HAMAU-T-81-001 G.2

an eson s u as Revealed by erial Photo ra s

Dennis Hwang

II lhti I!!] !

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C! C> Beach Changes on as Revealed by Aerial Photographs

Dennis Hwang

July 1981

This document was prepared for the State of Department of Planning and Economic Development by the Urban and Regional Planning Program and the Hawaii Institute of Geophysics, University of Hawaii

Technical Supplement Number 22, Coastal Zone Management Project, Urban and Regional Planning Program Technical Report HIG-81-3, Hawaii Institute of Geophysics Cooperative Report UNIHI-SEAGRANT-CR-81-07, UH Sea Grant College Program This report has been cataloged as follows:

Hwang, Dennis. l. Aerial photography in geomorphology. 2, Beach erosion-Hawaii. Beach changes on Oahu as revealed by aerial photographs. Prepared 3. Beaches.I. University of Hawaii !. Urban Regional Plan- by the Urban Regional Planning Program, Hawaii Institute of Geophys- ning Program. II. University of Hawaii Honolulu!, Hawaii Institute of ics, and Sea Grant Program, Univ. of Hawaii for the Dept. of Planning Geophysics. III. University of Hawaii Honolulu!. SeaGrant Program. and Economic Development, State of Hawaii. Honolulu: Hawaii Coas- IV. Hawaii. Department of Planning and Economic Development. V. tal Zone Management Program, DPED, State of Hawaii, 1981. Hawaii Coastal Zone Management Program; 1-Sup, 22. VI, Title. HT392.H321.No. 1-Sup. 22 x fr. Hawaii Coastal Zone Management Technical supplement 22 Hawaii Coastal Zone Management Pro- Program! gram; 1; HIG-81-3; UNIHI-SEAGRANT-CR-81-07! ABSTRACT

An aerial photographic analysis of the beaches of Oahu was conduct- The sandy shorehne on Oahu has been placed into the following ed for a period of up to 50 years. The results indicate that the most management categories: unstable beaches are on sand bodies projecting from the coastline, such as Kualoa Point, Iroquois Point, and Paiko Peninsula. I! Hazard Areas are subject to inundation by large winter waves. Beach changes on Oahu can be characterized by the coastline. On the , intermittent erosion occurs when the beach is overwashed ! Chronic Erosion Areas have a long-term history by waves of unusual height and force, Aerial photographs record the ef- which indicates erosion will continue in the future. fects of the December 1-4, 1969 storm, 1946 tsunami and possibly the 1957 tsunami. ! Unstable Beaches have an alternating history of ero- sion and accretion. These changes are unpredictable. Beaches facing the northeast trade wind direction are especially dynamic systems. The large long-term changes at Kualoa Beach, Kailua ! Stable Beacheshave had a small net change and range Beach and Lanikai Beach are partly caused by variations in sand trans- in the position of the vegetation line. port along the shoreline. Erosion problems on the windward coast exist at north Kahuku Golf Course Beach, Kalanai Point, Laniloa Beach, ! AccretingBeaches have grown continuously seaward. Hauula Beach Park, Swanzy Beach Park, Kaaawa Beach Park and Waimanalo Beach, The first three categories are of the greatest concern to coastal managers. Along much of the south shore, waves break at the seaward edge of a shallow fringing reef. As wave energy is reduced, many of the beaches are relatively stable. Erosion during the 1967 to 1971 interval, however, occurred at Hanauma Bay, east Kahala Beach and Paiko Peninsula, , which is not protected by a fringing reef, also eroded during that period. Ewa Beach experienced erosion between 1958 and 1967. West Iroquois Point has been chronically eroding.

On the leeward coast, the south end of Kahe Beach and the ends of Maili Beach have a history of persistent erosion, Most other beaches had no apparent long-term change. Nevertheless, periodic damage to the backshore area may occur from large Kona Storm waves or refracted North Pacific swell.

ACKNOWLEDGMENTS

This report was prepared for the State of Hawaii Department of Plan- This study was reviewed in whole or part by Earl Matsukawa Urban ning and Economic Developmentby the CoastalZone Management and RegionalPlanning Program, URPP!, Cindy Bower CZM!, Dr. Project, Urban and Regional Planning Program URPP!, and the JamesE. Maragos,Karl Keller and Elaine Tamaye U.S. Army Corps Hawaii Institute of Geophysics HIG!, University of Hawaii. of Engineers!,Lori Chee City and County of Honolulu, Land Utiliza- tion!, DonGriffin City andCounty of Honolulu,Department of Parks Research funding was provided through the Hawaii Coastal Zone and Recreation!,Dave Parsons Departmentof Transportation!,Scott Manageinent Program administered by the DPED. Publication funds Sullivan SeaEngineering Services! and Paul Bartram AECOS!. were provided by the Hawaii Institute of Geophysics, and the Universi- ty of Hawaii Sea Grant College Program under Institutional Grant No. Field assistancewas provided by Annabelle Lee East-West Center! NA79AA-D-00085 from NOAA, Office of Sea Grant, U. S. Depart- and Carol Leong. The photomapswere designedand developedby ment of Commerce. Nancy Brown with the help of Karen Fukushima and Donald Houston.

