Coastal currents and sewage disposal in the Hawaiian Islands final report

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APPENDIX 2-COASTAL CURRENTS
HAWAII INSTITUTE OF GEOPHYSICS
QE
500
.H35
no.64-1

HAWAII'S SHORELINE
Appendix II COASTAL CURRENTS AND SEWAGE DISPOSAL
IN THE HAWAIIAN ISLANDS

Taivo Laevastu, Don E. Avery, and Doak C. Cox

June 1964

FINAL REPORT

This report was prepared as part of the Coastal Currents Project supported by
contract with the Department of Planning and Economic Development, State of
Hawaii. The preparation of the report was financed in part through an Urban
Planning Grant from the Housin and Home Finance Agency under the provisions
of Section 701 of the Housing Act of 1954 as amended.

Approved by Director

Date: 30 June 1964

HAWAII INSTITUTE OF GEOPHYSICS
UNIVERSITY OF HAWAII

CONTENTS

Page

CONTENTS iii
List of Figures v
List of Tables viii

1. INTRODUCTION 1
1.1 Waste Disposal in Coastal Waters of Hawaii 1
1.2 Importance of Coastal Currents 5
1.3 Previous Studies of Currents in Hawaiian
Coastal Waters 6
1.4 The Present Studies 9
1.5 Scope and Organization of Report 11
1.6 Acknowlediments 12

2. COMPONENTS OF COASTAL CURRENTS IN HAVIAtj 13
@@.l Components of Coastal Currents in Hawaii 13
2.2 The Permanent Flow and its Eddie's 14
2.3 Tidal Currents 16
2.4 Island Effects 18
2.5 Island and Submarine Topographic Effects 22
2.6 Wind-driven Currents and Mass Transport
by Waves 24

3. COASTAL CURRENTS AROUND NIIHAU ADD KAUAI 29
3.1 Niihau 29
3.2 Western Kauai 29
3.3 Northern Kauai 30
3.4 Eastern Kauai 30
3.5 Southern Kauai 31
3.6 Summary of Coastal Currents Around Niihau
and Kauai 31

4. COASTAL CURRENTS AROUND OAHU 33
4.1 Northwest Coast 33
4.2 Northeast Coast-Kabuku to Ulupau Head 34
4.3 Kaneohe Day 35
4.4 Kailua. 36
4.5 Waimanalo 37
4.6 Koko Head to Makapuu 38
4.7 Mauhalua Bay 38
4-8 mamala Bay 39
4:9 Ala Wai to Kewalo 45
4.10 Honolulu Harbor-Keehi Lagoon 46
4.11 Pearl Harbor 46
4.12 Southwest Coast 47
4.13 Summary of Coastal Currents Around Oahu 49

iii

CONTENTS (continued)

Pa ge

5. COASTAL CURRENTS AROUND MOLOKAI., LANAI,
KAHOOLAWE, AND MAUI 53
5.1 Molokai 53
5.2 Lanai 53
5.3 Kahoolawe 54
5.4 West Maui 54
5.5 Kahului Bay and Harbor 55
5.6 North Coast of East Maui 56
5.7 South Coast 56
5.8 Alalakeiki Channel 57
5.9 Southwest Coast 57
5.10 Summary of Coastal Currents Around Islands
of the Maui Group 57

6. COASTAL CURRENTS AROUND HAWAII 59
6.1 Alenuihaha Channel 59
6.2 Northeast Coast 59
6.3 Hilo Harbor 6o
6.4 Southeast Coast 6o
6.5 Southwest Coast 61
6.6 Kailua-Kona 61
6.7 Northwest Coast 61
6.8 Summary of Coastal Currents Around Hawaii 62

7. SOME CHEMICAL., BIOLOGICAL, AND GEOLOGICAL
OBSERVATIONS PERTAINING TO SEWAGE DISPOSAL 63
7.1 Distribution of Chemical Properties off
Sand Island Sewer and in Kaneohe Bay 63
7.2 Bottom Deposits off Sand Island Sewer 64
7.3 Bacterial Die-off in the Sea 64
7.4 Biological Oxy@en Demand of Sea Water 67

8. APPLICATION OF COASTAL CURRENT AM RELATED
INFORMATION TO SEWAGE DISPOSAL PROBLEMS IN
COASTAL WATERS 69
8.1 Processes of Dispersal and Decomposition
of Sewage at Sea 69
8.2 Estimation of Rates of Transport, Disper-
sal, and Bacterial Die-off 72
8.3 Requirements in Coastal Current Studies
for Sewage Disposal Projects 75

9. CONCLUSIONS AND REC%ffv]EVDATI0VS 77

10. ANNOTATED BIBLIOGRAPHY OF COASTAL CURRENTS IN
HAWAII 81

COMETS (continued)@

Page

11. REFERENCES 95

List of Figures

Figure No. Facing Page

1. Index map of the Hawaiian Islands showing
points of waste disposal into the sea and
areas in which coastal currents have been
investigated 4

2. February surface currents in the vicinity of the
Hawaiian Islands indicating the permanent flow
-pattern as deduced from dead reckoning 14

3. August surface currents in the vicinity of the
Hawaiian Islands indicating the permanent flow
pattern as deduced from dead reckonin6 16

4. Co-tidal chart for the Hawaiian Islands 18

5. Diagram showing superposition of tidal current
vectors and resultants with permanent flow 20

6. Diagram showing current patterns around a simple
circular island 22

7. Diagram showing slope convergences resulting
from coupling of coastal reciprocating and
offshore rotary tidal currents 24

8. Directions of drift drogues frcm two 24-hour
cruises off Waianae 26

9. Results of droGue measurements of currents
around Kauai 30

10. Paddle-wheel current-meter measurements from
southeast of Nawiliwili, Kauai, (top) July
23-24, (bottom) July 25, 1963 32

11. Currents on the Kapaa Reef 32

COMENTS (continued)

Figure No. Facing Page

12. Index map to fiL;ures showing coastal currents
around Oahu 34

13. Results of measurements of currents near Kaena
Point, Oahu, on January 3-4, 1963 34

14. 'Results of drogue measurements of currents in
Kaneohe Bay, Oahu, September 4-6, 1962 36

15. Results of droL@ue measurements of currents
off Waimanalo, September 11, 1962 38

16. Results of drogue measurements of currents
off Waimanalo., February 23, 1963 38

17. Results of Paddle-wheel current-meter measure-
ments off Waimanalo, (top) July 15-16,
(bottom) July 16-17, 1963 38

18. Results of paddle-wheel current-meter measure-
ments off Wailupe Peninsula, July 11-12, 1963 38

19. Results of paadle-wheel current-meter measure-
ments off Diamond Head, (top) November 24-25,
(bottom) November 26-27, 1963 4o

20. Results of paddle-wheel current-meter measure-
ments off Diamond Head, (top) December 4-:5,
(bottom) December 8-9, 1963 4o

21. Results of paddle-wheel current-meter measure-
ments off MaE;ic Island, (top) November 11-12,
1963, and off Kewalo, (bottom) August 16-17,
1963 4o

22. Results of paddle-wheel current-meter measure-
ments near Sand Island sewer outfall, (top)
August 4-5, (bottom) August 9-10, 1963 4o

23. Results of paadle-wheel current-meter measure-
ments (top) southeast of Barbers Point, July
5-6y 1963, and (bottom) northwest of Barbers
Point, July 8-9, 1963 4o

vii

COMNTS (continued)

Figure No. Facing Page

24. Results of droGue measurements of currents
off Diamond Head, August 1, 1962, showing
effect of wind drag and mass transport 42

25. Results of drogue measurments of currents off
Diamond HeadY August 11, 1962. Quasi-
simultaneous observations at two stations 42

26. Results of drogue measurements of currents in
the eastern part of Mamala Bay in 1962
durinc@ predominantly flooding currents 42

27. Results of drogue measurements of currents in
the eastern part of Mamala. Bay in 1962
during predominantly ebbing currents 42

28. Results of drogue measurements of currents in
the eastern part of Mamala Bay, February 24,
1963 42

29. Results of drogue measurements of currents in
the eastern part of Mamala Day, March 3, 1963 42

30. Results of drogue measurements of currents in
the eastern part of Mamala Bay, March 24, 1963 42

31. Distribution of turbidity off Sand Island and
Ala Moana on December 28, 1962, during a
predominantly ebbing current 44

32. Distribution of turbidity off Sand Island and
Ala Moana on July 17, 1963, during a
predominantly flooding current 44

33. Coliform concentrations derived from old Kewalo
sewerY February 1941 46

34. Results of drogue measurements of currents
southeast of Barbers Point., April 8, 1963 48

35. Results of droGue measurements of currents
northwest of Barbers Point on April 9 and
July 9, 1963 48
36. Generalized flood (top) and ebb (bottom)
current patterns for Waianae area 50

viii

CONTENTS (continued)

Figure No. Facing Page

37. Generalized ebb current pattern around Oahu
during trade wind season. Inset shows
generalized flood current pattern 50

38. Generalized flood (left) and ebb (right)
current patterns for Kahului area 56

39. Generalized diagram of coastal currents around
the Hawaiian Islands 58

40. Distribution of chlorinity, dissolved oxygen,
and phosphates off the Sand Island sewer
outfall 64

41. Bacterial die-off in sewage disposed of in the
ocean 66

42. Schematic circulation at the outfall of a sewer 70

List of Tables

Table No. Pa,,e

1. Municipal and industrial waste disposal in
coastal waters of Hawaii in 1962 2

2. Summary of previous engineering investigations
of coastal currents in Hawaii 8

1. INTRODUCTION

1.1 Waste Disposal in Coastal Waters of Hawaii

Throughout the world man has found it expedient to dispose of his

domestic and industrial wastes in bodies of water, counting on the water's

natural flow for their transportation and dilution, and on the chemical

and biological processes in the water for their decomposition. In the

Hawaiian Islands, which essentially lack lakes and on which the streams are

steep and short, it is of course the ocean on which reliance is made. As

shown in Table 1 and Figure 1, wastes of various sorts are discharged at

many points into -the sea. Disregarding the solid wastes accumulated in

sanitary fills behind dikes, sugar-mill wastes and sewage have been the

most significant in Hawaii.

Wastes from -the sugar plantations were of small importance until mech-

anical harvesting operations were introduced in the late 1930's. By the late

1940's significant problems had arisen. Trash and mud brought in with the

cane and washed off at the mill were being wasted to the sea at many points.

The mud caused unsightly discoloration and probably affected significantly

the growth of marine organisms, although the extent of such effects is yet

undetermined. The trash had a tendency to raft sufficiently to constitute a

hazard to navigation, and has undoubtedly contributed to the problem of

stagnation in some harbors. In the last decade the problem has abated

somewhat with the installation of hydroseparators at the sugar mills. Solids

from the separators are trucked or sluiced to land disposal areas, but muddy

water is still discharged at many coastal points and trash continues to

escape at some.

Table 1.

Municipal and Industrial Waste Disposal in Coastal Waters of Hawaii in 1962

(Modified from Public Health Service, 1963)

Est. Pop. Discharge
Place Agency Served* Type* Treatment* Point

KAUAI
Kilauea Kilauea Sugar Co. sug. mill none Ocean
Kapaa Mahelona Hospital 140 san..-s.ew. Se Ocean
Kapaa Hawn. Fruit Packers Ltd. pine. can. Se Lagoon to ocean
Lihue Lihue Plantation Co. sug. mill none Ditch & ocean
Nawiliwili Kauai Surf Hotel 1,000 san. sew. Se, Cl Lagoon to ocean
Koloa Grove-Farm Co. sug. mill Sc Lagoon to ocean
Lawai Kauai Pineapple Co. pine. can. Sc Ocean
Port I-llen Kauai County 500 san. sew. none Ocean
Kekahe, Kekaha Sugar Co. sug. mill Sc Ditch & ocean

OAHU
Kahuku Kahuku Plantation Co. sug. mill Sc Lagoons & ocean
1-7aialua Waialua Agr. Co. sug. mill Se Ditch & ocean
Kaneohe Honolulu Div. Sewers 150 san. sew. Se, Cl Kaneohe Bay
Kaneohe Honolulu Div. Sewers 15,000 san. sew. Se, C1 Kaneohe Bay
Kailue. U.S.Marine Corps 8,700 san. sew. Se, Fi, Cl Ocean
Maunalua Kaiser-Hawaii Kai 2)600 san., sew. Se, Cl Lagoon to Kuapa
Pond & ocean
Honolulu Honolulu Div. Sewers 269,ooo san. sew. none Ocean
Honolulu Calif. Packing Corp. pine. can. Se, Cl Kapalama Basin
Honolulu Haim. Pine. Co. pine. can. Se; Cl Kapalama Basin
Honolulu Libby, McNeil & Libby pine. can. Sc Kapalama Basin
Honolulu Honolulu Airport ? san. sew. none Ocean
Honolulu Tripler Hospital ? san. sew. none Ocean
Hickam Field U.S. Air Force 9,000 san.sew. none Ocean
Pearl Harbor U.S. Navy ? several none Pearl Harbor
san. sew.

Table 1. (continued)

Est. Pop. Discharge
Place Agency Served Type* Treatment* Point

Halawa Honolulu Div. Sewers 4,700 san. sew. Se, Cl Pearl Harbor
Aiea Honolulu Div. Sewers 17,000 san. sew. Se., Cl Pearl Harbor
Pearl City Honolulu Div. Sewers 1,500 san. sew. Se Pearl Harbor
Waipahu Oahu Sugar Co. sug. mill Se Irrigation s1stem
& Pearl Harbor
Walpahu Honolulu Div. Sewers 3,000 san. sew. Se, Cl Ditch & Pearl Harbor
Ei,a U.S.Navy (Capehart Hsg) 5,000 san. sew. Se Pearl Harbor
Ewa U.S.N.Air Station, Barbers Pt. 8,779 san, sew. Se, Cl Ocean
Barber's Pt. Standard Oil Co. oil. ref. Se Lagoon to ocean
Waianae Honolulu Div. Sewers 2,000 san. sew. Se Ocean

MAUI
Lahaina Maui County 1@000 san. sew. none Ocean
Lahaina Pioneer Mill Co. sug. mill Se Ditch & ocean
Wailuku Wailuku Sugar Co. sug. mill Se Ditch & ocean
Wailuku Maui County T,000 san. sew. none Ocean
Kahului Maui County 4@200 san. sew. none Ocean
Kahului Hawn. Homes Comm. 300 san. sew. none Ocean
Paia Maui County 2,100 san. sew. none Ocean
Hana Hana Ranch Hotel 100 san. Sew. Se Ocean

HAWAII
Halaula Kohala Sugar Co. sug. mill none Ocean
Halaula Kohala Sugar Co. 1.1000 san. sew. none Ocean
Honokaa Honokaa Sugar Co. sug. mill none Ocean
Honokaa Honokaa Sugar Co. 550 san. sew. none Ocean
Paauhau Paauhau Sugar Co. sug. mill none Ocean
Paauhau Paauhau Sugar Co. 550 san. sew. none Ocean
Paauilo Hamakua Mill Co. sug. mill none Ocean
Paauilo Hamakua Mill Co. 550 san. sew. none Ocean
Ookala Kaiwiki Sugar Co. sug. mill none Ocean
Ookala Kaiwiki Sugar Co. 400 san. sew. none Ocean

Table 1. (continued)

Est. Pop. Discharge
Place Agency Served Type* Treatment* Point

HAWAII (cont'd)
Papaaloa Laupahoehoe Sugar Co. sug. mill none Ocean
Papaaloa Laupahoehoe Sugar Co. 950 san. sew. none Ocean
HakalEu Hakalau Sugar Co. sug. mill none Ocean
HakalLu Hakalau Sugar Co. 570 san. sew. none Ocean
Pepeekeo Pepeekeo Sugar Co. sug. mill none Ocean
Pepeekeo Pepeekeo Sugar Co. 700 san. sew. none Ocean
Papaikou Onomea Sugar Co. sug. mill rione Ocean
Papaikou Onomea Sugar Co. 1,600 san. sew. none Ocean
Wainaku Hilo Sugar Co. sug. mill none Ocean
Wainaku Hilo Sugar Co. 650 san. sew. none Ocean
Hilo Hilo Sugar Co. 250 san. sew. none Ocean
Hilo Hawaii County 5,100 san. sew. none Hilo Bay
Honuapo Hirtuchinson Sugar Co. sug. mill none Ocean

Abbreviations:
oil ref. = oil refinery Cl chlorination
pine. can. = pineapple cannery Fi filtration
san. sew. = sanitary sewer Sc screening
sug. mill = sugar mill Se se ttling

.............

C c

LANAI

KAHOOLAWE

LEGEND
..........
WASTE DISPOSALS
0 SANITARY SEWER
SU AR MILL
PINEAPPLE CANNERY
REFINERY
INVESTIGATIONS OF CURRENTS
0 RECENT COORDINATED INVESTIGATIONS
MAMALA BAY PREVIOUS INVESTIGATIONS
DATA ADEQUATE TO SHOW TIDAL EFFECTS
DATA ADEQUATE TO SHOW SEASONAL EFFECTS
+ CURRENT METER STUDY

Fig. 1. Index map of the Hawaiian Islands showing points of waste disposal into the sea and areas in wh
have been investigated.

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The major waste disposal problems, however, have had to do with sewage.

The disposal of most sanitary sewage in Hawaii was originally through

cesspools, even in most urban areas. The remarkable permeability of most

of the basaltic lavas, of which the islands are predominantly formed, and

the permeability of the coral reefs commonly interbedded with other sedi-

ments in the coastal plains bordering some of the islands, made such a

means of disposal simple and cheap. In some areas, however, cesspools were

hardly suitable even with a low concentration of population. With increas-

ing urbanization, and increased density of population in the urban areas,

cesspool disposal of sewage has had to give way to sanitary sewer systems

that discharge into the ocean. Such systems carry industrial wastes,

especially wastes from pineapple canneries, as well as domestic wastes. In

most of these systems there are no treatment facilities. The raw sewage is

discharged into the sea and the natural currents are relied upon to trans-

port and disperse it.

1.2 Importance of Coastal Currents

Although the high current velocities that are characteristic of conti-

nental areas having extreme tidal ranges are not to be found in Hawaii,

there still i@ considerable variation in current velocities from place to

place, and also from time to time. Together with the amount and character-

istics of the sewage, the currents in the vicinity of a sewer outfall are

of critical importance in determining effectiveness in disposing of the

v7aste without detrimental sanitary or esthetic effects. A surface drift

moving rapidly toward the shore from a sewer outlet may introduce essentially

still undecomposed sewage into a beach area that is otherwise highly desir-

able for si-rimming. A current moving seaward may carry the same sewage away

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.from shore and disperse it harmlessly. Thus under-.some current conditions

raw sewage may safely be introduced but, under,'other conditions, extensive

treatment would be required prior to release.

Ideally, what is required is a knowledge of: (a) the initial dilution

of the sewage as it is injected into the current moving past the sewer out-
let, (b) the time required before the sewage is sufficiently dispersed and

decomposed along the path it follows to be considered harmless, and (c) the

direction and distance traveled by the sewage in that time. Even if the

dischar.ge of the sewage is considered constant at some design ma_-I;imum value,

and the character of the sewage is considered constant also, the variability

of the current with time will require knowledge of the frequency of occurr-

ence of current sets of various directions and velocities, including the

evaluation.of periodic components. Furthermore, the geographic variability

of the current requires that the knowledge not be confined to the sewer

outlet but that it provide a complete picture of the currents within the

distances of concern.

1. 3 Previous Studies of Currents in Hawaiian Coastal Waters

Three kinds of previous investigations contribute to the understanding

of the coastal currents in Hawaiian coastal i-,,aters. The first of these

is the study of the general, more or less permanent current systems in the

vicinity of the Islands. For many decades such current systems have been

estimated by comparing the dead-reckoning positions of ships with navigational

fixes. General net surface current charts by month and by one-degree

squares are available for the portion of the Pacific in the vicinity of the

Hawaiian Islands (Hydrographic Office, 1947, 1950; Brown, ms,.). Net current

conditions for areas closer to shore, similarly obtained from ship reports,

-7-

are described in the U. S. Coast Pilot for the Pacific Coast and the Hawaiian

Islands (coast and Geodetic Survey, 1963a).

Only certain very general information, auxiliary to the problems of

sewage disposal in coastal waters, can be learned from the older current

charts. However, recently, more intensive studies on the ocean currents in

the areas around -the islands have been made by the Honolulu Biological

Laboratory of the U. S. Fish and Wildlife Service, using drift-bottle and

drift-cara sLrveys and -,,jater-mass analyses (Barkley, ms. ). These studies

have also been mainly concerned'with the general circulation pattern and

net flow and, therefore, are applicable only very indirectly to the problems

of coastal currents and mixing as they affect the disposal of sewage. How-

ever, the information is of use in studies of the possibilities of disposal

of solid waste in the sea.

