Coastal Circulation and 

Sediment Dynamics in Pelekane 

and Kawaihae Bays, Hawaii

Measurements of waves, currents, temperature, salinity, turbidity, and 

geochronology: November 2010–March 2011

By Curt D. Storlazzi, Michael E. Field, M. Katherine Presto, Peter W. Swarzenski, 

Joshua B. Logan, Thomas E. Reiss, Timothy C. Elfers, Susan A. Cochran, Michael E. 

Torresan, and Hank Chezar

Top: Image of Pelekane and Kawaihae Bays on a typical trade-wind day.

Bottom: Image of Pelekane and Kawaihae Bays during the November 2010 flood.

Open-File Report 2012-1264

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: 2013

For more information on the USGS—the Federal source for science about the Earth,

its natural and living resources, natural hazards, and the environment:

World Wide Web: http://www.usgs.gov

Telephone: 1-888-ASK-USGS

Suggested citation: 

Storlazzi, C.D., Field, M.E., Presto, M.K., Swarzenski, P.W., Logan, J.B., Reiss, T.E., 

Elfers, T.C., Cochran, S.A., Torresan M.E., and Chezar, H., 2013, Coastal circulation 

and sediment dynamics in Pelekane and Kawaihae Bays, Hawaii—measurements of 

waves, currents, temperature, salinity, turbidity, and geochronology—November 2010–

March 2011: U.S. Geological Survey Open-File Report 2012-1264, 102 pp.

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 information product, for the most part, is in the public domain, it also 

may contain copyrighted materials as noted in the text. Permission to reproduce 

copyrighted items must be secured from the copyright owner.
iii

Contents

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

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

Study Area ....................................................................................................................2

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

Research Platform and Field Operations ......................................................................4

Equipment and Data Review ........................................................................................4

Data Acquisition and Quality..........................................................................................12

Results...........................................................................................................................13

General Meteorology ..................................................................................................13

Tides ...........................................................................................................................14

Winds..........................................................................................................................16

Waves.........................................................................................................................16

Currents ......................................................................................................................16

Temporal Variations in Water-Column Properties.......................................................21

Spatial Variations in Water-Column Properties ..........................................................22

Seabed and Sediment Trap Grain Size, Composition, and Collection Rates .............23

Topographic/Bathymetric Survey of Pelekane Bay.....................................................30

Sedimentation Rates in Pelekane Bay .......................................................................30

Electrical Resistivity Values in Pelekane Bay .............................................................33

Discussion .....................................................................................................................34

Trade Winds ...............................................................................................................34

Flood...........................................................................................................................41

Large Waves...............................................................................................................45

Circulation and Sediment Dynamics ...........................................................................51

Conclusions ...................................................................................................................53

Acknowledgements........................................................................................................54

References Cited ...........................................................................................................55

Additional Digital Information .........................................................................................57

Direct Contact Information .............................................................................................57

Appendixes ....................................................................................................................72

Figures 

1. Map of Pelekane and Kawaihae Bays, Big Island, Hawaii, and locations

of the instrument packages ...................................................................................3

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

3. Map of sediment core locations .................................................................................10

4. Map of electrical resistivity line locations ...................................................................12

5. Time-series plots of barometric pressure, air temperature, rainfall, and stream 

height during the experiment...............................................................................14

6. Time-series plots of tide, wind, and wave data during the experiment.......................15

7. Map of mean and variability of wave height and direction..........................................17
iv

8. Map of mean and variability of current speeds and directions near the 

surface for the entire experiment.........................................................................18

9. Map of mean and variability of current speeds and directions near the 

seabed for the entire experiment.........................................................................19

10. Map of mean and variability of tidal currents during flood tide and ebb tide 

for the entire experiment ...................................................................................20

11. Map of sediment grain size collected in the simple tube traps (STTs) .....................25

12. Map of sediment composition collected in the simple tube traps (STTs) .................26

13. Time-series plots of trap collection rate, mean sediment grain size,

and sediment composition through time at the rotary sediment trap (RST) ........27

14. Map of seabed sediment grain size .........................................................................28

15. Map of seabed sediment composition......................................................................29

16. Map of bathymetric change in Pelekane Bay between 1928 and 2011....................30

17. Plot of down-core profiles of radionuclides from core PC3 ......................................31

18. Plot of down-core profiles of excess 210Pb and 7

Be from core SC7 .........................32

19. Plot of down-core profiles of total, inorganic, and organic carbon from core PC3....33

20. View of the electrical resistivity lines in Pelekane Bay .............................................35

21. Plot showing a pseudo-3D rendering of the eight resistivity lines ............................36

22. Photographs from the TIS that show pre-flood trade-wind conditions, 

during the flood, post-flood, and wave conditions ...............................................37

23. Photographs from the CIS that show pre-flood trade-wind conditions, 

during the flood, and post-flood conditions..........................................................38

24. Map of mean and variability of near-surface currents during trade-wind 

conditions............................................................................................................39

25. Map of mean and variability of near-bed currents during trade-wind conditions ......40

26. Map of mean daily suspended-sediment flux during trade-wind conditions .............42

27. Map of mean and variability of near-surface currents during the flood.....................43

28. Map of mean and variability of near-bed currents during the flood ..........................44

29. Map of mean daily suspended-sediment flux during the flood .................................47

30. Map of mean and variability of near-surface currents during the large-wave 

event ...................................................................................................................48

31. Map of mean and variability of near-bed currents during the large-wave event.......49

32. Map of mean suspended-sediment flux during the large-wave event ......................50

33. Time-series plots of forcing and sediment dynamics during the 

2010-2011 winter experiment..............................................................................52

Tables

1. Experiment personnel ................................................................................................57

2. Instrument package sensors......................................................................................58

3. Instrument package location information ...................................................................59

4. Water-column profiler cast locations and depth information ......................................60

5. Sediment core locations.............................................................................................61

6. Meterological statistics...............................................................................................61

7. Wave statistics...........................................................................................................62
v

8. Current statistics ........................................................................................................63

9. Temperature statistics................................................................................................63

10. Salinity statistics.......................................................................................................64

11. Turbidity statistics ....................................................................................................64

12. Water-column profiler statistics for the 6 November 2010 survey............................65

13. Water-column profiler statistics for the 10 March 2011 survey.................................66

14. Sediment trap location and depth information..........................................................67

15. Sediment trap grain size and composition information.............................................68

16. Seabed sample location and depth information .......................................................68

17. Seabed grain size and composition information.......................................................69

18. Constant rate of supply 210Pb model results from core PC3 ....................................69

19. Wave-current critical shear stress statistics .............................................................70

20. Suspended-sediment flux statistics..........................................................................71

Appendixes

Appendix 1. Acoustic Doppler current profiler (ADCP) information................................72

Appendix 2. Conductivity and temperature (CT) information .........................................74

Appendix 3. Turbidity sensor (SLOBS) information........................................................74

Appendix 4. Weather station (WS), Terrestrial Imaging System (TIS), and Coral 

Imaging System (CIS) information ......................................................................75

Appendix 5. Water-column profiler (WCP) information ..................................................75

Appendix 6. Water-column profiler (WCP) log: 6 November 2010.................................76

Appendix 7. Water-column profiler (WCP) log: 10 March 2011 .....................................77

Appendix 8. Topographic and bathymetric plots of Pelekane Bay .................................78

Appendix 9. Temporal variations in water level, wave heights, wave periods, and 

wave directions from the ADCPs.........................................................................79

Appendix 10. Temporal variations in water level, currents, and temperature from 

the ADCPs. .........................................................................................................85

Appendix 11. Temporal variations in temperature and salinity from the CT sensors .....90

Appendix 12. Temporal variations in turbidity from the SLOBS sensors........................91

Appendix 13. Spatial variations in temperature, salinity, turbidity, and fluorescence

from the WCP casts ............................................................................................92

Appendix 14. Time series plots of currents, waves, and combined wave-current 

critical shear stresses..........................................................................................10
vi

Abbreviations and acronyms 

USGS United States Geological Survey

NOAA National Oceanic and Atmospheric Administration

ARRA American Recovery and Reinvestment Act

CRAMP Coral Reef Assessment and Monitoring Program

WCP water column profiler

ADCP acoustic Doppler current profiler

MP MiniProbe

CT conductivity and temperature

SLOBS self-logging optical backscatter sensor

NTU Nephelometric Turbidity Units

TIS terrestrial imaging system

CIS coral imaging system

SG stream gage 

STT simple tube trap

RST rotary sediment trap

GPS Global Positioning System

NOS National Ocean Servicec

MLLW mean lower low water

MSL mean sea level

RMS root mean square

IDW inverse distance weighting

SC short core

PC long core

WAAS wide area augmentation system

DGPS differential Global Positioning System

IAEA International Atomic Energy Agency

SHOALS Scanning Hydrographic Operational Airborne Lidar Survey

Lidar light detection and ranging

PAR photosynthetically-available radiation
1

Coastal Circulation and 

Sediment Dynamics in Pelekane 

and Kawaihae Bays, Hawaii

Measurements of waves, currents, temperature, salinity, turbidity, and 

geochronology: November 2010–March 2011

By Curt D. Storlazzi, Michael E. Field, M. Katherine Presto, Peter W. Swarzenski, 

Joshua B. Logan, Thomas E. Reiss, Timothy C. Elfers, Susan A. Cochran, Michael E. 

Torresan, and Hank Chezar.

U.S. Geological Survey, Pacific Coastal and Marine Science Center, 400 Natural Bridges Drive, Santa 

Cruz, CA 95060.

Introduction 

Project Objectives 

Coral reef communities on the Island of Hawaii have been heavily affected by the 

construction of Kawaihae Harbor in the 1950s and by subsequent changes in land use in the 

adjacent watershed. Sedimentation and other forms of land-based pollution have led to declines 

in water quality and coral reef health over the past two decades (Tissot, 1998). Erosion 

mitigation efforts are underway on land, and there is a need to evaluate the impact of these 

actions on the adjacent coastal ecosystem. 

The Kohala Center and Kohala Watershed Partnership was awarded $2.69 million from 

the National Oceanographic and Atmospheric Administration’s (NOAA) Restoration Center as 

part of the American Recovery and Reinvestment Act of 2009 to stabilize soil and improve landuse practices in the Pelekane Bay watershed. The grant allowed the Kohala Watershed 

Partnership to implement various upland watershed management activities to reduce land-based 

sources of pollution into Pelekane Bay. However, a number of questions must be answered in 

order to: (1) evaluate the effectiveness of the terrestrial watershed remediation efforts; (2) 

understand the potential of the local marine ecosystem to recover; and (3) understand the 

potential threat that existing mud deposits in the bay pose to adjacent, relatively pristine coral 

reef ecosystems. The goal of this experiment was to help address these questions and establish a 

framework to evaluate the success of the Kohala Watershed Partnership restoration efforts. This 

research program will also provide resource managers with information relevant to other 

watershed restoration efforts currently being planned in neighboring watersheds. 

This project involved an interdisciplinary team of coral reef biologists from the 

University of Hawaii Coral Reef Assessment and Monitoring Program, who focused on the 

impact of sedimentation on the biota of Pelekane Bay, and a team of geologists and 
2

oceanographers from the U.S. Geological Survey (USGS), who focused on the circulation and 

sediment dynamics in Pelekane and Kawaihae Bays. The initial findings from the USGS research 

program are described in this report. These measurements support the ongoing studies being 

conducted as part of the USGS Coastal and Marine Geology Program’s Pacific Coral Reef 

Project to better understand the effect of geologic and oceanographic processes on coral reef 

systems. 

Study Area

Spatial and temporal measurements of meteorologic, oceanographic, and 

sedimentological data were made during the 2010-2011 winter in Pelekane and Kawaihae Bays, 

on the Kohala coast of the northwest side of the Island of Hawaii (fig. 1), to describe and assess 

circulation and sediment dynamics in the area. Pelekane Bay is a small, inshore portion of the 

larger Kawaihae Bay that is located just south of the harbor. Instruments were deployed and 

measurements made from north of Kawaihae Harbor south to Puako in order to understand 

circulation and sediment transport in Pelekane and Kawaihae Bays, their connection to the 

adjacent watersheds, and give the focused study in Pelekane Bay a more regional context. The 

bathymetric and geochemical studies were conducted only in Pelekane Bay to describe and 

evaluate the terrigenous sediment deposited after the construction of Kawaihae Harbor. 

The climate in the study area is exceptionally arid (Thornberry-Ehrlich, 2011); measured 

average rainfall rates at the coast are a little more than 10 cm/yr. This is in sharp contrast to 

precipitation rates recorded at the summit of Kohala Mountain (elevation = 1600 m) in the upper 

Pelekane watershed, where precipitation can approach 400 cm/yr. The Pelekane watershed (50 

square kilometers) is typically dry except during periods of heavy rainfall, which occur most 

frequently in winter. During these events, a series of erosional gullies fill with sediment-laden 

runoff and transport their muddy loads to the sea as ephemeral, flashy flows (Hoover and Gold, 

2006). Two distributary gulch systems (Makeahua and Pohaukole) collect this surface runoff and 

converge just before emptying into Pelekane Bay. 

Rocks in the watershed are mostly volcanic, and the soils include sandy to silty loams

that are easily erodible and further weathered during down-stream transport. Pelekane Bay is 

littered with many rocks and small boulders of varying sizes that were transported downstream 

during flash-flood events. From modeling, it has been estimated that roughly 4200 metric tons of 

sediment are delivered annually to Pelekane Bay by runoff (Group 70 International, Inc. and

Oceanit Center, 2007).

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–

5 for complete listings of instrument and deployment information. 

The circulation and sediment-dynamics portion of the study consisted of three suites of 

instruments, deployed to provide an integrated understanding of circulation and sediment 

dynamics: terrestrial instruments, bottom-mounted time-series oceanographic instrument 

packages, and oceanographic survey instruments that profiled the water column. The terrestrial 

instruments consisted of a weather station, stream gauge, and a digital imaging system (fig. 1). 
3

Figure 1. Aerial photograph and SHOALS bathymetric map of Pelekane Bay and vicinity, showing the locations of 

instrument packages and major landmarks; the location of the study area on the Island of Hawaii (the "Big Island") is 

shown in the inset, upper right. 
4

Bottom-mounted oceanographic instrument packages were deployed along the 5-m and 15-m 

isobaths, as well as a cross-shore array in the central region of Kawaihae Bay. This cross-shore 

array included three bottom-mounted oceanographic instrument packages on the 2-m, 5-m, and 

15-m isobaths, and two moorings on the 5-m and 15-m isobaths (fig. 1). In addition to these 

fixed, bottom-mounted, time-series measurements, spatial surveys of water-column properties 

were made in Pelekane and Kawaihae Bays at the beginning and end of the experiment. 

In order to understand the nature and thickness of the terrigenous sediment deposit in 

Pelekane Bay, a topographic/bathymetric survey was conducted for comparison with preKawaihae Harbor surveys. In addition, two complementary geochemical and geophysical 

techniques were used to assess the sediment dynamics within Pelekane Bay: short-lived 

radionuclides (that is, 210Pb, 137Cs, and 7Be) were used to develop a modern sediment 

geochronology; and multichannel electrical resistivity surveys were employed to estimate 

lithologic change and sediment thickness within the bay.

Research Platform and Field Operations

The instrument deployments and recoveries were conducted using the F/V Alyce C. 

Vessel operations, including mobilization and demobilization, were based out of Kawaihae 

Harbor, Hawaii. The water-column profiler (WCP) casts were conducted from a U.S. National 

Park Service vessel using a hand line. The starboard quarterdeck was outfitted with a davit for 

the profiler to be lowered into the water for water-column surveys. The topographic/bathymetric 

survey was conducted from shore either on foot or using a small inflatable boat.

Equipment and Data Review

Acoustic Doppler Current Profilers (ADCP)

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

MiniProbes (MPs) along the 2-m, 5-m, and 15-m isobaths in Pelekane and Kawaihae Bays (fig. 

2A). Please see appendix 1 for information about instrument settings to collect current and wave 

data from the ADCPs deployed at 2-m, 5-m, and 15-m isobaths. The ADCPs deployed on the 15-

m isobath and collected data for 50 s at 2 Hz every 15 min, measuring mean current speeds 

(m/s), and mean current directions (given as “going to,” in degrees clockwise from true north, 

°True) from 1.5 m above the sea floor up to the surface in 1-m bins, to allow calculation of tidal

heights (given in m). Directional wave data were recorded for 1024 s at 2 Hz every hour; these 

data included significant wave height (m), dominant wave period (s), mean wave direction 

(°True), and directional spread (°). The ADCPs deployed along the 2-m and 5-m isobaths 

collected data for 480 s at 2 Hz every 15 min, in 0.5-m bins from 1.0 m above the sea floor up to 

the surface. Directional wave data were recorded by a setup similar to those used with the 

ADCPs deployed along the 5-m and 15-m isobaths. Acoustic backscatter data (dB) collected 

from the ADCPs for the current measurements also provide information on the volume of 

particulates scattering the acoustic signals in the water column and are used as a qualitative 

measurement of turbidity. The sensor locations are listed in table 3; complete sensor and 

processing information is listed in appendix 1. 
5

Figure 2. Photographs of the equipment used in the 2010-2011 winter experiment. A, Underwater photograph of a 

MiniProbe with acoustic Doppler current profiler (ADCP), conductivity and temperature (CT) sensor, self-logging 

optical backscatter sensor (SLOBS), and simple tube trap (STT) along the 5-m isobath at the Central 5-m site; inset, 

underwater photograph of a mooring with CT and SLOBS at the Central 5-m site. B, Weather station (WS) on the 

USGS storage facility. C, Terrestrial Imaging System (TIS) located above Pelekane Bay at the NPS headquarters. D,

Coral Imaging System (CIS) at the Central 5-m site. E, Water-column profiler (WCP). F, Rotary sediment trap (RST) 

at the Central 5-m site.
6

Conductivity and Temperature (CT) Sensors

Four conductivity and temperature (CT) sensors collected and averaged four samples 

every 5 min to measure water temperature (°C) and conductivity (S/m), from which salinity in 

Practical Salinity Units (PSU) was calculated (PSU; fig. 2A). The rapid sampling rate was 

established in an attempt to record internal tidal bores, non-linear internal waves, and transient 

freshwater plumes and/or submarine groundwater discharge that may have been advected past 

the instruments. Two conductivity and temperature sensors (fig. 2A, inset) were deployed at the 

top of the moorings along the 5-m and 15-m isobaths in a cross-shore array to examine the 

dispersion of any freshwater plumes generated by stream flow into the bays. The other two CT 

sensors were mounted just above the sea floor at the Central 5-m and South 5-m MPs (fig. 2A). 