Sections of this paper were submitted to the Graduate Division of Numerousdrafts of this documentwere typed by the URPPstaff of the University of Hawaii as partial fulfillment for the degree of Master Paulette Dahlen, Pam Hunt and BarbaraAwa. Rita Pujalet HIG! of Sciencein Geology and Geophysics. edited the final report. Wendy Nakano of Sea Grant spent much time with the graphics and layout of the photomapsand text, Wendy Aerial photographs were obtained from the R, M. Towill Company, Yokota, URPP, set the type for this report, Air Survey Hawaii, U. S. Geological Survey and the U. S. Army Corps of Engineers,

During the various stages of research, Tom Dinell Director, Mahalo to all those who contributed. URPP!, Norman Okamura URPP! and J. FrisbeeCampbell HIG! I must also acknowledge my parents, John and Betty Hwang, who worked together to provide guidance to this study. I am grateful for their individual and collectiveefforts. I thank my thesischairman, Dr. supported my academic endeavors and whom provided much of the Ralph Moberly HIG!, for his critical review of the report, The other moral support to complete my studies, Many thanks. members of my committee who provided valuable input were Dr. Doak Cox EnvironmentalCenter! and Dr. Frank Peterson Geology Department! .

TABLE OF CONTENTS

INTRODUCTION 1 SECTION III - SOUTH SHORE

STUDY LIMITATIONS Sandy Beach Park 84 Hanauma Bay Beach Park 86 SECTION I - NORTH SHORE Paiko Peninsula 88 Niu Beach to Wailupe Peninsula 91 Mokuleia Beach 6 Wailupe Beach Park and Residential Area 93 Kaiaka Bay Beach 12 Kahala Beach 95 Haleiwa Residential Area to Alii Beach Park 14 Kaalawai Beach and Kuilei ClifTs Beach Park 97 Haleiwa Beach Park 16 Iroquois Point 99 Kawai l oa Beach 18 Ewa Beach 102 Beach Park 21 Oneula Beach 104 Pupukea Beach 24 Nimitz OAicers Beach 106 24 Nimitz Beach 108 Sunset Point to West Kawela 27 Barbers Point 110 Kawela Bay 29 Turtle Bay 31 SECTION IV - LEEWARD COAST 113 Kaihalulu Beach 33 Hanakailio Beach 35 Lanikuhonua Beach 114 Kahe Beach 114 SECTION II - WINDWARD COAST 37 Nanakuli Beach Park 116 Ulehawa Beach Park 118 Kahuku Golf Course Beach 38 Maili Beach 119 Malaekahana Beach 40 Pokai Bay 121 Laic Beach 42 Mauna Lahilahi Beach Park 122 Laic Point to Pali Kilo Ia 44 Papaoneone Beach Turtle Beach! 124 Kokololio Beach 46 Makaha Beach 126 Hauula Beach to Makao Beach 48 Keaau Beach 128 Kalaipaloa Point to Waiono Stream 50 Makua Beach 130 Punaluu Beach Park and Residential Area 52 Yokohama Beach Keawaula! 132 Kahana Bay Beach Park 55 Mahie Point to Swanzy Beach Park 57 MANAGEMENT PROBLEMS ON OAHU 135 Kaaawa Residential Area to Kalaeokaoio Point 59 Kualoa Beach 60 MANAGEMENT STRATEGY 137 Kai l ua Beach 67 Lanikai Beach 71 SUMMARY 143 Waimanalo Beach 76 Makapuu Beach Park 80 BIBLIOGRAPHY 145 LIST OF FIGURES

FIGURE

Map of Oahu Phototnap Arrangements - North Shore 2 5 Waimea Beach Erosion 23 Photomap Arrangements - Windward Coast 37 Kualoa Beach Erosion 64 Photomap Arrangements - South Shore 83 Photomap Arrangements - Leeward Coast 113

LIST OF PLATES

PLATE

1 Mokuleia Beach West End! 8 Sunset Beach West End! 26 Kahuku Airfield 35 Lani 1oa Beach 46 Kaluanui Beach 50 2468Punaluu 3579 54 Kualoa 62 Kualoa Beach Park 62 Kualoa Point 66 10 Kailua Beach Park 70 11 Lanikai Beach 74 12 Paiko Peninsula 90 13 Iroquois Point 101 14 Yokohama Beach Keawaula! 134