The second kind of investigation consists of local investigations,

conducted by engineering firms, of the currents at existing or proposed

sewer outfalls. There have been more than twenty such investigations, but

the extent of the work reported varies considerably. Some are limited to

descriptions of the amount of pollution prior to or following the construc-

tion of an outfall. Others report the results of a day, or of a few days,

of current measurements using floats or dye. Only two studies lasted as

long as a year. In some, the currents were related to wind conditions; in

J others, to the permanent flow; in a few, the effects of tides were recog-

nized. In conjunction with one there were studies of the dispersion of

sewage in the sea and of 'the rate of bacterial die-off. These local studies

are listed in Table 2, and the sites of those which produced significant

information on currents are plotted in Figure 1.

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Table 2.

Summary of Previous Engineering Investigations of Coastal Currents in Hawaii

Drift measurements Sewage or
by drogue, drift slick field
Place Agency Year card dye spot, etc. measurem't*

OAHU
Kaiaka Bay BC&-A 1962 x x
Waialua Bay BC&A 1962 x x
Kaneohe HDS 1957 x
Nuupia Pond H&N; BC&A 1957 x
Kailua H&Njp BC&A 1950/ S x
Waimanalo IVA 1963 T
Kalama (Hawaii-Kai) SLT&H 1962 T
Ala Moana A&A. L&W 196o T
Ke-vralo KT&C 1920 x
Honolulu BS 1941 F
Honolulu M&E 1944 F
Sand Island HDS 1951 x
Sand Island AS&A 1961 x
Pearl City HDS 1958 x
Pearl City AS&A 1961 T
Waipahu HDS 1957 x
Pearl Harbor Entrance AS&A 1962 T
Barber's Point TAMS 1961 x
Kaneilio Point BC&A 1962 x x
Pokai Bay SLT&H 1962 T x
MAUI
Kahului HO 1962 T x
HAWAII
Hilo BC&A 1961 x x
Kailua-Kona A&A 1961 x x

*Abbreviations:
Agencies
A&A HAR Austin & Assoc. H&R Herschler and Randolph
AS&A Austin, Smith..& Assoc. KT&C Keller, Tay, and Collins
BMA Belt, Collins, & Assoc. L&W Law and Wilson
BS Bur. of Sanitation, Terr.Foard MA Marine Advisers
of Health M&E Metcalf and Eddy
HDS Honolulu Division of Sewers SLT&H Sunn, Low, Tom, and Hara
H&N Holmes and N,@,_rver TAMS Tippets, Abbott, McCarthy,Stratton
Drogue, etc. measurements
x = measurements made
T = measurements adequate to determine tidal effects
S = measurements adequate to determine seasonal effects
Sewage or slick field measurements
x = measurements made
F = measurements adequate to define sewage field

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The third kind of investigation consists of current meter surveys by

the U. S. Coast and Geodetic Survey in the inter-island channels and in

other coastal waters. r'ualitative results of some of the studies are indi-

cated in the Coast Pilot and quantitative summaries of analyses of two

surveys in Auau and Kalohi Channels appear in the Tidal Current Tables of

the Coast and Geodetic Survey (1963b). Analyses of most of the surveys are

still incomplete, however.

1.4 The Present Studies

The investigation on which 41-his report is principally based was under-

taken as one component of the studies involved in the development of a

general shoreline plan by the Hawaii State Department of Planning and Economic

Development. It was undertaken under contract with that Department, with

financing in part through an Urban Planning grant from the Federal Housing

and Home Finance Agency. The proposal for the investigation was submitted

by the Hawaii Institute of Geophysics in recognition that disposal of sewage

from the urban areas of the Hawaiian Islands, in such a manner as to avoid

pollution to recreational waters, harm to fisheries, and other damage, is

becoming increasingly difficult as the urban areas and the amount of sewage

deEcriled from them increase. Engineering studies of the most economical

sites and means for sewage disposal at sea have been severely limited by

inadequate knowledge of the local conditions that affect the released

waste currents, mixinry,, and decomposition in -the sea. These conditions
J, tD

vary greatly from place to place, so that studies must be made locally. In

addition, however, basic studies were required, because very few studies

have been made of sewage disposal factors in tropical mar:.ne waters that

provide any fundamental and generally applicable data.

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As originally proposed, the general objectives of the study were:
(a) to summarize available information applicable to the problems of coastal

currents, mixing, and remineralization of sewage in Hairaii and similar areas;
(b) to provide answers to the most pressing local problems concerning the

marine environment and sewage disposal, e.g., information on current and

mixing conditions in specific areas where sewage outfalls are contemplated,

or where sewage disposal has been troublesomel- (c) to investigate the

seasonal changes in oceanographic and meteorological conditions, and to

define the "critical conditions" to be considered in planning and designing

of the outfalls; (d) to generalize from the interrelated information in

such a way as to permit its adaptation to a variety of locations; (e) to

prepare plans, procedures, methods, and equipment for such additional local

investigations as may be required -when new related problems arise.

The study was started in June 1962. The field work was carried out

using chartered vessels, especially the 4,@,-foot yawl, "Thunder Bird", as

well as the University's 83-foot research vessel, "Neptune V,:and.to scme

extent, the 40-foot "Salpa". The field work was concentrated mainly on the

island of Oahu for reasons of economy and because the most immediate and

serious practical problems of sewage disposal are concentrated on this

island. Some field work along the coasts of Kauai has been done, however.

The methods and instruments used are briefly described in an appendix to

this report, irhich also contains the actual numerical data collected in the

studies.

Office work included the analysis of the field data and plotting of

results, the review of previous reports and background literature, and the

analysis cr re-analysis of some of the data obtained in the previous

_11-

investigations. A preliminary report on the study (Avery, Cox, and Laevastu,

1963) was submitted in January 1963. The Institute of Geophysics investiga-

tion was closely coordinated with one undertaken by the Engineering Experi-

ment Station of the University of Hawaii under contract with the State

Department of Health and directed by William Tinniswood. Some of the most

important results of th-e latter investigation are included in this report.

1.5 Scope and Organization of Report

In the investigations reported here, the coastal currents of Hawaii

have been more extensively observed by floats and dye than in all previous

investigations, and more intensively than in most of the previous investi-

gations. In addition,.continubizs recording of currents has been-carried

on at a number of sites for periods ranging from a day to a month. It

must be admitted, however, that this more comprehensive work has not produced

a clear picture of the current systems which is satisfactory for practical

needs. It has indicated, instead, that the systems are much more complex

than could have been anticipated on the basis of previous knowledge and,

indeed, that many of the simple concepts, on the basis of which sewer

outfalls in Hawaii have been designed and even have been built, are inade-

quate and in some cases are generally erroneous. However, there has

emerged from the recent studies a clearer understanding of the canponents

that go to making up the coastal current at any specific place, and the

requirements in methods and instrumentation for the adequate study of these

components.

In this report the current components are first diq'aussed. serarately.."

The actual resultant coastal current systems around each of -the islands are

then described systematically in as much detail as present information

-12-

permits, regard-less of the source of the information. There follow sections

on the practical application of current data, some chemical, biological,:and.

geological aspects of sewage disposal, and the conclusions.

The report is intended for use by persons with some scientific or

engineering ccmpetence, including planners, sanitary engineers, and coastal

engineers, as well as oceanographers. For the most part, descriptions of

background oceanographic information that are available in textbooks have

been omitted. However, oceanographic factors and processes pertinent to

waste disposal in coastal i,,7aters that have not received sufficient attention

in the past are pointed out and described.

1.6 Acknowledgments

We are particularly indebted to the following: Roger Luther and

Donald Cameron, former marine superintendent and captain, respectively,

and the crew of the Neptune I, from which much of the field work was

done; William Tinniswood. of the College of Engineering, who generously

allowed the us-- of data derived in his concurrent study; Richard Barkley

and Gunter Seckel of the Honolulu Laborator-yr, U. S. Bureau of Commercial
d

Fisheries., who discussed at length the present status of knowledge of

the permanent flow; Bernard McMorrOW and Robert Tam of the Department

of Health who discussed sewage and sanitation problems with us;

William Morris of the Department of Planning and Economic Development,

who provided liaison with that Departi@ent-';* EthelMcAfee'. for editorial

assistance; Roy Kaneshiro and Jerry Kusunoki, for plotting the data; and
tD

Toshitsugu Sakou of the Institute of Qeophysics and the College of

Engineering, for assistance and advice in the preparation of this report.

2. COMPONENTS OF COASTAL CURRENTS IN HAWAII

2.1 Components of Coastal Currents in Hawaii

The actual surface current at any time and place is actually the re-

sultant of components having several different driving forces. The oceanic

current sweeping past the Islands is the underlying component. Generally,

this "permanent flow" sets tO'vTard the west, but its direction varies some-

what, especially seasonally, and it also has superimposed upon it large-scale

eddies that may cause considerable temporary changes in direction and in

strength. Tidal components result from the passage of the astronomical -tide

waves past the Islands, wind components are set up by the drag of the wind

on the surface, and there is also a mass transport associated with the

movement of wind waves. The resultant current is of course greatly in-

fluenced by the nearshore topography -- at some places the surface current

converges, at others it diverges, in still others eddies are formed.

Each of the components is variable in direction and in strength, and

for each kind of variability there are characteristic periods. The periods

for the tidal currents are well defined, semi-diurnal and diurnal. Vaxia-

bilities associated with the wind, the waves, and the permanent flow have

other periods, including an important annual one. No study of currents can

be considered comprehensive unless it includes either continuous observations

or observations at intervals close enough to disclose the effects of the

shorter period variations, in a continuing program or programs repeated over

at least a year to disclose the effects of the longer period variations.

-13-

-14-

2.2 The Permanent Flow and Its Eddies

A few years ago it was generally assumed that the currents around the

Hawaiian Islands were largely the result of the generally westerly flow,

the Pacific North Equatorial current in the vicinity of the Islands which

represents the clockwise circulation of the North Pacific. This "permanent"

flow certainly exists in a statistical sense, but even in the open ocean

it has been found to be so variable in direction and strength that -ener-

alizations as to its characteristics are very uncertain.

The data derived from ship reports and compiled by the Hydrographic

Office (1947, 1950) show the irregularity (Figs. 2 and 3). The direction

of set, although predominantly west or west-northwest, varies commonly

fromwest-southwest to north-northwest. Northwest sets are more common

within a few hundred miles of the Islands than elsewhere, probably in-

dicating a deflection by the archipelago. The average velocity is a
little less than 1/2 knot, but ranges from less than 0.1 knot to more than

1 knot. Monthly charts of the permanent flow at the surface prepared by

Brown (ms.) from Hydrographic Office data and from which Figures 2 and 3

have been drawn., indicate a somewhat more northwesterly set, on the aver-

age, in winter and spring than in summer and fall.

Drift-bottle studies by the Honolulu Biological Laboratory of the

Bureau of Commercial Fisheries (Barkley, ms.) particularly point up the

irregularities. Drift bottles released southeast of Oahu in May 1961, for

example, were recovered not only on Niihau and Kauai but also on the north-

east coasts of Lanai, Molokai, and Oahu. The Bureau of Commercial Fish-

eries' studies also indicate that the Islands cause eddies in the permanent

flow downstream., eddies that are 20 to 50 miles across, revolving at a rate

February

30 30

se 4,

IL A--, at

go,
20 20

.Z 4-

10 10
170 160 150

0 10 2o na. ml. day-1
Fig. 2. February surface currents in the vicinity of the Hawaiian Islands indicating the permanent
flow pattern as deduced from dead reckoning.

-15-

of one turn in 10 days (Anon., 1963). Velocities of nearly 2 knots may be

attained near the outer edge of the eddies, five times or more the average

velocity of the system.

In the coastal areas of Hawaii the permanent drift has proved surpris-

ingly difficult to disentangle from other current components, largely

because of the unexpected prevalence and strength of the reversing tidal

components and hence the necessity that the resultant currents be measured

over a period of at least a day in order to determine and subtract the

tidal effects.

Areas in which the current set is believed to be essentially uni-

directional, or in which the net permanent flow has been ascertained by

averaging out or analyzing the reversing tidal currents, are as follows

(sources of information are discussed in the sections on the current systems

around the various islands):

a. The northeast coast of Hawaii from Cape Kumukahi to Leleiwi

Point and from Pepeekeo to Upolu Point: Set northwest.

b. Southwest coast of Hawaii from Cape Kumukahi to Keauhou Point:

Set southwest.

c. West coast of Hawaii from Kauna Point to Keahole Point: Set

generally northwest.,

d. Alalakeiki Channel: Net set northwest on northeast side.

(A southeast set on the southwest side is also reported, however).

e. South coast of Kahoolawe: Set west.

f. North coast of Maui, Kahului Bay: Set northwest.

Kalohi and Auau channels: Net set east about 0.1 knot (?).

h. Southeast coast of Molokai: Net set northeast

-16-

i. Southwest coast of Molokai: Net set west.

j. Northeast coast of Oahu from Waimanalo to Kahuku: Set

generally northwest.

k. West coast of Oahu, south of Kaena Point: Set northwest

(possibly a combination of an eddy at flood and direct

tidal current at ebb).

1. South coast of Kauai near Puolo Point: Set west.

m. South coast of Niihau: Set west about 1.5 knots

Most of the directions of set are relatively easy to account for in

terms of the set of the permanent flow at sea and its probable deflection

close to the island chain. The appaxent easterly net drifts in the Kalohi

and Auau channels, along the Molokai coast of the Pailolo channel, and

along the Kahoolawe coast of the Alalakeiki Channel are not so easily

accounted for, but probably represent some form of eddying.

2-3 Tidal Currents

The tides in the vicinity of the Hawaiian Islands are of mixed type,

that is, they appear predominantly diurnal at some times and predominantly

semi-diurnal at other times, but generally semi-diurnal with a pronounced

diurnal inequality. The maximum range is about 3 feet. The tide waves

move through the archipelago from the north-northeast toward the sou-Lh-

southwest (Fig. 4). In the open ocean the propagation of these waves must

be accompanied by a current setting approximately southwest, more or less

in the direction of propagation of the tide wave, at high tide, and a

current setting in the opposite direction at low tide.

The nomenclature of tidal currents was developed on continental coasts

where the tides form essentially standing waves. On such coasts the

August

30 30

IL All

IF-

4&-
20 120

10 10
170 160 150

0 io 2o na. mi. day-1
I I
Fig. 3. August surface currents in the vicinity of the Hawaiian Islands indicating the permanent
flow pattern as deduced from dead reckoning.

-17-

flooding current which carries water landward across the continental shelf

and into estuaries is associated with the rising tide, and the ebbing

current which carries the water seaward again is associated with the

falling tide. In contrast, in the open ocean where the tides form pro-

gressive waves, the maximum current velocity in the direction of propaga-

tion of the tide wave tends to occur at high tide and the maximum current

velocity in the opposite direction tends to occur at low tide. By extension

of the original definitions of the tidal currents, the flood current under

these conditions is considered to be the current setting in the direction

of propagation of the tide wave, and the ebb current, that setting in the

opposite direction. In the ocean the actual current directions tend to be

rotated clockwise, in the northern hemisphere, from the directions they

would have without rotation, so that in offshore waters particles tend to

describe ellipses (Fig. 5C) instead of simply oscillating back and forth

(Fig. 5A).

The combination of a reciprocating tidal current and a permanent flow

creates a resultant current which changes direction, within a certain range

of directions, without quite reversing, as shown in Figure 5B. The ccmbi-

nation of a rotary tidal current and a permanent flow creates a resultant

current which may or may not have a restricted range in directions., de-

pending on the ratio between the minimum velocity of the tidal current and

the velocity of the permanent flow, but which has a lower velocity associ-

ated with some directions than with others, as shown in Figure 5D.

Considering the smallness of the tide range, the great depth of water

surrounding the Islands and the general steepness of their flanks, and the

smallness of the Islands in relation to the wave length of the tide., there

seemed to be no reason originally for anticipating that the tidal currents

would be of much significance in the vicinity of the Hawaiian Islands.

Investigations with drogues at Pokai Bay (Sunn, Low, Tom, and Hara, 1962)

were the first to indicate that the tidal currents are of consequence.

Drogue studies and especially paddle-wheel current-meter studies in the

present Institute of Geophysics project, and additional paddle-wheel

current-meter studies in the associated Engineering Experiment Station

project, also have indicated that tidal currents constitute one of the most

important current components, and in some places are the dominant component.

Further confirmation has been obtained from Roberts current-meter studies

recently published by the Coast and Geodetic Survey (1963b) and from

additional, unpublished Roberts meter data. The magnitude of the tidal

currents in the coastal waters of Hawaii must be due to the intensification

of the currents on the island shelves and in the inter-island channels,,

but the processes axe not yet quantitatively understood.

Further discussion of the tidal currents observed will be deferred

to the next section where they 'can be related to island effects.

2.4 Island Effects

Where the tides move perpendicularly onto an island shelf and toward

shore, the phase relations of the tide and the tidal component of the

current should expectably resemble those on a continental shelf, that is

the maximum current velocities should lead somewhat the,maximum and minimum

tide levels. A divergence of the flood tidal current component should be

expected off the shore of the island facing the direction from which the

tide wave approaches (Fig. 5A). From this divergence) currents should

sweep around both sides of the island to a convergence on the opposite

16D W 159 158 157 156

-90
60 75
C. 0 5
N KAUAI 9
22-- 0
15,, 0- > 6
@Sb /0
NIIHAj!
0-

OA*
--0--- 105-
--.90--

'--M6LOKAI
0
+15
03
'X@ 0
.... Kalohi C
0

LAN
MAUI
O\
N

C,5

HAV

t9
75
0
,45

0 10 20
Nadiwl Miles

160 W 159 158 157 156

Fig. 4. Co-tidal chart for the Hawaiian Islands.

_19-

s@de of the island. The positions of the convergence and divergence and

the directions of set of the currents around the island should approxi-

mately reverse with the ebb tide.

The current pattern around a simple circular island resulting from

a reciprocating tidal current superimposed on a permanent flow is shown in

Figure 5B; that resulting from a rotary tidal current superimposed on a

permanent flow is shown in Figure 5C. In both cases it will be noted

that:

(a) The flood and ebb convergences and divergences are not on the

same axis;

(b) There is a continuous clockwise flow between the flood con-

vergence and the ebb divergence, and a continuous counter-

clockwise flow between the ebb convergence and the flood

divergence; and

coastline during the times in which the current sets in

the ebbing direction and in the flooding direction.

Considering the complexities of the relationships between tides and

currents containing tidal components around even simple islands as dis-

cussed above and as shown in Figure 6, it is hardly surprising that the

correlation between the tides and the actual currents measured around the

Hawaiian Islands should not always be simple. Some additional sources of

complexity may also be mentioned. The tidal curves utilized in this study

and presented in figures in this report have been based on predictions for

Honolulu with standard adjustments for range and time differences at other

ports (U. S. Coast and Geodetic Survey, 1962). These standard adjustments

-20-

took no account of the differences in phase lags and amplitude factors

that can be expected between semi-diurnal and diurnal components. More-

over, the sea level changes that actually occur are influenced by unpre-

dicted meteorological factors, such as barometric pressure changes. The

ratio between maximum tidal current velocity and tide range for the semi-

diurnal tide should be double what it is for the diurnal tide. The ratio

between the minimum tidal current velocity and the permanent flow velocity

should be double for the semi-diurnal tidewhat it is for the diurnal tide.

None of the Hawaiian islands are circular, and some are quite irregular in

shape. The irregularities probably have considerable effect on phase and

strength of the tidal currents, and in -some areas result in eddies. Never-

theless in spi-be of the numerous sourbes of complexity the tidal current

picture in some areas has been found through paddle-wheel current-meter

studies to be relatively simple.

Near Diamond Head, Oahu, where the current is more regular than at

any other place tested, certain things occur rather consistently. In a

period of 25 days of continuous observation the current reversed 98 times,

without fail, for each change in the stage of the tide, indicating that

the current here is mainly controlled by the tide. The ebb current is the
strongest and lasts longer than the flood (See Fig. 20., Dec. 4 and 5, 1963)-

It appears that the maximum ebb current tends to occur at and near low

tide in anticipation of a high rise--the higher the rise the stronger the

ebb (for the effects of a relatively small tidal chan6e see Fig. 20, Dec. 8

and 9, 1963). The current changes tend to follow a traveling wave pattern.

See Figure 19, Nov. 25 and 26, 1963, and others.

