SURVEY of NUKULAELAE and NUKUFETAU LAGOONS TUVALU 3 April - 5 May 1989
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SOPAC Technical Report 105 July 1990 SURVEY OF NUKULAELAE AND NUKUFETAU LAGOONS TUVALU 3 April - 5 May 1989 by Robert B. Smith', Doug M. Rearic, Edward Saphore' and Falekofe Seneka SOPAC Technical Secretariat 'Lands Department, Tuvalu Prepared for: South Pacific Applied Geoscience Commission Nearshore and Coastal Programme, Tuvalu Projects: TU.1, TU.3, TU.9 [3] TABLE OF CONTENTS Page ABSTRACT ...................................................................................................................... 5 ACKNOWLEDGEMENT................................................................................................. 6 INTRODUCTION AND BACKGROUND ............................................................. 7 OBJECTIVES ................................................................................................................. 7 PARTICIPATING PERSONNEL .......................................................................... 8 EQUIPMENT & ANCILLARY GEAR .................................................................... 8 SURVEY METHODS ............................................................................................ 10 Navigation Control ..................................................................................... 10 Vertical Control .................................................................................................. 10 Seismic Profiling ................................................................................................. 11 Sampling ............................................................................................................ 11 Beach Profiling .................................................................................................. 11 Data Processing ................................................................................................... 11 RESULTS Nukulaelae Atoll ...................................................................................... 12 Nukufetau Atoll ....................................................................................... 16 CONCLUSIONS AND RECOMMENDATIONS ................................................. 27 REFERENCES .............................................................................................................. 28 APPENDICES I Navigation Point Listing Nukulaelae & Nukufetau .......................... 29 II Sampling Log ...................................................................................... 32 111 Plotted Beach Profiles: Nukulaelae BP1-8 ............................... 36 Nukufetau BP1-11 ............................ 45 IV Cruise Log .............................................................................. 57 [4] LIST OF FIGURES Figure Page 1 Trackplot of bathymetry and seismic profiles. Nukulaelae ................... 13 2 Geomorphology Nukulaelae lagoon ........................................................... 14 3 Rock sample and lagoon location map. Nukulaelae..........................................15 4 Location map beach profiles, Nukulaelae ................................................ 17 5 Location plot bathymetry and seismic profiles. Nukufetau ...................... 18 6 South Nukufetau trackplot .............................................................................. 20 7 North Nukufetau trackplot ......................................................................... 21 8 Location map beach profiles, Nukufetau.........................................................................22 9 Lagoon sample location map, Nukufetau................................................................. 23 10 Rock sample location map. Nukufetau....................................................................... 25 [5] ABSTRACT A reconnaisance geophysical and geological sampling survey for insular phosphate was carried out at Nukulaelae and Nukufetau atolls, Tuvalu, during April and May, 1989. At Nukulaelae 80 km of bathymetry and 3.5 kHz sub-bottom profiling was wried out, together with onshore and lagoon sampling. Sub-bottom penetration was minimal. Sample analysis revealed no phosphate content in the rock samples taken either from the reef flats or the islands. In general, the lagoon is quite shallow with a maximum depth of 30 m associated with an east-west depression across the lagoon floor. An additional 60 km of profiling was completed in two areas of interest at Nukufetau. Sub- bottom penetration was also limited here. Of the five rock samples collected, one returned a positive phosphatic mineral content. Further sub-bottom investigations using appropriate seismic systems are considered essential prior to initiating any drilling at Nukufetau atoll. Without information from