77450 21.26349 9.5

23 -157.78641 21.25703 8.2
47

Table 5. Meteorological Statistics.

[All statistics were calculated for 2008 Year Days 315-413; wind direction is “Going to”]

Site Name Mean ± 1 Std Deviation Minimum Maximum

Sea level barometric pressure [mb] 1008.40±2.60 998.31 1020.38

Air temperature [oC] 22.97±1.55 17.75 29.31

Precipitation [mm] 0.05±0.40 0 10.25

Wind speed [m/s] 4.77±2.83 0 15.75

Wind direction [o] 105.2±84.7 0.2 359.6

Table 6. Wave Statistics.

[All statistics were calculated for 2008 Year Days 315-413; wave direction is “From”]

Site Name Parameter Mean ± 1 Std Deviation Minimum Maximum

MP1 Height [m] 1.06 ±0.34 0.48 4.07

Period [s] 4.35±0.63 2.24 6.68

Direction [o] 146.1±17.2 109.4 216.1

MP2 Height [m] 0.96±0.37 0.40 7.01

Period [s] 6.04±0.68 2.6 9.7

Direction [o] 157.0±23.1 107.0 249.0

MP3 Height [m] 0.94±0.31 0.41 3.41

Period [s] 6.31±0.75 4.3 9.0

Direction [o] 161.1±35.8 79.0 269.0

MP4 Height [m] 1.01±0.33 0.43 3.31

Period [s] 4.42±0.63 2.93 8.06

Direction [o] 162.4±22.6 96.9 268.5

MP5 Height [m] 1.05±0.36 0.41 3.09

Period [s] 4.08±0.51 3.09 7.02

Direction [o] 132.0±17.8 38.3 313.3

MP6* Height [m] 0.72±0.27 0.35 2.64

Period [s] 5.71±0.78 3.9 9.3

Direction [o] 179.1±14.3 139.0 239.0

*Statistics were calculated only for 2008 Year Days 315-388.
48

Table 7. Current Statistics.

[All statistics were calculated for 2008 Year Days 315-413; current direction is “Going to”]

Site Name Parameter Depth

[m]

Mean ± 1 Std Deviation Minimum Maximum

MP1 Speed [m/s] 2 0.24±0.14 0.00 0.94

Direction [o

] 2 159.9±100.2 0.0 359.9

Speed [m/s] 21 0.18±0.10 0.00 0.74

Direction [o] 21 155.8±93.7 0.0 359.9

MP2 Speed [m/s] 2 0.30±0.16 0.00 1.01

Direction [o] 2 184.9±81.4 14.2 358.7

Speed [m/s] 19 0.20±0.11 0.00 0.65

Direction [o

] 19 187.9±84.1 14.3 359.5

MP3 Speed [m/s] 2 0.44±0.23 0.01 1.07

Direction [o

] 2 165.5±83.8 6.1 359.7

Speed [m/s] 19 0.26±0.14 0.01 0.71

Direction [o

] 19 164.6±80.6 0.8 358.6

MP4 Speed [m/s] 2 0.34±0.19 0.01 2.18

Direction [o] 2 193.2±64.7 0.0 359.9

Speed [m/s] 8 0.06±0.04 0.00 0.27

Direction [o] 8 162.1±81.5 0.0 359.5

MP5 Speed [m/s] 2 0.19±0.12 0.00 1.99

Direction [o

] 2 178.5±70.4 0.0 359.9

Speed [m/s] 8 0.04±0.03 0.00 0.24

Direction [o

] 8 191.7±83.9 0.0 359.9

MP6* Speed [m/s] 2 0.10±0.06 0.00 0.42

Direction [o

] 2 156.0±92.5 0.0 359.7

Speed [m/s] 7 0.06±0.03 0.00 0.27

Direction [o] 7 143.6±86.7 0.5 359.7

*Statistics were calculated only for 2008 Year Days 315-388.

Table 8. Temperature Statistics.