Farther west) toward Sand Island,, the current pattern becomes less

EBB EBB
EBB IX EBB 1X
Ix 7= X Ix IM
X 7= 7W M X 7M
M 7M N N Im
V1 XU

XU
in
I V

IV 11
M
31 X n
M
FLOOD FLOOD FLOOD FLOOD

A. RECIPROCATING B. RECIPROCATING C. ROTARY TIDAL D. ROTARY TIDAL
TIDAL CURRENTS TIDAL CURRENTS CURRENTS CURRENTS PLUS
PLUS PERMANENT PERMANENT FLOW
FLOW

Fig. 5. Diagram showing superposition of tidal current vectors and resultants with permanent flow.
1, 11, 111, etc. = 12ths of tide period after slack tidal current.
71M 11
7)
_2

Assumptions: Northern hemisphere
Azimuth of permanent flow set = 2920 Permanent flow velocity = 0. 5
Maximum tidal velocity

Azimuth of tide-wave propagation = 2020 Minor axis, tidal ellipse = 0.35
Major axis, tidal ellipse

_21-

regular. Figure 21 shows a sample of a 2-week record taken off Magic

Island., Ala Moana. As can be seen from data taken on November 11 and 12,

1963, the pattern nearly follows the Diamond Head pattern, but there is a

deviation during the early hours of November 12. Figure 21 also includes

a sample of data taken off Kewalo Basin in August 1963, which still shows

the Diamond Head pattern, but the current appears to be more confused.

Figure 22 shows a sample of data taken at the sewer outfall near Sand Island

during August, 1963. The Diamond Head pattern is barely recognizable--

apparently eddies are causing the difference--although when the tidal range

is greater the pattern is more recognizable. East of Diamond Head off

Wailupe Peninsula (see Fig. 18) the current pattern is essentially the same

as off Diamond Head.

Northwest of Barbers Point the current pattern is again very uniform,

as shcWn in.Rigure_23,'but the tidal current directions are opposite to

those at Diamond Head. On the Pearl Harbor side of Barbers Point, however,

there is considerable irregularity.

Except for the relative persistence of the ebb current at Diamond

Head., these observations fit in well with the concepts diagrammed in

Figure 6. Diamond Head is clearly east of the flood convergence and the

ebb divergence on the south side of Oahu, and Barbers Point is clearly

west of them. The current pattern west of Diamond Head is progressively

more confused and the pattern east of Barbers Point is similarly confusing

as the areas of convergence and divergence are approached.

-22-

2.5 Island and Submarine Topographic Effects

The currents resulting from the combination of the permanent flow

and the tidal currents are further complicated by the islands and their

submarine topographic irregularities. Upstream of an island (relative to

the instantaneous current direction), the approaching current diverges.

Downstream, although there is a general reconvergence, the most prominent

feature may be a zone of instability and eddying. The convergences and

divergences are likely to be intensified at the outer edge of the island

shelves where the most abrupt transitions in the tidal currents are likely

to occur between offshore elliptical orbits and nearshore oscillatory

motions.parallel to the coast.. The principle of slope convergence formation

is illustrated in Figure 7.

Slope convergences have be en observed on almost all cruises, and a

special-study of them was made in the area from.Mamala. Bay to.Barbers

Point on April 10-11, 1963, during a period of Kona weather when the winds

were very light. The convergences were well demarcated by streaks of calm

water and accumulations of seaweed and other flotsam, including sewage.

The convergences nearly always occurred over steep bottom slopes, generally

at 55 to 75 meters depth. Irregularities and branching were noted. Bathy-

thermograph casts were made on April 10 in the vicinity of one of the

convergences. These casts showed a depression of the thermocline where

and when a convergence was forming, differing thermal structures on the

two sides of the convergence, and mixing with minor inversions in the

convergence itself, consistent with the theory of origin illustrated in

Figure 7..

The surface divergences which tend to be beneficial in sewage disposal

due to their dispersing effects, are not so easily recognized. They seem

EBB CONVERGENCE
@ MAXIMUM
EBB UNI- MAXIMUM@ CLOCKWISE FLOOD
CONVERGENCE4 DIRECTIONAL VELOCITY4 POSITION DIVERGENCE
FLOW MAXIMUM
FLOOD DIVERGENCE COUNTER
BB CONVERGENCE CLOCKWISE Z
POSITION,-
FLOOD MAXIMUM
FLOOD EBB DIVERGENCE FLOOD EBB VELOCITY
DOMINATES DOMINATES DOMINATES DOMINATES
REVERSING
CURRENTS N REVERSING N N
CURRENTS

REVERSIN REVERSING
CURRENT ACURRENTS
SLACK
EBB FLOOD EBB FLOOD
FLOOD DOMINATES DOMINATES DOMINATES DOMINATES WATER
CONVERGENCE MAXIMUM DIVERGENCE
VELOCITY MAXIMUM 1@r
COUNTER
UNI- CLOCKWISE
FLOOD CONVERGENCE DIRECTIONAL EBB POSITION MAXIMUM
DIVERGENCE MAXIMUM, VELOCITY
EBB DIVERGENCE FLOW FLOOD CONVERGENCE CLOCKWISE
POSITION

EBB DIVERGENCE

A. RECIPROCATING B. RECIPROCATING D. ROTARY TIDAL
TIDAL CURRENTS TIDAL CURRENTS CURRENTS PLUS
PLUS PERMANENT PERMANENT FLOW
FLOW

Fig. 6. Diagram showing current patterns around a simple circular island.
I, II, III, etc. 12ths of tide period after slack tidal current.
E
POS
Fluti T'O
k0l

G
S
MA (@IMUMD@,Z"-"'

Assumptions- Northern hemisphere
Azimuth of permanent flow set = 2920 Permanent flow velocity = 0. 5
Maximum tidal velocity

Azimuth of tide-wave propagation = 2020 Minor axis, tidal ellipse = 0. 35
Major axis, tidal ellipse

-23-

to be distributed over wider areas than the convergences, but they are not

accompanied by elevations of the thermocline as distinct as the depressions

accompanying the convergences.

It is probable that the sudden appearance of large amountsof "limu"

(seaweed) on Hawaiian beaches is sometimes the result of the seaweed

accumulating for some timein aconvergence, and its concerted movement on

shore by wind action when the convergence weakens or breaks down.

La Fond (1962) has related slick streaks, observed close to the conti-

nental slope, to convergences associated with internal waves. Occasionally

in very calm weather we also have observed several slick streaks, which

may be of the sort described by La Fond, in addition to the main zones of

convergence on the island slopes.

Earlier studies (Neumann, 196o) have indicated that tidal current

ellipses are determined -to a great extent by bottom and coastal topography.

According to Fleming and Heggarty (1962) and to Lee (personal communication)

the currents tend to follow the depth contours, in general, rather than the

coastal outline. Some measurements of bottom currents have been carried

out on the Oahu shelf and slope using Carruthers' "Pisa" current indicator

and current cone. The results showed that the bottom currents tend to

follow the depth contours and are approximately the same strength as

surface currents or occasionally even stronger along steep slopes.

However, irregularities in coastal topography of the islands are also

reflected in irregularities in the depth contours. The irregularities

tend to cause eddies and anomalous currents. This is illustrated by the

generalized current patterns off@bjbziae, Oahu, during flood stage, as

shown in Figure 36. In the complex eddies shown, which change in tidal

rhythm, currents flowing in opposite directions can be found only a small

-24-

distance apart (see locations A and B).

An interesting eddy formation on the Pearl Harbor side of Barber's

Point, Oahu, is shown in Figure34 . The measurements indicate the eddy

formation around the headland. Because of the direction of the coast in

relation to the direction of ebbing current and the absence of irregular-

ities in bottom topography, no such eddies are formed on the nox@bh-4est

side of Barbers. Point, as shown in Figure 35.

Especially strong currents and large eddy formations can be expected

where the current sweeps around sharp-pointed headlands., such as Kaena

Point, Oahu, near which currents and eddy formations are illustrated for

the period of January 3 to 4, 1963 (Fig. 13)- It should be noted that

the strong current passing around Kaena Point appears not to reverse with

the tide. This may be due to the strength of the permanent flow in the

area, but it appears likely that it is due in part to the fact that the

direction of the flood current.eddy along the coast.southeast of Kaena

Point is the same as that of the ebb current itself along the same coast.

The eddies formed in the lee of islands or local topographic irregu-

larities are likely to persist due to inertia even after they move away

from the area of formation.

2.6 Wind-driven Currents and Mass Transport by Waves

The permanent flow described in section 2.2 is largely the result of

the drag of wind systems over the ocean. Locally, however, wind drag may

not parallel the permanent flow,.and the wind-driven current must be

treated a3 a separate component. Independent wind effects are Particularly

notable upwind and downwind of islands, where the currents may tend, at

the very surface, to set respecttvely onshore and offshore due to wind drag

Rotary tidal currents
offshore

Vectors for times
Vectors for times of divergence-
of convergence - '01_@ Period of divergence
Period of convergence
Convergence
(tide rip)

Continental slope

Reciprocating tidal- currents close to -the coast
Coast

Fig. 7. Diagram showing slope convergences resulting from coupling of coastal reciprocating and
offshore rotary tidal currents.

-25-

although in depth they may tend to parallel the shore.

The result of the drift of surface water towards the windward coast

of an island is a "piling up" of the surface mater, referred to as "Anstau".

The drift of surface water offshore from the leeward side of an island

results in a rise of the deeper water, referred to as "upwelling". A net

offshore drift resulting from offshore winds may be seen from drogue

measurements at Waianae, Oahu, as shown in Figure 8. Upwelling and anstau

effects, on the leeward and windward sides of the island respectively,

have also been demonstrated by observations of the depth of the thermocline,

as shown by the measurements off Diamond Head given in Figure 6 of the

Preliminary Report of this investigation (Avery, Cox, and Laevastu, 1963),

and might also be investigated by studies of the distribution of surface

temperature.

Differential movement of the water with depth has been studied on

windward and leeward sides of the islands in specially-designed experiments

with current crosses suspended at different depths. (See Figure 9 in the

Preliminary Report, Avery.,,-Cox, -and Laevastu-, .1963-. ) .-The. icoastward-seaward

components at the surface have been found to be compensated usually by

opposite components along the bottom (see Figs. 10 and 11 of Preliminary

Report).

Several simultaneous observations of the movement of current crosses,

drift cards, drift bottles, dye, and wetted -paper sheets at the surface

show that drift bottles and cards migrate much faster downwind than do the

paper sheets at the surface. The movement of dye spots is somewhat slower

than the movement of the sheets; and current crosses that have negligible

windage lag behind the dye. These observations confirm the conclusions of

, 26- 1

several earlier investigators that the movement of the drift bottles and

drift cards is greatly affected by the wind drag on the portion of the

bottle or card that extends above the surface. The comparison of the move-

ment of the wetted paper sheets on the surface with the movement of the

current crosses immediately below the surface, leads to the conclusion that

the very surface moves faster downwind than does the water layer a few

centimeters below it. This observation strengthens the hypothesis of

Tomczak (1962), who indicated that there is no discontinuity at the air-

water interface with respect to transfer of momentum. Rapid change of

current speed with depth causes sheer and turbulence, thus increasing the

mixing of any sewage close to the surface.

Besides the drift caused by the wind there is a mass transport of

water due to wave motion in the direction of the wave travel. This mass

transport by waves has recently been investigated experimentally, as well

as theoretically by Masch (1961), who gives appropriate formulae to account

for the speed in relation to depth for given wave conditions. As with

wind drag, the greatest velocity of mass transport by waves is at the

surface. The mass transport and associated mixing by waves are important

factors in sewage disposal in coastal waters.

Ordinarily, the mass transport is difficult to separate from the wind

drag, but in the lee of an island, where the wind blows offshore, the mass

transport may be predominantly alcr6shore due to the refraction of the

waves around the island. Such conditions are encountered off Waikiki.

Observations there of the differential current movement with depth plotted

in Figure 9 of the Preliminary Report on this investigation showed that

the movement of the surface relative to the deeper waters tended to be in

the direction of %propagation of the swell rather than in the direction

40 50 60

ON SHORE

X
x@ 5,
C) x lb

7.0%

0
Cli -39-0 4,30% Z
0

ro 0

OFF SHORE

0
ot'a 023 ozz

Fig. 8. Directions of drift drogues from two 24-hour cruises off Waianae. (After Sunn, Low,
Tom, and Hara, 1962.)

-27-

toward which the wind iras blowing.

The mass transport becomes accentuated in shallow water. Mass transport

of water over a reef, promoted by the breaking of the waves on the reef, is

likely to provide the principal circulation inside the lagoon and a pronoun-

ced current out through any existing channels.

The outgoing velocities may amount to several knots, depending on the

height, period, and direction of approach of the waves, the depth of water

over the reef, the width of the reef, and the length of reef from which

mass transport is tributary to a channel, although the current in the

channels may show some tidal fluctuation in velocity because of the

variation of water depth on the reef, there is no reversal. Well-devel'ored

examples of reef circulation on two very different scales are those of

Kaneohe Bay, Oahu ( Fig. 14) and of north Kapaa Reef, Kauai (Fig. 11).

Outgoing currents in reef channels in some localities might be used

effectively for sewage disposal, particularly if the sewage release could

be regulated in the tidal cycle.

The mass transport associated with waves breaking on a beach causes

the alongshore currents that are responsible in large measure for sand

transport and for the outgoing rip currents that threaten incompetent

swimmers.

3. COASTAL CURRENTS AROUND NIIHAU AND KAUAI

3.1 Niihau

According to the U. S. Coast Pilot for the Pacific Coast and Hawaii

(coast and Geodetic Survey, 1963a) reversing currents have been observed

in the Lehua Channel and in the vicinity of Kamalino. Probably the south-

setting current in the Lehua Channel and the south-setting current near

Kamalino represent flood tidal currents, the opposite sets representing

the ebb currents. South of Kawaihoa Point a prevailing westerly current

reaching a velocity of 1.5 knots is reported. Little is known about the

currents east of Niihau in the Kaulakahi Channel.

3.2 Western Kauai

According to the Coast Pilot (Coast and Geodetic Survey, 1963a):

"Current observations taken during a 24-hour period 0.5 mile off Mana

Point show a tidal current of 0.2 knot velocity at strength setting south-

ward and northward along the coast. The southward maximum occurs about

3 hours after low water at Honolulu and the northward maximum 3 hours after

high water. Similar observations taken near the coast about 3.5 miles

southeastward of Nohili Point show a tidal current with velocities general-

ly less than 0.5 knot."

These observations of tidal currents, which fit in with the theoret-

ical concepts discussed in section 2.4, are consistent with drogue measure-

ments made on 23-24 July 1963 (Fig. 9). The measurements show a south-

easterly current off Waimea during the change from ebb to flood, a south-

easterly current off Kekaha during the flood, no current off Mana.

during the change from flood to ebb, and northeasterly current off Nohili

_219@.

-30-

and Makuaiki Point during the ebb. The maximum current velocities, some-

what over 1 knot, were associated with the ebb current off Nchili. Other

velocities were generally considerably less than 1 knot.

3.3 Northern Kauai

Drogue measurements made 24 July north of Haena (Fig. 9) showed a

northeast current speed of about 1 knot at the time of a rising tide, but

measurements off Hanalei about two hours later during the same tide rise

showed a westerly current. Measurements made 25 July off Kilauea and

Anahola showed northwest to west currents with speeds as much as 1.8 knots

at the time of a high tide. These measurements can be accounted for only

by the persistence of the ebb current during the rising tide. The dif-

ference in current directions off Haena and off Hanalei may be the result

of an eddy or an abrupt reversal from ebb to flood directions or, most

probably, the location of the ebb convergence in the region between Haena

and Hanalei.

3.4 Eastern Kauai

Drogue measurements on 25 July 1963 showed a north-setting current

of 1.8 knotsstrength at low tide'off Anahola and a north-setting current

of 0.5 to 1.0 knot off Kapaa about-two - hours later (Fig. 9). Off

Hanamaulu, about the time of the middle of the rising tide., a series of

drogues showed a current changing rapidly in both direction and strength.

Drogue measurements on 23 July off NaWiliwili showed a southeast-setting

current of 1.5 knots strength at high tide. These measurements are all

consistent with a flood current setting southward and an ebb current

setting northward along this coast.

xaII

ix,

K A U A I

Mr.

VII

Tp- C... 11, N-Ii-1,
z, VE
%ddll WhIll
mS

11 1, N
Cho nge of tidal currents off Nowiliwili indi-
cated with bar on the tido I curves. (Ti e
of fid I current change taken the m
rec ord: of the Paddle- @hse f':umrrent

3 4
N-1-L "LES

Fig. 9. Results of drogue measurements of currents around Kauai.

-31-

Paddle wheel current-meter records for the period 23-25 July 1963

taken at a station a mile south of the entrance of Nawiliwili Bay (Fig.

10) show currents reversing apparently as the result of, but not easily

correlated withl tidal changes. The flood flows dominate and the phase

relations are difficult to account for. Since the drogue measurements

in the area agree with the theoretical pattern mentioned above, it is

probable that the meter was in an area affected by eddies.

A study of the currents on the north Kapaa reef by Helfrich and

Kohn (1955) showed a typical reef-lagoon circulation (Fig. 11). The

water was introduced over the reef edge by mass transport and flowed

continuously southward on the reefY regardless of wind and tide condi-

tions, escaping back to the ocean again in a deep-water inlet. Inter-

estingly, Inman', Gayman, and Cox (1963) found that in spite of the

strength of the southerly current the sand was transported westward

across the reef by the oscillatory currents associated with the waves

and under the guiding influence of small channels on the reef surface.

3.5 Southern Kauai

Drogue measurements on 23 July 1963 (Fig. Q) showed west-setting

currents averaging about 1 knot from off Makahuena Point to off Port

Allen during a time when the tide was approaching low, was low, and

beginning to rise. This direction is consistent with an ebb tide only

if this part of the coast lies between the flood convergence to the west

and the ebb divergence to -the east, as discussed in section 2.4.

3.6 Summary of Coastal Currents Axound Niihau and Kauai

The comparatively regular shape of the island of Kauai lea to the

-32-

hope that the coastal currents around it would be more regular than those

around the other islands.

The drogue measurements made around Kauai are consistent with a

current pattern with both tidal and permanent flow ccmponents in which

the flood current impinges on the island and diverges somewhere west of

Hanalei and possibly even as far southwest as Hanamaulu and converges

again in the vicinity of Waimea, and in which the ebb current impinges

on the island and diverges in the vicinity of or west of Makahuena, pos-

sibly even as far northwest as Navilivili, and converges again in the,

vicinity of Haena. The measurements are, however, insufficient to demon-

strate the current pattern with certainty.

Current-meter measurements off Nawilivili support the belief that

the currents are.controlled in part by the tides, but indicate that their

correlation with the tides is not simple.

The current reports from Niihau are consistent with a combination

of tidal and permanent flow components in which the resultant flood con-

vergence and ebb divergence are at the northeast point of the island,

and in which the ebb divergence is east of Kawaihoa Point and the flood

convergence northwest of the Point.

The currents around Niihau and Kauai are shown in simplified dia-

grammatic form in Figure 39.

6 A.M. 6A.M- NOON 6 RM.
N010N 6 7M. MIDMIGHT I - 1 .1 1 1
JULY 23.1963 JULY 24,1963
SPEED SCALE

;0
kW.
0 '0
TRUE NORTI
0

90E

0 -0

DEPTH OF WATER (M.L. L.W.) TO FT - 24 on
METER FROM BOTTOM 3T Ft 10

I T

MIDNIGHT SA@M. NOON 6 Pf M. MIDHIGHT 6A.M.
JULY 25,1963 I.LY

2- 2

0 - -0

Fig. 10. Paddle-wheel current-meter measurements from southeast of Nawiliwili, Kauai, (top) July 23-24, (bottom)
July 25, 1963.

M
0 30' 40'
10, 20' 50'

Iti

Ilk

V. KEY TO CURRENT VECTORS

....... 29 OCT 1630- 1900
30 OCT 1030- 1300
-------30 OCT. 1100- 1300
301- .-.-.-.24 NOV. 1000- 1200
/,"2 O'-X44 40000", 24 NOV. 1300- 1500
v --.---25 NOV. 1100- 1300

0 150 300 met
ers

0 1/8 1/4 mile
12 0 Current Vector Scale
-,26' 0 50 cm/sec
of i
0 1 knot

DEPTH CONTOURS IN FEET

Fig. 11. Currents on the Kapaa Reef (after Helfrich and Kohn, 1955, and Inman, Gayman,
and Cox, 1963).

4. COASTAL CURRENTS AROUND OAHU

Because of the number of separate drogue studies and current-meter

studies made during the present investigation around Oahu, an index map

showing the sites of these studies is included (Fig. 12). The sites of

additional studies made in the course of engineering investigations are

shown in Figure 1.

4.1 Northwest Coast

Off Kaena Point, as reported by the Coast Pilot (Coast and Geodetic

Survey, 196"
@a) and as observed in the present investigations, there is a

generally continuous northwestward current. Coast and Geodetic Survey

observations with a Roberts current meter over a 24-hour period showed

the northwest current, 0.8 mile., south of the Kaena Point light house,

to have an average velocity of 0.8 knot and a maximum velocity of 1 knot.