The sensor locations are listed in table 3; complete sensor and processing information is listed in 

appendix 2. 

Turbidity Sensors (SLOBS) 

Eight self-logging optical backscatter sensors (SLOBS) collected 8 samples every 5 

minutes to measure turbidity in Nephelometric Turbidity Units (NTU). The SLOBSs were 

mounted on all of the MPs above the ADCPs (fig. 2A) so that the turbidity data could be 

correlated with co-located ADCP acoustic backscatter data using the methodology described in 

Storlazzi and Jaffe (2008). The SLOBSs on the 5-m and 15-m moorings were mounted at the 

same depth as the CT sensors to correlate the two data sets (fig. 2A, inset). The sensor locations 

are listed in table 3; complete sensor information is listed in appendix 3.

Weather Station (WS)

A weather station (WS) was deployed approximately 3 m above ground on top of a 

storage container in the YMCA yard at Kawaihae Harbor to quantify the influence of 

meteorologic forcing on circulation and water-column properties in Pelekane and Kawaihae 

Bays (fig. 2B). The WS recorded 25-min averages of barometric pressure (mb), air temperature 

(°C), precipitation (mm), wind speed (m/s), and wind direction (°True) every 30 min. The 

instrument’s location is listed in table 3; complete sensor information is listed in appendix 4. 

Terrestrial Imaging System (TIS)

Imagery of surface waters in Pelekane and central Kawaihae Bays was collected using 

the USGS Terrestrial Imaging System (TIS). The system consists of a 10.1-megapixel digital 

SLR camera, a control unit, and battery in a waterproof housing with an external solar panel. 

Both the housing and the solar panel were mounted on a vertical pole just above Pelekane Bay 

near the Puukohola Heiau National Historic Site (NPS-PUHE) offices (fig. 2C). This system was 

used to collect a time series of images to provide information on the natural frequency and 

duration of visually-observable processes impacting Pelekane Bay (for example, stream 

discharge, freshwater plumes, and sediment plumes). The TIS took images every hour during the 

morning and every other hour until dark (07:00, 08:00, 09:00, 10:00, 11:00, 13:00, 15:00, and 

17:00, Hawaii Standard Time [HST]) throughout the deployments. The sensor location is listed 

in table 3; complete sensor information is listed in appendix 4.
7

Coral Imaging System (CIS)

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

images and consists of a 6.3-megapixel digital SLR camera with a 24-mm lens, an external TTL 

strobe, a control unit, and batteries that are mounted on a tetrapod (fig. 2D). The CIS was 

deployed in a patch of sand at the Central 5-m site, and the camera and strobe were angled to

record images of the adjacent reef and seabed. 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 day (00:00, 04:00, 08:00, 12:00, 16:00, and 20:00 HST).

The sensor location is listed in table 3; complete sensor information is listed in appendix 4.

Water-Column Profiler (WCP)

Surveys of water properties throughout the water column were made using a watercolumn profiler (WCP) with conductivity, temperature, depth, optical backscatter, light 

transmission, and chlorophyll sensors (fig. 2E). The surveys were conducted on 6 November

2010 (2010 year day [YD] 310) and 10 March 2011 (2010 YD 434), from north of Kawaihae 

Harbor south to Puako. During each cast, the sensors collected data at 4 Hz and the data were

binned at 0.5-m depth intervals in order to examine variations in water properties throughout the 

water column. The WCP location and depth information are listed in table 4; complete sensor 

information and individual cast acquisition logs are listed in appendixes 5–7.

Stream Gauge (SG)

A simple water-level (stream) gauge, consisting of a pressure sensor in a perforated steel 

pipe set into concrete, was deployed in the lagoon landward of the sand bar that separated 

Pohaukole Gulch from Pelekane Bay (table 3). The purpose of this sensor was to measure water 

levels in the lagoon, provide some insight on the relative magnitude of discharge from Pohaukole 

Gulch, and give some information on the presence or absence of the sand bar at the mouth of the 

gulch.

Simple Tube Traps (STT), Rotary Sediment Trap (RST), and Seabed Sediment 

Samples

Two types of sediment traps collected suspended sediment from the water column in the 

bays. Simple tube traps (STT), consisting of a clear plastic tube 30-cm long, with an internal 

diameter of 6.7 cm, were deployed with their openings 0.4 m above the seabed at the 6 main 

instrument sites (fig. 2A). A baffle was placed in the top of each tube trap to reduce turbulence 

and minimize disturbance by aquatic organisms (see Bothner and others, 2006). A programmable 

rotary sediment trap (RST) was deployed with its opening 1.4 m above the seabed at the central 

5-m site (fig. 2F). The RST consisted of a 20-cm internal-diameter, 75-cm-long cylinder 

equipped with a funnel in the lower 15 cm of the cylinder to direct settling sediment into one of 

21 plastic bottles (500 ml). Sampling bottles were mounted on a carousel that rotated a new 

bottle under the funnel approximately every 5 days. Both types of sediment traps were employed 

in this study to obtain a relative measure of suspended sediment collection rates and sufficient 
8

quantity of suspended material for physical and chemical characterization. Because of the 

energetics of the insular shelf environment, the traps did not measure net vertical sediment flux 

to the coral reef surface. This is because material falling into the trap has a much lower potential 

for resuspension than the same material settling on the adjacent reef surface (Bothner and others, 

2006). The traps were also likely to preferentially collect coarser particle sizes because of their 

higher settling velocities than finer particles. 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 average daily trap 

collection rate for both the STTs and RST was calculated by measuring the total mass of 

sediment in the trap or bottle and dividing by the trap cross-sectional area and the collection 

period. Because the STTs were deployed with their openings 0.4 m above the seabed, compared 

to the RSTs’ opening 1.4-m above the seabed, the average daily trap collection rate for the STTs 

was much greater (even orders of magnitude greater) than the RST (Storlazzi and others, 2011).

In addition to these trapped-sediment samples, divers collected seabed-sediment samples by hand 

by in March 2011 at the instrument sites using 15-cm diameter by 25-cm long acrylic tubes with 

delrin caps.

The relatively small volumes of sediment collected in some of the RST bottles were due 

to their short (~5 day) sampling intervals; thus sediment grain-size and composition analyses 

were made only on selected RST samples with sufficient sample volume. All of the STT samples 

contained enough sample material to be processed. Sediment grain-size analysis was conducted 

on wet aliquots of the trap and seabed samples using sieving and Coulter Counter® techniques 

described by Poppe and others (2000). Total carbon and carbonate carbon measurements were 

made using a Perkin Elmer CHN analyzer and a UIC coulometer, respectively. Organic carbon 

(C) was determined by difference between total carbon and carbonate carbon. Critical shear 

stresses for the different types of sediment were calculated using the modified Shield parameter 

methodology of Madsen (1999).

Topographic/Bathymetric Survey

A topographic survey of the beach and nearshore portions of Pelekane Bay was 

conducted on 11-12 March 2011 (2010 YD 435-436). A continuously-recording GPS receiver 

acquired raw satellite data, at 1 Hz, while the investigators walked or boated throughout the 

survey area. The acquired data was then post-processed against a concurrently-running GPS base 

station to obtain preliminary coordinates of the track lines (appendix 8.1). Replicate (stationary) 

points and points not suitable for generating the topographic surface (for example, transit points) 

were removed, resulting in a final set of topographic points. In order to reference this survey to a 

true tidal datum, a GPS static survey was conducted between the survey base station and a 

National Ocean Service (NOS) tidal benchmark located at Kawaihae Harbor, approximately 1 

km from the survey site (National Ocean Service, National Oceanographic and Atmospheric 

Administration). The NOS tidal benchmark used for this static occupation was “161 7433 B” 

(NGS PID DK3434).

Topographic elevations are expressed as both ellipsoid heights and orthometric heights 

(derived by subtracting the Geoid09 undulation values from the ellipsoid heights). In order to 

reference the Pelekane topographic/bathymetric survey to a tidal datum, the GPS-derived heights 

had to be adjusted by an amount equivalent to forcing the tidal benchmark ellipsoid height onto 

the tidal height of the tidal datum of choice. In other words, to render the topographic survey into 

a surface relative to mean lower-low water (MLLW), 20.967 m (23.207 m – 2.240 m) would 
9

have to be subtracted from each ellipsoid height to obtain the corresponding MLLW height 

value. A separate GPS receiver was set up on a boat in the Kawaihae Small Boat Harbor near the 

NOS tide gage. This receiver was allowed to record water elevations at 1 Hz. The GPS receiver 

file was downloaded and post-processed against the base station data that was collected 

concurrently. The resulting coordinate ellipsoid elevations were adjusted to MLLW according to 

the NAD83 (1993) to MLLW offset value listed above (20.967 m). Additionally, NOS data from 

the tide station at Kawaihae was downloaded from the NOS/Center for Operational 

Oceanographic Products and Services (CO-OPS) website (National Ocean Service, National 

Oceanographic and Atmospheric Administration) for the same time period.

Historical bathymetric data were taken from the 1928 U.S. Coast and Geodetic 

Hydrographic Survey #5007 (appendix 8.2). The resolution of the historical 1928 survey was 

±1/6 fathom (±1 ft or ±0.3 m). In order to place the digital map into a frame of reference, the 

1970 U.S. Coast and Geodetic Hydrographic Survey #9018 that was in the Old Hawaii Datum 

was referenced to the 1928 survey using both graticule tics and known benchmark latitudes and 

longitudes at both the Kawaihae Light and Puako. The georeferencing of 1970 survey map 

matched fairly well (root mean square, RMS error = 3.93080 m spatially) and aligned with the 

currently available coastline. The match between the georeferencing of the 1970 survey map and 

the harbor boundary of the coastline was good. Any differences along the coastline itself were 

most likely due to different tidal ranges during interpretation. The historical 1928 survey was 

then rubber-sheeted to the 1970 survey using the Kawaihae Light mark, latitudes and longitudes 

graticules, and prominent landmarks along the coastline (RMS, error = 12.58580 m). U.S. Coast 

and Geodetic Hydrographic Survey soundings within the area of interest were digitized and 

recorded as noted using both fathoms (2 fathoms and greater) and fathoms plus feet (when less 

than 2 fathoms).

In addition to aligning the historical map with the recently-collected data in horizontal, or 

coordinate space (georeferencing), it was aligned vertically with respect to depth so that the two 

datasets can be compared. The 1928 survey soundings were fixed to MLLW that was calculated 

from concurrent readings at a portable tide gage established at Kawaihae during the survey, and 

by comparison with observations at Honolulu during the same period of the survey, according to 

the report accompanying the chart. The USGS 2011 topographic/bathymetric survey was 

adjusted to the 2001 tidal epoch. The historical data were then transformed to that same tidal 

datum. Unfortunately there are no tidal data at Kawaihae prior to 1960. Data are available from 

Honolulu, but due to isostatic loading on the sea floor between the island of Hawaii (in a 

depression), and Oahu (on a bulge), the tidal data are not comparable. It would be beyond the 

scope of this calculation to model or account for the isostatic differences. According to the 

National Ocean Service data (National Ocean Service, National Oceanographic and Atmospheric 

Administration, n.d.), there is a 0.51-ft difference in mean sea level (MSL) at Kawaihae between 

the 1960-1978 tidal epoch and the 1983-2001 tidal epoch, which was added to the historical 

soundings to bring them into a comparable plane of reference.

A raster-interpolation inverse-distance weighting (IDW) method was used to create a 

raster for both the historical 1928 survey and the USGS 2011 topographic/bathymetric survey. 

The USGS 2011 survey data were then subtracted from the historical 1928 survey data in order 

to generate a map of gain in elevation (sedimentation) or decrease in elevation (erosion) between 

the surveys. 
10

Sediment Coring

A series of seven short (“SC”, ~15-cm long) and three long (“PC”, ~50-cm long) 

sediment cores, 15.2 cm in diameter, were collected in Pelekane Bay during March 2011 (fig. 3, 

table 5). The 15.2-cm core barrels (fig. 3, inset) were used because they greatly diminish the 

effects of compaction during core collection and allow for a large interval sample size. Of note is 

that coring occurred both before and after a series of large but diminishing tsunami waves 

generated from the catastrophic 2011 Japanese Tohoku earthquake in Japan. These tsunamigenic 

waves lasted several days, effectively pumping seawater into and out of Pelekane Bay several 

times each day, causing widespread and prolonged sediment resuspension. Core sites were 

selected based on observations of an intact sediment/water interface, low degree of infaunal 

bioturbation, and ubiquity of fine-grained sediment. As will be shown, tsunamigenic shear and 

resuspension did affect the sediment/water interface in many of the post-tsunami cores. Cores 

were carefully collected and immediately extruded in the field from the top down into 1-cm and 

2-cm intervals. The sectioned sediment slices were sealed in plastic bags and kept chilled for 

transport to the laboratory in Santa Cruz, CA. Based on weight loss after drying at 60 °C for 48 

hours, water content (and thus porosity) of the wet sediment was determined and used to derive 

cumulative mass depths (g/cm2

). Dried samples were then transferred into 10-ml plastic vials, 

Figure 3. Map showing the location of short (green) and long (orange) cores (15.2-cm diameter tube) in Pelekane 

Bay. Locations of cores PC5 and PC6 are not shown. Inset photograph showing one of the long cores with about 65 

cm of mud.
11

equilibrated for 3 weeks to account for radon (Rn) ingrowth, and subsequently analyzed by ultralow background, gamma spectrometry.

 

Radionuclides

Three radionuclides (210Pb, 137Cs, and 7Be) were analyzed by non-destructive gamma 

spectrometry. The uranium-series radioisotope 210Pb (t1/2= 22.2 years; 46.5 keV) and the nuclear 

fission product 137Cs (t1/2= 30.2 years; 661.62 keV) are used as complementary sediment 

chronometers, while cosmogenic 7Be (t1/2 = 53.2 days; 477.56 keV) is used to potentially trace 

flood-induced sedimentation. In the atmosphere, 210Pb occurs as a decay product of the noble gas 

222Rn, and falls back to Earth’s surface in precipitation and dry fall out. In the oceans, 210Pb is 

rapidly adsorbed onto sediment particles, and so where sedimentation is occurring there is more 

210Pb than would be present from only atmospheric deposition. This “excess” amount of 210Pb is 

directly related to the sedimentation rate, and may be determined by comparing down-core total 

210Pb activity to the activity of the radiogenic parent, 226Ra (t1/2= 1600 y; 351.99 and 609 keV).

A fallout radionuclide from nuclear weapons testing and nuclear accidents, 137Cs does not 

occur naturally. The first observations of appreciable 137Cs activities in the atmosphere occurred 

in the early 1950s, and peak quantities were released in 1963–1964. Like 210Pb, 137Cs is washed 

out of the atmosphere by wet and dry precipitation and accumulates and also decays in sediment 

after burial. Theoretically, down-core profiles of 137Cs will exhibit a pronounced peak that 

corresponds to the 1963 atmospheric maximum. Secondary 137Cs peaks may resolve the 1986 

Chernobyl accident, and most recently, the 2011 Japanese nuclear accident at Fukushima.

Radionuclide activities were measured in the radioisotope laboratory at the USGS Pacific 

Coastal and Marine Science Center in Santa Cruz, California, using ultra-low-background, highpurity germanium (HPGe) positive-voltage (P-type) well detectors that are routinely calibrated 

with the International Atomic Energy Association (IAEA). RGU-1, RGTH-1 and IAEA 300 

standards. Each standard is prepared to the same geometry as the sample.

Electrical Resistivity

Electrical resistivity surveys of Pelekane Bay were conducted using a multi-channel system. 

An external switching box controlled the flow of current along a 56-electrode (2-m electrode 

spacing), stationary cable that is 112 m long. In stationary (land-based) mode, current potentials 

are measured in a distributed array, with array geometry (for example, dipole: dipole) defined by 

the user. For every resistivity measurement (~1 per second), the system injects an optimized 

current, reverses the polarity, and then re-injects the current again to cancel spontaneous voltages 

that may occur down-cable. This process is typically repeated and if the recorded error is less 

than a pre-determined threshold value (for example, 5 percent), then the next reading advances. 

Replicate measurements provide a means to assess electronic noise or other artifacts. Each 

survey consisted of more than 600 readings and was completed in approximately 25 min. 

Resistivity measurements were subsequently processed using a user-defined inverse modeling 

routine. Resolution was optimized using a starting model with the apparent-resistivity pseudosection, and a best-fitting layered model was then developed using an iterative, least-squares,

smooth-model-inversion method.
12

A series of 8 lines, or electrical resistivity surveys, were conducted in Pelekane Bay (fig. 

4) to cover the full extent of the bay. The position and orientation of these lines within the bay 

was optimized for sea floor coverage and expected electrical signal contrasts. Whenever 

possible, resistivity data were collected only when the cable was exposed subaerially. Relative 

electrode elevations per line were manually obtained with the high-precision GPS system used 

for the topographic/bathymetric survey. Concurrent with the GPS work, a rough approximation 

of depth-to-bedrock per electrode was established using a simple probing rod. 

Figure 4. Map showing the position of the eight electrical resistivity lines in Pelekane Bay. Inset photograph was 

taken from the terminal sand bar, close to the intersection of lines PB8 and PB5 and looking down-cable along line 

PB8, across the bay. Note the scattered, fluvial rock debris exposed on the seabed as the tide approached low stage. 

Miscellaneous Data Sources 

 Navigation equipment for deployment, recovery, and survey operations included handheld WAAS-equipped DGPS units and a computer with positioning and mapping software. The 

positioning and mapping software enabled real-time DGPS data to be combined with previouslycollected, high-resolution images of SHOALS color-coded lidar, shaded-relief bathymetry, 5-m 

isobaths, and aerial photographs of terrestrial portions of the maps (fig. 1).