such studies, the sub-bottom phosphate potential of this atoll cannot be ruled out. From the accumulated data, two bathymetric maps are to be published by SOPAC, 1:12,500 of Nukulaelae Atoll, and 1:25,000 of Nukufetau Atoll. Beach profiles were established on the islands of Fangaua and Savave at Nukulaelae and Nukufetau respectively. Data from these profiles will provide information for assessing the effects of the existing coastal barrier protection and for evaluating future coastal protection schemes. Exploratory dives were carried out at Nukulaelae and Nukufetau to assess black coral potential. Specimens were found at both atolls with a very large specimen found at Nukufetau and reports of additional large specimens in the vicinity. It is recommended that further work be done to establish the quantity and quality of black coral present and to assess the viability of a local cottage industry in Tuvalu. [6] ACKNOWLEDGEMENTS The support of the Tuvalu Government and people, and the excellent assistance provided by the Captain and crew of the Te Kaaleva in gathering the data for this report are gratefully acknowledged. The Commonwealth Fund for Technical Co-operation, the US Geological Survey and ESCAP/UNDP contributed to the survey. [7] INTRODUCTION AND BACKGROUND Following the 17th Session of CCOP/SOPAC and a follow-up courtesy call to Tuvalu by the Director and Training Co-ordinator in early 1989, three tasks were planned in the Coastal and Nearshore Programme for Tuvalu. The first was a follow-up on previous work done by Radke in 1985/86 on the prospectivity of high-grade but localised sub-surface phosphatic deposits within the atoll lagoons, particularly Nukufetau and Nukulaelae. The second was to investigate the coastal erosion in Nukufetau and Nukulaelae that had been reported as a serious problem (Fawcett, 1982; Radke, 1985; and Reynolds, 1988/89). In these reports it was recommended that a suitable coastal erosion monitoring programme be established to provide the necessary data from which a coastal barrier protection scheme could be implemented for the islands of Fangaua, Nukulaelae and Savave, Nukufetau. The third was to study precious coral. To date, no precious coral surveys had been conducted in Tuvalu (Harper, 1988) and the resource potential was unknown. Potential habitats for black corals were believed to exist around the islands, and it has been estimated that less than a 500 kg/year sustainable yield would be adequate to support a local black coral cottage industry. OBJECTIVES 1. To investigate the potential for sub-bottom phosphate at Nukulaelae and Nukufetau lagoons, and to see if there is sufficient justification to initiate a drilling programme. 2. To sample any possible phosphate occurrences. 3. To establish a beach profile monitoring programme to assess coastal erosion and sediment movements on Fangaua Island, Nukulaelae and on Savave, Nukufetau. 4. To establish whether black coral is present at Nukulaelae and Nukufetau. [8] PARTICIPATING PERSONNEL Robert Smith Marine Geophysicist (CFTC) Doug Rearic Marine Geologist (USGS) Ed Saphore Electronics Technician (UNDP) Falekofe Seneka Technical Officer (Lands Department, Tuvalu) Lotto Pacifica Captain "Te Kaaleva" (Save the Children Fund vessel) survey vessel Foumalie Sakalua Engineer "Te Kaaleva" Teuai Lekasa Deckhand "Te Kaaleva" Taingi Foetasi Deckhand "Te Kaaleva" Dennis Manu Deckhand "Te Kaaleva" During the course of the survey the following personnel were contacted: Funafuti Kelese Kolone Secretary for Commerce and Natural Resources Tauaasa Taafaki Secretary for Local Government Colin Reynolds PWD Coastal Erosion Engineer Richard Weeks Director Save the Children Fund Nukulaelae Members of Executive Island Council (only 2 present) Nukulaelae Island Chief and Village Elders Teleke Lauti Island Executive Officer Mausalii Kaitu Boat owner, guide Filipo Alama Diver (Black Coral) Nukufetau Vaguna Seluselu Island Executive Officer Nafa Samisoni Boat owner, diver, guide Tetikua Control point guide, labourer EQUIPMENT AND ANCILLARY GEAR For this work programme the following SOPAC equipment was used during the course of the survey: [9] Navigation Equipment Del Norte 520 Digital Distance Measuring Unit Two Toshiba 1000 laptops One Zenith superPort 286 laptop Seismic Equipment Data Sonic 3.5kHz sub-bottom profiling system SBT 220 Transceiver Bathymetry Raytheons De 719C echo sounder Odoms depth digitizer Odoms Digibar Dive equipment 4 Luxfer 80 CFM tanks 1 4.5 CFM Bauer Diving Compressor 2 sets Scuba equipment Survey Equipment 1 Sokkisha C3E Automatic Level & stadia rod Tide gauge 1 Aanderra water level gauge Data Processing 1 Zenith 286 Computer 1 Diconix printer 1 Hipad Digitizer Sampling Gear 1 Van Veen Grab Sampler Crow bar hammer [10] AC-DC power 12 12v dc lead acid batteries EF 600 Yamaha generator SURVEY