Drogue measurements in the present investigation made on 3-4 January 1963

(Fig. 13) showed a west or west-northwest current, of 1 or 2 knots speed,

west of the point except at low tide when the current turned north-north-

west and over one trajectory increased to 5 knots speed. At all tide

stages the current west of the point was fed by convergent currents follow-

ing both the north and south coasts of the Waianae Range. However, at

high tide there was a divergence of about two miles southeast of Kaena

Point so that at 4 miles southeast a southeast-setting current suggested

the existence of a counter-clockwise eddy south of the point during the

flood. A north-northwest set north of the point at low tide, together with

eastward sets farther east at Waialua, similarly suggests the existence of

a clockwise eddy north of the point during the ebb.

-33-

-34-

From Kaena Point to Kahuku Point the only current studies which have

been made are those of BeltY CollinsY and Associates (1962a, 0) in Kaiaka

Bay, in Waialua Bay, and immediately offshore. In these studies, performed

during two days in October and December 1961, the currents were observed

by surface floats of various sorts, subsurface drogues, and dye. The

results of the studies indicate that the floats and drogues were greatly

affected directly by the wind. The records of the dye trajectories are

very useful, however, in indicating current sets both in and outside the

bays. Both in Waialua Bay inside the breakwater and in Kaiaka Bay the

current apparently sets continuously seaward, no doubt as a result of the

fresh-water streams entering the heads of the bays. Velocities are about

0-1 to 0.3 knot. Outside Kaiaka Bay the only measurements were on a ris-

ing tide, when the current set southwestward with a velocity of 0.1 knot.

This set agrees with that measured on a rising tideand at high tide out-

side Waialua, Bay, where the velocities ranged from 0.2 to 0.3 knot.

However, at low tide the:.current was..-found to set northward with a velocity

of 0.1 to 0.2 knot from Waialua Bay.

The currents in Kaiaka Bay are insufficient to prevent stagnation, as

indicated by low oxygen content and high biological oxygen demand, and

both bays are contaminated bacteriologically.

The reversing tidal currents off Waialua, Bay are probably typical of

much of the northwest coast of Oahu.

4.2 Northeast Coast-Kahuku to Ulupau Head

According to the Coast Pilot, the "currentsoff Kahuku Point set weast-

ward or northwest-mard but are sometimes negligible; tide rips have been

reported a mile eastward of the point." Assuming that the tide rips occur

----------

21'40'-

------------- 0
0

/0
------- Gialuo
;3,
Bay 0
aena Pt.

Fig. 13 --------

kai Bay.
A

F i g. 15,16
Pearl Harbor
Fi g. 17

g.35

-21, 20, A
Ewa AP'PEN.
Fig. 5
Hono@lulu -Makopuu

- ----------

F i g.31,32
----------
..... Fig.34
Fig. 26,27
LFig. 23 128,29,30
ig. I APPEIN. Fig. 6

158120' 158' _7140'

Fig. 12. Index map to figures showing coastal currents around Oahu. Locations of paddle-wheel current-
meter measurements are shown by solid circles; Ekman current-meter measurements, by
crosses; and locations of chemical studies, by triangles.

1 1
158* 20' 158*10'

21* 40'-

Koeno Pt.
-------------- -------- --------

6 =4
-----------------

Scheme of Eddy Formation
JM4

IE, KAENA PT

SPEED SCALE

0 2 KNOTS

------------ I"

TIDE CHART
TIDE CHART
JANUARY 3,1963 JANUARY 4,1963
6A.M. NOON 6PIVI. 6A@M. NOON 6PIVI.

4
21*30'--0-
or-

Fig. 13. Results of measurements of currents near Kaena Point, Oahu, on January 3-4,
1963. (Measurements made during predominantly ebbing tides.)

-35-

at times when the current parallel to the shore is slight, observations are

consistent with the concept that the ebb-stage current convergence is

located in the vicinity of Kahuku Point and flood-stage current divergence

is located somewhere to the southeast.

The Coast Pilot also indicates that "an eastward current is reported

in the vicinity of Mokumanu Islands.," near Ulupau Head. Judging from the

current measurements in the vicinity of Kailua, described in section 4.4,

it is unlikely that there is a continuous eastward current at this place.

The report is probably meant to call attention to an occasional exception

to the general westward or northipard flow described as passing the island.

If so the flood-stage current convergence occurs, at least sometimes, off

or northwest of Ulupau Head.

Unfortunately there have been no really reliable current measurements

made offshore along the coast between Kahuku Point and Ulupau Head.

4.3 Kaneohe Bay

Measurments of the circulation in Kaneohe Bay (Fig. 14) indicate a

well developed reef and lagoon circulation of the sort discussed in section

4.5. Water is introduced into the bay by mass transport over the reef and

even through the shallow east channel. The surface circulation within the

bay is apparently wind driven, and the flow along the bottom is controlled

by the configuration of the channels and reefs. Discharge from the bay

occurs through the deeper west channel.

The measurements available indicate no tidal reversal in either channel,

although it is conceivable that, during periods of calm when mass transport

is minimized, there might be an outflow with the ebbing tide through the

east channel and an inflow with the flooding tide through the west channel.

-36-

Some additional current measurements and analyses of water quality made

by students in connection with studies of the distribution of zooplankton

(T@,Tesukdi Piyakarnchana, oral communication) indicate that the southeast

section of Kaneohe Bay, especially, is rather effectively isolated from

the ocean. Although there is separate circulation within the southeast

section resulting ma.'nly from wind drag, which maintains aeration even at

depth, there is little exchange with the rest of the bay.

A study of Nuupia Pond, a shallow walled-off arm of -the bay (Holmes

and Narver and Belt, Collins, and Associates, 1959b)showed the currents in

the pond to be wind-driven.

A sampling program by the Division of Sewers (1957a)showed low bacter-

ial concentrations except close to shore.

4.4 Kailua

Mention was made of the parallelism of current sets off Kailua to the

shore in a Holmes and Narver report of 1957, but the most extensive current

observations in the vicinity of Kailua are those of Holmes and Narver and

Belt, Collins, and Associates in 19501. Five daytime surveys were made off

the base of Mokapu peninsula, one each in January, May, June, July, and

August. The currents were observed with surface floats, subsurface floats,

and dye. The results indicate that the floats, especially the subsurface

ones, were greatly affected by direct wind drag. The dye patch trajectories,

not affected by wind drag, indicated that the current set north during

rising tide stages, west during a falling tide stage, and northwest at low

tide. Velocities are not directly indicated but seem to have been on the

order of 0.1 knot.

Moku Manu

Speed Scale
0
0.5 knots

S,pt 4 S.@" 5 S,pt 6
0 6 12 Is 0 18 0 6 2@

............
Distance Scale (no. iles

-6, 1962
September 4
0

K.P.P. 1.

Mok.11@ it
0
Ahu 0 Lako I/
.-Ut W-d
G

00 (Z) 00 ......
00
Cy 0 0
0
0
0 4Z),
10 0

...... WI:
m

Fig. 14. Results of drogue measurements of currents in Kaneohe Bay, Oahu, Septemb
1962.

-37-

These observations are consistent with the location of the ebb-stage

convergence somewhere northwest of Kailua, but suggest that the flood-stage

divergence is generally southeast of Kailua.

In connection with the current surveys, a study was made of bacterial

die-off as reported by Iha (1960). Even after allowing for dispersion the

bacterial survival rate was only between .01 and .001 after 90 minutes.

Details are discussed in section 7.3.

4.5 Waimanalo

Current measurements off Waimanalo have been made by the Hawaii Insti-

tute of Geophysics (see Figs.15, 16, 17) and by Marine Advisers at various

times for more than a year from September 1961 to October 1962. The results

of these measurements show that the currents off Waimanalo are complex and

with the available data it is difficult to fit them into a definite pattern

with any degree of certainty.

Although northwesterly sets predominate the currents reverse at times

especially in shallow water. Drogue measurements on September 11, 1962

(Fig. 15) show no reversals but a fluctuation in strength with tidal rhythm.

The upper layers of water have a downwind- component toward shore. This

effect is most pronounced at the surface and has been noticed at all

locations where this type of measurement has been made.

Drogue measurements on February 23, 1963 (Fig. 16) show currents with

light trade winds blowing. The currents are weak, and since the one-meter

drogues are moving up wind there certainly must be eddies here in the

vertical plane as well as the horizontal. The southeast currents on the

south side of Manana Island are representative of what Marine - Advisers, --Inc.

found on several occasions. On January 31, 1962, and February 3, 1962,

_38-

their drogues traveled from inshore of Manana Island clockwise around

Makapuu Point. On the second date mentioned there was no -,rind. The

drogues were picked up off Hanauma Bay with an apparent av@@rage speed of

more than 1 knot.

Paddle-wheel cu,.rent-meter observations in 80 feet of water on July 15-

17, 1963 (Fig. 17) showed irregular current reversals.

Much of th2 difference in c,,arent tat-terns a-t- Waimanalo at different

times probably results a shf_ft in -Uhe pasition of -the flood current

divergence from Mlakapulu '11oint, to so_,_.'.e@qbez@e no-th-uest of Waimanalo. The

consequence would be a change in the set of the flood current at Waimanalo

from northwest to southe-ast. [email protected] and othe-2 changes in the direction

of the permanent flow are allso probably involved.

4.6 Koko Head to Makapuu

Between Koko Head. and [email protected], the only current data available consists

of drogu-- measurenents obtained by Sunn, Loi,-, Tom, and Hara on 8 April,

25 June, and 9 Septeh'@.Der, 19S__ (Sunn, Low, Tom, and Hara, 1962b@. These

show a very clear a-_-_@d siziiple ti-d-e response. The flood flows, which set

southwest., correspoi-Ild iii pha::;_e to the rising tide and the ebb flows, which

set northeast. izl phase to the falling tide. Velocities as

high as 1. 5 lu-ots fo-.' the flood current and. 0.8 knct for the ebb current

I
were measured, but 1-'hese rLight jaa'%?-e b,,-_@n _,(jmewhat intensified by wind

drift. associat-ed w-lth @a 'Grade wind and a kona wind.

4.7 Maunalual B.ay

Data frc@ai the paddle-ofnc@el curreut set in 80 feet of water off

Wailupe Peninsula (Aina Haina) in July 10,63 (see Fig. 18) shows that a

current pattern essentially like the one at Diamond Head holds for that

11570 40, w
I \\ Depths of
k current crosses
5 m, _-jO rn
/0
1.5 rn

Speed Scale
01
0
'0 SET V
OL .5 1 knot

0 6 12 18 24 h
EX
21023'N -1\', M 0
B
A

3M
Currents
WAIMANALO at 5nn depth 'to

210 20'N
(J@ Monana
11 Island

MAKAPUU PT.
_@E X)
MO,
@@not
Ik

157043'W 15704 'W
U )w
r-/
Fig. 15. Results of drogue measurements of currents off Waimanalo, September 11, 1962.

SPEED SCALE
0.,5 knot

6 12 -18 24 h
5
QV 11
5 2

5
21023'N

5 /WIND
5 cm sec
X 10 knots)
WAIMANALO 10

10
210 20'N 'r
Monona t. 50
5
ri

5-,
5
'----"MAKAPUU PT
t@)7043'W GII

(Depth contours in fathoms) 157040'
Y5 0

040,W

Fig. 16. Results of drogue measurements of currents off Waimanalo, February
23, 1963.

NOON GPM MIDNIGHT 6A.M. NOON

JULY 15, 1963 JULY 16.1963

SPEED SCALE

0 so
knots
..........
0 1.0

TRUE NORTH

W270 90E

W
j Nlo
4

0- -0
DEPTH OF WATER (M-L.L.W)-30FT=9tn
METER FROM BOTTOM 10 FT - 3

-2-

NOON 6 PM. MIDNIGHT 6A.M. NOON
I

JULY 16. 1963 SPEED SCALE JULY 17. 1963
C./se.
.50
knots
0 1.0
TRUE NORTH
0
-2

W270 90E

z
0 ISO
S

0 - 0
DEPTH OF WATER (M.L.L.W.)- 79 FT- 24.

METER FROM BOTTOM 371 FT - 11.3 .

Fig. 17. Results of paddle-wheel current-meter measurements off Waimanalo, (top) July 15-16, (bottom)
July 16-17, 1963.

NOON 6 PM. MIDNIGHT 6A,M. NOON

JULY11, 1qr03 JULY12,11963
SPEED SCALE
cm/sec
1-7-1--F@T@7-1
0 50
knots

0 1.0
2- TRUE: NORTH 2
0

2 W 270
>1
W
W 180
_j I-

DEPTH OF WATER (M.L.L.W.)=79 FT=24m
METER FROM BOTTOM = 37 FT. z 11.3 m

0- -0

Fig. 18. Results of paddle-wheel current-meter measurements off Wailupe Pensinsula, July 11-12, 1963.

-39-

area and probably as far as Koko Head.,

No current measurements were taken inside the bay near Kuliouou Beach

Park. Here one would expect to find weak currents caused by eddies, currents

caused by mass transport over the reef, and currents that are wind driven.

4.8 Mamala Bay

Mamala Bay is the broad indentation of the southern coast of Oahu

lying between Diamond Head and Barber's Point. Irt-')this bay open the Ala

Moana Yacht basin, Kei!alo basi.,., Honolulu Harbor via the Honolulu Channel

and via the Kal1bi Channel, a,-d Pearl Harbor. Information on the currents

of Mamala, Bay has been derived from the following sources:

(a) Institute of Geophysics drogue studies off Diamond Head (Figs. 24,

2.5, 26, 2T, 28, 2'9., - 30).
(b) Engi neering Experiment Station paddle-wheel current meter record-
ing off Diamond Head continuously for nearly a month'(Figs. 19, 20).
(c) Institute of Geophysics drogue studies off Waikiki (Figs. 26, 27).
(d) H.A.R. Austin and Associates and Law and Wilson (1961) drogue

studies off Ala Moana.

(e) Engineering Experiment Station paddle-wheel current-meter study

off Magic Island (Fig. 2lip top).
(f) Engineering Experiment Station paddle-wheel current meter study

off Keiralo Basin (Fig. 21, bottom),
(g) Institute of Geophysics drogue studies off Kewalo and Honolulu

Harbors (Figs. 26, 27, 28, 29, 30).
(h) Bureau of Sanitation (191i'l) studies of bacterial concentrations

off the former Kewalo sewer outfall (Pig. 33).

-40-

(i) Metcalf and Eddy (1944) studies of bacterial concentration and

slick fields from the former Kewalo outfall.

(j) Division of Sewers (1951) drogue studies near the Sand Island

sewer outfall.

(k) Hyperion Engineers (1957) calculations based on the Division

of Sewers (1952) studies.

(l) Austin, Smith, and Associates (1961b)observations on the slick

field from the Sand Island outfall.

(m) Institute of Geophysics measurements of turbidity from the

Sand Island outfall (Figs. 31 and 32).

(n) Engineering Experiment Station paddle-wheel current measure-

ments and dye studies in the vicinity of the Sand Island

outfall. (Fig. 22).

(o) Austin, Smith, and Associates (1960) drogue studies off

Pearl Harbor.

(p) Institute of Geophysics drogue studies off Pearl Harbor.

(q) Institute of Geophysics drogue studies off Ewa (Fig. 34).

(r) Institute of Geophysics paddle-wheel current-meter study

southeast of Barber's Point (Fig. 23).

The Institute of Geophysics current-meter study northwest of Barber's

Point, although not in Mamala Bay, is also of critical importance in under-

standing the current behavior in the Bay.

Off Diamond Head the paddle-wheel current meter measurements continued

by Tinniswood and Avery over a period from 24 November to 19 December 1963

indicate the predominance of tidal currents. Figure 19 shows some samples

of the records obtained. The flood current, which persists during the rise

NOON 6 P.M. MIDNIGHT 6 A.M. NOON 6 P.M. MIDNIGHT
3 - . I . . . I . . . I . . . I . I . I . . . I . . . . .
NOVEMBER 24,1963 NOVEMBER 25,1963

SPEED SCALE
TRUE NORTH =/"c
0 .1 '3'0'4'
0 10 20
2- rj-@ knots
W 270 90E I -I
- 01 0!2 '0.14'OIS 0!8 110
z
180
S

W I

DEPTH OF WATER (M.L.L.W.) =42 FT.= 12.8m
METER FROM BOTTOM 27 FT.= 8.2nn

MIDNIGHT 6 A.M. NOON 6 P.M. MIDNIGHT 6 A.M. NOON 6 RIO. MIDNIGHT
3 1 , , I I , I I . . I . , I , , I . . j I I . . I . . . I
NOV EMBER 26,1963 NOVEMBER 2T,1963
SPEED SCALE
cm/soc
TRUE NORTH
0 0 10 20 30 40 50
rr'@ kn ots
W 270 @OE 0 0.2 0.4 0.. 0.8 1.0

2; ISO
2 S

6 c-ffVw

DEPTH OF WATER (M.L.L.W.)=42 FT.= 12.8m
METER FROM BOTTOM = 27 FT.= 8.2m 47 61 cm/sec
58 m/...

Fig. 19. Results of paddle-wheel current-meter measurements off Diamond Head, (top)
November 24-25, (bottom) November 26-27, 1963.

MIDNIGHT 6 A.M. NOON 6 P.M. MIDNIGHT 6 A.M. NOON 6 P.M. MIDNIGHT

DECEMBER 4,1963 DECEMBER 5,1963
SPEED SCALE
0 10 2@0' 3'0' 4!0' 56

knots
I II I I I I I T-1
0 0.2 0.4 0.6 08 1.0

2- TRUE NORTH
0

W 270 SOE

ISO
S

DE PTH 0 F WAT E R (M. L. L.W.) 42 FT. 12. 8 rn 78 ..A..'
P METER FROM BOTTOM 27 FT. - 8.2 nn

MIDNIGHT 6 A.M. NOON 6 P.M. MIDNIGHT 6 A.M NOON 6 P.M. MIDNIGHT

DECEMBER 8,1963 DECEMBER 9,1963
SPEED S
3- cm":@L'
@0'3'0'46' 50
It no ts
I I I I I T-1
0 0.2 0.4 0.6 0.8 1.0

TRUE NORTH
0
W 270C )90E
w ISO
w S

DEPTH OF WATER (M.L.L.W.) 42 FT. 12.8 rn
METER FROM BOTTOM 27 FT. - 8. 2 nn

Fig. 20. Results of paddle-wheel current-meter measurements off Diamond Head, (top)
December 4-5, (bottom) December 8-9, 1963.

MIDNIGHT 6 A.M. NOON 6 P.M. MIDNIGHT 6 A.M. N N
3- 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 , I I I I I I I I I L
NOVEMBER 11,1963 NOVEMBER 12,1963

SPEED SCALE
TRUE NORTH ctn/aac
0 1 T-T-T---l
0 5 10 15 20 25
KT@ knots
2 W 270 90E r--r-i i
0 0.1 0.2 03 0.4 0.5
2F ISO
2 S

W
I
W

0 -

DEPTH OF WATER (M.L.L.W.) 42 FT. 12.8m
METER FROM BOTTOM 27 FT. 8.2 nn

MIDNIGHT 6 A.M. NOON 6 PM. MIDNIGHT 6 A.M. NOrN 6 P.M. MIDNIGHT
3- 1 , I , @ I I @ I I I @ I I I I I I I I I I I I I I
AUGUST 16,1963 AUGUST 17,1963

TRUE NORTH SPEED SCALE
0

0 5 10 15 20 25
2 IN 270 90E knots

> 0 0.1 0.2 03 0.4 0.5
180
4 S
7

0-
DEPTH OF WATER (M.L.L.W.) =42 FT.= 12.8m
METER FROM BOTTOM z 27 FT.= 8.2nn
I I I I I -T-1- r

Fig. 21. Results of paddle-wheel current-meter measurements off Magic Island, (top)
November 11-12, 1963, and off Kewalo, (bottom) August 16-17, 1963.

MIDNIGHT 6 A.M. NOON 6 P.M. MIDNIGHT 6 A.M- NOON 6 P.M. MIDNIGHT
3 . . . I . I . . I I I . I . . I . I I . , I . . . I . . . I , . . , . I I . I I . 3
AUGUST 4,1963 AUGUST 5,1963

SPEED SCALE

0 5 10 15 20 25
knots TRUE NORTH
2- F-F-1 I -I , 1 1 1 0 -2
0 0.1 0.2 Q3 0.4 0.5

z - W 270 90E

180S

0- -0

DEPTH OF WATER (M.L.L.W.)-42 FT.-I2.8nn
METER FROM BOTTOM 2T FT. - 8.2 m

MIDNIGHT 6A.M. NOON 6 P.M. MIDNIGHT 6 A-M. NOON 6 P.M. MIDNIGHT
3 . . . . I I - I - - - I . I . - I I . . I I I , . I I . I . I I , I . . I . . I . I
AUGUST 9, 1963 AUGUST 10,1963

TRUE NORTH
SPEED SCALE 0
crn/sac
1 3 10 410 510
0 10 20
2- knots W 2TO 90E
I I I I I 1 -1
2@ 0 02 0.4 OL6 Q8 1.0 ISO
0
t-

0-
- DEPTH OF WATER (M.L.L.W.) 48 FT. 14.6 M
METER FROM BOTTOM 33 FT. - 1O.Om

Fig. 22. Results of paddle-wheel current-meter measurements near Sand Island sewer out-
fall, (top) August 4-5, -(bottom) August 9-10, 1963.