Data Acquisition and Quality

Data were acquired for 120 days during the period between 6 November 2010 and 6 

March 2011 (2010 YD 310–430). More than 2 million data points were recorded by the ADCPs, 

CTs, SLOBSs, and WS; more than 8,000 data points were recorded by the WCP. The raw data 
13

were archived and copies of all the data were post-processed for analysis. The ADCPs, CTs, 

SLOBSs, WS, TIS, SG, and WCP data generally appeared to be of high quality. The ADCP at 

the Central 2-m site was damaged, and as a result, the current data were not of sufficient quality 

to be included in this report. A series of large-wave events in late January to early February 2011 

moved and/or buried some of the instruments deployed on the seabed, reducing the quality of 

some of the pressure, wave, current, and conductivity data. The CIS was dislodged from its 

anchors and deposited on its side during one of these events, rendering the photos unusable after 

the January 2011 wave event. In addition, some of the SLOBSs’ optical sensors began to foul 

because of biologic growth and wiper failure toward the end of the deployment. The RST’s main 

funnel was plugged with sediment in January 2011 and thus there was no sediment collected in 

the remaining 7 bottles. For these reasons, the range of data included for the analyses presented 

in this report is limited from 6 November 2010 to 4 February 2011 (2010 YD 310–390). 

The quality of the topographic/bathymetric survey of Pelekane Bay was determined by 

comparing the GPS-derived water levels to the NOS tidal elevations. Ideally, the NOS tidal 

elevations should match up and superimpose themselves on the GPS-derived water surface 

elevations. Although the signal from the GPS base station was very noisy, near the end of the 

occupation, the NOS heights were typically lower than the GPS-derived elevations. It is difficult 

to determine the magnitude of this offset, but it may be as much as 0.2 m. At this time, there is 

not enough information to determine whether the ellipsoid to tidal datum corrections are accurate 

or if the difference shown above is a function of ellipsoid/datum problems, smoothing of the 

NOS tide data to a 6-min interval, or an undetermined source of error.

Results

General Meteorology

The study period from 2010 YD 310–390 covered the wet winter season in Hawaii. The 

general meteorology of the study area, including barometric pressure, air temperature, 

precipitation, and stream depth, was recorded by the USGS weather station (WS) and stream 

gage (SG) (fig. 5). The barometric pressure ranged from 1005.56 to 1017.75 mb, with a mean 

and standard deviation of 1012.95±1.99 mb (table 6). The barometric pressure was relatively 

stable throughout the deployment, except during the large-wave events that occurred towards the 

end of the deployment (fig. 5A). The air temperature ranged from 17.69 oC to 31.06 oC, with a 

mean temperature ± one standard deviation of 24.36±2.24oC (table 6). The air temperature 

fluctuated on the order of 5 °C daily, with a slight decreasing trend in temperature over the 

period of study (fig. 5B). The precipitation ranged from 0 to 24 mm during the 25-min sampling 

intervals, with a mean rainfall ± one standard deviation of 0.05±0.83 mm (table 6). The rainfall 

was episodic, with heavy rainfall often occurring over short periods of time (fig. 5C). The data 

from the SG deployed in the lagoon landward of the sand bar that separated Pohaukole Gulch

from Pelekane Bay ranged in height from 0.00 m to 1.00 m, with a mean depth ± one standard 

deviation of 0.14±0.13 m (table 6). The SG showed little fluctuation prior to the large rainfall 

event on 19 November 2010 (2010 YD 323). After the breach of the sand bar by fluvial 

discharge in mid-November 2010, the SG was able to measure the propagation of the higher high 

tides into the lagoon (fig. 5D).
14

Figure 5. Time-series plots of meteorological data from the USGS weather station (WS) during the 2010–2011 winter 

experiment. A, Barometric pressure, in millibars, showing relatively stable pressure except during low-pressure 

systems. B, Air temperature, in degrees Celsius, showing the approximately 5° change every day. C, Rainfall, in 

millimeters, showing the episodic and short-term events during the winter experiment. D, Stream height, in meters, 

showing fluvial and tidal components to the signal inshore of the sand bar. 

Tides

The study period encompassed more than five complete spring-neap tidal cycles (fig. 6A). 

The tides in Pelekane and Kawaihae Bays are typical for the Hawaiian Islands: microtidal, 

mixed, semidiurnal with two uneven high tides and two uneven low tides per day; so the tides
15

Figure 6. Time-series plots of meteorologic and oceanographic forcing during the 2010–2011 winter experiment. A,

Tidal height, in meters, showing the semi-diurnal nature of the tides. The study period encompassed 5 spring-neap 

tidal cycles. B, Wind speed, in meters per second, with mean speed in black and peak speed in red. C, Wind velocity, 

with direction given in degrees clockwise from true north and speed in meters per second, showing that the winds 

were predominantly from the northwest and southeast due to trade-wind interaction with island topography. D, Wave 

height, in meters, showing the relatively low wave energy during the winter, with a few periods of elevated wave 

activity toward the end of the deployment. E, Wave vectors, with direction from true north and height in meters, 

showing that the waves were predominantly from the northwest either due to trade winds or the north Pacific swell.
16

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.

Winds

The mean wind speeds at the weather station (WS) ranged from 0 to 8.25 m/s, with a 

mean speed ± one standard deviation of 1.83±1.45 m/s during the deployment. The mean wind 

direction ± one standard deviation during the deployment was 197°±99°(table 6). The daily 

fluctuations in winds due to heating and cooling of the land (thus, land breeze and sea breeze) 

were fairly consistent throughout the deployment, with a few periods of strong winds from the 

southeast (figs. 6B, C), likely during the passage of storms through the study area.

Waves

The directional wave gage at the Central 15-m site provided time-series information 

about the size and direction of waves that impacted Kawaihae and Pelekane Bays during the 

course of the experiment (figs. 6D, E). Significant wave heights at this site ranged from 0.16 m 

to 4.12 m (maximum wave heights exceeded 6 m), with a mean significant height ± one standard 

deviation of 0.72±0.57 m. Dominant wave periods varied from 2.8 to 14.7 s, with a mean 

dominant period ± one standard deviation of 7.4±2.6 s. The mean wave direction ± one standard 

deviation was 276°±7° (table 7). The time-series wave data for all of the sites are shown in 

appendixes 9.1–9.6. The mean wave direction for all of the instrument sites was predominantly 

from the west, with the largest mean wave heights located in the central part of the experiment 

area, at the Central 5-m and 15-m sites and the South 5-m site (fig. 7). 

Currents

The mean current speeds at the shallow (depth~5 m) sites (depth ~5 m) averaged

0.02±0.06 m/s close to the surface and 0.01±0.04 m/s close to the sea floor (table 8). The range 

in current speeds was 0.00-0.84 m/s near the surface and 0.00-0.58 m/s near the bed. The mean 

current speeds at the deeper sites (depth~15 m) averaged 0.02±0.04 m/s close to the surface and 

0.01±0.02 m/s close to the sea floor (table 8). The range in current speeds at these deeper sites 

was 0.00-0.35 m/s near the surface and 0.00-0.19 m/s near the bed. The time-series data for each 

ADCP are shown in appendixes 10.1–10.5. The mean and variability of near-surface and nearbed current speeds and directions for the entire deployment period (YD 310–390) for the ADCPs 

at each site are shown in figures 8 and 9. The mean near-surface currents were strongest in the 

central part of the experiment area, at the Central 5-m and 15-m sites and the South 5-m site. The 

mean near-surface current speeds at the North 15-m and South 15-m sites were significantly 

weaker than the other instrument sites (fig. 8). The near-surface currents were predominantly 

oriented offshore, except at the North 15-m and Central 15-m sites. The near-bed mean currents 

were also strongest in the central part of the experiment area, at the Central 15-m and South 5-m 

sites (fig. 9). The dominant near-bed current direction was to the south and onshore at all of the 

sites except the South 5-m site. This may be the result of the instrument at this site being 

deployed in a channel where offshore-directed bottom flow may have balanced the wave-driven 

onshore flow over the adjacent bathymetric highs (fig. 9). 
17

Figure 7. Map showing the mean (white arrows) and variability (red ellipses) of wave directions and heights, in 

meters, during the 2010–2011 winter experiment for the Central 15-m, Central 5-m, Central 2-m, North 15-m, South 

15-m, and South 5-m sites. All of the sites showed a predominant wave direction from the northwest, with the largest 

wave heights measured in the more-exposed central portion of the bay.
18

Figure 8. Map showing the mean (white arrows) and variability (red ellipses) of near-surface current directions and 

speeds, in meters per second, near the surface for the 2010–2011 winter experiment. Currents speeds and directions 

in the bays varied due to local bathymetry and exposure to wind and waves. 
19

Figure 9. Map showing the mean (white arrows) and variability (red ellipses) of near-bed current directions and 

speeds, in meters per second, near the bed for the 2010–2011 winter experiment. Near-bed current directions in the 

bay were variable, with more cross-shore flow than in the near-surface currents. The current speeds were greatest in 

the more-exposed central part of the bay. 
20

Figure 10. Map showing the mean (blue and green arrows) and variability (red ellipses) of current directions and 

speeds, in meters per second, during flood and ebb tides for the 2010–2011 winter experiment. Flood-tide current 

directions (blue arrows) in the bay were predominantly to the south and onshore. Ebb-tide current directions (green 

arrows) in the bay were more variable. 
21

The tidal currents measured at mid-water depth at the instrument sites also provide 

insight into the general nature of flow under ebb- and flood-tidal conditions (fig. 10). The floodtidal currents at all of the instrument sites were primarily to the south and onshore, with speeds 

of 0.10 m/s or less (fig. 10, blue arrows). The ebb-tidal currents were generally more to the north, 

offshore, and weaker than the flood-tidal currents (fig. 10, green arrows).

Temporal Variations in Water-Column Properties

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

temperature (oC), salinity (PSU), and turbidity (NTU). These measurements were made to

address the temporal variability in water-column properties during the experiment and to provide 

additional information about the physical controls on the hydrography of the bays.

Temperature

Water temperatures in Pelekane and Kawaihae Bays ranged from 23.91 to 29.03 °C, with 

a mean temperature ± one standard deviation of 25.91±0.58 °C (table 9) during the deployment 

(2010 YD 310–390). On average, the coolest temperatures were at the Central 15-m mooring 

(depth ~2 m), as it was more exposed to cooler oceanic waters. The warmest average 

temperatures were measured at the Central 2-m site, which was the shallowest, most restricted 

location and may have been subject to the greatest solar heating (table 9). The water temperature 

at all the sites showed daily cooling and heating on the order of 1–2 °C, with the largest 

variations at the Central 2-m site, and an overall decreasing trend in temperature throughout the 

experiment (appendix 11.1A).

Salinity

Salinity in Pelekane and Kawaihae Bays ranged between 24.99 and 35.21 PSU, with a 

mean salinity ± one standard deviation of 34.05±0.29 PSU (table 10). The highest average 

salinity was measured at the Central 15-m mooring, most likely due to the influence of more 

saline oceanic water (table 10). The lowest average salinity was located at the Central 2-m site, 

probably due to fluvial discharge (this site was close to Pohaukole Gulch) or submarine 

groundwater discharge, known to be prevalent in this region (table 10). Overall, the salinity 

signal was fairly stable throughout the deployment at Central 5-m site, Central 5-m mooring, and 

Central 15-m mooring, with small, short-lived decreases due to freshwater inputs (appendix 

11.1B). 

Turbidity

Turbidity in the bays ranged between 0 and 1524.30 NTU, with a mean turbidity ± one 

standard deviation of 8.07±15.59 NTU (table 11). The turbidity statistics were calculated from 

2010 Year Day 310–390, omitting days 340–370.5 due to biofouling of the optical sensors or 

other instrument problems. The mean turbidity and variability were lowest (1.67±2.95 NTU) at 

the Central 15-m mooring for the deployment period (table 11). The mean turbidity was greatest 

(20.71 NTU) at the Central 5-m mooring for the deployment period (table 11). Appendix 12.1 

shows the time-series plots of turbidity for all of the instruments deployed in Pelekane and 
22

Kawaihae Bays, with the period that was excluded from the statistics due to poor data quality 

(2010 YD 340–370.5) shaded gray. 

Spatial Variations in Water-Column Properties

Spatial variability of water-column properties in Pelekane and Kawaihae Bays was

measured using the WCP at the beginning of the experiment on 6 November 2010 (2010 YD 

310) and the end of the experiment on 10 March 2011 (2010 YD 434), with cast locations shown 

in appendix 13.1. The water-column properties that were measured by the WCP included 

temperature (oC), salinity (PSU), turbidity (NTU), light transmission (percent) and fluorescence 

(mg/m3

) as measured by the chlorophyll sensor. The cast location identification information is 

listed in table 4, and the WCP logs are listed in appendixes 6 and 7. The mean and standard 

deviation statistics for the measured parameters are listed in tables 12 and 13. The surveys were 

conducted to place the spatially-limited time-series instrument measurements made at the main 

study sites in the context of the greater southern Kohala region.

Temperature 

The mean temperature in Pelekane and Kawaihae Bays ranged from 26.44 °C to 26.93 °C 

during the November 2010 survey and from 25.05 °C to 26.50 °C during the March 2011 survey

(tables 12 and 13). Overall, the temperatures were warmer in November 2010 than March 2011 

due to seasonal cooling through the winter months, which was also observed in the time-series 

data collected by the CT sensors (appendix 11.1). In November, the warmest and most variable 

temperatures were located close to shore in Pelekane Bay (appendix 13.2); this area is very 

shallow and appears to have restricted wave-driven mixing and circulation due to shadowing by 

the Kawaihae Harbor breakwaters. The coolest temperatures were measured in the southern part 

of the study area near Puako (appendix 13.2); these cooler temperatures may have been a result 

of unobstructed mixing with cooler, offshore oceanic waters. The warmest temperatures 

measured during the March 2011 water-column surveys were located close to shore in Pelekane 

Bay (appendix 13.3). Temperatures were cooler in the southern part than the northern part of the 

study area; the coolest temperatures were measured in the southern part of the study area during 

the March 2011 survey (appendix 13.3). 

Salinity 

The mean salinity in Pelekane Bay and the surrounding area ranged from 33.80 to 35.09 

PSU during the November 2010 survey and from 33.73 to 34.60 PSU during the March 2011 

survey (tables 12-13). Overall, the salinity values were lower during the March 2011 survey, 

likely due to increased surface runoff and/or submarine groundwater discharge resulting from 

rainfall over the winter. The spatial variability in salinity during the November 2010 survey 

showed the lowest salinity values close to shore in Pelekane Bay near Pohaukole Gulch 

(appendix 13.4). Outside of this area, the salinity was fairly uniform, with higher salinities and 

low variability up and down the coast, except near Honokoa Gulch just to the north of Kawaihae 

Harbor, which was discharging water and sediment during this survey. The spatial variability 

during the March 2011 survey also showed the lowest salinities near the shore in Pelekane Bay,

where the Pohaukole stream discharges (appendix 13.5). 
23

Turbidity

The mean turbidity in Pelekane Bay and the surrounding area ranged from 0.40 to 4.72

NTU during the November 2010 survey and from 0.32 to 20.24 NTU during the March 2011 

survey (tables 12-13). Although the mean turbidity values during the November 2010 and March 

2011 surveys were greater close to shore in Pelekane Bay, overall the mean turbidity values were 

generally low in the surrounding area (appendixes 13.6 and 13.7).

Turbidity in Pelekane Bay was also measured in percent light transmission, with higher 

percentages indicating clearer water and lower percentages indicating more turbid water. The 

mean percent light transmission in Pelekane Bay ranged from 69.86 to 96.51 percent during the 

November 2010 survey and from 44.79 to 96.13 percent during the March 2011 survey (tables

12 and 13). The lowest light transmission (or most turbid water) measured was located inshore in 

Pelekane Bay for both the November 2010 and March 2011 surveys (appendixes 13.8-13.9). The 

slightly lower mean percentages during the March 2011 surveys may have been a result of the 

input of terrigenous sediment during the November 2010 flood (which occurred after the 

November 2010 WCP measurements).

Fluorescence

The mean values of fluorescence in Pelekane Bay ranged from 0.56 to 1.96 mg/m3 during 

the November 2010 survey and from 0.19 to 1.77 mg/m3 during the March 2011 survey (tables

12 and 13). Fluorescence was highest and most variable close to shore during both surveys and 

generally near areas of infrastructure and freshwater input. Overall, the November 2010 survey 

had more areas of higher fluorescence, potentially due to land-derived inputs of nutrients. The 

spatial variability in fluorescence during the November 2010 survey showed elevated

fluorescence in areas off the potential point sources of Honokoa Gulch and Pohaukole Gulch, 

and off Kaunaoa Beach to the south of Pelekane Bay (appendix 13.10). The fluorescence values 

generally decreased with distance from shore and away from gulches or stream mouths. The 

spatial variability in fluorescence during the March 2011 survey showed elevated fluorescence 

near Pelekane Bay and off Kaunaoa Beach to the south of Pelekane Bay (appendix 13.11). The 

fluorescence quickly decreased to the south, away from the stream input. The rest of the study 

area was characterized by low fluorescence both close to shore and farther offshore (appendix

13.11).

Seabed and Sediment Trap Grain Size, Composition, and Collection Rates

The simple tube trap (STT) average trap collection rates ranged from 156.70 milligrams 

per cubic centimeter per day (mg/cm2

/d), at the mouth of Pelekane Bay (Central 2-m site), to 

537.24 mg/cm2/d, at the South 5-m site (table 14). Although the Central 2-m site had the lowest 

average trap collection rate, the material collected in the trap was predominantly mud-sized 

(silt+clay) material by mass (93.29 percent, fig. 11, table 15); this sediment was composed of 

almost exclusively (93.28 percent) terrigenous material (fig. 12, table 15). The other STTs 

collected predominantly carbonate (76.01–94.31 percent), sand-sized (80.74–95.59 percent) 

material by mass (table 15). The south 5-m site off Waiulaula Gulch had the second-highest 

percentage of terrigenous material by mass (23.99 percent)—after the Central 2-m site at the 
24

mouth of Pelekane Bay—showing a clear relationship between the terrigenous component of the 

sediment in the near-bed water column to the proximity of onshore sediment sources (for 

example, Pokuhoale and Waiulaula Gulches).

The mean trap accumulation rates at the rotary sediment trap (RST) ranged from 0.01 

mg/cm2/d, just before the small-wave event and November 2010 flood (2010 YD 319–323), to 

12.91 mg/cm2/d during the large-wave events in January 2011 (YD 2010 380–390), as shown in 

figure 13 and tables 14 and 15. The sediment collected in the RST was primarily terrigenous 

clayey silt of volcanic origin in the first half of the deployment, becoming coarser and 

predominantly carbonate in origin by the end of the deployment; these trends were more rapid 

during the large-wave events in January 2011.