[All statistics were calculated for 2008 Year Days 315-356]

Site Name Depth

[m]

Mean ± 1 Std Deviation

[

o

C]

Minimum

[

o

C]

Maximum

[

o

C]

MP1 22 24.32±0.39 23.71 26.19

MP2 20 25.25±0.38 23.73 26.08

MP3 20 25.34±0.40 23.89 26.24

MP4 9 25.19±0.40 23.94 26.28

MP5 9 25.11±0.48 23.65 26.36

MP6 8 25.20±0.41 23.87 26.18

UH 5 25.30±0.37 24.49 26.17
49

Table 9. Salinity Statistics.

[All statistics were calculated for 2008 Year Days 315-356]

Site Name Depth

[m]

Mean ± 1 Std Deviation

[PSU]

Minimum

[PSU]

Maximum

[PSU]

MP1 22 34.92±0.11 34.35 35.16

MP2 20 34.83±0.17 34.07 35.13

MP3 20 34.71±0.19 34.22 35.13

MP4 9 34.69±0.73 19.64 35.09

MP5 9 34.63±0.38 32.92 35.07

MP6 8 34.94±0.55 22.99 35.18

UH 5 35.07±0.08 34.62 35.21

Table 10. Turbidity Statistics.

[All statistics were calculated for 2008 Year Days 315-325]

Site Name Depth

[m]

Mean ± 1 Std Deviation

[NTU]

Minimum

[NTU]

Maximum

[NTU]

MP2 20 0.21±0.20 0.09 5.96

MP3 20 0.39±0.27 0.15 2.28

MP4 9 1.19±1.20 [1.72±3.64]* 0.34 [0.21]* 11.36 [114.47]*

MP5 9 2.43±3.60 [5.54±7.44]* 0.41 [0.41]* 31.94 [136.57]*

MP6 8 0.54±0.46 [0.80±1.98]* 0.21 [0.16]* 5.38 [43.24]*

UH 5 0.46±0.85 0 10.03

*Additional statistics were calculated for 2008 Year Days 315-396.

Table 11. Sediment Sample Location and Depth Information.

USGS Sample 

Identifier

Site Name Sample Type Average Trap 

Collection Rate

[mg/cm2/day]

Latitude

[decimal degrees]

Longitude

[decimal degrees]

Depth

[m]

OA-0209-SF2 MP-2 Sea floor - 21.25989 -157.71616 20

OA-0209-SF3 MP-3 Sea floor - 21.24471 -157.79857 20

OA-0209-SF4 MP-4 Sea floor - 21.27082 -157.74967 9 

OA-0209-SF5 MP-5 Sea floor - 21.26383 -157.77490 9 

OA-0209-SF6 MP-6 Sea floor - 21.27194 -157.72472 8 

OA-0209-TP2 MP-2 Sediment trap 63.49 21.25989 -157.71616 20

OA-0209-TP3 MP-3 Sediment trap 10.22 21.24471 -157.79857 20

OA-0209-TP4 MP-4 Sediment trap 126.35 21.27082 -157.74967 9 

OA-0209-TP5 MP-5 Sediment trap 206.49 21.26383 -157.77490 9 

OA-0209-TP6 MP-6 Sediment trap 80.40 21.27194 -157.72472 8 
50

Table 12. Sediment sample grain size Information.

USGS Sample 

Identifier

Gravel

[percent]

Sand

[percent]

Silt

[percent]

Clay

[percent]

Mud

[percent]

Mean Size

[mm]

OA-0209-SF2 0.47 98.93 0.33 0.28 0.60 0.205

OA-0209-SF3 19.58 79.81 0.34 0.26 0.60 0.744

OA-0209-SF4 0.00 99.67 0.18 0.15 0.33 0.341

OA-0209-SF5 2.56 97.12 0.14 0.17 0.31 0.479

OA-0209-SF6 0.64 99.36 0.00 0.00 0.01 0.792

OA-0209-TP2 0.05 96.36 2.45 1.14 3.59 0.176

OA-0209-TP3 0.25 73.59 19.19 6.97 26.16 0.069

OA-0209-TP4 0.00 96.83 1.79 1.39 3.17 0.242

OA-0209-TP5 0.41 87.15 7.11 5.33 12.44 0.120

OA-0209-TP6 0.21 89.72 6.72 3.36 10.08 0.318
51

Table 13. Sediment Sample Composition Information.