6 P@M. MIDNIGHT 6 A.M. NOON 6 P.M.
I

JULY 5, 1963 JULY 6, 1963
SPEED SCALE

0 0

0 1.0

2- TRUE NORTH 2
0

W270 90E
z
0

180
>
W
W

DEPTH OF WATER (M.L.LV1=79FT,24.
0- DISTANCE OF METER FROM BOTTOM= 3TI FT= 113. -0

6PM. MIDNIGHT 6kht. NOON
I I

JULY 8,1963 JULY 9,1963

SPEED SCALE
cm/sec
I I - I ' 1 .510
knDts
0 10
TRUE NORTH
0

2@
W270 OE

DEPTH OF WATER (M.L.L.W.)- 62 FT - 19 m
METER FROM BOTTOM = 37 FT. = 11.3 m

0-
'JO

Fig. 23. Results of paddle-wheel current-meter measurements (top) southeast of Barbers Point, July 5-6, 1963,
and (bottom) northwest of Barbers Point, July 8-9, 1963.

_41-

of the tide and at the time of high tide, sets northwest in accordance with

the theory discussed in section 2.4. The ebb current has the reverse set.

The average velocity is approximately 0.6 knot. Characteristically the ebb

velocity is greater than the flood velocity, and the ebb current before a

large tide rise has reached a maximum of more than 2 knots. An offshore set

during the turn of the current may be partly the effect of the winds,

although it was also noted during the calm weather that predominated during

the period of the current meter measurements. The records appear sufficiently

regular to encourage the belief that harmonic analysis will provide the

basis for useable current predictions. Drogue measurements made off Diamond

Head at various times agree with the current-meter measurement's and provide,

as well, some additional information to be discussed elsewhere.
Less extensive paddle-wheel current measurements made about 1-1 miles
2

northwest of Barbers Point in July 1963 show similar although somewhat less
regular results (Fig. 23,@bottom), -.with the flood-current :a6tting south and

the ebb current setting northwest, as discussed in more detail in section

@4.12. Still more irregular paddle-wheel- current-meter results were obtained

a few days earlier about 3 miles east-southeast of Barbers Point as shown

in F'igure 23 ("top). . Velocities averaged about 3/4 knot and reached a
maximum of about 1-@- knots. Drogue measurements made in the same area in

April 1963 indicate that a major part of the irregularity results from the

formation of eddies especially from the swing of the flood current around

the Point.

Apparently the area of convergence of the flood current and the area

of divergence of the ebb current must lie somewhere between Diamond Head

and Barbers Point, in other words somewhere in Mamale. Bay. It is not

surprising that the current patterns in the Bay are complex and irregular.

-42-

Between Sand Island and Diamond Head the currents generally show some

similarities in phase to the currents at Diamond Head, although the velocities

are lower and the irregularities increase toward Sand Island. Figure 26

summarizes drogue measurements in the area made during predominantly flood-

current phases in 1962, and Figure 27 similarly s=marizes measurements for

the ebb phases. Figures 28, 29, and 30 show the results of additional

drogue measurements in February and March 1963 in relation to tide phases.

Altogether more than 80 drogue settinEpwere made.in this area. Exceptions

to the general westerly set of the flood current and easterly set of the

ebb current are found in sets III and V on 24 February (Fig. 28) and set

VI on 3 March (Fig. 29). These sets are in shallow water and the reversals

are probably due to eddies.

A comparison of Figures 29 and 30 shows that the strength of the tidal

current is not alTays simply correlated with tidal amplitudes. It is also

apparent, from Figure 28, that the change of direction of tidal current

can occur at different times within short distances in the area west of

Waikiki (cf. Fig. 28, sets IV, V, and VI). As a result of the complex

current pattern and owing to the effect of variations in phase of currents

in shallow and deep water, currents in opposite directions can exist with-

in relatively small horizontal distances (see for example Fig. 29, sets

A and* B).

The effects of -vrind and mass transport were observed to depths of

several fathoms in most measurements involving drogues set at several depths.

However, except in direct wind-drift effects, only minor differences have

been found between trade and kona conditions.

Drogue measurements by H. A. R. Austin and Lawand Wilson (1961) in

20
iio
21* 16'

.............
...............

.........
HEAD
........ P.IAMOND
.............
SET
...............
5@ 15

... .............
200,

SET

"SET I

5 5

15m (depth of the
5m current cross)
im

SPEED SCALE 21- 14'-

0 0.5 1 KNOT
SET=

15
5 TIDE CHART
AUGUST 1, 1962

Jul

157 50'

6A.M NOON 6PM.
(Depth contours in fathoms)
Fig. 24. Results of drogue measurements of currents off Diamond Head, August 1, 1962,
showing effect of wind drag and mass transport.

SAN

7052'W 157050'W

Speed Scale
L
0 0*5 1 knot

0 6 12 18 24
81 2 DIAMOND
/7 AL) 21016'N
'06@
5 0

71
0 5 1
4

TIDAL CURVE
21014'N
DIAMOND
21016'N HEAD
00 0\

7 2
6
5
21" 14'N
157052'W 157*50'W
0 1 5 km

Fig. 25. Results of drogue measurements of currents off Diamond Head, August 17, 1962.
Quasi-simultaneous observations at two stations.

S nd
,sland OV-1

Nearly
-'-stationary
21017'N--t -No
movement

Diamond
e a

2101SN

Speed Scale

I I I I I l
0 1 knot
a

kDk

157 055'W 157050'W

Fig. 26. Results of drogue measurements of currents in the eastern part of Mamala Bay in
1962 during predominantly flooding currents.

Y
Sand
Island

1CO
no movement
21017'N 8 \A

Abb Diamond
Head

21013'N

.1111@@no movement Speed Scale

0 1 knot
S asn d
I.. lq@nd
,ment@
kD 0n @d
ic
H ,ad
(D

157055'W 157-50'W

Fig. 27. Results of drogue measurements of currents in the eastern part of Mamala Bay in
1962 during predominantly ebbing currents.

TIDES.

SAND ISLAND H 0 N

'of ALA MOANA

-------------
x"
--------- ----
]Z5

21-16! AX
dSAN@DML N'D
@A

ALA MOANA

3m 115

Fig. 28. Results of drogue measurements of currents in the eastern part of Mamala Bay, Feb

1@ 54' 52, '58. W,

0
n ts;

SAND ISLAND H 0 N 0 L U L U

3M
1,5
ix, ALA MOANA
IM,
A
A -------------- -------

5of

_10of

--------------------
B =5
..........

'of

sot
AL.,

Fig. 29. Results of drogue measurements of currents in the eastern part of Mamala Bay, M

158-54! 15W50'

SAND ISLAND H 0 N 0 L U L U

IK5
--------- XV71 ALA MOANA

Z
--501
x -----------

------------------------- ------

21-16-

v1-

lof
-3E5
ALA MOANA

Fig. 30. Results of drogue measurements of currents in the eastern part of Mamala Bay,

_43-

front of the Ala Moana reef show quite consistent tidal-current reverses

with the current setting north-northeast on the rising tide and south-

southwest on the falling tide. The apparent reversal of phase may be the

result of eddies consistently set up by both the flood and ebb current.

The velocities measured for the south-southwesterly current sometimes

exceeded 1 knot, considerably greater than those measured for the reverse

current but the differenceG are probably the result of trade wind effects

on the floats as well as trade wind-induced surface current.

Dye and current-meter studies conducted by Tinniswood and Avery in

the vicinity of the Sand Island ::ewer outfall during trade-wind weather

indicate that the sewage may be carried either toward Diamond Head or

toward Barber's Point. The paddle-wheel current meter showed a reversing

current with some tendency to follow the Diamond Head pattern, but with

stronger superimposed erratic currentj that probably repre3ented eddies.

Velocities averaged about 0.2 knot and reached a maximum of about 0.4 knot.

On one occasion, the paddle-wheel current meter showed that the current

at the sewer outlet, 15 feet below the surface, flowed cont-inuously for

51 hours in the general direction of Waikiki; and, on another occasion,

dye was followed from the sewer outlet in mid-morning to just off the

Kewalo Channel by mid-afternoon. With the trade winds blowing, the surface

layer moves with an offshore component that should carry floatables out

to sea, but, with a kona wind blowing, the same process would carry the

floatables shoreward.

Additional tracer studies have used turbidity as the trace material.

Figures 31 and 32 show the distribution of turbidity in the eastern part

of Mamala Bay respectively during an ebbing current under "k=a conitions

and during a predominantly flooding current under trade-wind conditions.

-44-

it should be noted that the distributions shown represent specific tide

conditions and cannot be taken as averages. In Figure 31 a tongue of

high turbidity at (A) results from the flow of sewage southwestward from

the sewer outfall. Another tongue of high turbidity water at (B) may

represent the outflow of turbid water from the Kalihi Channel. A tongue

of clear water (C), from farther off shore, is flowing along the slope

towards Waikiki. A sharp gradient in the concentration of pollutant is

indicated by the turbidity measurements over the slope at (D).

In Figure 32 the sewage flows at point (A) towards Pearl Harbor with

a slight offshore component. A tongue of clear water flows in the same

direction at (B) farther offshore. However, there are two concentrations

of polluted water at points (C) and (D) still farther offshore over the

slope. These have probably resulted from previous injections of sewage

during periods of relatively low current velocity past the sewer outlet.

Their distribution suggests that the net flow past the outlet first set

toward the west and then swung toward the southeast during the few tide

cycles that preceded the measurements.

Similar studies were made by Tay monthly from June 1940 to September
1941 (Bureau of Sanitation, 1941) and by Metcalf and Eddy (1944) monthly

from April to July 1944 using bacterial concentrations from the old Kewalo

sewer outfall as tracers. Because of the nature of the sampling program

the results cannot be expected to show fine detail, and times and tide

stages at the times of collection are not indicated. Nevertheless the

studies are extremely valuable because of the range of time and conditions

they span. Metcalf and Eddy found that the contaminated water from the

Kewalo sewer was moving only to the west or offshore, but Tay generally

found a tongue of contaminated water moving eastward. The greatest

SAND

ISLAND

SEWER 41

------------
------ ---- ------

1.5
-@O ------------
1@0

- ------ ----- ---------

/,,-0-6
SAND

ISLAND

1@ 7-5,@VW 157 *52'W

Fig. 31. Distribution of turbidity off Sand Island and Ala Moana on December 28, 1962, during a predon

A V,

SAND ISLAND

----- 6F -----------
-----------
A'@' 4
-----------
----------
------------ ------
------------
c --------

1 5
2 77777@1

--100 F

00,

157-54'W 157.52'W
I

Fig. 32. Distribution of turbidity off Sand Island and Ala Moana on July 17, 1963, during a predomir

-45-

eastward flow was in February 1941 (Fig. 33) when there was a concentration

of Bacterium coli greater than 1000 per 100 ml one mile off' Kuhio Beach

and a concentration greater than 100 per 100 ml 0.25 mile off the natatorium.

It seems inescapable that sewage from the Sind Island outfall must at

one time or another be carried to all parts of Mamala Bay, and that it must

at times enter Keehi Lagoon, B.6nolulu Harbor, and probably inshore areas

farther east.

Drogue measurements by Austin, Smith, and Associates (196o) off the

Pearl Harbor entrance and Hickam Field showed some tidal response, generally

in phase with that at Diamond Head, but dominance by some other component

that set continuously southwest during the six days of the study in Febru-

ary, March, and April 1960, and on one day in December 1958, and that set

northeast in two other days in December. The latter component probably

involves wind drag. Wind data were not given for the times of the measure-

ments, but it seems probable that kona winds prevailed on the two days

when the set was northeast and trade winds on the other days.

4.9 Ala Wai to Kewalo

Prior to the construction of the Ala Wai Yacht Harbor channel and

the isolation of Kewalo Basin from the channel along the front of Ala Moana

Park, there was a strong, unidirectional current flowing from the Ala Wai

canal through the Yacht Harbor, augmented in the Ala Moana Park channel by

water carried by mass transport over the reef, continuing through Kewalo

Basin and out to sea through the Kewalo channel.

Since the Ala Wai Yacht channel was dredged, and the channel along the

front of Ala Moana Park was blocked off from both the Yacht Harbor and

Kewalo Basin, the Ala Wai canal water has drained seaward through the yacht

channel. Groundwater and storm-sewer discharge continues to flow seaward

_46-

through the Kewalo channU, however. Float studies by H. A. R. Austin and

Associates and Law and Wilson (19a ) show that the seaward currents in both

the Ala Wai and the Kewalo channels have velocities on the order of 0.1 to

0.2knot. There continues to be a slight westward flow in the Ala Moana

Park channel, probably resulting from a combination of mass transport over

the reef and wind drag in the channel.

In the "Magic Island" channel configuration planned for construction

on the Ala Moana reef (H.A.R. Austin and Associates and Law and Wilson, 1961),

mass transport over a weir at the east entrance to the channel will be

counted on to flush the channel westward.

4.10 Honolulu Harbor - Keehi Lagoon

There seems to be practically no information on currents in Honolulu

Harbor under present conditions. Keller, Tay, and Collins in 1920

described stagnant and polluted conditions that indicated inadequate tidal

and stream-flow flushing. The isocol maps of Metcalf and Eddy in 1944

indicated high bacterial concentration in Honolulu Harbor and also in some

tarts of Keehi Lagoon. The opening of the Kalihi ship channel frcm

'Honolulu Harbor west through Keehi Lagoon to the sea, however, has restored

an original but long-closed route for circulation. The currents in the

loop around Sand Island seem not to have been investigated.

4.11 Pearl Harbor

Problems of sewage contamination in Pearl Harbor have been noted in

several reports (Div. Sewers, 195-(b) Div. Sewers, 1958; Austin, Smith, and
and Metcalf and Eddy,
Assoc. 11962). A survey by Austin, Smith, and Associates (1961a) in Middle

Loch off Pearl City, using surface and subsurface floats, indica-ted the

X
Q CANA PARK
A
Broken
Line

z
-;/A 0'

0
0
)10
`30 /@r I
01,
1000
000

/@77
10,000
1,000 Z
500
100
0

MAP SHOWING ISOCOLS PER 100 M.L.

SAMPLES AND B-COLI DENSITIES TAKEN
CO DURING THE MONTH OF FEB. 1941

0 0.5 1.0

SCALE IN MILES
FROM TERRITORY
BUREAU

Fig. 33. Coliform concentrations derived from old Kewalo sewer, February 1941 (from Bureau of

-47-

existence of weak but well defined tidal components. The flood, correspond-

ing in phase to the rising tide, set generally northwest toward the head

of the Loch, and the ebb, corresponding in phase to the falling tide, gener-

ally set southeast toward Ford Island. Superimposed on the tidal oscillations,

which involved velocities only on the order of a tenth or tenths of a knot,

were a prevailing seaward flow on the surface resulting from stream and

spring discharge, and wind drag. The wind affected particularly the surface

floats. Presumably similar conditions prevail in other parts of the Harbor.

In another survey made at the harbor entrance by Austin, Smith, and

Associates (1960), involving surface and subsurface floats, the flood

current was shown entering the harbor with a velocity on the order of 0.2

knot, generally with the tide rise as expected.

4.12 Southwest Coast

Information on currents along the southwest coast of Oahu is derived

from:

(a) the Coast and Geodetic Survey (1963a) Roberts current meter

study just south of Kaena Point previously referred to;

(b) the Institute of Geophysics drogue studies of 3-4 January 1963

at Kaena Point and 4 miles southeastY previously referred to

(Fig.13).

the town of Waianae repeated through most of 1961 by Sunn, Low,

Tom, and Hara (1962a) (Figs. 8, 36, 37).

(d) similar surveys southwest of Kaneilio Point in October and

November 1961 conducted by Belt, Collins, and Associates (1962b);

-48-

(e) remarks by Tippetts, Abbett, McCarthy, and Stratton (1961)

concerning currents off BroTms Camp;

(f) Institute of Geophysics drogue studies 1 to 2 miles northwest

of Barber's Point in April and July 1963 (Fig. 35); and

(g) an Institute of Geophysics paddle-wheel current meter study about
1-1 miles northwest of Barber's Point conducted in July 196'
2

(Fig. 23).

The paddle-wheel current meter data from northwest of Barber's Point

(Fig. 23) indicate, for that areal a clear though somewhat complicated tidal

behavior, the flood current setting south and the ebb current setting

north-northwest. The flood current was more persistent than the ebb current

at the time of the measurement, although the opposite should have been

expected from the theory discussed in section 2.4. The currents, instead

of leading the tides, seem in general to lag behind. The maximum flood

current of about 1 knot was associated with the lower of the two high tides,

and the ebb tide velocities reached a still higher maximum of about 1.5 knot,

The nearby drogue observations (Figs. 34,..35) agree v@lth the -current meter

observations as to directions and strength of the currents. They indicate,

in addition, that the current strength tends to be considerably greater

in the shallow water close to shore than in the deeper water offshore, and

that there is a shoreward set in the deeper water during the ebb current

not found at the surface. The clockwise swing in current directions observed

in the early afternoon of 9 July occurred during a change from flood current

to ebb current.

The Tippetts, Abbett, McCarthy, and Stratton notes on currents at Browns

Camp are not inconsistent with the above information, but they add nothing

to it except that the current speed may occasionally reach 2 knots.

OSISAL
Barbers Pt.

AERO
0

M
e
T s
ARBERS PT

12 31 \0 Scheme of the

2 SET 13T MAGNITUDE
DUE TO POOF
1[4

T
SPEED SCALE

0.5 1KNOT
0
3 6A.M. NOON 6PM.

2- 4

0 Wind
-1 /-\N
10 5m sec-I (=10 knots)
I I
TIDE
APRIL 8, 1963 Depth contours in fathoms
A@ar b e r

06' 041 02' 1580 0 O'W 58'

Fig. 34. Results of drogue measurements of currents southeast of Barbers Point, April

SPEED SCALE

0 0.5 1 KNOT

TIDE CHARTS

6 A.M. 6 A.M. NOON 6 RM. 6 A.M. NOON 6 PM.
2- / -- 2 - /- \
I -\"I- @Iim - I / /1 11
0- 0

JULY 9, 1963 APRIL 9, 1963

-21022 21022,

10
210201- 210 20' 210 20'
M3 M,
M 2
3 14
1? 3 J14 5

3
'r5
50 10010 10
5
1@ 0 BARBER 50m CROSSES BARBERS
PT. PT.

one@
158010' 5e 158010, 158009'
4

Ir.
8 A R B E @R@

FATHOMS

Fig. 35. Results of drogue, measurements of currents northwest of Barbers Point on April 9
and July 9, 1963.

_49-

The Sunn, Low, Tom, and Hara (196&)study of the current systems in

Pokai Bay and off Waianae was in general a very intensive one, lasting a

year and utilizing drift cards, drift bottles, drogues, and dye. Two of

the drogue studies were carried through a 24-hour period. Together with

the Belt, Collins, and Associates (1962b)study of the currents off Kaneilio

Point, it provides an excellent picture of the current system of the area.

Off the points the currents are essentially reversing, but generally with

the same or a more exaggerated phase anomaly to the tides, as was described

from the current meter observations northwest of Barbers Point.

Phase anomalies were found similar to or more exaggerated than those

at Barbers Point, currents setting in the direction of the flood occurring

sometimes at low tide and currents setting in the ebb direction, at high

tide. Inshore, between the points, the currents were more erratic as a

result of eddy formation. The generalized patterns of ebb and flood currents

found are shown in Figure.36. Trade winds tended. to, deflect -the @

surface currents seaward and kona,winds to deflect them landward resulting

in upwelling and anstau conditions.

As previously discussed, the ebb current continues to set northwest-

ward to Kaena Point, whereas the southwestward flood flow along the Waianae

coast must stem from a divergence about 2 miles south of the Point.

4.13 Summary of Coastal Currents Around Oahu

The coastal currents around Oahu are apparently consistent in general

with the pattern expected from the distortion by the island of a current

while results from the superposition of a tidal current on a permanent

flow. The irregular shape of the island introduces considerable irregu-

larities into the pattern, and a few features of the currents do not

-50-

easily fit with the pattern expected.

The flood current apparently impinges on the island and diverges

generally at Makapuu. Point or in the vicinity of Waimanalo, but possibly

on occasion as far northwest as Ulupau Head. It appears to converge some-

where in the western part of Mamala, Bay. The ebb current diverges some-

where off Mamala Bay, probably off the western part and appears to have a

main reconvergence at Kahuku Point. Currents set almost continuously

northwesterly along the northeast coast and perhaps not quite so continuously

in the vicinity of Waimanalo consistent with expectations for the coastline

between the flood divergence and the ebb convergence. The currents also

set almost continuously westward past Kaena Point, as the result perhaps

of eddying around the point. Along other shores they generally reverse

with the tides, but one direction frequently predominates over the other.