The seabed samples collected from the instrument sites in March 2011 at the end of the 

experiment were predominantly sand-sized material by mass (fig. 14, tables 16 and 17). The 

sediment composition at the instrument sites was also predominantly carbonate (>90 percent),

except at the Central 2-m and South 5-m sites, where the composition was approximately half 

terrigenous and half carbonate (fig. 15, tables 16–17). Similar to the sediment trap samples, the 

large percentage of terrigenous material at these two sites was likely due to their proximity to 

terrestrial sediment sources. Overall, the seabed samples had a higher percentage of sand-sized

carbonate sediment than the trap samples. This may have been a result of the timing of the 

sample collection after the large-wave events in January 2011, which likely resuspended the fine,

silty, terrigenous sediment deposited in Pelekane Bay during the November 2010 flood and 

advected it out of the bays.
25

Figure 11. Map showing the spatial variability of sediment grain size collected by the simple tube traps (STTs) at the 

instrument sites. The STTs primarily collected sand-sized material except at the Central 2-m site, at the mouth of 

Pelekane Bay, which was primarily mud (silt and clay).
26

Figure 12. Map showing the spatial variability of sediment composition collected by the simple tube traps (STTs) at 

the instrument sites. The STTs primarily collected carbonate material except at the Central 2-m site, at the mouth of 

Pelekane Bay, which was primarily terrigenous material. Although the South 5-m site off Waiulaula Gulch was 

predominantly carbonate material, it had almost twice the percentage of terrigenous material as the rest of the sites 

(except for the Central 2-m site).
27

Figure 13. Time-series plots of weather and hydrologic data in Pelekane Bay (various instrument sites, as noted) and 

the corresponding data from the rotary sediment trap (RST) at the Central 5-m site. A, Stream gage depth, in meters. 

B, Wave height, in meters, measured at the Central 15-m site. C, Rainfall, in millimeters per 25 minutes, measured at 

the weather station. D, Mean accumulation rate of material collected in the RST, in milligrams per square centimeter 

per day. E, Mean grain size, in millimeters, of material collected in the RST. F, Bulk composition of material collected 

in the RST, in percent by mass, with red and blue denoting the terrigenous (volcanic) and carbonate material, 

respectively. The November 2010 flood was concurrent with an increase in trap accumulation and finer-grained 

terrigenous material collected in the RST; during the January 2011 large-wave events there were much higher trap 

accumulation rates of coarser-grained carbonate sediment than following the flood.
28

Figure 14. Map showing the spatial variability of mean sediment grain size on the seabed at the instrument sites, 

March 2011. All of the seabed samples collected from the instrument sites were predominantly sand-sized, except for 

the small percentages of silt and clay at the Central 2-m site. 
29

Figure 15. Map showing the spatial variability of sediment composition on the seabed at the instrument sites. The 

composition of the seabed samples was predominantly carbonate, with the exception of Central 2-m site and South 

5-m site. This may be a result of their proximity to onshore terrestrial sediment sources.
30

Topographic/Bathymetric Survey of Pelekane Bay

In order to visualize the changes in elevation between the 1928 and 2011 surveys, 

contour lines at 0.25-m intervals were generated. Since the resolution of the historical 1928 

survey was ±1/6 fathom (±1 ft or ±0.3 m), the error of measure is ±0.3 m. To accommodate this 

error for visualization, the range of change in depth between -0.25 and +0.25 m was colored 

green on the map to acknowledge that changes in this range are within the error of measurement 

(fig. 16). A gain in elevation implies net sedimentation on the seabed; a decrease in elevation 

implies erosion between the surveys. Based on the range in survey and datum error, overall the 

bay became 0.41 m to 0.61 m shallower, due to the accumulation of 22,500 to 37,500 m3 of 

sediment above the sea floor mapped in the historical 1928 survey.

Figure 16. Map of bathymetric change, in meters, in Pelekane Bay between 1928 and 2011. The red colors denote 

areas that became shallower due to sediment accumulation, and the blue colors denote areas that became deeper 

due to erosion. Areas colored green represent depth changes between -0.25 m and +0.25 m, which are within the 

error of measurement and thus potentially not real.

Sedimentation Rates in Pelekane Bay

In Pelekane Bay sediment, the down-core distribution of excess 210Pb (210Pbxs = 

210Pbtot – 214Pb) followed exponential decreases (fig. 17) below the bioturbated layer (depths >10–15 cm). 

Bioturbation effectively mixes all geochemical signals; the onset of burial or accumulation, t0, 

must consequently be defined to the bottom of this biologically mixed layer. Such 210Pbxs

profiles can be interpreted by a steady-state advection-decay model, assuming that fluxes of 

sediment and 210Pb are constant at a given location. Thus, influx of 210Pbxs by precipitation at the
31

Figure 17. Plots showing down-core profiles from core PC3 of A, 226Ra and total 210Pb. B, Excess 210Pb as a function 

of linear depth, and the best-fit line, corresponding to sedimentation rate, which is represented by the slope, S, given 

in centimeters per year (cm/yr). C, Excess 210Pb as a function of cumulative depth, and the corresponding best-fit 

line, corresponding to a mass accumulation rate, represented by the slope, S, given in milligrams per square 

centimeter per year (mg/cm2/yr.), and D, 137Cs.

sediment/water interface must be balanced by radioactive decay following deposition and burial. 

The down-core distribution of 210Pbxs must therefore be invariable with time and can be 

described as:

(

210Pbxs)z = (210Pbxs)0 exp(-λ/S)

,
32

where (

210Pbxs)0 and (210Pbxs)z are excess 210Pb activities at the sediment/water interface and at 

some depth z, respectively, λ is the 210Pb decay constant (0.03114/yr), and S is the sedimentation 

rate. The slope of a regression line (-λ/S) defines either a linear sedimentation rate (cm/yr) or a 

mass accumulation rate (g/cm2/yr), depending on whether an apparent depth (cm) or a 

cumulative mass (g/cm2) is used as the depth variable. The radionuclide data were also modeled 

using the classic constant rate of supply (CRS) age model, following Appleby and Oldfield, 1978 

(table 18). The age models produced using these two approaches yielded consistent results.

Activities of the radionuclides are reported in disintegrations per minute per gram, dpm/g, 

where 60 dpm = 1 Becquerel (Bq) = 27.027 pCi. Activities of 226Ra were generally low (<1 

dpm/g) and did not change dramatically either down-core or from one core to the next. In 

contrast, corrected total 210Pb activities were typically about 3–4 dpm/g or more in the uppermost sediment layers, and then decreased systematically to background (thus, 226Ra) values at 

depth. Bomb-produced 137Cs activities were usually low (<0.3 dpm/g), but did show a defined 

subsurface peak in some cores that could be used to develop a secondary geochronology. 7Be has 

a high affinity for aerosols and is thus delivered to the Earth’s surface via wet and dry deposition. 

In aqueous environments, it becomes quickly associated with particles and colloids by cation 

exchange reactions. Because of this rapid scavenging of 7

Be onto particle surfaces once 

introduced into aqueous environments, this radioisotope may be useful for assessing particle 

movement, including deposition and resuspension. In Pelekane Bay, where annual rainfall rates 

are very low, 7Be activities in the surface sediment were expectedly low and did not reveal clear 

systematic trends (fig. 18).

Figure 18. Plots showing down-core profiles of excess 210Pb and 7Be from core SC7.

In Pelekane Bay sediment, 210Pb-based sedimentation rates (PC3 = 0.59 cm/yr) agree 

reasonably well with those estimated from the subsurface 137Cs peak (1963–1964; 0.52 cm/yr),

and the penetration depth of 137Cs (1950s) was beyond the bottom of the sediment column 

collected in core PC3. The mass accumulation rate of core PC3 was 524.5 mg/cm2/yr (fig. 17C). 
33

This suggests that in Pelekane Bay, sediment profiles of such particle-reactive radionuclides as 

210Pb and 137Cs are controlled principally by syndepositional processes and that post-depositional 

processes (for example, reversible sorption, redox-mediated transport, preferential mobility) are

less important. These physio-chemical processes do not rule out biologically mediated postdepositional transport in the upper sediment column since the upper 10-15 cm of the 210Pb 

profiles suggest active bioturbation. 

Radionuclide inventories per whole core (dpm/cm2

) can be computed using the 

cumulative mass depths, and when assessed against local atmospheric fallout rates, can provide 

an estimate of sediment focusing or winnowing. Here, as sediment resuspension was event 

driven by the recurring tsunami waves, the radionuclide inventories can be used to determine 

tsunamigenic resuspension and sediment movement. 

Various components of sedimentary carbon in core PC3 are shown in Figure 19. Of note 

is that the total carbon (TC) content was elevated for such an arid coastal system and likely 

reflected recent high watershed inputs. While the down-core TC profile varied consistently 

between 6 and 7 percent, the total inorganic carbon (TIC) and total organic carbon (TOC)

components fluctuated with depth. TOC was maintained at about 5 percent beyond a depth of 30

cm, while at those depths, the TIC decreased to less than 2 percent. Percent calcium carbonate 

(CaCO3) followed the down-core profile of TIC and ranged between 15 and 30 percent.

Figure 19. Plots showing down-core profiles from core PC3 of A, Percent total inorganic carbon (TIC). B, Percent 

carbonate. C, Percent total carbon (TC). D, Percent total organic carbon (TOC). Note that total carbon (TC) in core 

PC3 exceeds 6 percent, which is surprisingly high for such a dry coastal system.

Electrical Resistivity Values in Pelekane Bay 

Two-dimensional (2D) electrical resistivity surveys were conducted to estimate the 

subsurface electrical resistivity distribution along the survey lines. Each measurement requires 

electrical current to be injected into the sediment through two current-producing electrodes while 

voltage readings are conducted at two potential electrodes spaced at some variable distance down 
34

the cable. An apparent resistivity is then calculated using the injected current, the measured 

voltage, and a geometric factor defined by the electrode arrangement (in this case, dipole-dipole). 

The maximum exploration depth for this technique depends on the spacing of the currentinjecting electrodes. Sampling different depths is accomplished by changing the electrode 

spacing. Individual measurements are taken along a survey line using pre-determined 

combinations of electrodes and spacings to produce a cross section of apparent resistivity. 

Apparent resistivity is an averaged value with contributions from both horizontal and vertical 

directions.

Apparent resistivity data are then inverted into an electrical resistivity model that 

increases the resolution and allows interpretation of the subsurface structure and stratigraphy (de

Groot-Hedlin and Constable, 1990; Oldenburg and Li, 1999; Loke, 2001). Many factors, 

including the sediment type, the amount of water in the subsurface, and the salinity of the pore 

fluid, affect the apparent resistivity. Electrical resistivity inversion models are used to identify, 

delineate, and map subsurface features such as electrically conductive contamination plumes, 

bedrock fracture zones, the saltwater/freshwater interface, the vadose zone, and electrically 

conductive lithologic units such as clays and silts (Behiry and Hanafy, 2000; Benson and others, 

1997).

Electrical resistivity is reported here in Ohm-meters (Ω•m). In all but one of the 8 lines 

collected from Pelekane Bay, values of apparent electrical resistivity were typically less than 10 

Ω•m, except for the most landward Line 5, where values ranged up to approximately 25 Ω•m 

(fig. 20). Such resistivity values are indicative of mixed lithologies (Swarzenski and others, 

2009; Dimova and others, 2012). Based on the 8 resistivity lines collected in Pelekane Bay, 

values of apparent electrical resistivity typically increased with depth, while the sharpest contact 

appeared at about 13 m below the sediment surface. This electrical-resistivity contact possibly 

defines a transition from volcanic basement rock to the overlying carbonate reef structure (figs.

20–21). 

Discussion

The winter 2010–2011 experiment conducted by the USGS in Pelekane and Kawaihae

Bays coincided with three different sets of meterologic and oceanographic forcing conditions 

that characterize sediment dynamics on many Hawaiian fringe reefs: trade-wind conditions, a 

heavy rainfall event that generated a flood, and large-wave events (for example, Storlazzi and 

Jaffe, 2008). The TIS and CIS captured these events qualitatively from above and below the 

water surface, respectively, providing a visual photographic context (figs. 22–23) to the timeseries instrument data. Trade winds, terrestrial flooding, and large-wave events are all important 

controls on circulation and sediment dynamics in the bays. 

Trade Winds

Trade-wind conditions in the Hawaiian Islands occur approximately 50 percent of the 

time during the winter months and are characterized by consistent winds from the northeast at 5–

10 m/s, stable weather patterns and barometric pressure, and little rainfall (Moberly and 

Chamberlain, 1964). The winds in Pelekane and Kawaihae Bays, as measured by the USGS 

weather station, generally showed wind speeds on average of 3–5 m/s from the northwest 
35

Figure 20. View of the electrical resistivity lines in Pelekane Bay. A, Cross-sectional plots of all 8 multi-channel 

electrical resistivity lines from Pelekane Bay. B, Inset photograph showing numbered locations of electrical resistivity 

lines in Pelekane Bay. A resistivity value, given in Ohm-meters (Ohm-m) reflects both pore fluid and sediment 

resistivity and is affected by such physical parameters as porosity and temperature. Hotter colors indicate more 

resistive values, which correspond to lower porosity and colder temperatures (note that the resistivity scale was 

maximized for each image). Several lines show a sharp electrical resistivity contact at a depth of about 13 m, which 

may represent the transition from the volcanic basement rock to the overlying carbonate reef structure.
36

Figure 21. Plot showing a pseudo-three dimensional rendering of the 8 resistivity lines, normalized to a single color 

scale. The horizontal scale is expressed as Universal Transverse Mercator (UTM) easting (x) and northing (y) 

coordinates; the vertical scale is depth in meters, where zero is the surface. The volcanic bedrock that outcrops on 

the northeastern corner of the bay is clearly evident in the hotter colors of Line 5. From these resistivity lines, a 

shallow transition zone that separates finer from coarser material appears to be approximately 2–3 meters thick, 

although the resolution of the 56-electrode cable makes it difficult to obtain more quantitative estimates.

direction. These northwesterly winds, divergent from the regional northeasterly winds, were

likely due to the orographic steering of the air around Kohala Volcano. Two time periods, 2010 

YD 317–320 (before the flood) and 2010 YD 340–360 (after the flood), showed consistent winds 

from the northwest, small waves, and stable barometric pressure; these time frames were used to 

examine currents, turbidity, critical shear stresses, and sediment flux during trade-wind 

conditions (figs. 5 and 6).

The near-surface current speeds and directions measured by the instruments showed 

stronger currents at the Central 5-m, South 5-m, and Central 15-m sites than at the North 15-m 

and South 15-m sites (fig. 24). The near-surface currents were faster and directed to the southeast 

in the central part of the bay (Central 15-m and Central 5-m sites), although rarely exceeding 

0.05 m/s, and were to the north-northeast and slower at the North 15-m and South 15-m sites. 

The near-bed currents at the instrument sites had current speeds and directions similar to those 

near the surface, suggesting little vertical velocity shear through the water column, likely in part 

due to the weak wind forcing and slow currents (fig. 25). 

The turbidity levels at the instrument sites during trade-wind conditions were, on average, 

the lowest for any period during the entire experiment. The highest mean turbidity during the 

trade-wind period (1.65 NTU) was measured at the Central 5-m MP (table 11). This was 

expected, as its location was near the seabed and closest to the area of terrigenous sediment

accumulation in Pelekane Bay offshore from Pohaukole Gulch. The lowest mean turbidity values 

were measured at the Central 15-m mooring. This was also expected, as it was deployed 

approximately 2 m below the surface in clear water and away from possible terrestrial sediment 

sources (appendix 12).
37

Figure 22. Photographs from the Terrestrial Imaging System (TIS) showing surface conditions in the study area. A,

Pre-flood trade-wind conditions. B, Flood conditions in November 2010. C, Post-flood trade-wind conditions. D. 

Large-wave conditions in February 2011. The images showed the differences in surface turbidity in the bays resulting 

from these different conditions. Note the return to clear, blue surficial water after the November flood due to calm 

trade-wind conditions. 

The critical shear stress levels necessary for resuspending terrigenous (volcanically 

derived) coarse silt and clay due to currents, waves, and the combination of waves and currents is 

shown in appendixes 14.1–14.2. During trade-wind conditions (2010 YD 317–320 and 340–

360), the shear stresses from currents alone rarely exceeded the threshold needed to suspend 

terrigenous coarse silt or clay at most of the instrument sites (table 19; appendixes 14.1–14.2, 

green shaded area). Very few wave events occurred during these time periods, and consequently

there was little sediment resuspension from shear stresses due to waves at the instrument sites. 

Only at the South 5-m site were the wave shear stresses and combined wave-current shear 

stresses high enough during trade-wind conditions to resuspend terrigenous coarse silt and clay 

for brief periods of time (appendix 14.2, green shaded area). The weak combined shear stresses 

resulted in little terrigenous (silt and clay) and/or carbonate (sand-sized) sediment being 

resuspended and contributing to turbidity recorded by the SLOBS.
38

Figure 23. Photographs from the Coral Imaging System (CIS) showing underwater conditions at the Central 5-m site. 

A, Pre-flood trade-wind conditions. B, Flood conditions in November 2010. C. Post-flood trade-wind conditions. There 

were no photos taken during the large-wave conditions in February 2011, as the large waves knocked over the CIS. 

These images showed the differences in turbidity and sediment accumulation resulting from these different 

conditions.
39

Figure 24. Map showing the mean (white arrows) and variability (red ellipses) of near-surface current directions and 

speeds, in meters per second, during trade-wind conditions for the 2010–2011 winter experiment. In the central part 

of the bay, currents were stronger and in the direction of the winds. At the North 15-m and South 15-m sites, currents 

were weaker and to the north.
40

Figure 25. Map showing the mean (white arrows) and variability (red ellipses) of near-bed current directions and 

speeds, in meters per second, during trade-wind conditions for the 2010–2011 winter experiment. The currents were 

strongest in the central part of the bay, with variable directions, and weakest at the North 15-m and South 15-m sites,

with onshore directions.
41

Suspended-sediment flux was calculated using turbidity values from the SLOBSs and 

current speed and direction from the ADCPs at co-located depths to examine where and how 

much sediment was transported through Pelekane and Kawaihae Bays area during the pre-flood 

trade-wind conditions (2010 YD 317–320; fig. 26). The suspended-sediment flux measured over 

the 3-day period near the seabed was directed to the south at the northern sites and to the north at 

the southern sites. The largest suspended-sediment flux was measured at the South 5-m site, as 

the currents and shear stresses were largest at this site. The smallest suspended-sediment flux 

was measured at the North 15-m site, where the currents and turbidity values were low (fig. 26). 