USGS Sample 

Identifier

Component Analyzed Total Inorganic carbon 

[percent]

Calcium Carbonate

[percent]]

Terrigenous

[percent]

OA-0209-SF2 Bulk 11.08 92.31 7.69

OA-0209-SF3 Bulk 11.40 94.94 5.06

OA-0209-SF4 Bulk 11.42 95.15 4.85

OA-0209-SF5 Bulk 11.33 94.36 5.64

OA-0209-SF6 Bulk 11.52 95.98 4.02

OA-0209-TP2 Bulk 10.81 90.03 9.97

OA-0209-TP3 Bulk 8.72 72.64 27.36

OA-0209-TP4 Bulk 11.34 94.43 5.57

OA-0209-TP5 Bulk 10.63 88.55 11.45

OA-0209-TP6 Bulk 10.22 85.13 14.87

OA-0209-SF2 Sand 11.20 93.26 6.74

OA-0209-SF3 Sand 11.50 95.82 4.18

OA-0209-SF4 Sand 11.56 96.34 3.66

OA-0209-SF5 Sand 11.59 96.52 3.48

OA-0209-SF6 Sand 11.68 97.31 2.69

OA-0209-TP2 Sand 11.23 93.55 6.45

OA-0209-TP3 Sand 11.33 94.38 5.62

OA-0209-TP4 Sand 11.29 94.08 5.92

OA-0209-TP5 Sand 11.34 94.46 5.54

OA-0209-TP6 Sand 11.56 96.31 3.69

OA-0209-TP2 Silt* 10.18 84.82 15.18

OA-0209-TP3 Silt* 10.46 87.16 12.84

OA-0209-TP4 Silt* 10.38 86.49 13.51

OA-0209-TP5 Silt* 10.26 85.46 14.54

OA-0209-TP6 Silt* 10.19 84.88 15.12

OA-0209-TP2 Clay* 9.64 80.33 19.67

OA-0209-TP3 Clay* 7.98 66.45 33.55

OA-0209-TP4 Clay* 9.01 75.04 24.96

OA-0209-TP5 Clay* 8.63 71.85 28.15

OA-0209-TP6 Clay* 7.95 66.18 33.82

*The seabed sediment samples had insufficient silt and clay fractions for geochemical analyses.
52

Table 14. Sediment Flux Statistics

All statistics were calculated for 2008 Year Days 315-325.

Site Name Depth

[m]

Sediment Flux 

[kg/cm2]

Direction

[degrees]

MP2 20 1.60 148

MP3 20 5.60 136

MP4 9 25.06 [1468.00]* 117 [116]*

MP5 9 52.48 [2680.05]* 113 [132]*

MP6 8 4.50 [519.03]* 125 [117]*

*Additional statistics were calculated for 2008 Year Days 315-396.
53

Appendixes

Appendix 1

ADCP Information

RD Instruments 600 kHz Workhorse Monitor upward-looking acoustic Doppler current profiler

s/n: 2074, 2432, 7449

Transmitting Frequency: 614 kHz

Depth of Transducer: 20 m

Blanking Distance: 0.25 m

Height of First Bin above Bed: 1.11 m

Bin Size: 0.5 m

Number of Bins: 48

Operating Mode: High-resolution, broad bandwidth

 Sampling Frequency: 2 Hz

 Time per Ping: 00:03.00

 Pings per Ensemble: 100

 Profile Ensemble Interval: 0:10:00.00

Wave Ensemble Interval: 2:00:00.00

Sound Speed Calculation: Set salinity, updating temperature via sensor

Nortek Instruments 2 MHz Aquadopp upward-looking acoustic Doppler current profiler

