IDENTIFYING AND ANALYZING COASTLINE CHANGES ALONG THE CORAL COAST, SOUTH- WEST VITI LEVU, FIJI ISLANDS, VIA MULTI- TEMPORAL IMAGE ANALYSES by Prerna Bharti Chand A thesis submitted in partial fulfilment of the requirements for the degree of Master of Science School of Islands and Oceans Faculty of Science, Technology and Environment The University of the South Pacific Copyright © 2010 Prerna Bharti Chand ACKNOWLEDGEMENT I would like to present my sincere acknowledgement to those who have aided and inspired me to accomplish the goals of this research. Firstly, I would like to thank my supervisors; Dr. Susanne Pohler, (Principal Supervisor) who has guided and encouraged me throughout my research, Dr. Gennady Gienko, for his constant guidance, inspiration, support and advice in achieving the appropriate methods for the multi-temporal data analyses and Professor Patrick Nunn, for guiding me through the initial stages of my research. I am grateful to Mr. Shingo Takeda who taught me the mapping techniques needed for the final presentation of the results. I would also like to thank Mr. Laisiasa Cavakiqali, and Miss Yashika Nand for assisting me with the field work and Mr. Laisiasa Cavakiqali for driving me to my study sites in the Coral Coast, area. My acknowledgement to all the villages and resorts along the Coral Coast who accommodated me for my field work, including, Beach House, Hideaway Resort, Tabakula Resort, Outrigger Resort, Navutulevu, Namatakula, Tagaqe, Yadua and Vatukarasa Villages and Korolevu Settlement. I would like to show my appreciation to Mr. Rinel Ram, and Ms Shirleen Bala who provided constant words of encouragement, advice and unfailing support and aided me with the final formatting of the thesis. I am also grateful to my fellow post- graduate friends, Ms. Simita Singh, Mr. Naushad Yakub, Mr. Zulfikar Begg, Mr. Pranesh Kishore and Ms Kirti Lal, for their generosity, friendship and support. Finally, I would like to thank my parents, who have been a constant pillar of support throughout my life, I will always be grateful to my mother and father who are my tower of strength, for their firm believe in me. I thank them for their consistent words of encouragement and moral support which inspired me to complete my thesis. i ABSTRACT This research identifies the nature of temporal coastline changes along the Coral Coast area in Fiji Islands. Prograding, resilient and eroding coastlines were identified by comparison of historical aerial photographs and satellite images. For this study 1967 aerial photographs and 2002 IKONOS satellite images were compared to observe and classify the coastline changes over the 35 year period. Subsequently, a ground truthing exercise along the Coral Coast was carried out to re-evaluate the results obtained from the desktop study of historical aerial photographs and satellite images. The desktop comparison did not reveal any prominent coherent coastline change patterns. However, a slight pattern is evident; the far west (Fijian Resort area) and the far east (Naboutini Village area) sides of the study area generally indicate resilient and prograding coastlines. Along the shoreline in the central region it was found that stretches of prograding coastlines alternate with resilient and eroding coastlines. The rates of coastline change for prograding and eroding coastlines were quantified in terms of area (in square meters) and maximum distance (in meters) of landward and seaward movement. For prograding coastline segments the area advancement ranged from 1 564 ± 6 m2 to 97 285 ± 6 m2 and the maximum distance of progradation ranged from 13 ± 3 m to 400 ± 3 m. For eroding coastline segments the area recession ranged from 840 ± 6 m2 to 21 487 ± 6 m2 and the maximum distance of coastline recession ranged from 14 ± 3 m to 40 ± 3 m. The area and maximum distance values for progradation and erosion indicate that the Coral Coast coastline change is influenced more by progradation than erosion. However, the ground truthing exercise revealed only two sections of the study area to be naturally prograding; the region at the head of Sovi Bay and Namatakula Village front. All other prograding and resilient coastlines had been fortified by coastal engineering structures; indicating artificial progradation and foreshore reclamation. Beach erosion was prominent on most of the beaches with fortified coastlines. ii The wave energy along the Coral Coast, set up by the dominant southeast trade winds is relatively high. Since this area only possesses a narrow fringing reef system, interrupted by numerous channels, the wave energy does not dissipate significantly upon reaching the shore. Hence, the Coral Coast coastline is a “High Energy Coastline”. Due to fortification of the coastline by the construction of seawalls, a large portion of the Coral Coast coastline is showing signs of artificial progradation. Coastal processes, erosion, progradation and resilience are depended on the local wind, wave and geomorphological characteristics of an area. Therefore, the dominant coastal process at any given area would be specific to that area, respective to the local characteristics. Keywords: Temporal coastline change, coastline erosion, coastline progradation, resilient coastline, remote sensing methods. iii TABLE OF CONTENTS ABSTRACT..............................................................................................................................ii TABLE OF CONTENTS.........................................................................................................iv LIST OF FIGURES ................................................................................................................vii LIST OF TABLES....................................................................................................................x LIST OF APPENDICES..........................................................................................................xi CHAPTER 1 – INTRODUCTION .......................................................................................... 1 1.1 INTRODUCTION ......................................................................................................... 1 1.2 THESIS RATIONALE .................................................................................................. 3 1.3 THESIS OBJECTIVES ................................................................................................. 5 1.4 STUDY AREA .............................................................................................................. 5 1.5 THESIS FRAMEWORK ............................................................................................... 7 CHAPTER 2 – COASTLINE CHANGE PROCESSES IN THE PACIFIC ISLANDS.......... 9 2.1 INTRODUCTION ......................................................................................................... 9 2.2 SHORELINE CHANGES USING THE REMOTE SENSING METHOD .................. 9 2.2.1 Remote Sensing Methods and Shoreline Change.................................................. 10 2.2.2 Role of GIS in Coastline Change Studies.............................................................. 11 2.2.3 Mapping Shoreline Changes................................................................................. 12 2.3 COASTAL PROCESSES ............................................................................................ 15 2.3.1 Waves, Tides and Currents ................................................................................... 17 2.3.2 Sediment Budget and Longshore Drifting............................................................. 19 2.3.3 Coastal Accretion Processes................................................................................. 22 2.3.4 Coastal and Beach Erosion Processes.................................................................. 23 2.4 CHARATERISTIC COASTAL ZONES OF THE PACIFIC ISLANDS.................... 26 2.4.1 Coastal Geography of Pacific Islands .................................................................. 26 iv 2.4.2 Sediment Sources of the Coastal Zones ................................................................ 29 2.5 CAUSES OF COASTAL EROSION IN THE PACIFIC ISLANDS .......................... 31 2.5.1 Natural Causes of Coastal Erosion ...................................................................... 32 2.5.2 Human-induced Causes of Coastal Erosion ......................................................... 42 2.6 SUMMARY................................................................................................................. 44 CHAPTER 3 – METHODOLOGY ....................................................................................... 45 3.1 INTRODUCTION ....................................................................................................... 45 3.2 WORKFLOW IN DETERMINING THE RANGE OF COASTLINE CHANGE...... 45 3.2.1 Phenomenal Range of Spatial Change.................................................................. 48 3.2.2 Identification of Source Data................................................................................ 48 3.2.3 Range of Coastline Change Methods.................................................................... 49 3.2.4 The Error Budget and A-priori Accuracy Estimation........................................... 50 3.3 THE STUDY SITE ...................................................................................................... 51 3.4 RESEARCH METHODOLOGY................................................................................