In the bays and at other irregularities in the shoreline eddies are

formed. In some areas of Mamala Bay the current patterns are especially

irregular as the result of eddying and also of the relative weakness of

the tidal currents compared with wind drag and mass transport. In the

shallow water near Sand Island the currents sometimes set for several days

in one direction., then reverse.

Pearl Harbor shows the typical tidal circulation of a deep bay with a

narrow entrance. Reef and lagoon circulation is notable at Kaneohe Bay

and Ala Moana.

Figure37 shows diagrammatically the general pattern of the ebb currents

around Oahu during the trade-wind season. In interpreting this diagram

several points must be kept in mind. First, the degree of generalization

is somewhat variable from place to place. In some areas, particularly the

area of east-west divergence in Mamala Bay there are likely to be several

WAIANAE

.@@04

BAY
POKAI

@ZD

P 590 1000
YARDS

WAIANAE
Not% POK I BAY

0 500 1000

YARDS

Fig. 36. Generalized flood (top) and ebb (bottom) current patterns for Waianae area (from
Sunn, Low, Tom, and Hara, 1962).

Probable area
a, convergence
ring ebb current

Kahuku Pt.
c"

-21*401
Flood Curre

------ ------

-------- Waialuo
Say
Koeno Pt.
Strong current
I to 4 knots),\,--
usually not reversing
in tidol cycle

Current
directed
'I,,- awards
Pokoi Bay 0 A H

Current at the 1 , Current
su rface flows at',\ Pearl Harbor reversin
a small angle away---, but fl
from the coast.
I knot
\\1
2 1* 20'-
10
Barbers Pt. E.0 Honolulu Mokapuu P int
kll\ ------

Irregular Currents
----- ------

Area of divergence
during
ebb current

158* 20' 158* 1571 40'

Fig. 37. Generalized ebb current pattern around Oahu during trade wind season. Inset shows
flood current pattern.

_51-

zones of slope (north-south) convergence and many eddies whose positions

are not predictable, whereas in other areas the predicted prevailing current
be
may be expected to/strong and regular. Second, the chart should not be

regarded as a strictly synoptic one because the tide phases vary somewhat

in time from place to place, in general being about an hour earlier on

the north coast than on the south coast. The inset shows diagrammatically

the general pattern of the flood currents during the trade wind season.

The pattern during kona weather is less well outlined, but apparently

the main differences are in the irind effects on the surface currents.

Although there may be changes due to the seasonal shifts in the permanent

drift, these have not been identifiable. In any case they are likely to

be less pronounced than the random changes in the permanent drift, and

they are certainly less pronounced than the tidal changes.

5. COASTAL CURRENTS AROUND MOLOKA.I, LANAI, KAHOOLAVTE, AND 14AUI

5.1 Molokai

According to the Coast Pilot (Coast and Geodetic Survey, 1963a)

currents are re-ported to set westward along the entire northern coast of

Molokai, but there seem to have been no reliable observations.

Again according to the Coast Pilot: "Current observations have been

made at several places along the southern shore of Molokai between

Kamalo and Laau Point. They indicate, in general, an eastward flow

along the shore in the vicinity of Kaunakahai and Kamalo [with a velocity

of about 1 knot off Kamalo], and a westward flow near Laau Point.

Combined with these movements are tidal currents [with the flood setting

west and the ebb setting east] . . . The westward flow near Laau Point

is reported to turn sharply northward at the point A current

rip often observed off Laau Point is probably the result of the conver-

gence of the northwesterly current rounding the point and a southerly

current following the west coast. Currents are said to set northeastward

along the southeast coast. Coast and Geodetic Survey (1963b) observations

in the Kalohi Channel in 1961 show reversing currents, the flood current

with an average maximum velocity of 0.4 knot setting west-southwest and

the ebb current with an average mw,limum velocity of 0.5 knot setting

east-northeast.

5.2 Lanai

No reliable current measurements have been made around Lanai except

those in the Kalohi Channel, discussed in section 5.1, and those in the

-53-

-54-

A:uau Channel, discussed in section 5.4. It seems probably that the

flood tide current diverging off the northeast coast of Lanai converges

again off the southwest coast, and that the ebb tide current shows the

apposite relationshi-
.p. However, the tidal currents should be weaker

on the southwest side becuase of the lack of constriction in the narrow

channels, and the permanent west or northwest drift may predominate.

5.3 Kahoola,.@Te

According to the Coast Pilot the Drevailing current is westerly along

the south coast of Kahoolawe, swinging to northwesterly at the westerly

tip of the island. The currents in the Kealaikahiki Channel were found

by Coast and Geodetic Survey (1963a) measurements in 1962 to be weak and

variable and influenced by the wind. The mw:imum velocity observed was

0.'-- knot in a generally northeast direction. One may suspect that

systematic tidal currents could be found by careful analysis As

previously described, the currents in the Alalakeiki Channel are variable,

but the prevailing drift on the Kahoolawe coast is southeasterly,

5.4 West Maui

According to the Coast Pilot (Coast and Geodetic Survey, 1963a):

"The current at Lahaina usually sets northward and reaches a maximum

velocity of 1 or 2 knots before low water. Before high water the current

is normally quite weak and may set either northward or southward." A

confused current setting generally southward is reported at Mala, only a

mile north of Lahaina. Still farther north at Kekaa Point reversing north

and south tidal currents of 0.5 knot strength have been measured. The

phase relations are not stated. Offshore in the Auau Channel tidal

-55-

currents were measured by the Coast and Geodetic Survey in 1962. The

flood current, with an average maximurn velocity of 0.6 knot, sets east,

arid the ebb current, with an average maximum velocity of 0.5 knot, sets

west (Coast and Geodetic Survey, 1963b). In the Pailolo Channel,

farther north, weak, variable currents with a maximum velocity of 0.6 knot

were measured in the same season. It seems probably from these rather

meager and somewhat inconsistent data that (a) the dominant systematic

currents along the west coast of West Maui, as well as in the channels

between Maui and Lanai and Molokai, are tidal in nature, with the flood

current setting generally southwest in the Pailolo Channel, west in the

Kalohi Channel, and southeast in the Auau Channel@ (b) these tidal

currents, e:,-cept in the middle of the Auau Channel, are sufficiently

weak for wind or other random effects to complicate the general pattern;

and (c) the patternclose to shore, is complicated by topographic effects.

Northerly currents are reported off Napili Day by the Coast Pilot, but no

reliable current measurements seem to have been made along the north

coast of Maui from Kekaa Point to Kahului Bay.

5.5 Kahului Bay and Harbor

An intensive study of the current systems in Kahului Harbor and in

the bay just outside was conducted in August and September 1962 by

Herschler and RandolDh (1962) using surface and subsurface drogues, lath

floats, drift bottles, drift cards, and dye. All measurements vere made

during daylight hours in tradewind weather. The floats and especially

the cards and drogues were found to be affected directly by the wind, and

almost all of the apparent sets both inside and outside the harbor were

west or southwest, parallel to the wind. The dye studies showed tidal

currents reversizig near the harbor mouth and in the harbor, the flood

-56-

currents entering and the ebb current leaving the harbor, each with

maximum velocities of about 0.3 knot (Fig _ 36);..: i3ut_sade'the_qaar:&or

the dye studies showed a continuous westward drift past the entrance

with an average velocity of about 0.2 knot and no tidal reversal. This

drift turned northwest just west of the entrance, leaving room for an

eddy in the vicinity of the Wailuku S-_Wer outfall west of the harbor.

Upwelling outside the east breakwater was shown on a rising tide by

chloride content greater than normal. The chloride content of the surface

water in the harbor was progressively lower closer to shore as a result of

ground-water discharge. The dissolved o,,,njgen content and biological

oxygen demand of the water in the harbor indicated efficient flushing by

the tidal currents.

5.6 Worth Coast of East Maui

An eastward current has been reported off Pauwela Point and a

northeastward current off Nahiku by the Coast Pilot. It seems very

unlikely that these reports indicate the prevailing current direction,

and there seem to have been no reliable current observations between

Kahului and Hana.

5.7 South Coast

The reversing currents in the Alenuihaha Channel are described in

section 6.1. Near the south Maui coast, the dominance of the tidal

components is pronounced. At Kauihi Head, to the east, the Coast and

Geodetic Survey (1963a) has measured the south-setting flood current with

a velocity of 1 kno@,and according to the Coast Pilot, the north-setting

ebb current has a velocity of 1.5 knots. Near Alau Island the tidal

K A HU LUI BAY KAHULUI BAY
t
A'
WAILUKU
OUTFALL WAILUKU OUTFALL

Ilk
f 'f *. Ilk
K AHULUI OUTFALL KAHULUI OUTFALL

4- Ar

N HARBOR N 'HARBOR

1@00 2000 0 1000 2000
FEET KAHULUI TO@N FEET KAHULUI TOWN
1 962 1962
from from
HERSCHLER AND RANDOLPH HERSCHLER AND RANDOLPH
CONSULTING ENGINEERS RISING TIDE CONSULTING ENGIN EERS FALLING TIDE
HONOLULU, HAWAII WATER MOVEMENTI HONOLULU, HAWAII WATER MOVEMENT

Fig. 38. Generalized flood aeft) and ebb (right) current patterns for Kahului area (from Herschler and Randolph, 1962).

-57-

currents have velocities of 0.5 knot, and there is said to be an eddy

between the Island and Kauiki Head. Tidal currents of as much as

0.8 knot have been observed 1 niile southeast of Cape Hanamanioa

(Coast and.Geodetic Survey, 1963a), but the phase relations are uncertain.

5.8 Alalakeiki Channel

Coast and Geodetic Survey (1961a) observations in 1962 show the

current in the Alalake 41@i Channel to be variable, probably as a result of

tidal effects., with maximum velocities of 1 knot, and with a general net

northwesterly, drift of 0 - '5 knot aiOng the 1--laui shore

5.9 Southi,.@est Coast

A northwestward current has been reported in Maalaea Bay (Coast and

Geodetic Survey, 1963a) but no reliable current observations seem to have

been made anywhere along the southwest coast of 11aui from Makena to

Lahaina.

5.10 Summary of Coastal Currents Around Islands of the Maui GrouT)

Because of the shallow water connecting t@'iem, Molokai, Lanai,

Kahoolawe, and Maui probably act some@,,,hat as a unit in diverting the

permanent flow and tidal currents. It seems best therefore to summarize

together the currents around these islands of the Maui group. The

available coastal current data is shown in simplified diagrammatic form

in Figure 39, together with some speculative interpretations of current

directions shown with question marks.

On the basis of the theory discussed in section 2.5, it seems probable

that the principal flood current divergence is near the eastern point of

Maui, although the report of easterly currents along the northeast coast

-58-

of East Maui may indicate that the divergence moves sometimes to the

north point of East Maui. Supplementary areas of flood divergence -must

be located near the east end of Yioloka 4, the northeast point of Lanai,

and the east Doint of Kahoolawe. Flood convergences are probably

located somewhere in the vicinity of Olowalu, Maui, off the southwest

7)oints of Kahoolawe and Lanai, and off Laau Point, the southwestern

T)oint of Molokai. The principal convergence may be in any of the last

three areas, but seer-is most likely to be off Laau Point.

The DrinciDal ebb divergence is probably off the south point of

Kahoolawe. Subsidiary divergences are probably located in Maalaea Bay,

Maui, off the south coast of Lanai, and somewhere between Laau Point and

Kaunakakai, Molokai. The principal ebb convergence is probably off the

northeast tip of Molokai, and subsidiary convergences off the north

point of West Maui, the northeast point of Lanai, and the east point of

Kahoolawe.

160* 159* 158* 157o 156o

22o-NII AU

..........

I ena P -o

OAH X

MOLOKAI
C,

L... P

...........
Kahului B.
LANAI MAU I
A

KEAL IKAHI@l C.-/
KA LAWE A
ALALAKEIKI C. w4l

?
a/,

20*

K..h.W P.
HAWA

0 10 20 30

Scale in
Nautical Miles Kauna P.
Approx.
19*
LEGEND ?
A
H

FLOOD CURRENT
EBB CURRENT
-------- 100 FATHOMS

160* 159* 158* 1570 156'

Fig. 39. Generalized diagram of coastal currents around the Hawaiian Islands.

6. COASTAL CURRENTS AROUND HAWAII

6.1 Alenuihaha Channel

According to the Coast Pilot (Coast and Geodetic Survey, 1963a):

"Daring strong trade winds the [Alenuihahal channel is quite rough and

a current of 1 to 2 knots sets westward, but during the calms which fre-

quently follow, there is at times an easterly set of about 1 knot, and

during kona winds the easterly set may reach a velocity of 2 or 3 knots."

It seems probable that these observations pertain strictly only to the

surface layers most affected by wind drift. At depth, the reversibility

is probably a function not only of wind direction and speed but of tide

phase, the flood current vector setting southwest and the ebb current

vector setting northeast.

6.2 Northeast Coast

Along the northeast coast of Hawaii from Cape Kumukahi, the eastern

extremity, to Upolu Point, the northern extremity, the current sets

generally to the northwest, according to the Coast Pilot. However, as

noted by Belt, Collins, and Associates (1961a) muddy water frcm the sugar

mills along the Hilo Coast may frequently be seen moving southward. It

seems possible that at some times the permanent flow follows the coast

into Hilo Bay but at other times diverges from the coast at Leleiwi Point,

permitting an eddy or -tidal effects to cause a reversal in Hilo Bay. The

direction and strength of the trade winds may be influential in deter-

mining the current direction in the outer part of Hilo Bay.

-59-

-6o-

6.3 Hilo Harbor

Currents within Hilo Harbor, as shown by two surveys in January and

April le
,161, consist of a reversing component setting into and out of the

harbor, superimposed upon a net drift- out of the harbor resulting from

the discharge of the Wailuku and Wailoa Rivers (Belt, Collins, and Assoc.,

196-l'O. Velocities are not directly indicated in the report on the surveys

but appear to be less than 0.1 knot below the surface, as indicated by the

trajectories of dye patches. Subsurface drogues and especially surface

floats showed longer trajectories apparently influenced by the wind as

well as by the more rapid outflow of the fresher water at the surface. A

dye patch outside of the entrance drifted to the northwest, at less than

0.1 knot, showing no digression toward -Che entrance on a rising tide.

According to the Coast Pilot a north-northwest setting current of as much

as 1 knot has been reported in the approach to the harbor, probably when

the rivers are in flood.

The Belt-Collins study found pollution and stagnation in the harbor

indicated by both chemical and bacteriological conditions.

6.4 Southeast Coast

According to the Coast Pilot, the current sets generally to the

soixthwest along the southeast coast from Cape Kumukahi to Ka Lae, the

southern extremity of the Island. However, also according to the Coast

Pilot, there is an inshore counter current passing around Ka Lae in the

reverse direction and traceable as far as Keauhou Poirr@. It seems prob-

able that these observations indicate, in reality, a reversal with time

rather than a reversal with position, the stronger southwesterly current

resulting from the reinfcrcement of the permanent flow by a tidal current

-61-

during the flood and by the prevailing tradewind drift, a weaker reversed

current resulting at -the ebb.

6-5 SouthwestCoast

The configuration of Ka Lae suggests that an eddy may be formed in

its lee durink-11 the floodl so 'Uhat the current sets generally east-south-

east. The Coast Pilot in fact describes an inshore, southeast-settingg

counter current along the coast from Ka Lae to Kauna Point. From Kauna

Point to Keahole Point the current usually sets to the north-northwest.

Velocities approaching 2 knots have been reported in the vicinity of

Milolii, according to the Coast Pilot.

6.6 Kailua-Kona

Float observations off Kailua-Kona by the Department of Health in

may 1961 (H.A'.R. Austin and Assoc., 1961) appear to confirm the gener-

ally northwest set there. The floats used were obviously Greatly in-

fluenced by winds, and showed reversing trajectories that are probably

almost entirely the result of the sea breeze-land breeze wind pattern

characteristic of the area. There is some suggestion of the existence

of a south-setting ccmponent, or at least a slackening of the northwest

current, with the rising tide, but if so the tidal current is in phase

with the current expectable west of !Volu Point rather than the current

expectable west of Ka Lae. Austin, Smith, and Associates point out that

the sea-breeze would drive floatables on shore at Kailua-Kona.

6.7 Northwest Coast

Current rips are frequently reported north of Keahole Point, ac-

cording to the Coast Pilot; a 0.5 knot southwesterly current has been

-62-

observed at Kiholo Bay; and there is practically no current at Kawaihae.

These observations sugCest that the northerly current following the coast

south of Keahole Point sets offshore from the coast north of that PointY

leavin6 room for a south-setting eddy inshore. There are persistent

reports of a constant north-setting current off MahuJ4@ona, conver-inr, off

Upolu Point with the northwest-settini-, current following the northeast

coast of the Island. However, Coast and Geodetic Survey measurements off

Mahukona showed both north- and south-settinZ currents with velocities of

nearly 1 knot. It seems probable that these reversing currents are tidal,

the south set representing the flood and the north set the ebb, and that

the divergence between the normal north set at Upolu. and the normal south

set in Kawadhae Bay shifts north and south of Mahukona with the tide

stage.

6.8 Summary of Coastal Currents Around Hawaii

The available data on coastal currents around Hawaii, although

meager, suggest that the major flood divergence on the island is off

Cape Kumukahi. The location of the major flood convergence is uncertain

and may be anywhere from Kauna Point to Kailua-Kona. The major ebb

divergence is probably off Kauna Point, and the major ebb convergence

is probably off Upolu Point. There appears to be a large ebb counter-

current in the vicinity of Kawaihae, and there may be a counter current

at any tide stage in Hilo Bay. The available current information and

additional interpretation are diagrammed in Figure

7. SOME CHEMICAL, BIOLOGICAL, AND GEOLOGICAL OBSERVATIONS

PERTAINING To SEWAGE DISPOSAL

7.1 Distribution of Chemical Properties off Sand Island Sewer and in

Kaneohe Bay

The distributions of chlorinity, dissolved oxygen, and phosphates were

measured off the Sand Island sewer outfall in August 1962. The results,

shown in Appendix Table 5a and plotted in Figure 40, indicate that most

of the sewage is confined to a relatively thin surface layer, the thickness

of which increases slightly with distance from the source. The oxygen and

phosphate values suggest that the breakdown of organic matter is relatively

slow close to the source but speeds up farther away. Intensive phyto-

plankton growth has been noticed at a distance from the outfall,, presumably

resulting from the supply of nutrients from the sewage to the originally

relatively nutrient-poor oceanic waters.

Some additional chemical studies were carried out in Kaneohe Bay in

September 1962 to ascertain whether any stagnation of deep water occurs

there. The results are shown in Appendix Table 5a. A slight stagnation

of the deeper waters in the southeastern part of the Bay can be noticed

with respect to sewage disposal in these waters. The water exchange and

flushing of this part of the Bay are slow and the sewage is carried by

surface wind-driven currents toward the Kaneohe shore. Continued attention

should be given to the conditions in this part of the Bay, although the

values are not alarming at present.

-63-

-64-

7.2 Bottom Deposits off Sand Island Sewer

Pn intensive sampling of bottom deposits was made off the Sand

Island sewer outfall to a distance of about lffile. Bare areas of old

coral and other consolidated calcareous rocks were common, and where

there was a mantle of unconsolidated sediment, it was usually coral sand.

No organic or directly polluted sediments were found. The sampling indi-

cated vigorous biological growth on the bottom, especially downslope about

One -hQf dle from the shore where there were large colonies of mussels.

The relatively richer biological growth on the bottom suggests that the

sewage has a fertilizing influence. No direct effects of sewage on coral

growth or its breakdown were observed. There were no living corals in the

area investigated, and the pieces of coral brought up from the bottom did

not indicate any acceleration of breakdown.

7-3 Bacterial Die-off in the Sea

It has been universally found the bacterial concentrations in sea

water polluted with sewage are lower than can be accounted for by dilution

alone. The extra decrease in concentration has been variously attributed

to the activity of bactericidal agents in the sea water, bacteriophages,

or protozoans, to adsorption on sedimentary particles followed by sedi-

mentation, or to the effects of solar radiation. Various bacteria have

been found to be differentially resistant, but prior to 1959 the studies

on bacterial die-off in sea water had been dcne only in the laboratory or,

if in the sea, with dialysis tubes and laboratory cultures. The results

were therefore quantitatively suspect, and in any case could not have been

expected to pertain closely to conditions in Hawaiian waters.

DEPTH IN METERS DEPTH IN METERS DEPT
CD 0) .4 N 0
Q cp --------

tl N

(D III

0
bD

(D 0

0
t
0

b
CD w OD
0 -4
Z Ln
CD
0--o

_65-

A special study of the survival of sewage bacteria in the sea was

made by Iha in connection with the Holmes and Narver and Belt, Collins,

and Associates (1959a)study of sewage disposal possibilities ia Kailua

Bay (Iha, 196o). Actual sewage, dosed with a radioactive tracer and a

dye tracer, was introduced into the bay on five occasions, one each in

the months from April through September 1959. The movement of the dis-

persing cloud of sewage was tracked visually by means of the dye. A

sample was taken within a few minutes of the initial introduction and

additional samples were taken at intervals thereafter through periods

ranging from 40 to 116 minutes. The dilution of the sample was measured

by the decrease in radioactivity. Concentrations of both coliform bac-

teria and enterococci were measured by standard techniques.