Overall, the suspended-sediment flux during trade-wind periods was the lowest of the 

deployment period, as little sediment was resuspended into the water column and transported by 

weak trade-wind currents (table 20). 

Qualitatively, the TIS showed blue, clear water at the surface during pre-flood trade-wind 

conditions (fig. 22A, photo taken 11 November 2010 at 11:00 HST). The CIS at the Central 5-m 

site also showed clear water during this period (fig. 23A, photo taken 16 November 2010 at 

17:00 HST). These photographs suggest that the few times critical shear stresses were sufficient 

to resuspend sediment from the seabed, the hydrodynamics were not sufficient to advect it high 

enough above the seabed to be imaged by either the TIS or CIS systems, and it must have been 

constrained to a thin near-bed nepheloid layer.

Flood

The heavy rainfall event on 19 November 2010 (2010 YD 323) flooded Pohaukole Gulch

and delivered large quantities of both freshwater and sediment to Pelekane Bay. This was the 

heaviest rainfall event of the study period, with 49 mm recorded in 2 hours at the WS. High 

discharge from Pohaukole Gulch resulted in the breaching of the sand bar that separated the 

lagoon at the base of the gulch from Pelekane Bay (fig. 5). This single rainfall event contributed 

approximately half the rainfall that was measured over the entire 80-day study (YD 2010 310–

390). The winds during this event were predominantly from the northwest at 3–5 m/s, similar to 

trade-wind conditions (fig. 6). A small-wave event (significant wave heights <2 m) from the 

northwest was measured by the ADCPs during the time of the flood (fig. 6). The data from 18-21 

November 2010 (YD 2010 322–325) were analyzed to describe the circulation, turbidity, critical 

shear stresses, and suspended-sediment flux resulting from the rainfall and subsequent flood. 

The near-surface currents during the flood event (0.08–0.10 m/s) were stronger than those 

measured during trade-wind conditions and directed offshore, to the west, at the Central 5-m, 

Central 15-m, and South 5-m sites. The near-surface currents at the North 15-m and South 15-m 

sites (~0.03 m/s) were slower than in the central portion of Kawaihae Bay and oriented to the 

north (fig. 27). The near-bed currents (~0.10 m/s) were also stronger at the Central 5-m, Central 

15-m, and South 5-m sites than those measured at the North 15-m and South 15-m sites (~0.02 

m/s), although the directions of flow were not consistent at any of the sites (fig. 28). The 

turbidity at the instrument sites was slightly elevated prior to the flood on 19 November 2010 

(YD 2010 323) due to a small-wave event from the northwest. The greatest increases in turbidity 

were measured at the Central 2-m and 5-m sites (>100 NTU) and coincided with the flood 

(appendix 12.1). The other instrument sites recorded much smaller increases in turbidity during 

this time, possibly as a result of sluggish circulation in the area (figs. 27–28).
42

Figure 26. Map showing the mean daily near-surface (red arrows) and near-bed (blue arrows) suspended-sediment 

flux, in metric tons per square meter, during trade-wind conditions for the 2010–2011 winter experiment. Suspendedsediment flux was small at all of the instrument sites due to low turbidity and weak, variable currents.
43

Figure 27. Map showing the mean (white arrows) and variability (red ellipses) of near-surface current directions and 

speeds, in meters per second, during flood conditions for the 2010–2011 winter experiment. The strongest currents 

were located in the central part of the bay, with offshore directions. The currents at the North 15-m and South 15-m 

sites were weaker and directed to the north.
44

Figure 28. Map showing the mean (white arrows) and variability (red ellipses) of near-bed current directions and 

speeds, in meters per second, during flood conditions for the 2010–2011 winter experiment. The near-bed currents 

were primarily onshore at all sites except the South 5-m site.
45

The shear stresses due to currents alone were small and below the threshold for the 

resuspension of terrigenous clay- and silt-sized particles at all of the instrument sites (table 19; 

appendixes 14.1–14.2, orange shaded area). The small-wave event, however, generated enough

wave-driven stress that the threshold for both of these particle sizes was exceeded at the majority 

of instrument sites.

The suspended-sediment flux during the flood event was four times greater than during 

the trade-wind conditions at the Central 5-m and South 5-m sites, due to stronger currents and 

higher turbidity (fig. 29; table 20). The other instrument sites showed relatively little increase in 

suspended-sediment flux due to the weak currents and relatively low turbidity. The orientations 

of suspended-sediment flux near the seabed were predominantly onshore and to the south (fig.29, 

blue arrows); the near-surface suspended-sediment fluxes at the Central 5-m and Central 15-m 

moorings were small in magnitude and varied in direction (fig. 29, red arrows). The calculated 

shear stresses and suspended-sediment fluxes suggest that even though a large input of sediment 

entered the system due to the flood at Pohaukole Gulch, the sediment fluxes were small due to 

relatively weak currents, likely resulting in much of the flood material being deposited on the 

seabed inshore of the Central 5-m and South 5-m sites.

Visually, the flood event delivered a large volume of terrigenous sediment to the bays, as 

recorded by the TIS and CIS. The TIS photo taken on 19 November 2010 at 13:00 HST (fig. 

22B) showed red, terrigenous sediment throughout Pelekane Bay and the inner portion of 

Kawaihae Bay. The turbidity caused by the flood sediment was so great at the Central 5-m site 

that it blocked all surface light from reaching the CIS only 4 m below the water surface (fig. 23B, 

photo taken 19 November 2010 at 11:00 HST). The TIS and CIS also captured the rapid return of 

relatively clear water to the water column (fig. 22C, photo taken 20 November 2010 at 08:00 

HST) due to rapid settling of the flood material and the deposition of the red, terrigenous 

sediment on the adjacent coral reef and sea floor (fig. 23C, photo taken 21 November 2010 at 

08:00 HST).

Large Waves

Large waves impacted Kawaihae and Pelekane Bays from 15-25 January 2011 (YD 2010 

380–390). The mean significant wave heights exceeded 4 m and the maximum wave heights 

exceeded 6 m; these waves were from the northwest at 12–14 s (figs. 6D, 6E). During this event,

the winds were moderate (fig. 6B), and minor rainfall was measured at the WS (fig. 5C). The fast 

current speeds (figs. 30, 31) and large waves generated high shear stresses that resulted in high 

turbidity values and generated large suspended-sediment fluxes during this time period (fig. 32). 

The suspended-sediment fluxes during the large-wave events were the greatest of all the time 

periods analyzed at all of the instrument sites during the experiment (table 20). The mean 

direction of suspended-sediment fluxes during the large-wave events was variable at the 

instrument sites.

Near-surface currents during the large-wave events were the fastest measured during the 

deployment, exceeding 1.0 m/s and directed offshore at the Central 5-m and South 5-m sites. 

Moderate onshore flow was measured at the North 15-m, Central 15-m, and South 15-m sites 

(fig. 30). The near-bed currents were also vigorous (>1 m/s) during this time period, with 

offshore flow at the Central 5-m site and northerly flow at the South 5-m site. The other sites 

exhibited primarily weaker onshore flow (fig. 31). The fast currents directed offshore and to the 

north at the 5-m MP sites may have been due to circulation cells or return flows that were likely 
46

generated by large gradients in wave-driven set-up, resulting from the complex morphology of 

the reef in this area.

The turbidity values during these large-wave events were the highest on average at all of 

the sites except the Central 2-m site (appendix 12.1). The turbidity at the Central 2-m site was

lower during the wave events than during the flood event, likely due to the large waves 

dissipating most of their energy by breaking further offshore; relatively small waves were 

measured at the shallow Central 2-m site at that time. The wave shear stresses and combined 

wave-current shear stresses during these large-wave events were the highest measured for all of 

the instrument sites and greatly exceeded the threshold for the resuspension of terrigenous clayand silt-sized material for the majority of the 15-25 January 2011 (YD 2010 380-390) time 

period spanning 15–25 January 2011 (YD 2010380–390) (table 19; appendix 14, blue shaded 

area). Only at the Central 5-m and 15-m sites did the current shear stress alone exceed the 

threshold for the resuspension of terrigenous clay- and silt-sized material. The current shear 

stress exceeded the silt threshold for resuspension at the 

South 5- and 15-m sites for the duration of the large-wave events (appendix 14, blue shaded 

area). The largest suspended-sediment fluxes occurred at the Central 5-m mooring and Central 5-

m site; these were predominantly oriented offshore (fig. 32). Onshore suspended-sediment flux 

was measured at the Central 15-m mooring, the Central 15-m site, and North 15-m site. Wave

asymmetry during shoaling likely drove the currents and resultant suspended-sediment fluxes 

onshore at these sites, which was balanced by offshore-directed return flow through the large 

paleo-stream channel in the reef at the Central 5-m site. The TIS captured the large-wave events 

that impacted Pelekane and Kawaihae Bays in January 2011 (fig. 22D, photo taken 16 January 

2011 at 11:00 HST). The normally quiescent Pelekane Bay was turbid due to dark, resuspended 

terrigenous sediment (not new flood material); the lighter color of the turbid water in Kawaihae 

Bay may have been due to either more wave-breaking-induced bubbles or resuspended seabed 

carbonate material diluting the darker terrigenous material. The CIS did not capture the turbidity 

from the wave events, as it was damaged at the arrival of the first of the large waves and did not 

take usable photos afterwards.
47

Figure 29. Map showing the mean daily near-surface (red arrows) and near-bed (blue arrows) suspended-sediment 

flux, in metric tons per square meter, during flood conditions for the 2010-2011 winter experiment. The near-surface 

suspended-sediment flux in the central part of the bay was variable and smaller than the near-bed suspendedsediment flux. Suspended-sediment flux near the seabed was primarily onshore.
48

Figure 30. Map showing the mean (white arrows) and variability (red ellipses) of near-surface current directions and 

speeds, in meters per second, during large-wave events for the 2010–2011 winter experiment. The near-surface 

currents were onshore at the North 15-m, Central 15-m, and South 15-m sites, and offshore at the Central 5-m and 

south 5-m sites. The current speeds were highest of the entire deployment during this time period.
49

Figure 31. Map showing the mean (white arrows) and variability (red ellipses) of near-bed current directions and 

speeds, in meters per second, during large-wave events for the 2010–2011 winter experiment. The near-bed current

speeds at the South 5-m and Central 5-m sites were higher during the large-wave events than any other time during 

the deployment.
50

Figure 32. Map showing the mean daily near-surface (red arrows) and near-bed (blue arrows) suspended-sediment 

flux, in metric tons per square meter, during large-wave events for the 2010-2011 winter experiment. The suspendedsediment flux was highest during the deployment at the Central 5-m site due to the strong currents and high turbidity; 

the flux was predominantly directed offshore throughout the water column at this location. Elsewhere, the suspendedsediment flux was smaller and predominantly directed onshore or alongshore. 
51

Circulation and Sediment Dynamics

The instrument measurements and sediment-trap data presented here indicate that 

sediment transport processes in Pelekane and Kawihae Bays result from a combination of (1)

relatively common, longer-duration, low-intensity processes such as tides and trade winds and 

(2) episodic, short-term, energetic processes such as floods and large-wave events (fig. 33). The 

19 November 2010 flood (2010 YD 323) breached the sand bar that separated Pohaukole Gulch

from Pelekane Bay and delivered terrigenous material to Pelekane Bay (fig. 33A,G). This

resulted in elevated turbidity levels that were highest close to shore but extended across the reef 

(fig. 33D-F). During the subsequent trade-wind period (2010 YD 330–365), some of this 

terrigenous sediment was mobilized by moderate waves and tidal currents and slowly advected at 

low levels out to the upper forereef (fig. 33E) and, to a lesser extent, the lower fore reef (fig. 

33F) during falling tides. The impact of the large-wave events during 15-25 January 2011 (2010 

YD 380–390) to nearshore Pelekane Bay appears to have been relatively minor compared to the 

fore reef. This was likely a result of depth-induced breaking of the large waves on the fore reef, 

which dissipated most of the energy and left the inner reef flat relatively quiescent (but still more 

energetic than during trade-wind periods). These larger-than-normal waves in Pelekane Bay 

during January 2011 resuspended terrigenous flood sediment at low levels—although lower than 

measured during the November 2010 flood—suggesting that much of the mobile, fine-grained 

terrigenous material delivered by the flood had already been slowly advected out to the fore reef

at low levels by moderate waves and tidal currents under trade-wind forcing. The large-wave 

shear stresses on the exposed fore reef during January 2011 resuspended not only the terrigenous

flood sediment but also large quantities of carbonate seabed material (fig. 33G). 

It appears that episodic floods from Pohaukole Gulch deposit much of their sediment in 

Pelekane Bay. In addition, it appears that some of the sediment is advected during the flood out 

and over the fore reef (fig. 22B), causing high turbidity (fig. 33D–F), low light penetration (fig. 

23B), and temporary deposition on the upper fore reef (fig. 23C). During relatively low-energy 

trade-wind conditions, a small amount of fine-grained terrigenous sediment was resuspended 

from the reef flat and advected out over the fore reef into Kawaihae Bay (fig. 33), where it can 

decrease photosynthetically available radiation (PAR) and potentially desorb nutrients and/or 

contributing toxicants. Quiescent conditions (as observed during trade-wind conditions) can 

result in temporary accumulation of fine-grained terrigenous sediment on the fore reef, 

potentially settling on corals or at potential sites for new coral recruitment. Large waves appear 

to be very effective at resuspending terrigenous flood material on the fore reef and advecting it 

offshore to the insular shelf. Thus the phasing of sediment-injection events (for example, floods)

relative to resuspension and advection events (for example, large-wave events) is critical to the 

residence time of sediment on the reef flat and fore reef. If floods are coincident with or closely 

followed in time by energetic oceanographic conditions, the residence time for the terrigenous

flood sediment is lower relative to other scenarios. This suggests that early spring (or summer) 

floods during the transition to summer trade-wind conditions are more likely to result in longer 

residence times for terrigenous sediment on the reefs of these bays than floods that occur in the 

winter, when energetic wave conditions are more common.
52

Figure 33. Time-series plots of oceanographic conditions and sediment dynamics during the 2010–2011 winter 

experiment. A, Stream gauge depth, in meters. B, Wind speed, in meters per second, measured at the USGS 

weather station. C, Wave height, in meters, measured at the Central 15-m site. D, Turbidity, in Nephelometric

Turbidity Units (NTU), at the Central 2-m site. E, Turbidity, in Nephelometric Turbidity Units (NTU), at the Central 5-m 

site. F, Turbidity, in Nephelometric Turbidity Units (NTU), at the Central 15-m site. G, Rotary sediment trap bulk 

composition, in percent by mass, with red and blue lines denoting the terrigenous (volcanic) and carbonate 

components, respectively. 

On average, about 50 cm (41–61 cm) of sediment has accumulated in Pelekane Bay 

between the 1928 topographic/bathymetric survey and the 2011 survey (fig. 16). This average 

accumulation rate (50 cm in 83 years = 0.6 cm per year) is consistent with the accumulation rate 

derived from excess 210Pb activities (0.59 cm per year). Based on a constant-rate-of-supply 

(CRS) model of the excess 210Pb down-core profile, sediment accumulation rates in core PC3 

from Pelekane Bay have increased through recent time (table 18). It is likely that the expansion 

of the small craft breakwater on the southwest side of the harbor in the 1970s has impacted 

sediment accumulation rates in Pelekane Bay by restricting flow and reducing the propagation of 

wave energy into the bay. It is also possible that other external forcing factors such as climatic 

shifts and/or recent watershed impacts have affected trends in sediment accumulation. The 

observed shear stresses imparted by waves and currents during normal trade-wind conditions 

(table 19), which characterize most of the year (for example, Fletcher and others, 2002), are 

generally insufficient to resuspend the fine-grained terrigenous sediment in the bay. Although the 
53

shear stresses imparted by waves and currents during episodic large-wave events are sufficient to 

resuspend the fine-grained terrigenous sediment in the bay (table 19), the historical accumulation 

of sediment and apparent recent increase in accumulation rates (table 18) suggest the rate of new 

sediment delivery to the bay from the adjacent watersheds is exceeding the ability of infrequent 

large-wave events to resuspend and transport the terrigenous material out of the bay.

Conclusions 

In all, more than 2 million measurements of meteorologic and oceanographic conditions 

and water-column properties were made between November 2010 and March 2011 to assess 

circulation and sediment dynamics in Pelekane and Kawaihae Bays. Key findings from these 

measurements and subsequent analyses include:

1. The salinity values were consistently lower closer to shore due to runoff and possibly 

submarine groundwater discharge and increased offshore and away from Pelekane Bay. The 

temperatures were warmest in shallow Pelekane Bay and were cooler offshore and downcoast. 

The highest turbidity values were observed in Pelekane Bay; turbidity decreased to the south, 

away from Pelekane Bay, and offshore. The fluorescence in the region was highest close to shore 

and was variable alongshore, generally greater closer to human development and stream inputs.

2. Based on the range in bathymetric survey and considering datum error, overall the bay became 

0.41 m to 0.61 m shallower between 1928 and 2011, due to the accumulation of 22,500 m3 to 

37,500 m3 of sediment above the sea floor mapped in the 1928 survey.

3. Trade winds occurred during most of the deployment. Suspended-sediment transport during 

trade-wind conditions was limited due to sluggish currents and low shear stresses in Pelekane 

Bay, resulting in little to no sediment resuspension from the seabed or the capability to transport 

it.

4. The heavy rainfall and resulting flood event on 19 November 2010 occurred during relatively 

quiescent conditions, with average wind speeds and small waves. Suspended-sediment transport 

in Kawaihae Bay during the flood was minimal due to these weak forcing conditions. The data 

from the in situ oceanographic instruments and imagery (both terrestrial and underwater) indicate 

that although there was a large input of sediment into the coastal system, most of it remained in 

Pelekane Bay and the inner portion of Kawaihae Bay (inshore of the 15-m isobath), where it 

settled out of suspension and accumulated on the seabed. 

5. The large-wave events that impacted the region in January and February 2011 were 

responsible for the highest turbidity values and sediment flux in the bays during the experiment. 