s/n: 1862, 1851

Transmitting Frequency: 2000 kHz

Depth of Transducer: 10 m

Blanking Distance: 0.25 m

Height of First Bin above Bed: 0.75 m

Bin Size: 0.50 m

Number of Bins: 20

Average interval: 0:02:00.00

Profile interval: 0:10:00.00

Wave interval: 1:00:00.00

Wave cell size: 2 m

Operating Mode: High-resolution

Sound Speed Calculation: Set salinity, updating temperature via sensor
54

Nortek Instruments 600 kHz AWAC upward-looking acoustic Doppler current profiler

s/n: 5461

Transmitting Frequency: 600 kHz

Depth of Transducer: 20 m

Blanking Distance: 0.25 m

Height of First Bin above Bed: 0.75 m

Bin Size: 0.50 m

Number of Bins: 20

Average interval: 0:02:00.00

Profile interval: 0:10:00.00

Wave interval: 1:00:00.00

Wave cell size: 2 m

Operating Mode: High-resolution

Sound Speed Calculation: Set salinity, updating temperature via sensor

Data Processing:

The RDI current data were processed using the WinADCPprogram and the wave data using the WavesMon 

program. The Nortek current data were processed using the Prof2NDP program and the wave data using 

the QuickWave program.

The data were averaged over 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 80% were removed for 

visualization and analysis.

 

 
55

Appendix 2

CT and SLOBS Information

Seabird Microcat SBE-37SM temperature-conductivity (CT) sensors

s/n: 3800, 3801, 4087, 4089, 4368, and 4369 

 Sampling Frequency: 2 Hz

 Measurements per Burst: 8 

 Time Between Bursts: 00:05:00.00

Aquatec/Seapoint 200-TY self-logging optical backscatter sensors (SLOBS)

s/n: 371-013, 371-026

Aquatec/Seapoint 210-TYT self-logging optical backscatter sensors (SLOBS)

s/n: 024-002, 024-005, 024-006, 024-007 

 Sampling Frequency: 2 Hz

 Measurements per Burst: 8 

 Time Between Bursts: 00:05:00.00

Data Processing:

The CT and SLOBS 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.

Appendix 3

WS, CIS, and TIS Information

NovaLynx WS-16N-A Marine-grade Weather Station:

Anemometer: 200-05106-MA (marine model)

Temperature & Relative Humidity: 110-WS-16TH-A w/radiation shield

Barometric Pressure Sensor: 110-WS-16BP

Rain Gauge: 110-WS-16RC

Sampling Frequency: 1 Hz

Measurements per Burst: 1800

 Time Between Bursts: 00:30:00.00

USGS Terrestrial Imaging System:

Camera: Nikon CoolPix 8700 8-megapixel digital camera

Programmable Automated Controller: Campbell Scientific Scientific CR200

Sampling Times: 06:00, 07:00, 08:00, 10:00, 12:00, 14:00, 16:00, and

18:00 HST

USGS Coral Imaging System

Camera: Nikon CoolPix 8700 8-megapixel digital camera

Programmable Automated Controller: Campbell Scientific Scientific CR200

Sampling Times: 00:00, 04:00, 08:00, 12:00, 16:00, and 20:00 HST

 
56

Appendix 4

Water Column Profiler Information

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

Photosynthetically-Available Radiation (PAR), Dissolved Oxygen (DO), and

Chlorophyll (chl) Sensors

Instruments:

Seabird 19plus CTD sensor; s/n: 4299

D&A Instruments OBS-3 sensor; s/n: 19830-2000

Licor #lI-193SA PAR sensor; s/n: SPQA-3562

Seabird SBE 43 oxygen sensor; s/n: 430731

Wet Labs 9502016 fluorometer; s/n: WS3-017, 0-75 ug/l

Sampling Frequency: 4 Hz

Position Information:

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

Data Processing:

The profiler data were processed using the SBEData Processing program.

 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).