The decreasing concentrations of both coliform bacteria and entero-

cocci, even after corrections for dilution, showed less t3aan 0.01 per

cent survival after 30 minutes. Sedimentation was found to be insigni-

ficant and bactericidal action of the sea water was judged predominantly

responsible for the die-off. The survival rate for the enterococci was

found to be higher than that for the coliform bacteria.

Iha's results were not expressed in terms that are directly usable

for computations of bacterial die-off in practical sewage disposal prob-

lems. Bacterial die-off has been expressed by previous investigators in

several ways, reducible to the following forms:
CB 1 = X k (Conway, date?)
CBO D

= exp (-kT) (Chick, 1900; Brooks, 1960)

-66-

= exp [-k (t -to)] (Ketchum and others, 1949;

Vaccavo and others, 1950)

where CB = concentration of bacteria

CBo = initial concentration of bacteria

D = dilution factor

X = distance from point of injection

t = time elapsed from injection

to = lag

k, k', k" = constants

Iha's results have been plotted in figure 41 in terms of the natural log

of the bacterial concentration ratios, allowing for dilution. To these

data linear regression lines have been fitted by least squares. The

results fit the form;

CB . CTo
= exp [ -k (t-to)]
CBo CT

where: CT = concentration of tracer

CTo= initial concentration of tracer

and the constants are:

Coliform
bacteria Enterococci
k 9.76 x 10-3 2.15 X 10-3

to -72 min. -308 min.

It will be noted that initial rates of decline in bacterial concen-

tration in Iha's experiments were more rapid than subsequent rates. The

apparent negative values for the lag, to, are a consequence. The reasons

for this behavior are not apparent, and the values of to are, perhaps open

4- __ I - L 1

A.COLIFORMS
T1076

-4-

-10

10 20 30 40 50 60 70 so 90 100 I;o 120

TIME, t min.

2- B.ENTEROCOCCI

0- .-4\

-2-
U: W
ix
ME
-4
\_OV

10 20 30 40 50 60 70 80 90 100 110 120

TIME, t , min.

Fig. 41. Bacterial die-off in sewage disposed off in the ocean.
(Computed from data of Iha, 1960.)
Roman numbers indicate months of experimental runs.
CB = concentration of bacteria
CBO = initial concentration of bacteria
CT = concentration of tracer
CTO = initial concentration of tracer

-67-

to question. Certainly a curvilinear relationship would fit the data

better than the linear relationship used, but the significance of the

improvement in fit would be questionable. It seems probable, however,

that the values of k are reasonably accurate for Kailua conditionsY and

certainly the over-all relationships are the best that are available for

Hawaiian conditions in Seneral.

7.4 Biological Oxyg@en Demand of Sea It7ater

A special study of the biolor,ical oxygen demand (BOD) of sea water

has been carried out by Laevastu, Zeitlin, and Song (me). With respect

to sewage disposal the main results of this study, which will be published

in a separate report, are that the routine methods of BOD determination,

as used with fresh water, are of questionable value in marine waters. The

oxygen consumption of sea water depends on numerous factors but is largely

a function of the ratio of solid surfaces and does not indicate directly

the degree of pollution or the power of self-purification. A method of

BOD determination involving filtration of the sea water after collection,

the use of standaxdized sample bottles, and the use of standardized

incubation conditions is recommended.

171
0)
0-

Sewer
CD out! a 11

CD
0 Surface current
r-

Sewer
CD
CD Subsurface Outfall
current

Section A-A

8. APPLICATION OF COASTAL CURRENT AND RELATED INFORMATION TO

SEWAGE DISPOSAL PROBLEMS IN COASV1 WATERS

It is the aim in disposing of sewage into natural waters that the

sewage be decomposed and dispersed in as short a time and distance as

possible, and paxticularly before the waters reach any shoreline or other

region where the sewage can be deleterious. In this discussion of means

to approach problems of sewage disposal at sea, the processes of dis-

pcrsal and decomposition will be discussed first, then methods of

analysis using coastal current data and other related information.

8.1 Processes of Dispersal and Decomposition of Sewage at Sea

When fresh s:--wage is introduced into the sea from an outfall on -the

bottom,, the sewage riszs to the surface because of i'U-s lower density,

diffasinr@, on th-- way up becauso of th.-- -turbulence induced by its own

motio@i. The diffusion may be promoted by injecting the sewage horizon-

tally through a "diffus-.@r" having several outlets. t the sc-trface the

sewage forms a s-mi-discrete body floating on and displacinn' the salt

wat,Dr. Within this body there i@ a radial spread from the point of its

emergence under the influence of any residual head undissipated in the

,iets rising to the surface. Eddy diffusion associated with the turbulence

of the ocea)i waters mixes the sewage with the flanking and underlying

salt water. The concentration of sewage in the body decreases, its

salinity increases, atid its boundaries gradually disappear. The ocean

current provides the continuous supply of sea water into which the sewage

can be mixed, and carries away the diluted sewage. A convective

-70-

circulation is also set up to replace sea water mixed into the

sewage Figure 42 shows diagramically the circulation pattern

established at a sewer outlet.

The currents transport the continuously expanding and diluting cloud

of sewage away from the area of its injection. Variations in current

direction and strangth complicate the picture, of course. In a rapidly

moving current the initial dilution may be great, whereas in a sluggish

current the sewage may remain relatively concentrated. With a tidal

current reversal, sewage that is born away from the sewer outlet and

diluted can later be carried back over the outlet and thus receive an

additional dose of pollution. Mass transport and particularly wind drag

may cause the surface and submerged parts of the sewage cloud to move in

different directions The wind may drive any floatables in a direction

quite unlike that taken by the suspended matter and the floatables may be re-

concentrated and transported in a concentrated state in a surface convergence.

The continuing dispersal of the sewage is largely the result of

turbulent mixing which is generated in several ways and on several

scales. On the largest scale is the eddying resulting from the insta-

bility of the major ocean currents. This major eddying and the orbital

motion associated with the tides lead to shearing which is responsible

for eddying on a smaller scale. Large-scale eddies are generated as

the currents move past islands- smaller scale eddies, as they move

past irregularities in the coastline or over irregularities in the

bottom. Still smaller scale eddies result from the shearing of the

surface waters over deeper waters, as with wind-driven currents and

mass transport. Regardless of the initial scale of the eddying,

-71-

the larger eddies break down to smaller ones with shorter characteris-

tic periods. Recordings of currents by paddle-wheel current meters

(Figs. 10, 17 through 23) or by Ekman current meters (Appendix Figs. 5

and 6) always show evidences of moderate-period turbulent fluctuations

of current speeds and directions. Shorter period fluctuations invariably

present cannot be recorded except by instruments having rapid responses.

The biochemical T)rocesses involved in the decomposition of sewage

in sea water are certainly at least as complicated as the physical

processes of transport and dispersal of the sewage, and can be no raore

than briefly summarized here. Depending on the o.7rygen availability in

the water, itself in part a function of the dilution of the sewage, either

of two possible causes of decomposition may be taken. Under stagnant,

anaerobic conditions the rate of decomposition is slower and the

products remain objectionable on both sanitary and aesthetic grounds.

Under the aerobic conditions that generally obtain where the dilution

is satisfactory, the rate is higher and the products are harmless.

The decomposition is accomplished mainly by the action of micro-

organisms, and under aerobic condibuions, is promoted by factors

favoring the growth and activity of the micro-organisms Temperature

is particularly important, the rate of deco=osition being materially

higher in the warm waters characteristic of Hawaii than in the cold

waters of or flowing froin high latitudes. The particle size is

important because with fineness of particles goes a high ratio of

surface to volume. Hydrogen ion and other chemical concentrations may

be influential.

-72-

The most important effect ol" decomposition is, of course, the

reduction in concentration of pathogenic micro-organisins, notably

bacteria. This is not ordinarily measured directly, bLit by concen-

tration of certain index coliforms streptococci, etc.
Local studie@s

(Iha-, 1960) have shown that bacteria! action of the sea water Dredomi-.

natdsover the effects of bacteriophages, protozoans, sedimentaticn,-or

solar radiation in reducint@ numbers of sewaL-e bacteria.

8,2 Estimation of Rates of Transport Disper-sal and Bacterial Die-off

Although the various processes in bacterial transport, dispersal,

and die-off in the sewage overlan and influence each other, their effects

cannot be estimated unless they are assumed to be somewhat separable.

Conventionally, two to five separate calculations have been involved

treating two separate stages as follows:

1. In.itial stage: Estimation of initial dilution and dimensions

of initial field.

2. Final stage: Calculation of combined effects of eddy diffusion,

advection and bacterial die-off in a steady current: calculation

of effects of eddy diffusion and bacterial die-off and super-

position of effects of steady or slowly varying currents; or

calculation of either of the above without the bacterial

die-off and superposition of the effects of bacterial die-off.

For the calculation of the effects in the jet or cone from a

diffuser several formulas are available, some rational and some empi-

rical (for a summary see Hyperion Engineers, 1957), the most complete
of which is one by Rawn, Bowerman, and Brooks (19 %). The results

vary somewhat, and there is some uncertainty as to their correspondence

-73-

to the initial parameters required in the eddy diffusion calculation.

Most significantly perhaps, the effects of the radial spread of the

sewage due to its head at the surface appear never to have been inclu-

ded in an analysis.

The great diversity o., methods of estimation occurs in the cal-

culation of diffusion effects. The basic reasons for the diversity are

the following:

1. Eddy diffusion is so extremely coriiplicated a phenomenon that

there is as yet no coikolete agreement even as to basic concep-

tions of its mechanism.

2. (a) The eddy diffusivity is riot a constant in a particular

fluid, as is its molecular diffusivity, but varies with the

scale of the phenomenon being studied. (b) The relationship

between diffusivity and scale may be quite complex. (c) Even

for simple cases there is disagreement as to the scale law

appropriate for adoption,

3. The differential equations, at best, are so complex that, in

oi@der to permit their solution, assumptions and approximations

must be made that render questionable the extent to which the

solutions are valid.

Good summaries of diffusion concepts and scale laws are given by

Sch6@nfeld and Groen (1961) and Okubo (i962), a simple method of analysis

is given by Brooks (1960), enO. a practical evaluation of several

formulas, rational and empirical, is given by Hyperion Engi-i-leers (1957).

Bacterial die-off is usually assumed to be exponential with tjxae,

although other, generally more complicated, relationships have been

-74-

proposed (see Hyperion Engineers, 1957). However@ the appropriate

exponential constant obviously must vary considerably, depending on

the availability of oxygen in the water, the temperature of the water,

the particle size distribution in the sewage, and other chemical and

physical characteristics of the sewage.

The current data, by itself or in combination with calculated

diffusion effects, may be used in the following ways:

1. The estimation of the range of likely transport directions

and velocities from prospective sewage release points. The

distances to which the directions of trans-Dort and the velo-

cities are of interest depend, of course, on the rates of

dilution and bacterial die-off and the lengths to which the

sewage may travel before the bacterial concentrations drop to

insignificance.

2. Appraisal of the likelihood of reinjection of sewage into a

dispersing sewage field due to current reversal.

3. Estimation of the general magnitude of dilution as a function

of distance and direction from prospective sewage release

points, using Lagrangian types of approach, such as those of

Joseph and Sendner (10,58) and Hela and Voipio (1960) from the

center of a patch of sewage introduced essentially instanta-

neously into the current and integrating numeri6ally-to

determine the effects of continuous introduction and advection.

4. Estimation of the efficiency of general flushing of bays and

similar coastal areas, using the strengths of current in and

out of the bays by the method discussed by Schoenfeld and

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Groen (1961).

5. The selection of -points probably favorable for sewage release,

i.e., points from which transport to shorelines of concern is

very slow or infrequent.

6. Appraisal of the possibility of accumulation of sewage in

current convergences.

8.3 Requirements in Coastal Current Studies for Sewage Disposal Projects

Certain complications seem liable in Hawaii to render inadequate

for actual design purposes the accuracy of predictions of sewage dis-

persal based solely on assumed currents and either rational or

empirical formulas for diffusion. Among these may be mentioned:

1. The effects of the similarities in size between the sewage

clouds of interest and both tidal ellipses and coastal and

bottom irregularities, which restrict the approximation of

eddy and tidal effects by either pure eddy diffusion of

simple scale law or pure advection.

2. The co=lications of wind-driven currents at variance with

deeper currents.

3. The significant increase in thicliness of the sewage fields

as the sewage is diluted.

The inescapable conclusion, then, is that a thorough local inves-

tigation must be made at the site of any major sewer outfall of uncer-

tain effects,,or at any major planned sewer outfall. Such an investi-

gation would involve the following stages:

1. Establishment of at least one and for a complicated area

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preferably two or more current-meter stations for long-term

(1 year or more) continuous operation in the area, at points

to be determined on the basis of the current components and

-nattern anticipated.

2. Conduction of drogue, dye, and supplementary short-term. current

meter studies throughout the area, at intervals and over

periods, to outline tidal and climatic effects.. correlating

these with wind, waves, tide, and tidal currents.

3. Determination from general considerations, from the results of

monitoring, and from estimates of dilution and estimates of

bacterial die-off, the critical conditions in the area.

At times rei)resentative of critical conditions determine

dilution over the field by release of dye or other traces in

sufficient quantities, and preferably b3@ continuous introduction,

at outfall sites or prospective outfall sites.

Studies of the sort outlined, to be adequate for design purposes,

will be far more extensive and costly than the studies that have

customarily been made in the past in Hawaii in connection with sewer

outfall projects. They will be jUStif4 ed, however, by the gains from

economies in sewage treatment and outfall construction that they will

make possible, and by the avoidance of losses that may be incurred

through restriction of shoreline uses due to health hazards if sewer

outfall plans prove inadequate.

9. CONCLUSIONS AND RECOMMENDATIONS

Various wastes are discharged at sea in Hawaii. Problems arise from

several, especially from sewage. The following major conclusions and

recommendations regarding the coastal currents of the Islands and their

effects on the dispersal of sewage at sea may be listed:

1. The dispersal of the sewage in the sea is critically deter-

mined by coastal currents in the vicinity of outfalls.

2. The coastal current may have several significant components:

the permanent flow, tidal currents, irind-driven currents, and mass

transport. At most places the tidal components predominate.

3. The tide waves move through the archipelago from north-

northeast to south-southwest. As a result of the superposition of

the generally west-northwest setting permanent flow, -'Uhe flood

currents diverge somewhere off the northeast side of each island,

swing clockwise around the southeastern shore and counterclockwise

around the southwestern shore, and converge off the southwest side.

The ebb currents diverge somewhere on the south side of the island,

swing clockwise around the western shore and counterclockwise around

the eastern shore,, and converge on the north side. Along certain

north-northeastern shores the current may set almost constantly

west-northwesterly, and along certain south-southeastern shores there

may be almost constantly a reverse set.

4. The tidal current movements tend to be reciprocating near

shore and elliptical offshore. Convergences and diveigences result

over the slopes of the islands.

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5. Irregularities in the shoreline and bottom configuration,

together with inertial effects, cause considerable phase disturbances,

distortion, and eddies in the current patterns.

6. Over reefs and in lagoons the major currents are generally

initiated by mass transport associated with waves.

7. The wind tends to drive the surface water in the direction of the

wind"s travel, which may be onshore or offshore although the currents

in depth set predominantly alongshore. Wind effects predominate in

the control of surface currents in protected bays.

8. Except in the irind-driven surface currents, seasonal changes

appear to be of minor significance.
C>

9. With the outflow of fresh sewage into salt water, an

independent circulation is induced in the vicinity of the outfall.

10. Turbidity, bacterial concentrations, and dye have proved

useable as tracers fcr sewage.

11. The critical conditions with regard to sewage disposal are

likely to result from a combination of onshore wind-driven current

and some particular tidal current direction.

12. There may be a very few sites at which an offshore set of

the current is so predominant that untreated sewage may safely be

introduced through outfalls of normal length. In general, however,

alongshore and shoreward sets occur, especially in the surface

layers due to wind action, with sufficient frequency as to make

inadvisable large discharges of untreated sewage within a few miles

in any direction from a shoreline intensively used for recreation

or for fishing.

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13. The critical conditions for the Sand Island sewer on Oahu

are an ebb current, perhaps prolonged by an eddy, and a kona wind.

Even during trade-wind conditions, se-vrage-laden water has been

traced east as far as the Kewalo entrance in about 6 hours. It

must flow farther east on occasion, and the floatables, in particular,

may be driven onshore. On other occasions the sewage-laden water

drifts north or west.

14. The bottom deposits off Sand Island sewer do not indicate

any accumulation or excessive pollution at the bottom.

15. Current velocities and mixing in depth are sufficient on

open coasts generally to minimize the risk of stagnation.

16. In deep estuaries, protected bays, and harbors, however,

there may be stagnant conditions. Such conditions have been noted

in parts of Kaneohe Bay and in Hilo Harbor.

17. The complexities of the coastal current patterns and the

status of theoretical knowledge of the eddy diffusivity associated

with them are such that no calculations of sewage dispersal from

general principles and assumed conditions are likely to be entirely

satisfactory.

18. Intensive local investigation should be made of dispersal

from major existing outfalls and planned outfalls, involving

continuous monitoring by current meter at a few sites, drogue and

dye studies to outline current patterns, and dye dilution studies

to indicate dilution at critical periods.

10. A14NOTATED BIBLIOGRAPHY OF COASTAL CURRENTS IN HAWAII

Austin,, H.A.R. & Associates. 1961.

Investigation, studies, and preliminary plans with recommendations

for a sewerage system within the Kailua-Kona area, Kona, Hawaii.

Report to Hawaii County.

Contamination in Kailua Bay now stems from cesspools near shore.
Central sewer system with complete treatment and inlan-1 discharge
is recommended because floatables from any ocean outfall would be
driven onshore by winds. Currents are not discussed, but measure-
ments by Department of Health, shown in exhibits, indicate current
setting usually northwest along shore sometimes having onshore or
offshore components, and sometimes reversing southeast.

Austin,, H.A.R. & Associates and Law & Wilson. 1960.

Engineering feasibility studies: Part I of the comprehensive plan,

Ala Moana Reef. Report to Hawaii Deparment of Land and Natural

Resources.

Current measurements made off Ala Moana reef and in channels Novem-
ber 1959 to March 1960 by 10-ft. float. Current generally set out-
ward through Kewalo, and Ala Mcana channels, but may briefly set
inward on a rising tide. Illustration shows currents off reef set-
ting generally to northwest though sometimes in reverse direction.
Most measurements were made at high or falling tide.

Austin, Smith, & Associates. 1960,

Engineering investigation report for improvement to Pearl Harbor

sewerage system, Pearl Harbor, Oahu, Hawaii. Report to U. S. Navy

Dist. Public Works Office, 14th Naval District.

Current studies made in and outside Pearl Harbor entrance by surface
and subsurface floats. Surface floats indicated current sets result-

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ing from wind, away from shore in trade weather, toward shore in
Kona. Subsurface floats indicated reversing current off Hickam
AFB and in Pearl Harbor entrance, but with a southwestward set
superimposed at the entrance which dominates at slack water.

Austin, Smith, & Associates. 1961.

Engineering investigation for the proposed Pearl City Sewage treat-

ment plant, Ewa, Oahu, Hawaii. Report to Division of Sewers, City

and County of Honolulu.

Tides in Middle Loch found to correspond in place with those in ocean,
though water level higher owing to fresh water discharge. Current
studies indicate that floating material discharged from proposed out-
fall in Middle Loch will be deposited on Middle Loch beaches, depend-
ing on wind. Stream flows and tides are also influential. Studies
are continuing.

Austin, Smith, & Associates. 1961.

North Honolulu sewerage studies. Report to Division of Sewers, City

and County of Honolulu.

Describes performance of Sand Island sewer outfall., constructed in
1950. Illustrations show slick fields from outfall Jln tradewind and
kona conditions. Time, tide, and detailed wind conditions are not
given.

Austin, Smith, & Associates and Metcalf & Eddy. 1962.

Report and master plan of the Pearl City Sewage Treatment Plant near

Pearl City, Oahu, Hawaii. Report to Department of Public Works,

City and County of Honolulu,

Results of bacteriological surveys show generally progressively
increasing coliform indices throughout harbor. No new current
surveys reported, but results of Austin, Smith,& Associates 1962
surveys used to estimate 8- and 24-hx@ "influence areas" about
proposed sewer outlet in middle Loch for various tide and wind
conditions. Treatment in successively greater degrees is proposed.

-83-

Belt, Collins, & Associates. 1961.