Based on the data from the in situ oceanographic instruments and imagery (both terrestrial and 

underwater), it appears that these large-wave events resuspended large quantities of terrigenous 

sediment that had been delivered to the system during the November 2010 flood, as well as 

carbonate sand resuspended from the seabed. The strong wave-driven currents transported large 

quantities of resuspended sediment from the inner portion of the reef offshore to the insular shelf, 

effectively removing sediment delivered by the November 2010 flood from portions of the reef.
54

6. It appears that floods from Pohaukole Gulch deposit much of their sediment in Pelekane Bay. 

Although some of the fluvial sediment was advected seaward over the fore reef during the flood, 

causing high turbidity and low light penetration, most of the sediment was temporarily deposited 

on the reef flat in Pelekane Bay. During relatively low-energy trade-wind conditions, low-levels 

of fine-grained terrigenous sediment were resuspended from the reef flat in Pelekane Bay and 

advected seaward over the fore reef in Kawaihae Bay, resulting in the temporary accumulation of 

this material on the fore reef. Large-wave events appear to be effective at resuspending 

terrigenous flood material on the fore reef and advecting it offshore to the deeper, outer portions 

of the fringing reefs where there is currently high coral coverage.

7. Short-lived radionuclides (for example, 210Pb, 137Cs) were measured to estimate recent 

sediment geochronologies. Based on the down-core excess 210Pb and 137Cs profiles, the linear 

sedimentation rate at site PC3 was approximately 0.6 cm/yr, which corresponds to a mass 

accumulation rate of 524.5 mg/cm2/yr. The measured whole-core inventory of excess 210Pb was 

49.3 dpm/cm2, and assuming a latitudinally corrected atmospheric deposition rate of about 0.9 

dpm/cm/yr, the expected sediment inventory would amount to ~30 dpm/cm2

. This suggests that 

Pelekane Bay has effectively retained the majority of sediment that is delivered to the bay. This 

sequestered sediment is then also prone to repeat resuspension events, driven by large-wave 

events or tsunami waves.

Coastal circulation and sediment dynamics in Pelekane and Kawaihae Bays are complex 

in nature. Our results provide specific information on the physical oceanographic processes and 

sediment transport within the bays during winter conditions that can be applied to understanding 

their relation to coral reef health.

Acknowledgements

This work was carried out as part of the U.S. Geological Survey’s (USGS) Coral Reef Project in 

support of a larger effort in the U.S. and its trust territories to better understand the effect of 

geologic processes on coral reef systems. The work was funded by the USGS Coastal and 

Marine Geology Program (CMGP) and through a grant from the National Oceanographic and 

Atmospheric Administration’s (NOAA) Hawaiian Coral Reef Initiative, “Impact of Land-derived 

Sediment on the Coral Reef Ecosystem of Pelekane Bay, Hawaii,” which was awarded to Paul 

Jokiel (University of Hawaii Institute for Marine Biology), Mike Field (USGS), and Curt 

Storlazzi (USGS). Pete Hendricks (YMCA) graciously allowed us to store our field gear and 

deploy our weather station in the YMCA yard at Kawaihae Harbor. Sallie Beavers (National 

Park Service) and the maintenance staff at the Puukohola Heiau National Historic Site (NPSPUHE) provided critical support through the use of the NPS boat for profiler surveys and 

provided space at the NPS-PUHE headquarters for deploying our Terrestrial Imaging System.
55

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57

Additional Digital Information

For additional information on the instrument deployments, please see:

http://walrus.wr.usgs.gov/infobank/a/a510bi/html/a-5-10-bi.meta.html

http://walrus.wr.usgs.gov/infobank/a/a111bi/html/a-1-11-bi.meta.html

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

Regarding this report:

Curt D. Storlazzi (USGS Pacific Coral Reef Project chief): cstorlazzi@usgs.gov

Table 1: Experiment personnel.

Person Affiliation Responsibilities

Michael Field USGS Co-chief scientist, diver

Curt Storlazzi USGS Co-chief scientist, diver

Kathy Presto USGS Oceanographer, instrument specialist

Joshua Logan USGS Physical scientist, diver

Tom Reiss USGS Dive safety officer, surveying specialist

Tim Elfers USGS Mechanical technician

Peter Swarzenski USGS Core geochemistry, electrical resistivity

Michael Torresan USGS Sediment sampling and processing

Susan Cochran USGS Sediment sampling and processing

Hank Chezar USGS Camera technician

Joe Reich F/V Alyce C Vessel captain
58

Table 2: Instrument package sensors.

Site Name Depth

[m]

Sensors

North Pressure Sensor 2 Onset pressure sensor

North 15-m MiniProbe 15 RD Instruments 600 kHz Workhorse Monitor acoustic Doppler current profiler

15 Aquatec 210TYT turbidity sensor

Central 15-m MiniProbe 15 RD Instruments 600 kHz Workhorse Monitor acoustic Doppler current profiler

15 Aquatec 210TYT turbidity sensor

Central 15-m mooring 2 Aquatec 210TYT turbidity sensor

2 Seabird SBE-37SI Microcat conductivity-temperature sensor

Central 5-m MiniProbe 5 Nortek 2 MHz Aquadopp acoustic Doppler current profiler

5 Seabird SBE-37SI Microcat conductivity-temperature sensor

5 Aquatec 210TYT turbidity sensor

Coral imaging system (CIS) 5 Canon D60 6.3 MP digital SLR

Rotary sediment trap (RST) 5 USGS programmable, 21-bottle 

Central 5-m mooring 5 Aquatec 210TYT turbidity sensor

5 Seabird SBE-37SI Microcat conductivity-temperature sensor

Central 2-m MiniProbe 2 Nortek 2 MHz Aquadopp acoustic Doppler current profiler

2 YSI Ecowatch 6600-EDS temperature, salinity, turbidity sensor

South 15-m MiniProbe 13 RD Instruments 600 kHz Workhorse Monitor acoustic Doppler current profiler

13 Aquatec 210TYT turbidity sensor

South 5-m MiniProbe 5 Nortek 2 MHz Aquadopp acoustic Doppler current profiler

5 Seabird SBE-37SI Microcat conductivity-temperature sensor

5 Aquatec 210TYT turbidity sensor

South pressure sensor 2 Onset pressure sensor

Terrestrial imaging system (TIS) [38]* Canon EOS Rebel Xti 10.1 MP digital SLR

Stream gage [1]* Onset pressure sensor

Weather station (WS) [3]* NovaLynx WS-16N-A weather station

*Height, in meters
59

Table 3: Instrument package location information. Site Name Latitude

[decimal degrees]

Longitude

[decimal degrees]

North 15-m MiniProbe 20.029227 -155.835508

Central 15-m MiniProbe 20.023265 -155.827783

Central 15-m mooring 20.019481 -155.831628

Central 5-m MiniProbe 20.023302 -155.827743

Central 5-m mooring 20.023278 -155.827786

Central 5-m camera (CIS) 20.023265 -155.827783

Central 2-m MiniProbe 20.027089 -155.824247

South 15-m MiniProbe 19.986714 -155.833797

South 5-m MiniProbe 20.011733 -155.827024

South pressure sensor 19.943791 -155.872963

Terrestrial Camera (TIS) 20.026102 -155.820538

Stream gage 20.028547 -155.823369

Weather station 21.287697 -157.719459
60

Table 4: Water-column profiler cast locations and depth information. Cast Number Latitude

[decimal degrees]

Longitude

[decimal degrees]

Depth

[m]

1 19.97859 -155.84153 24.15

2 19.97600 -155.83407 6.98

3 19.98144 -155.83188 5.93

4 19.98445 -155.84052 24.65

5 19.98691 -155.83394 10.24

6 19.99203 -155.82839 6.38

7 19.99295 -155.83747 22.04

8 20.00522 -155.83607 24.21

9 20.00453 -155.82692 5.67

10 20.01166 -155.82743 5.95

11 20.01211 -155.83662 23.34

12 20.01755 -155.83576 38.77

13 20.01705 -155.82521 4.58

14 20.01940 -155.83180 16.52

15 20.02311 -155.83645 35.00

16 20.02331 -155.82800 4.78

17 20.02372 -155.82367 2.81

18 20.02490 -155.82394 1.93

19 20.02616 -155.82858 5.27

20 20.02481 -155.83326 22.99

21 20.02633 -155.83400 19.62

23 20.02561 -155.82411 2.48

24 20.02692 -155.82429 1.50

25 20.02902 -155.83192 3.12

26 20.02937 -155.83565 15.62

27 20.02882 -155.83783 43.00

28 20.03530 -155.83806 36.77

29 20.03818 -155.83489 12.37

30 20.04950 -155.84022 9.99

31 20.04800 -155.84302 22.82

32 20.06548 -155.85451 7.95

33 20.06437 -155.85595 29.12

34 19.94436 -155.87297 10.50
61

Table 5: Sediment core locations.

Core ID Latitude

[decimal degrees]

Longitude

[decimal degrees]

PC1 20.0271 -155.8251

PC2 20.0272 -155.8252

PC3* 20.0270 -155.8250

SC1 20.0270 -155.8250

SC2 20.0272 -155.8242

SC3 20.0272 -155.8250

SC4 20.0274 -155.8235

SC6 20.0287 -155.8232

SC7 20.0276 -155.8263

* Core PC3 was used for subsequent geochemical analyses.

Table 6: Meteorological statistics. [All statistics were calculated for 2010 Year Days 312.5–390; wind direction is “going to”]

Parameter Mean ± 1 std. deviation Minimum Maximum

Barometric pressure [mb] 1012.95±1.99 1005.56 1017.75

Air temperature [oC] 24.36±2.24 17.69 31.06

Precipitation [mm] 0.1±0.8 0 24.0

Wind speed [m/s] 1.83±1.45 0 8.25

Wind direction [o] 196.8±98.9 0.1 359.8

Stream gauge depth [m] 0.14±0.13 0 1.00
62

Table 7: Wave statistics. [All statistics were calculated for 2010 Year Days 310–390; wave direction is “from”]

Site Name Parameter Mean ± 1 std.

deviation

Minimum Maximum

North 15-m MiniProbe Height [m] 0.52±0.39 0.15 2.92

Period [s] 10.4±2.3 4.3 18.0

Direction [o] 263.3±11.5 224.0 309.0

Central 15-m MiniProbe Height [m] 0.72±0.57 0.16 4.12

Period [s] 7.4±2.6 2.8 14.7

Direction [o] 275.6±6.7 217.5 292.3

Central 5-m MiniProbe Height [m] 0.39±0.22 0.14 1.82

Period [s] 6.1±1.4 2.9 10.8

Direction [o] 269.1±15.0 8.2 324.9

Central 2-m MiniProbe Height [m] 0.18±0.06 0.1 0.61

Period [s] 4.0±0.7 2.6 7.8

Direction [o] 224.6±24.8 1.3 342.3

South 15-m MiniProbe Height [m] 0.57±0.43 0.15 3.00

Period [s] 9.7±2.6 3.4 18.4

Direction [o] 286.4±9.6 233.0 337.0

South 5-m MiniProbe Height [m] 0.80±0.62 0.21 4.29

Period [s] 7.1±1.4 3.6 11.8

Direction [o] 291.1±7.6 256.4 320.9
63

Table 8: Current statistics. [All statistics were calculated for 2010 Year Days 310–390; current direction is “going to;” N.S. = near 

surface, N.B. = near bed]

Site Name Parameter Depth [m] Mean ± 1 std. deviation Minimum Maximum

North 15-m MiniProbe Speed [m/s] 2 [N.S.] 0.01±0.04 0.00 0.34

Direction [o] 2 [N.S.] 106.8±104.8 0.0 359.6

Speed [m/s] 13 [N.B.] 0.01±0.02 0.00 0.19

Direction [o] 13 [N.B.] 119.2±103.1 0.0 359.7

Central 15-m MiniProbe Speed [m/s] 2 [N.S.] 0.03±0.04 0.00 0.32

Direction [o] 2 [N.S.] 153.2±85.2 0.0 359.9

Speed [m/s] 13 [N.B.] 0.02±0.02 0.00 0.08

Direction [o] 13 [N.B.] 133.3±62.6 0.0 359.5

Central 5-m MiniProbe Speed [m/s] 2 [N.S.] 0.013±0.09 0.00 0.84

Direction [o] 2 [N.S.] 251.4±89.8 0.0 359.9

Speed [m/s] 4 [N.B.] 0.01±0.05 0.00 0.58

Direction [o] 4 [N.B.] 163.4±88.5 0.0 359.5

Central 2-m MiniProbe Speed [m/s] 1 [N.S.] N.D.±N.D. N.D. N.D.

Direction [o] 1 [N.S.] N.D.±N.D. N.D. N.D.

Speed [m/s] 3 [N.B.] N.D.±N.D. N.D. N.D.

Direction [o] 3 [N.B.] N.D.±N.D. N.D. N.D.

South 15-m MiniProbe Speed [m/s] 2 [N.S.] 0.01±0.05 0.00 0.35

Direction [o] 2 [N.S.] 289.6±113.7 0.0 359.9

Speed [m/s] 11 [N.B.] 0.01±0.02 0.00 0.16

Direction [o] 11 [N.B.] 110.0±90.8 0.0 359.0

South 5-m MiniProbe Speed [m/s] 2 [N.S.] 0.02±0.03 0.00 0.25

Direction [o] 2 [N.S.] 279.0±87.3 0.0 359.9

Speed [m/s] 4 [N.B.] 0.02±0.04 0.00 0.34

Direction [o] 4 [N.B.] 324.5±103.0 0.0 359.9

Table 9: Temperature statistics. [All statistics were calculated for 2010 Year Days 310–390]

Site Name Depth

[m]

Mean ± 1 std. deviation

[oC]

Minimum

[oC]

Maximum

[oC]

Central 15-m Mooring 2 25.78±0.48 24.45 27.01

Central 5-m Mooring 2 25.85±0.54 24.58 27.27

Central 5-m MiniProbe 5 25.81±0.51 24.23 27.08

Central 2-m MiniProbe 2 26.26±0.91 23.91 29.03

South 5-m MiniProbe* 5 25.84±0.47* 24.81* 26.92*

*Statistics were calculated for 2010 Year Days 310–381.
64

Table 10: Salinity statistics. [All statistics were calculated for 2010 Year Days 310–390]

Site Name Depth

[m]

Mean ± 1 std. deviation

[PSU]

Minimum

[PSU]

Maximum

[PSU]

Central 15-m Mooring 2 34.91±0.11 34.01 35.16

Central 5-m Mooring 2 34.85±0.12 32.94 35.21

Central 5-m MiniProbe 5 34.74±0.15 32.82 35.08

Central 2-m MiniProbe 2 30.99±0.93 24.99 33.20

South 5-m MiniProbe * 5 34.77±0.16* 32.51* 35.09*

*Statistics were calculated for 2010 Year Days 310-381.

Table 11: Turbidity statistics. [All statistics were calculated for 2010 Year Days 310–390, removing 2010 Year Days 340.0–370.5 due 

to biofouling]

Site Name Depth 

[m]

Mean ± 1 std deviation

[NTU]

Minimum

[NTU]

Maximum

[NTU]

North 15-m MiniProbe 15 3.38±6.84 0.23 73.21

Central 15-m MiniProbe 15 7.25±14.77 0.12 204.61

Central 15-m Mooring 2 1.67±2.95 0.01 45.49

Central 5-m MiniProbe 5 13.49±21.07 0.36 232.23

Central 5-m Mooring 2 20.71±20.24 0.00 102.12

Central 2-m MiniProbe 2 7.35±30.92 1.60 1524.30

South 15-m MiniProbe 15 7.60±22.46 0.25 441.13

South 5-m MiniProbe 5 3.08±5.49 0.00 55.83
65

Table 12: Water-column profiler statistics for the 6 November 2010 

survey. Station 

ID

Mean temperature 

± 1 std. deviation 

[

o

C]

Mean salinity ± 1 std 

deviation

[PSU]

Mean turbidity ± 1 std. 

deviation

[NTU]

Mean light 

transmission ± 1 std. 

deviation [percent]

Mean fluorescence 

± 1 std deviation 

[mg/m3]

1 26.47±0.01 35.07±0.00 0.41±0.12 95.71±4.61 0.91±0.05

2 26.44±0.07 34.89±0.01 1.50±3.73 90.58±14.54 0.60±0.04

3 26.45±0.00 35.00±0.00 0.51±0.02 94.99±0.04 0.82±0.03

4 26.48±0.01 35.06±0.01 0.41±0.15 94.45±0.19 0.92±0.07

5 26.45±0.03 35.03±0.02 2.41±13.45 93.13±10.31 1.08±0.13

6 26.52±0.02 34.97±0.06 0.56±0.06 92.33±5.28 1.39±0.11

7 26.50±0.01 35.06±0.01 0.40±0.11 94.48±9.71 1.18±0.08

8 26.57±0.02 35.07±0.01 0.46±0.06 95.10±0.45 1.15±0.12

9 26.63±0.02 35.03±0.05 0.52±0.09 90.82±2.84 1.96±0.53

10 26.66±0.02 35.06±0.02 0.62±0.31 94.33±6.30 0.59±0.06

11 26.61±0.01 35.09±0.01 0.44±0.03 96.51±3.69 0.65±0.12

12 26.56±0.07 35.06±0.12 0.50±0.10 96.12±2.68 0.80±0.10

13 26.64±0.03 34.90±0.14 4.72±16.93 88.04±14.81 0.94±0.06

14 26.65±0.03 35.02±0.22 0.44±0.07 95.96±1.17 0.75±0.09

15 26.55±0.07 35.05±0.10 1.69±11.13 94.84±9.82 0.86±0.14

16 26.65±0.04 34.93±0.10 0.94±2.03 91.28±14.77 1.06±0.08

17 26.76±0.00 34.73±0.00 1.62±0.04 84.50±4.65 0.63±0.05

18 26.70±0.01 34.67±0.17 1.69±0.37 83.38±9.54 0.58±0.05

19 26.66±0.01 34.90±0.01 0.67±0.06 89.31±15.60 0.82±0.08

20 26.60±0.03 35.04±0.12 0.48±0.10 94.90±6.37 0.88±0.05

21 26.59±0.04 35.01±0.09 2.91±16.24 93.25±11.75 0.91±0.14

23 26.71±0.02 34.19±0.02 4.76±4.08 71.84±0.23 1.39±0.06

24 26.93±0.22 33.80±0.20 3.76±0.28 69.86±1.28 1.36±0.32

25 26.64±0.00 34.81±0.00 0.59±0.05 92.00±6.98 0.80±0.04

26 26.62±0.01 35.06±0.02 0.44±0.25 94.93±3.39 0.86±0.11

27 26.60±0.01 35.07±0.02 0.43±0.07 96.15±6.24 0.86±0.14

28 26.61±0.02 35.06±0.02 0.44±0.10 95.41±8.52 0.94±0.09

29 26.64±0.03 35.00±0.03 0.79±0.18 92.46±8.29 1.14±0.53

30 26.57±0.05 34.58±0.91 1.85±2.17 83.73±5.61 1.46±0.60

31 26.61±0.01 35.02±0.01 0.67±1.83 93.45±6.80 1.36±0.10

32 26.63±0.01 35.00±0.08 1.32±4.98 92.92±8.67 0.56±0.04

33 26.62±0.01 35.08±0.01 1.10±7.35 95.37±11.89 0.86±0.13

34 26.50±0.03 35.06±0.01 0.53±0.03 94.59±6.32 0.65±0.04
66

Table 13: Water-column profiler statistics for the 10 March 2011 survey. Station 

ID

Mean temperature 

± 1 std deviation 

[

o

C]