 

 
57

Appendix 5

Water column profiler log: November 2008 

Cast 

Number/Site

Date Time

[HST]

Latitude

[decimal degrees]

Longitude

[decimal degrees]

Depth

[m]

1 11/09/2008 07:50 -157.79839 21.24416 19.6

2 11/09/2008 08:15 -157.74876 21.25575 19.0

3 11/09/2008 08:33 -157.71508 21.25974 19.8

4 11/09/2008 08:39 -157.71798 21.26610 8.1

5 11/09/2008 09:04 -157.72517 21.27300 5.1

6 11/09/2008 09:10 -157.72991 21.26546 14.1

7 11/09/2008 09:18 -157.71614 21.27097 5.0

8 11/09/2008 09:22 -157.71457 21.27447 1.6

9 11/09/2008 09:26 -157.71372 21.27645 4.9

10 11/09/2008 09:29 -157.71306 21.27780 4.5

11 11/09/2008 09:31 -157.71339 21.27885 3.9

12 11/09/2008 09:34 -157.71181 21.28121 1.8

13 11/09/2008 09:47 -157.73419 21.27342 7.4

14 11/09/2008 09:55 -157.74914 21.27110 6.5

15 11/09/2008 10:01 -157.75034 21.26324 14.5

16 11/09/2008 10:08 -157.76058 21.26740 6.7

17 11/09/2008 10:16 -157.77426 21.26371 7.0

18 11/09/2008 10:22 -157.77305 21.25686 14.8

19 11/09/2008 10:30 -157.78619 21.25718 7.3

20 11/09/2008 10:40 -157.79980 21.25111 10.5

21 11/09/2008 10:43 -157.80019 21.24799 12.4
58

Appendix 6

Water column profiler log: February 2009 

Cast 

Number/Site

Date Time

[HST]

Latitude

[decimal degrees]

Longitude

[decimal degrees]

Depth

[m]

1 02/20/2009 07:54 -157.79820 21.24400 19.9

2 02/20/2009 08:01 -157.80016 21.24809 12.2

3 02/20/2009 08:05 -157.79985 21.25112 9.5

4 02/20/2009 08:21 -157.77017 21.25021 21.3

5 02/20/2009 08:33 -157.74876 21.25558 19.5

6 02/20/2009 08:42 -157.73181 21.25807 18.6

7 02/20/2009 08:53 -157.71502 21.25971 19.8

8 02/20/2009 09:00 -157.71805 21.26598 7.9

9 02/20/2009 09:05 -157.71607 21.27085 4.9

10 02/20/2009 09:09 -157.71440 21.27455 0.9

11 02/20/2009 09:12 -157.71360 21.27632 4.6

12 02/20/2009 09:15 -157.71305 21.27774 4.3

13 02/20/2009 09:19 -157.71338 21.27884 3.7

14 02/20/2009 09:23 -157.71180 21.28114 1.7

15 02/20/2009 09:34 -157.72521 21.27286 5.5

16 02/20/2009 09:40 -157.73001 21.26533 14.0

17 02/20/2009 09:47 -157.73428 21.27334 7.3

18 02/20/2009 09:55 -157.74930 21.27100 6.1

19 02/20/2009 10:00 -157.75042 21.26298 14.9

20 02/20/2009 10:07 -157.76071 21.26722 8.2

21 02/20/2009 10:15 -157.77315 21.25671 14.3

22 02/20/2009 10:22 -157.77450 21.26349 9.5

23 02/20/2009 10:29 -157.78641 21.25703 8.2
59

Appendix 7

Suspended Sediment Concentration (SSC) Calibration Information

Sample/Site Filter mass, 

initial

(g)

Sample 

volume

(l)

Filter mass, 

final

(g)

Sediment 

mass

(g)

Concentration

(mg/l)

OBS, 

observed

(N.T.U.)

OBS, 

corrected

(N.T.U.)

MB-1 0.096 0.558 0.104 0.008 14.34 30 2 

MB-2 0.098 0.561 0.191 0.093 165.78 41 13

MB-3 0.097 0.568 0.468 0.371 653.17 105 77

SSC = 8.6001 x NTU

R2 = 0.9865

Significant at the 5% level

0

100

200

300

400

500

600

700

0 20 40 60 80 100

Maunalua Bay SSC (mg/l)

Maunalua Bay Turbidity (NTU)