Hilo sewer system study. Vol. I. Hilo Bay area pollution and

preliminary investigation on its abatement and other related

studies. Report to Department of' Public Works, County of Hawaii.

Study of physical, chemical, and bacteriological conditions in Hilo
Bay in 10
.,60 showed efffect.-s of pol-Lution and st-agnation. Salinity
was low) turbidity high, pH generally on acid side, DO low, BOD
high, nitrates and phosphates high, Polii)tion sources were princi-
pally Waiakea Mill, Flintcote wallboard plant, and sewer outfall.
Water in bay is bact--rio-logically in prohibited class for bathing
33% of time, completely satisfactory only 16% of time. Muddy water
patches from sugar mills fron Hakalau south show southward drift,
at Laupahoehoe sometimes southward sometimes northward. Current
observations in western part of bay in April 1960 and January 1961
by dye, surface, and subsur-ILace floats show reversing movements
with outward trend resulting from discharge of Wailuku River.
Wind effects were negligible. Tidal effects were not described but
seem very important from charts provided.

Belt., Collins, & Associates. 1962.

Kaiale Bay small boat harbor: Preliminary engineering and feasibility

study.

Currents were observed on 2 mornings in the winter of 1961 by dye
and various sorts of surface floats. On both days surface drift in
Kaiaka Bay paralleled the wind, setting northwest on one morning,
west on the other. Direct wind effect on the floats was not taken
into account, Outside the bay the current set was southwesterly
on one morning. Bacterial counts in the bay were high inside the
bay, low outside, the oxygen content is low in the bay, indicating
stagnation.

Belt, Collins, & Associates. !Q62,

Kaneilio Point small beat harbor, Waianae, Oahu: Preliminary

engineering and feasibility study. Report to Harbors Division,

Hawaii Department of Transportation.

Off Kaneilio point currents, investigated by dye and floats, set
consistently northerly during one day's observation (on flood tide)

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in stormy kona weather, northerly in the morning (ebb tide) and
southerly in the afternoon (after tide turn) in one day in trade
weather. Bacterial analyses showed excessive pollution near the
sewage outfall but generally satisfactory to doubtful levels
elsewherealong the shoreline.

Belt., Collins, & Associates. 1962.

Waialua Bay pollution study, Haleiwa, Oahu, Hawaii. Report to

Harbors Division, Hawaii Department of Transportation.

Currents studied by surface and subsurface floats, dye, and drift
cards. Bacteriological analysis run on samples. In trade weather
on rising tide and just after high tide, current from bay sets
southwest. When streams were in flood, kona wind currents were to
NW just after low tide, moving to N on falling tide. During light
westerlies and with heavy surf currents set toward WNW on rising
tide, NNW just after high tide. Coliform counts were high at Haleiwa
Beach during trade wind conditions, high generally during flood and
high surf conditions.

Bureau of Sanitation. 1941.

Honolulu sewage disposal survey, May 1940 - September 1941.

Report to Honolulu Chamber of Commerce and Territory Board of Health.

Refers to float surveys of currents made in vicinity of Kewalo out-
fall, 1926, described as inadequate. Currents are difficult to
determine but seem to flow either in Diamond Head or &ra direction.
Slicks are noted frequently on calm days to extend toward Waikiki,
,once to about 5000 feet., with small organic particles going beyond.
Thorough bacterial analyses showed pollution field southeast of
outfall over 17 months. Practically all monthly sample fields
showed a tongue of high pollution extending southwestward from out-
falls; the greatest extent being in February 1941, when there was
a B.coli concentration >1000/100 ml 1 mile off Kuhio Beach and
>1706/-100 ml 1 mile off the natatorium. The Ala Wai canal served as
4
an additional center of pollution.

Coast and Geodetic Survey. 1963.

U. S. Coast Pilot 7: Pacific Coast 9th edition4

There is a prevailing westerly drift in the vicinity of the Hawaiian
Islands. Variability is believed mostly a function of wind, but

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strong northeast currents setting against trades have been reported.
The currents in the Alenuihaha Channel and around Kauai are reported
to be controlled especially by the wind. Around each island currents
have been reported to set generally to west or northwest, however,
counter currents have been reported close inshore in some areas, as
around the southern part of Hawaii. Rips have been noted near Keahole
Point on Hawaii, Laau Point on Molokai, Kaena Point and Kahuku Point
on Oahu. Recent observations, mostly in 1962,indicate that the
currents reverse with tides in many places, even at some places where
previous information suggested a non-reversing current. Tidal currents
were noted specifically near Aahukona on Hawaii; Hana, Cape Hanamanioa,
Lahainal and Kekaa Point on Maui; in the Kalohi Channel; Maunalua Bay
and Honolulu on Oahu; Mana and Nohili on Kauai; Kamalino on Niihau,
and in the Lehua Channel.

Coast and Geodetic Survey. 1963.

Tidal Current Tables, 1963, Pacific Coast of North America and Asia.

The following tidal currents are listed in Hawaiian waters:

Place Lat. Long. Max. flood Max.-,ebb
Dir. Vel. Dir. Vel.
Kalohi Channel 21 0021 156056, 2350 o.4 kt 700 0.5 kt
Auau Channel 20053' lc6043' 700 o.6 kt 2700 0.5 kt

Divi.sion of Sewers. 1951.

Report on ocean current studies for Sand Island outfall sewer,

Honolulu, Oahu,T. H.

Drogue and current pole measurements were conducted 2 or 3 times a
week in various periods of weather September 1950 to May 1951 from
near the end of the Sand Island outfall. Current pole measurements
indicated currents setting on the average 30 0to the right of the
wind and averaging about 4% of wind velocity .with better correlation
when winds were strong than otherwise. A "tide" current was men-
tioned but apparently in the sense of a prevailing flow. Possibility
of reversing tidal currents was not recognized. Current reversals
CD
were noted but ascribed to eddies or to tidal outflow from Pearl
Harbor. Current at the outfall was estimated to set W,, 270,daysl
E, 37 days, S, 44 days and N, 14 days out of the year. Report does
not include nor illustrate data except for 16-17 May 1951.

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Division of Sewers. 1957.

A report on sewerage master plan for Kaneohe, Koolaupoko, Oahu.

Report to Department of Public Works, City and County of Honolulu.

Bacterial analyses in Kaneohe Bay show very low concentrations except
close to shore. No current studies were made and wind and tide
conditions at times of sampling are not given.

Division of Sewers. 1957.

A report on sewerage master plan for Waipahu, aTa, Oahu.

Report to Department of PuIblic Works, City and County of Honolulu.

Recommends outfalls for treated sewage in shallow water in West Loch
in belief oxygen will be adequate for aerobic decomposition, and
slick field will not be objectionable. Need for control of hydro-
graph at outfall recognized to prevent anaerobic bottom deposits.
No current measurements.

Division of Sewers. 1958.

Report on sewerage master plan for Aiea to Pearl City, Ewa, Oahu.

Report to Department of Public Works, City and County of Honolulu.

Present Aiea sewer outfall in East LochPearl Harbor at base Pearl
City Peninsula. Waiawa Stream discharge counted on for dispersal
from proposed outfall for sewage in Middle Loch, but current studies
recommended.

Helfrich, P., and Kohn, A. J. 1955.

A survey to estimate the major biological effect of a dredging

operation by the Lihue Plantation Company on North Kapaa Reef,

Kapaa, Kauai. Report to Lihue Plantation Company.

Float measurements in October and November 1955 in a variety of wave
and wind conditions showed southerly currents on the North Kapaa reef
resulting from mass transport by breakers onto the reef. Average
values of current were about 1 ft/sec on the central portion of the
reef'and abcut 1.5 ft/sec at the south edge near an inlet.

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Herschler & Randolph. 1962.

Study of pollution in Kahului Bay, Maui, Hwjaii.

Report to Hawaii State Department of Health.

Sewage is discharged to bay through Kahului outfall east of' Kahului
Harbor and Wailuku outfall west of harbor. Additional pollution
reaches bay through Iao and Kalialinui Streams. Currents were
measured with surfaCe and subsurface drogubs, lath floats, drift
bottles, drift cards, and dye. All measurements were made during
the day during trade wind weather. Drogues, especially', were
observed to be affected directly by the wind and almost all apparent
sets, both inside and outside harbor, were toward west or southwest
parallel to the wind. Dye studies showed tidal currents reversing
near harbor mouth and a possible eddy near Wailuku outfall, but
otherwise westward drift outside harbor, turning to northwest off
Iao Stream mouth; but no tidal reversal. Upwelling was noted out-
side the east breakwater on a, rising tide. Chemical sampling
showed generally high DO and low BOD except, in the vicinity of the
Kahului outfall. Chlorides were in general low at the surface at
the southwest shore of the harbor and increased toward the harbor
mouth and in depth. Bacteriological sampling showed a high coli-
form field at the surface outside the breakwaters .7 but low concen-
tration generally at the surface elsewhere. Illustrations show
that in the harbor coliform the concentrations were consistently
greater at depth than@at the surface. In the vicinity of the
Wailuku outfall the pollution field seems from'an illustration
to drift southeastward at low tide and northward at high tide.
A new Kahului outfall to deeper water is recommended.

Holmes'& Narver,.Inc. 1957.

Report and master plan of sewerage facility for Kailua, Koolaupoko,

Oahu. Report to City and County of Honolulu.

Currents outside reefs in Kailua Bay are reported to parallel shore,
though direction is not indicated. The currents inside the reefs
are reported to be only wind-generated and weak. Oxygen concentra-
tions are hign. No details of times or conditions of observation
are given. A sewage treatment plant on Mokapu peninsula, a tempor-
ary outfall to Nuupia Pondand an eventual outfall to Kailua Bay
are recommended.

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Holmes & Narver and Belt, Collins, & Associates. 1959.

Kailua ocean outfall sewer., ocean portion. Kailua sewage treatment

plant, Kailua, Koolaupoko, Oahu, Hawaii. Report to Department of

Public Works,, City and County of Honolulu.

Report on oceanographic environment of proposed Kailua sewer outfall
at base of Mokapu peninsula based on 12-months observations. Current
observations made with dye, surface floatsand subsurface drogues.
Wind conditions and tide during period of observations illustrated,
but not in such a way that changes can be correlated with current
changes. Conclusions are drawn that surface currents are wind driven,
sometimes slower, sometimes faster than Eckman's theory indicates,
but usually trending to the right of the downwind direction, in accor-
dance with theory. Subsurface currents, however, move generally to
the north and never to the south, in spite of winds generally from
the north. Tide effects are not discussed and are not apparent in
charts. Kailua Bay is now unpolluted except at the outlet of the
Kawainui Canal. Chemistry is normal except for lower salinity, higher
nitrogen, and lower oxygen near the canal outlet. Dilution and bac-
terial die-off at the proposed sewer outlet were checked with injected
mixtures of dye, radioactive carbonate, and sewage. Dilution gener-
ally reduced chemical concentrations within 90 minutes to 0.1 to 0.3
of concentration 5 minutes after injection. Bacterial die-off in
the same time reduced concentrations to 1/1000 to 1/100, even allow-
ing for dilution. The outfall site is judged satisfactory.

Holmes & Narver and Belt., Collins, & Associates.. 1959.

Nuupia Pond outfall study. Kailua sewage treatment plant, Kailua,

Koolaupoko, Oahu. Report to Department of Public Works, City and

County of Honolulu.

Investigation of Nuupia Pond (shallow walled-off arm of Kaneohe Bay)
as a potential temporary outfall site for the Kailua sewer system.
Currents in the pond were found to be wind driven. Aeration and
mixing are sufficient to allow- -treated sewage to be discharged into
the pond as an interim measure.

Hyperion Engineers. 1957.

Ocean outfall design.

Brooks T (coefficient of time required for 90% bacterial die-off)
and Con-ways K (log dilution ratio/distance) are estimated from
1952 survey of pollution from Ala Moana and Ward Avenue outfalls

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and estimated or assumed values. Assumptions are: initial dilutions
of 8 for Ala Moana, 20 for Ward Avenue; initial concentration of
430,000 coli-forms/ml in the boils, field depth 3 to 4 ft and width
1000 ft, 1-1@7tward current of 0.7 ft/sec., initial eddy aiffusivity
of 3.68 ft 3 hr-1. T ranged from 0.21 hr at 1700 ft to_@'-05 br
L
at 12,000 ft; K from 21 x 10-4/ft at 1700 ft to 4.7 x 10 /ft at
12,1000 ft. The values of T are particularly low and those of K
particularly high as compared with East and West Coast experience.
The increase in T and decrease in K with distance are generally
found, although there are supposed to be ccnstants.

Iha, T. H. 196o.

Survival of sewage bacteria in the sea.

M.S. Thesis, University of Hawaii.

Review of previous work shows bacterial concentrations in polluted
sea water always lower than explicable by dilution alone. Bacterial
disappearance attributed variously to bactericidal agents in sea
water, bacteriophages, protozoans, adsorption and sedimentation,
solar radiation. Various bacteria found differentially resistant.
Previous work all either done in laboratory or with dialysis tubes
and laboratory cultures in sea. Present experiment introduced radio-
active sewage in Kailua Bay. Dilution measured by decrease in
radioactivity. Concentrations of both coliforms and enterococci,
corrected for dilution, showed reduction of 99.99 percent in 30 min-
utes. Sedimentation was insignificant and bactericidal action
judged predominant. Enterococci survival was higher than coliform.
Laboratory studies confirmed insignificance'of sedimentation. Longer
bacterial survival in laboratory considered due to higher ratio- of
solid surfaces to volume in laboratory. Effects of temperature
variation were found insignificant. Storage of samples might account
for 101;,Io at most of bacterial reduction in dilute samples.

Industrial Waste Disposal Study Coimission. 1955.

Report of Industrial Waste Disposal Study Commission to 28th

Legislature, Territory of Hawaii.

Tabulation of industrial waste disposals and reports from concerns
and agencies disposing of wastes or interested in results. Board
of Agriculture and Forestry and Tuna Boat Owner's Assn. reported
frequent oxygen deficiency in Honolulu and pollution in West Loch,
Pearl Harbor on Oahu. Damage to inshore fisheries on Kauai,
reduction in bait fish production in Hilo Harbor and interference
with shore recreation and fishing along liamakua Coast on Ha-vraii,
interference with shore recreation near Iao Stream mouth on Maui.

-go-

Department of Health reported -odor problems in Hilo Bay, reduction
in problems on Maui. American Factors reported that at the outfall
for muddy water from Lihue Mill on Kauai current sets usually to
south, though sometimes to the north in kona weather.

Keller, A. R., S. W. Tay, & G. M. Collins. 1920.

Preliminary report on proposed sewer extensions in the Waikiki and

Kali4i Districts; ai-so alleviation of the nuisance of Nuuanu Stream,

Report to Mayor and Board of Supervisors, City and County of Honolulu,

Tidal and stream-flow flushing is insufficient to overcome pollution
and stagnation caused by overflows from the sanitary sewer. Though
no current measurements appear to have been made at Waikiki tidal
currents are reported such that sewage discharged offshore might be
carried inshore. No outfall closer to Waikiki than that at Kakaako
is recommended. Float observations in Kalihi channel indicate that
prevailing current will carry sewage seaward from a proposed new
outfall at Kalihi. Ultimately this sewage, that from the old Kalihi
outfall and from Fort Shafter,will have to be connected to a central
pumping plant discharging over the reef.

Lublin, 1* Gaughey, & Associates. 1962.

Plan of development for Hana Harbor. Report to Hawaii State

Depattment of Transportation.

Tidal currents are reported of relatively low velocity in Hana
Harbor except in vicinity of existing wharf and Puukii Islandi,
Direction of current not given. No details as to time of
observation nor conditions pertaining at time.

Lublin, McGauhey, & Associates. 1962.

Plan of development for sampan harbor, Wailoa River, Hilo, Hawaii.

Report to Hawaii Department of Transportation.

Wailoa River peak discharge of 1000 ft-/sec (1.3 ft/sec) can be
expected annually. Maximum tidal current 1.0 ft/sec on spring
ebb.

_91-

Marine Advisers, Inc. 1961-1962.
Oceanographic investigation in connection with proposed Waimanalo
outfall. Report made to R.M. Towill. Corporation-Engineers.

Set of charts of the Waimanalo Bay area of data taken on 16 differ-
ent days between September 25, 1961 and October 31, 1962. Fifteen
charts show drogue tracks vs tides and wind conditions on as many
days; nine charts show temperature and salinity; and nine charts
show dissolved oxygen concentration and water density for as many
days. Three charts show bacterial analysis on four different days:
standard plate count, coliform count, and enterococci count. Three
charts show nitrates and phosphates and three charts show biochemical
oxygen demands and pH for as many days. One chart shows suspended
solids on one day.

Currents were found to reverse, but do not follow any simple pattern.
On two days drogues released in the bay drifted around Makapuu. Point
and were picked up off Hanauma Bay. On one of these days there was
a slight kona wind, and on the other day there was no wind. In
general the surface drogues showed a definite tendency to go down
wind, with the deep drogues (depth not known) showing a tendency to
follow the depth contours. [Report text not seen.)

Metcalf & Eddy. 1944.

Report to Honolulu Sewerage Committee upon sewerage and sewerage

disposal, vols. I and II. Boston.

Comprehensive report on Honolulu sewerage problems. Discusses
history of sewer system and outfalls. Reports observations April-
June 1944 o.n slick field, sewage solids, and bacteria from Kewalo
sewer outfalls; also Tay's observations in December 1940-January
1941 (Bureau of Sanitation, 1941). Concludes that under trade-wind
conditions sewage moves entirely toward west from Kewalo, though
easterly movement was found by Tay in winter. No details of times
and tide conditions at times of observation, except for two days
in July 1944 when milk bottle caps traced from Kewalo outlet,
moving west on one day and north and west on second, with wind
from south. Concludes that sewage should be led to Sand Island.,
and subjected there to short-period sedimentation.

Public Health Service. 1963.

Municipal and industrial waste facilities, 1962 inventory, Hawaii.

U. S. Department of Health, Education, and Welfare.

Tabulation of municipal and industrial waste facilities for all of

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the islands, with notes on type of waste, treatment, etc. and
reference to health problems resulting. No information on currents.

Sunn, Low, Tom, & Hara. 1962.

Report on oceanographic survey and study to sewage disposal for

WaianaeY Oahu. Report to Department Public Works, City and

County of Honolulu.

Bacteriological analyses showed Waianae beaches to be generally
Class A except in vicinity exi St4 ng Kaneilio Point outfall. High
coliform counts were found more than 1000 feet from this outfall.
Dissolved oxygen was generally high except near outfall and in a
sometimes-isolated stream mouth. BOD phosphates. and nitrates
were generally low. Salinity was generally reduced from normal
but salinity profiles were inconsistent. Transparency was
exceptionally high. The depth to the thermocline was about
300 feet in winter, 150 feet in summer. Current studies extended
a year and included two 24-hr studies. Drift cards, drift bottles,
drogues and dye were used. Current-meter studies were unsuccess-
ful. Currents were correlated with tides as locally recorded.
Some drift cards and drift bottles released off Waianae beaches
were found on shores to southeast within several tenths of a mile
in a few hours, and as far as &-a Beach in 8 days, and Keehi
Lagoon in 27 days. Others were found on shores to the northwest
within several tenths of a mile in a few hours, as far as Kaena
Point in 7 days, and on Kauai and Niihau in 10 to 23 days. Drogue
studies indicated currents induced largely by tides, with movements
preponderantly oscillatory parallel to shore. Off points, flood
current sets southeast, ebb current northwest. Eddies are set up
by irregular bottom topography, as at Pokai Bay. Generalized flood
and ebb patterns were portrayed. Trade winds tended to deflect
drogues seaward; kona winds landward. Preliminary dilution was
calculated by Rawn-Palmer formula and subsequent dilution and die-
off by Pomeroy formula for proposed outfalls. Primary sewage
treatment with a 2400-foot outfall was recommended.

Sunn, Low, Tom, & Hara. 1962.

Report on sewage disposal for the Hawaii-Kai development.

[Report text not seen.] Illustrations of results of three cruises
show semi-diurnal tidal currents measured by drogues, setting north-
east with ebb (velocities to 89 ft/min), southwest with flood
(velocities to 107 ft/min). Change from flood to ebb. Drift cards
and bottles released in area were picked up at Hanauma Bay (2 days
min.), Makapuu Beach (2 days), Kailua Beach (2 days), Kaneohe Bay
(2 days), Maunalua Bay (14 days), Black Point (5 days), Honolulu
Harbor (16 days), wailua, Kauai (23 days).

-93-

Tippets, Abbett, McCarthy, & Stratton. 1961.

Development plan, deepwater port at Barbers Point, Oahu, Hawaii.

Report to Estate of James Campbell.

Tidal currents are reported generally weak. A westward drift is
said to prevail. Current measurements at Erown's Camp indicate
variability in direction and velocity range from 0 to 0.5 kts,
occasionally to 2 k-ts.

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DATE DUE

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