Mean salinity ± 1 

std. deviation 

[PSU]

Mean turbidity ± 1 std. 

deviation

[NTU]

Mean light 

transmission ± 1 std. 

deviation [percent]

Mean fluorescence 

± 1 std deviation 

[mg/m3]

1 25.12±0.006 34.55±0.01 1.12±5.92 94.35±11.68 0.48±0.07

2 25.13±0.069 34.37±0.06 0.48±0.59 92.74±12.84 0.28±0.04

3 25.20±0.028 34.42±0.06 1.60±4.03 93.49±8.29 0.30±0.03

4 25.24±0.023 34.59±0.01 2.41±5.57 95.64±8.53 0.27±0.05

5 25.16±0.011 34.48±0.05 0.59±0.71 93.69±11.72 0.33±0.05

6 25.22±0.005 34.47±0.02 4.24±17.64 94.56±6.68 0.29±0.03

7 25.25±0.006 34.59±0.01 1.00±6.89 93.96±9.83 0.26±0.05

8 25.29±0.034 34.57±0.01 0.41±1.84 94.94±5.92 0.20±0.04

9 25.26±0.033 34.49±0.06 3.71±12.26 92.03±14.22 0.33±0.03

10 25.32±0.043 34.53±0.05 3.20±12.54 93.52±10.30 0.31±0.02

11 25.29±0.031 34.58±0.00 0.66±1.24 95.32±8.51 0.28±0.03

12 25.28±0.023 34.60±0.01 0.32±0.13 96.13±7.00 0.31±0.05

13 25.53±0.121 34.32±0.23 4.58±14.26 90.62±14.81 0.43±0.10

14 25.32±0.003 34.60±0.00 0.38±0.44 93.33±11.30 0.30±0.04

15 25.29±0.014 34.58±0.01 1.19±7.06 94.49±7.09 0.29±0.06

16 25.39±0.035 34.54±0.03 6.65±24.52 91.35±11.07 0.27±0.02

17 25.48±0.008 34.38±0.08 6.95±14.50 79.79±15.88 0.34±0.06

18 25.62±0.070 34.35±0.08 3.18±0.95 76.15±3.31 0.63±0.09

19 25.40±0.008 34.55±0.02 7.52±20.38 91.24±13.64 0.35±0.02

20 25.31±0.012 34.59±0.02 0.42±0.24 94.50±0.17 0.34±0.06

21 25.33±0.034 34.59±0.01 1.22±7.60 94.16±1.96 0.32±0.08

23 26.13±0.070 34.05±0.15 3.80±2.77 70.47±11.92 0.83±0.13

24 26.49±0.012 33.73±0.12 20.24±20.24 44.79±8.22 1.77±0.10

25 25.53±0.012 34.49±0.01 6.17±15.33 95.09±1.54 0.25±0.02

26 25.35±0.057 34.58±0.01 0.33±0.05 94.95±11.84 0.23±0.03

27 25.29±0.033 34.59±0.02 1.07±6.94 93.45±3.39 0.28±0.08

28 25.32±0.018 34.58±0.00 0.38±0.76 96.09±6.24 0.29±0.04

29 25.43±0.117 34.60±0.03 1.57±7.94 93.15±8.52 0.41±0.12

30 25.30±0.005 34.57±0.01 0.99±3.83 95.48±8.29 0.20±0.02

31 25.28±0.022 34.58±0.01 0.67±3.71 92.91±5.61 0.28±0.04

32 25.27±0.025 34.58±0.02 1.36±3.41 95.39±6.80 0.19±0.02

33 25.25±0.007 34.58±0.01 1.73±12.62 96.08±8.67 0.23±0.04

34 25.05±0.057 34.32±0.27 0.70±1.99 93.79±11.89 0.25±0.07
67

Table 14. Sediment trap location and depth information. [Note: simple tube traps (STT) were deployed with their openings 0.4 m above the seabed; the rotary 

sediment trap (RST) was deployed with its opening 1.4 m above the seabed, hence the different orders of 

magnitude in the collection rates between trap types]

USGS Sample 

Identifier

Site name Sample type Average trap 

collection rate

[mg/cm2/day]

Latitude

[decimal degrees]

Longitude

[decimal degrees]

Depth

[m]

BI-0311-13 Central 2 m STT 156.70 20.02709 -155.82425 2

BI-0311-14 South 15 m STT 531.91 19.98671 -155.83380 15

BI-0311-15 North 15 m STT 501.55 20.02923 -155.83551 15

BI-0311-16 Central 5 m STT 306.34 20.02330 -155.82774 5

BI-0311-17 South 5 m STT 537.24 20.01173 -155.82702 5

BI-0311-18 Central 15 m STT 359.10 20.01947 -155.83154 15

BI-0311-19 Central 5 m RST 0.01 20.02330 -155.82774 5

BI-0311-20 Central 5 m RST 0.02 20.02330 -155.82774 5

BI-0311-21 Central 5 m RST 1.23 20.02330 -155.82774 5

BI-0311-22 Central 5 m RST 0.27 20.02330 -155.82774 5

BI-0311-23 Central 5 m RST 0.19 20.02330 -155.82774 5

BI-0311-24 Central 5 m RST 0.20 20.02330 -155.82774 5

BI-0311-25 Central 5 m RST 0.30 20.02330 -155.82774 5

BI-0311-26 Central 5 m RST 0.11 20.02330 -155.82774 5

BI-0311-27 Central 5 m RST 0.49 20.02330 -155.82774 5

BI-0311-28 Central 5 m RST 0.14 20.02330 -155.82774 5

BI-0311-29 Central 5 m RST 1.05 20.02330 -155.82774 5

BI-0311-30 Central 5 m RST 7.92 20.02330 -155.82774 5

BI-0311-31 Central 5 m RST 3.20 20.02330 -155.82774 5

BI-0311-32 Central 5 m RST 12.91 20.02330 -155.82774 5
68

Table 15. Sediment trap grain size and composition information. USGS Sample 

Identifier

Sand

[percent]

Silt

[percent]

Clay

[percent]

Mean size

[mm]

Carbonate

[percent]

Terrigenous

[percent]

BI-0311-13 6.61 71.50 21.79 0.011 6.72 93.28

BI-0311-14 88.64 7.47 3.36 0.137 83.74 16.26

BI-0311-15 95.59 1.87 1.60 0.188 94.31 5.69

BI-0311-16 83.74 10.45 5.53 0.194 90.38 9.62

BI-0311-17 93.01 3.87 1.96 0.179 76.01 23.99

BI-0311-18 80.74 10.60 5.17 0.135 89.82 10.18

BI-0311-19 3.53 66.04 30.42 0.008 34.85 65.15

BI-0311-20 3.11 63.53 33.36 0.008 45.92 54.08

BI-0311-21 9.16 70.26 20.59 0.011 43.25 56.75

BI-0311-22 8.77 66.28 24.95 0.010 37.73 62.27

BI-0311-23 7.53 74.80 17.67 0.012 31.46 68.54

BI-0311-24 9.99 72.84 17.17 0.013 35.41 64.59

BI-0311-25 10.03 69.06 20.92 0.012 57.85 42.15

BI-0311-26 8.19 64.23 27.57 0.010 60.13 39.87

BI-0311-27 8.78 62.90 28.32 0.010 61.55 38.45

BI-0311-28 6.84 61.67 31.49 0.009 62.42 37.58

BI-0311-29 9.40 68.12 22.48 0.011 63.93 36.07

BI-0311-30 37.90 42.70 19.33 0.022 80.68 19.32

BI-0311-31 18.09 59.86 22.05 0.013 75.61 24.39

BI-0311-32 80.21 13.09 5.80 0.150 92.33 7.67

Table 16. Seabed sample location and depth information. USGS Sample 

Identifier

Site Name Sample Type Latitude

[decimal degrees]

Longitude

[decimal degrees]

Depth

[m]

BI-0311-1 – S15 South 15 m Grab 19.98671 -155.83380 15

BI-0311-2 – C5 Central 5 m Grab 20.02330 -155.82774 5

BI-0311-3 – N15 North 15 m Grab 20.02923 -155.83551 15

BI-0311-4 – C15 Central 15 m Grab 20.01947 -155.83154 15

BI-0311-5 – S5 South 5 m Grab 20.01173 -155.82702 5

BI-0311-6 – C2 Central 2 m Grab 20.02709 -155.82425 2
69

Table 17. Seabed grain size and composition. USGS Sample 

Identifier

Sand

[percent]

Silt

[percent]

Clay

[percent]

Mean Size

[mm]

Carbonate

[percent]

Terrigenous

[percent]

BI-0311-1 – S15 98.72 0.77 0.16 0.225 89.65 10.35

BI-0311-2 – C5 99.21 0.22 0.15 0.477 96.15 3.85

BI-0311-3 – N15 98.17 0.47 0.27 0.254 96.83 3.17

BI-0311-4 – C15 90.16 0.19 0.18 0.682 94.99 5.01

BI-0311-5 – S5 98.67 0.27 0.16 0.450 47.54 52.46

BI-0311-6 – C2 84.30 7.58 6.94 0.105 49.08 50.92

Table 18: Geochronologic results for core PC3.

Mid 

depth

[cm]

Mass 

depth

[g/cm2]

Cum. 

mass

[g/cm2]

Total 210Pb ± 

1 std. 

deviation

[dpm/g]

Total 226Ra ± 

1 std. 

deviation

[dpm/g]

Excess

210Pb

[dpm/g]

Total 137Cs

[dpm/g]

Linear sed. 

rate

[cm/yr]

Mass 

accumulation 

rate

[mg/cm2/yr]

Avg. year 

interval ± 1 

std. deviation

[A.D.]

0.5 1.26 1.26 3.53±0.33 0.32±0.07 3.22 0.16 - - -

2.5 1.24 2.50 3.46±0.40 0.49±0.05 2.97 0.19 - - -

4.5 1.25 3.74 3.90±0.51 0.24±0.08 3.65 0.16 - - -

6.5 1.18 4.93 3.89±0.42 0.53±0.07 3.36 0.18 - - -

8.5 1.30 6.23 3.27±0.47 0.42±0.07 2.85 0.18 - - -

11 1.33 7.56 3.80±0.25 0.52±0.06 3.27 0.18 2.48 550.28 2008.8±1.1

13 1.29 8.85 3.80±0.50 0.57±0.07 3.23 0.21 1.36 475.74 2003.6±0.9

15 1.29 10.14 3.79±0.56 0.58±0.09 3.21 0.18 0.95 397.58 1997.7±0.9

17 1.22 11.35 3.34±0.51 0.48±0.07 2.86 0.17 0.77 364.39 1991.1±1.1

19 1.25 12.60 3.37±0.48 0.49±0.09 2.88 0.17 0.62 284.68 1983.3±1.5

21 1.19 14.99 2.78±0.63 0.42±0.08 2.36 0.20 0.53 263.01 1974.3±2.3

23 1.25 17.48 2.75±0.61 0.52±0.07 2.23 0.21 0.44 200.42 1963.5±4.0

25 1.32 20.12 2.23±0.36 0.54±0.07 1.70 0.26 0.37 170.88 1949.3±7.1

28 1.15 22.41 1.80±0.35 0.26±0.06 1.54 0.17 - - -
70

Table 19: Wave-current critical shear stress statistics.

Site name Condition [time period, 

in 2010 Year Days]

Depth 

[m]

Mean shear 

stress ± 1 std.

deviation 

[N/m2

]

Time shear stress 

exceeded threshold 

for suspension of 

silt-sized particles

[percent]

Time shear stress 

exceeded threshold 

for suspension of 

clay-sized particles 

[percent]

North 15-m Experiment [310–390] 15 0.22±0.34 19.68 44.82

Trade winds [317–320] 15 0.09±0.05 0.62 22.45

Wave resuspension 

[380–383] 15 0.79±0.63 80.08 99.17

Central 15-m Experiment [310–390] 15 0.34±0.50 31.65 58.40

Trade winds [317–320] 15 0.12±0.46 1.60 41.60

Wave resuspension 

[380–383] 15 1.19±0.91 95.40 99.59

Central 5-m Experiment [310–390] 5 0.26±0.38 20.15 62.05

Trade Winds [317–

320] 5 0.15±0.06 3.12 59.67

Wave resuspension 

[380–383] 5 0.65±0.57 75.52 99.17

Central 2-m* Experiment [310–390] 1 0.08±0.08 4.74 20.09

Trade winds [317–320] 1 0.09±0.06 1.37 26.03

Wave resuspension 

[380–383] 1 0.29±0.13 52.05 89.04

South 15-m Experiment [310–390] 15 0.24±0.36 22.44 46.75

Trade winds [317–320] 15 0.09±0.05 0.83 18.50

Wave resuspension 

[380–383] 15 0.85±0.67 83.40 99.59

South 5-m Experiment [310–390] 5 0.80±1.25 61.17 85.27

Trade winds [317–320] 5 0.30±0.13 57.59 84.8

Wave resuspension 

[380–383] 5 2.88±2.15 100.00 100.00

*Statistics were calculated using a proxy current velocity of 0.025 m/s and average wave periods
71

Table 20: Suspended-sediment flux statistics. Site Name Condition [time period, in

2010 Year Days]

Depth

[m]

Average daily 

suspendedsediment flux [metric 

tons/m2]

Direction of 

transport

[°True]

North 15-m MiniProbe Experiment [310–390] 15 3.67 87.36

Trade winds [317–320] 15 0.07 145.27

Flood [322–325] 15 0.07 9.04

Wave resuspension [380–383] 15 2.48 94.19

Central 15-m MiniProbe Experiment [310–390] 15 20.64 147.95

Trade winds [317–320] 15 0.10 119.65

Flood [322–325] 15 0.24 156.40

Wave resuspension [380–383] 15 4.05 161.68

Central 15-m Mooring Experiment [310–390] 2 8.63 128.39

Trade winds [317–320] 2 0.14 148.72

Flood [322–325] 2 0.07 247.64

Wave resuspension [380–383] 2 5.52 112.93

Central 5-m MiniProbe Experiment [310–390] 5 58.04 248.16

Trade winds [317–320] 5 0.21 95.96

Flood [322–325] 5 1.08 120.53

Wave resuspension [380–383] 5 49.38 259.24

Central 5-m mooring Experiment [310–390] 2 133.93 266.37

Trade winds [317–320] 2 0.03 64.67

Flood [322–325] 2 0.07 130.13

Wave resuspension [380–383] 2 95.97 277.51

Central 2-m MiniProbe Experiment [310–390] 1 N.D.* N.D.*

Trade winds [317–320] 1 N.D.* N.D.*

Flood [322–325] 1 N.D.* N.D.*

Wave resuspension [380–383] 15 N.D.* N.D.*

South 15-m MiniProbe Experiment [310–390] 15 5.41 147.65

Trade winds [317–320] 15 0.03 21.49

Flood [322–325] 15 0.03 128.51

Wave resuspension [380–383] 15 4.51 218.80

South 5-m MiniProbe Experiment [310–390] 5 37.33 358.20

Trade winds [317–320] 5 0.24 333.50

Flood [322–325] 5 0.94 332.26

Wave resuspension [380–383] 5 18.26 5.05

*N.D. = No data.
72

Appendix 1. Acoustic Doppler Current Profiler (ADCP) Information

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

s/n: 2074

Transmitting Frequency: 614 kHz

Depth of Transducer: 12.8 m

Blanking Distance: 0.25 m

Height of First Bin above Transducer: 1.45 m

Bin Size: 1.0 m

Number of Bins: 18

Operating Mode: High-resolution, broad bandwidth

Sampling Frequency: 2 Hz

Time per Ping: 00:04.00

Pings per Ensemble: 50

Profile Ensemble Interval: 0:15:00.00

Wave Ensemble Interval: 1:00:00.00

Sound Speed Calculation: Set salinity, updating temperature via

sensor

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

s/n: 2432

Transmitting Frequency: 614 kHz

Depth of Transducer: 13.6 m

Blanking Distance: 0.25 m

Height of First Bin above Transducer: 1.45 m

Bin Size: 1.0 m

Number of Bins: 18

Operating Mode: High-resolution, broad bandwidth

Sampling Frequency: 2 Hz

Time per Ping: 00:04.00

Pings per Ensemble: 50

Profile Ensemble Interval: 0:15:00.00

Wave Ensemble Interval: 1:00:00.00

Sound Speed Calculation: Set salinity, updating temperature via 

sensor

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

s/n: 1861

Transmitting Frequency: 2 MHz

Depth of Transducer: 5 m

Blanking Distance: 0.20 m

Height of First Bin above Bed: 1.00 m

Bin Size: 0.5 m
73

Number of Bins: 12

Average interval: 0:08:00.00

Profile interval: 0:15:00.00

Wave interval: 1:00:00.00

Wave cell size: 0.5 m

Operating Mode: High-resolution

Sound Speed Calculation: Set salinity, updating temperature via 

sensor

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

s/n: 1852

Transmitting Frequency: 2 MHz

Depth of Transducer: 5 m

Blanking Distance: 0.20 m

Height of First Bin above Bed: 1.00 m

Bin Size: 0.5 m

Number of Bins: 12

Average interval: 0:08:00.00

Profile interval: 0:15:00.00

Wave interval: 1:00:00.00

Wave cell size: 0.5 m

Operating Mode: High-resolution

Sound Speed Calculation: Set salinity, updating temperature via 

sensor

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

s/n: 1757

Transmitting Frequency: 2 MHz

Depth of Transducer: 3 m

Blanking Distance: 0.20 m

Height of First Bin above Bed: 1.00 m

Bin Size: 0.5 m

Number of Bins: 10

Average interval: 0:08:00.00

Profile interval: 0:15:00.00

Wave interval: 1:00:00.00

Wave cell size: 0.5 m

Operating Mode: High-resolution

Sound Speed Calculation: Set salinity, updating temperature via 

sensor

Nortek Instruments 1 MHz AWAC upward-looking acoustic Doppler current profiler

s/n: 5156

Transmitting Frequency: 1 MHz

Depth of Transducer: 15 m

Blanking Distance: 0.40 m
74

Height of First Bin above Bed: 1.50 m

Bin Size: 1.00 m

Number of Bins: 18

Average interval: 0:06:00.00

Profile interval: 0:15:00.00

Wave interval: 1:00:00.00

Wave cell size: 1.8 m

Operating Mode: High-resolution

Sound Speed Calculation: Set salinity, updating temperature via 

sensor

Data Processing:

The RDI current data were processed using the WinADCP program 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.

