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

                                                                                                Ae

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

                                                              By

                                    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

                                                        iv

                                               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

                                                       v

                                            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

                                                         Vi

                                               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

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

                                                                                0

                                                                                     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.

                                                       -5-

                        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

                                                  -6-

              .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.

                                                             -8-

                                                          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

                                                      -9-

                        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.

                                                  -10-

                    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

                                                     if

                                    se 4,

                                          IL A--,                        at

                                                                           go,
                     20                                                                                                         20

                                .Z  4-

                                                            VL

                      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

                                                                                               N@

                     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

                               zo

                                                                                                                                                                                                                                                HAV

                                                                                                                                                                                                                             0

                                                                                                                                                                                                                                  5i

                               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

                        (c)  In general there are inequalities on most parts of the

                             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

                                                                                        M

                                                                    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

                      in

                                                       OFF SHORE

                                 0

                                      0

                                            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

                             +

                                                            CL

                           /*

                       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.

                                                                                                 2

                                                                                  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@

                                                                                    0

                                                                                                                     0

                                                                                                                                                                                                                        ............
                                                                                                                     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. ECLd@.-ing 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 t1@3.hapuu, 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

                                                             0

                                                                                                                       3M
                                                                                                Currents
                                                           WAIMANALO                         at 5nn depth                            'to

                    210 20'N
                                                                                                                        (J@   Monana
                                                                                                                             11     Island

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

                                                                                             at

                                                                               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

                                                                       0

                                                                                       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

                                                                               5

                                                                         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

                                                                                    0-

                                                                                                                                                     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

                                                            w

                                                                0-

                                                                                                                                                                                                                                                               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

                                                                      0-

                                                                                                      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

                                                                      0-

                                                                                 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

                                                                                                                                                                                                                                                                 A

                                                             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-

                                                               W

                                                                   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

                                                                                                                                                                                                     S

                                                                    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

                                                            10

                                                        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

                                                                                             2-

                                                                                                            Jul

                                                                                            0

                                                                         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.

                                                                                                                                                                       Z:

                                                                                          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;

                                                                                                                                                                                                            0

                                                                                                                SAND ISLAND                                 H 0 N 0 L U L U

                                                                                  3M
                                                                                     1,5
                                                                                     ix,                                                                       ALA MOANA
                                                                                                                                     IM,
                                                                                                                                    A
                                                                                         A        --------------  -------

                                                       5of

                                                   _10of

                                                                          --------------------
                                                                                         B =5
                                                                  ..........

                                                                                                                                                                                                             AX

                                                                                                                                                                                                                    'of

                                                                                                                                                                                                                  sot
                                                                                                                                                               AL.,

                                            Fig. 29.           Results of drogue measurements of currents in the eastern part of Mamala Bay, M

                                                                                     158-54!                                                                                               15W50'

                                                                                                                                                                                                             T,

                                                                                                            SAND ISLAND                                      H   0   N   0  L   U   L  U

                                         _2

                                                                                  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

                                                                                                                                                                                                       :v

                                                                                                                                                            @F

                                                                                                                                                                                                  A

                                                                                   ----- 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

                              LU

                             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

                        V4

                                                     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).

                        (c) float,drogue, and dye surveys in Pokai Bay and in general off

                            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

                                                                         A

                                                                                         2 SET 13T  MAGNITUDE
                                                                                                    DUE TO POOF
                                                                     1[4

                                                          T
                               SPEED  SCALE

                                    0.5       1KNOT
                         0
                        3      6A.M. NOON   6PM.

                        2-                                                               4

                                       IV

                        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,

                                                                                                           12

                                                  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*

                                                                                                          N

                                                                                                                                                                                                        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

                        CD

                                                                                                                           LW

                                                                                                                                                                                               3

                                                    _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

                      5

                      U_

                           -4-

                         -10

                                      10       20       30      40       50        60      70        so      90       100      I;o      120

                                                                             TIME, t   min.

                            4-

                            2-                                                                         B.ENTEROCOCCI

                            0- .-4\

                           -2-
                      U:                                          W
                                                                                                               ix
                                                                                                                                   ME
                          -4
                                                                            \_OV

                            8-

                           10

                                      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

                                                      -75-

                            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

                                                  -76-

                        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.

                                                     -77-

                                                -78-

                         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.

                                                    -79-

                             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-

                                                    -81-

                      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)

                                                    -84-

                      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

                                                          -85-

                           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.

                                                   -86-

                 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.

                                                     -87-

                  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.

                                                   -88-

                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

                                                      -89-

                         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

                                                     -92-

                       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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                                                    -95-

                                                  -96-

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                                                     -97-

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                                                 -98-

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                                                   -99-

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                                                 -101-

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