Appendix 2. Conductivity and Temperature (CT) Information

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

s/n: 3800, 3801, 7046, and 7047

Sampling Frequency: 2 Hz

Measurements per Burst: 8

Time Between Bursts: 00:05:00.00

Data Processing:

The 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.

Appendix 3. Turbidity Sensor (SLOBS) Information

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

s/n: 371-026

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

s/n: 024-002, 024-005, 024-006, 024-013, 024-018 ,024-052

Sampling Frequency: 2 Hz

Measurements per Burst: 8

Time Between Bursts: 00:05:00.00
75

Data Processing:

The 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 4. Weather Station (WS), Terrestrial Imaging System (TIS), and Coral 

Imaging System (CIS) 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 Gage: 110-WS-16RC

Sampling Frequency: 1 Hz

Measurements per Burst: 1800

Time Between Bursts: 00:30:00.00

USGS Terrestrial Imaging System

Camera: Canon EOS Digital Rebel Xti 10.1 megapixel 

ProgrammableAutomated Controller: Campbell Scientific Scientific CR200

Sampling Times: 07:00, 08:00, 09:00, 10:00, 11:00, 13:00, 15:00, and 

17:00 HST

USGS Coral Imaging System

Camera: Nikon CoolPix 8700 8-megapixel digital camera

ProgrammableAutomated Controller: Campbell Scientific Scientific CR200

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

Appendix 5. Water-Column Profiler (WCP) 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: 5250

D&A Instruments OBS-3 sensor; s/n: 1134

Seabird pressure sensor; s/n: 2632709

Wet Labs CStar; s/n: 712

Sampling Frequency: 4 Hz

Position Information:

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

Data Processing:

The profiler data were processed using the SBEDataProcessing 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).

Appendix 6. Water-Column Profiler (WCP) log: 6 November 2010

Cast 

Number/Site

Date [MM/DD/YYY] Time

[HST]

Latitude

[decimal degrees]

Longitude

[decimal degrees]

Depth

[m]

1 11/06/2010 09:57:46 20.0269961 -155.8242271 2

2 11/06/2010 10:03:30 20.0258809 -155.8241391 <1

3 11/06/2010 10:07:13 20.0248816 -155.8240163 <1

4 11/06/2010 10:11:02 20.0235571 -155.8238250 <1

5 11/06/2010 10:21:30 20.0117810 -155.8273887 16

6 11/06/2010 11:13:40 19.9443847 -155.8727774 28

7 11/06/2010 11:29:00 19.9785747 -155.8412896 70

8 11/06/2010 11:35:41 19.9758262 -155.8340876 12

9 11/06/2010 11:40:45 19.9815847 -155.8318523 14

10 11/06/2010 11:44:23 19.9844308 -155.8403968 60

11 11/06/2010 11:48:20 19.9869389 -155.8337882 38

12 11/06/2010 11:53:06 19.9922507 -155.8284970 16

13 11/06/2010 11:56:06 19.9931553 -155.8373494 62

14 11/06/2010 12:01:42 20.0052388 -155.8359194 63

15 11/06/2010 12:06:52 20.0043909 -155.8269207 15

16 11/06/2010 12:23:32 20.0122077 -155.8364979 68

17 11/06/2010 12:27:13 20.0177151 -155.8357232 93

18 11/06/2010 12:34:42 20.0170263 -155.8251168 10

19 11/06/2010 12:39:24 20.0194201 -155.8318590 35

20 11/06/2010 12:43:39 20.0231293 -155.8363725 103

21 11/06/2010 12:47:32 20.0249106 -155.8332369 68

22 11/06/2010 12:51:56 20.0232811 -155.8279341 15

23 11/06/2010 12:56:44 20.0260841 -155.8287010 15

24 11/06/2010 13:00:30 20.0264197 -155.8339061 50

25 11/06/2010 13:05:50 20.0289800 -155.8320484 12

26 11/06/2010 13:09:55 20.0290288 -155.8376493 91

27 11/06/2010 13:13:55 20.0293112 -155.8357052 43

28 11/06/2010 13:17:35 20.0353828 -155.8381160 111

29 11/06/2010 13:22:48 20.0380800 -155.8347245 20

30 11/06/2010 13:40:03 20.0494285 -155.8402751 30

31 11/06/2010 13:43:12 20.0479930 -155.8431138 70

32 11/06/2010 13:52:33 20.0655462 -155.8545657 20

33 11/06/2010 13:55:20 20.0644229 -155.8558560 86
77

Appendix 7. Water-column profiler (WCP) log: 10 March 2011

Cast 

Number/Site

Date [MM/DD/YYY] Time

[HST]

Latitude

[decimal degrees]

Longitude

[decimal degrees]

Depth

[m]

1 03/10/2011 09:53:17 20.0654793 -155.8545055 22

2 03/10/2011 09:55:25 20.0643726 -155.8559496 85

3 03/10/2011 10:01:58 20.0479995 -155.8430153 67

4 03/10/2011 10:05:43 20.0495011 -155.8402219 28

5 03/10/2011 10:12:32 20.0381756 -155.8348914 28

6 03/10/2011 10:17:24 20.0353047 -155.8380641 110

7 03/10/2011 10:22:32 20.0288226 -155.8378312 126

8 03/10/2011 10:27:07 20.0293713 -155.8356479 42

9 03/10/2011 10:30:27 20.0290158 -155.8319154 9

10 03/10/2011 10:33:45 20.0263292 -155.8340037 50

11 03/10/2011 10:36:52 20.0248069 -155.8332565 67

12 03/10/2011 10:40:40 20.0231114 -155.8364469 110

13 03/10/2011 10:45:45 20.0175509 -155.8357611 108

14 03/10/2011 10:50:54 20.0194043 -155.8317982 35

15 03/10/2011 10:56:29 20.0233086 -155.8280029 13

16 03/10/2011 10:59:54 20.0261581 -155.8285829 13

17 03/10/2011 11:07:47 20.0237224 -155.8236656 7

18 03/10/2011 11:12:53 20.0248951 -155.8239361 6

19 03/10/2011 11:21:11 20.0269211 -155.8242938 3

20 03/10/2011 11:27:02 20.0256073 -155.8241111 5

21 03/10/2011 12:00:25 20.0170518 -155.8252093 11

22 03/10/2011 12:12:42 20.0121125 -155.8366229 67

23 03/10/2011 12:18:00 20.0116591 -155.8274271 19

24 03/10/2011 12:23:42 20.0045298 -155.8269249 14

25 03/10/2011 12:28:58 20.0052225 -155.8360652 68

26 03/10/2011 12:38:41 19.9929535 -155.8374674 63

27 03/10/2011 12:46:05 19.9920303 -155.8283855 16

28 03/10/2011 12:50:48 19.9869106 -155.8339371 27

29 03/10/2011 12:55:10 19.9844524 -155.8405241 70

30 03/10/2011 13:02:33 19.9814444 -155.8318827 16

31 03/10/2011 13:08:02 19.9759981 -155.8340725 18

32 03/10/2011 13:14:26 19.9785870 -155.8415335 71

33 03/10/2011 13:27:55 19.9443606 -155.8729729 28
78

Appendix 8. Topographic and bathymetric plots of Pelekane Bay

Appendix 8.1. Track lines from the topographic survey of the beach and nearshore portions of Pelekane Bay, 

Hawaii, conducted on March 11–12, 2011.

Appendix 8.2. Map showing the historical bathymetric data from the 1928 U.S. Coast and Geodetic Hydrographic 

Survey #5007. Sounding depths given in fathoms.
79

Appendix 9. Time-series plots of variations in water level, wave heights, wave periods, 

and wave directions from the acoustic Doppler current profilers (ADCPs)

Appendix 9.1. Tide and wave data from the ADCP at Central 15-m site. A. Tidal height, in meters. B. Wave height, in 

meters. C. Wave period, in seconds. D. Wave height (red), in meters, and wave vectors (blue), with directions given 

as “going to,” measured in degrees clockwise from true north.
80

Appendix 9.2. Tide and wave data from the ADCP at the North 15-m site. A, Tidal height, in meters. B, Wave height, 

in meters. C, Wave period, in seconds. D, Wave height (red), in meters, and wave vectors (blue), with directions 

given as “going to,” measured in degrees clockwise from true north.
81

Appendix 9.3. Tide and wave data from the ADCP at the South 15-m site. A, Tidal height, in meters. B, Wave height, 

in meters. C, Wave period, in seconds. D, Wave height (red), in meters, and wave vectors (blue), with directions 

given as “going to,” measured in degrees clockwise from true north.
82

Appendix 9.4. Tide and wave data from the ADCP at the Central 5-m site. A, Tidal height, in meters. B, Wave height, 

in meters. C, Wave period, in seconds. D, Wave height (red), in meters, and wave vectors (blue), with direction given 

as “going to,” measured in degrees clockwise from true north.
83

Appendix 9.5. Tide and wave data from the ADCP at the South 5-m site. A, Tidal height, in meters. B, Wave height, 

in meters. C, Wave period, in seconds. D, Wave height (red), in meters, and wave vectors (blue), with direction given 

as “going to,” measured in degrees clockwise from true north.
84

Appendix 9.6. Tide and wave data from the ADCP at the Central 2-m site. A, Tidal height, in meters. B, Wave height, 

in meters. C, Wave period, in seconds. D, Wave height (red), in meters, and wave vectors (blue), with direction given 

as “going to,” measured in degrees clockwise from true north.
85

Appendix 10. Time-series plots of variations in water level, currents, and temperature 

from the acoustic Doppler current profilers (ADCPs).

Appendix 10.1. Tide, current, and water temperature data from the ADCP at the Central 15-m site. A, Tidal height, in 

meters. B, Near-surface current velocity, with direction given in degrees clockwise from true north and speed given in 

meters per second. C, Mid-depth current velocity, with direction given in degrees clockwise from true north and speed 

given in meters per second. D, Near-bed current velocity, with direction given in degrees clockwise from true north

and speed in meters per second. E, Water temperature, in degrees Celsius. 
86

Appendix 10.2. Tide, current, and water temperature data from the ADCP at the North 15-m site. A, Tidal height, in 

meters. B, Near-surface current velocity, with direction in degrees from true north and speed in meters per second. C,

Mid-depth current velocity, with direction in degrees from true north and speed in meters per second. D, Near-bed 

current velocity, with direction in degrees from true north and speed in meters per second. E, Water temperature, in 

degrees Celsius.
87

Appendix 10.3. Tide, current, and water temperature data from the ADCP at the South 15-m site. A,Tidal height, in 

meters. B, Near-surface current velocity, with direction in degrees from true north and speed in meters per second. C,

Mid-depth current velocity, with direction in degrees from true north and speed in meters per second. D, Near-bed 

current velocity, with direction in degrees from true north and speed in meters per second. E, Water temperature, in 

degrees Celsius.
88

Appendix 10.4. Tide, current, and water temperature data from the ADCP at the Central 5-m site. A, Tidal height, in 

meters. B, Near-surface current velocity, with direction in degrees from true north and speed in meters per second. C,

Mid-depth current velocity, with direction in degrees from true north and speed in meters per second. D, Near-bed 

current velocity, with direction in degrees from true north and speed in meters per second. E, Water temperature, in 

degrees Celsius.
89

Appendix 10.5. Tide, current, and water temperature data from the ADCP at the South 5-m site. A, Tidal height, in 

meters. B, Near-surface current velocity, with direction in degrees from true north and speed in meters per second. C,

Mid-depth current velocity, with direction in degrees from true north and speed in meters per second. D, Near-bed 

current velocity, with direction in degrees from true north and speed in meters per second. E, Water temperature, in 

degrees Celsius.
90

Appendix 11. Time-series plots of data from the conductivity and temperature (CT)

sensors

Appendix 11.1. Temperature and salinity data from the CT sensors at the instrument sites. A, Water temperature, in 

degrees Celsius. Green, Central 2-m MiniProbe; blue, Central 5-m MiniProbe; red, Central 5-m ,mooring; cyan,

Central 15-m mooring. B, Salinity, in Practical Salinity Units (PSU). Green, Central 2-m MiniProbe; blue, Central 5-m 

MiniProbe; red, Central 5-m mooring; cyan, Central 15-m mooring.
91

Appendix 12. Time series plots of variations in turbidity from the self-logging optical 

backscatter sensors (SLOBS)

Appendix 12.1. Turbidity data for the 2010–2011 winter from the SLOBSs, in Nephelometric Turbidity Units (NTU);

data from the shaded areas were not used for statistics or analysis. A, Turbidity at the Central 5-m mooring. B,

Turbidity at the Central 15-m mooring. C, Turbidity at the Central 15-m MiniProbe. D, Turbidity at the North 15-m 

MiniProbe. E, Turbidity at the South 15-m MiniProbe. F, Turbidity at the Central 5-m MiniProbe. G, Turbidity at the 

South 5-m MiniProbe. H, Turbidity at the Central 2-m MiniProbe.
92

Appendix 13. Maps showing the spatial variability in water parameters from the watercolumn profiler (WCP) casts in November 2010 and March 2011

Appendix 13.1. Map showing the locations for the WCP casts in November 2010 and March 2011.
93

Appendix 13.2. Map showing the spatial variability of water temperature, in degrees Celsius, during the survey on 6 

November 2010. The warmest area measured was in Pelekane Bay, possibly due to the shallow depths. The coldest 

area of the survey was located to the south, near Puako.
94

Appendix 13.3. Map showing the spatial variability of temperature, in degrees Celsius, during the survey on 10 

March 2011. The warmest area of the survey was located near shore in Pelekane Bay. The coldest temperatures 

were measured to the south, near Puako. Overall, the temperatures during the March 2011 survey were colder than 

the November 2010 survey, due to seasonal cooling.
95

Appendix 13.4. Map showing the spatial variability of salinity, in Practical Salinity Units (PSU), during the survey on 6 

November 2010. Salinity values were lower offshore of streams in the northern part of the survey and near

Pohokohaule stream in Pelekane Bay.
96

Appendix 13.5. Map showing the spatial variability of salinity, in Practical Salinity Units (PSU), during the survey on 

10 March 2011. Salinity values during this survey were lower overall than during the November survey, possibly due 

to an increase in surface runoff and submarine groundwater discharge following rainfall during the winter months.
97

Appendix 13.6. Map showing the spatial variability of turbidity, measured by optical backscatter, in Nephelometric 

Turbidity Units (NTU), during the survey on 6 November 2010. There was relatively clear water overall, with the 

highest turbidity in Pelekane Bay. 
98

Appendix 13.7. Map showing the spatial variability of turbidity, measured by optical backscatter, in Nephelometric 

Turbidity Units (NTU), during the survey on 10 March 2011. The water was relatively clear overall, with the highest 

turbidity in Pelekane Bay and just south of the bay. The turbidity was higher than the early-November 2010 survey,

possibly due to the input of sediment from the late November 2010 flood.
99

Appendix 13.8. Map showing the spatial variability of light transmission, in percent, during the survey on 6 November 

2010. There was relatively clear water overall with lower light transmission (higher turbidity) in Pelekane Bay. 
100

Appendix 13.9. Map figure showing the spatial variability of light transmission, in percent, during the survey on 10 

March 2011 survey. There survey showed relatively clear water overall with lower light transmission (higher turbidity) 

in Pelekane Bay. The light transmission was lower in Pelekane Bay at this time than during the early November 2010 

survey, possibly due to the input of sediment from the late November 2010 flood.
101

Appendix 13.10. Map showing the spatial variability of fluorescence, in milligrams per cubic meter, during the survey

on 6 November 2010. The areas with greatest fluorescence were located near shore in the vicinity of streams and 

human development. The offshore casts show low fluorescence and little variability.
102

Appendix 13.11. Map showing the spatial variability of fluorescence, in milligrams per cubic meter, during the survey 

on 10 March 2011. The area with greatest fluorescence was located nearshore in Pelekane Bay. The fluorescence 

was lower in the rest of the areas of the survey.
103

Appendix 14. Time-series plots of variations in current, wave, and combined wavecurrent critical shear stresses for silt- and clay-sized particles

Appendix 14.1. Calculated critical shear stress values from the acoustic Doppler current profiler (ADCP) sensors at 

the deep (>15 m) instrument sites. A, Current shear stress, in Newtons per square meter (N/m2

). B, Wave shear 

stress, in Newtons per square meter. C, Combined wave-current shear stress, in Newtons per square meter. Blue

lines, Central 15-m site; red lines, North 15-m site; green lines, South 15-m site. Green shading, trade-wind

conditions; orange shading, flood event; blue shading, large-wave event. The black lines at 0.10 Newtons per square 

meter is the critical shear stress for carbonate sand and terrigenous mud. If the shear stress exceeds this value, the 

material will be resuspended from the seabed; if not, the material will remain stable on the seabed.
104

Appendix 14.2 Calculated critical shear stress values from the acoustic Doppler current profiler (ADCP) sensors at 

the shallow (<5 m) instrument sites. A, Current shear stress, in Newtons per square meter (N/m2

). B, Wave shear 

stress, in Newtons per square meter. C, Combined wave-current shear stress, in Newtons per square meter. Blue

lines, Central 5-m site; red lines, South 5-m site; green lines, Central 2-m site. Green shading, trade-wind conditions;

orange shading, flood event; blue shading, large-wave event. The black lines at 0.10 Newtons per square meter is 

the critical shear stress for carbonate sand and terrigenous mud. If the shear stress exceeds this value, the material 

will be resuspended from the seabed; if not, the material will remain stable on the seabed.