Mapping the Coastal Morphology from to Pu’apu’a on the island of Savai’i,

S. P. Kim and S.-R. Lee KIGAM

April 1999 SOPAC Miscellaneous Report 281

Address : Petroleum and Marine Research Division Korea Institute of Geology, Mining and Materials(KIGAM), 30, Kajong-dong,, Yusung-Ku,, Taejon, 305-350 KOREA

THIS STUDY WAS FUNDED BY THE MINISTRY OF SCIENCE AND TECHNOLOGY, GOVERNMENT OF KOREA

TABLE OF CONTENTS

ACKNOWLEDGEMENT ...... 4

INTRODUCTION...... 5

STUDY AREA...... 5

MATERIALS AND METHODS...... 8

RESULTS...... 9

1. MAPPING THE COASTAL MORPHOLOGY...... 9 Salelologa to Safua ...... 9 Safua to Eve’eve ...... 10 Eve’eve to ...... 10 Fogapoa to Si’ufaga ...... 10 Si’ufaga to Sa’asa’ai ...... 10 Sa’asa’ai to Pu’apu’a (Lesolo Point) ...... 11 2. BEACH PROFILING...... 11 3. SURFACE SAMPLING ...... 11

DISCUSSION AND CONCLUSION ...... 13

REFERENCES...... 14

APPENDICES...... 15

APPENDIX 1: ...... 15 SOPAC draft Task Profile Coastal Morphology Mapping Salelologa to Pu’apua on the island of Savai’i, Samoa...... 15 APPENDIX 2: ...... 17 Map of coastal morphology of Savai’i Island (from Salelologa to Pu’apu’a) ...... 17 APPENDIX 3: ...... 18 List of rock specimen and surface sediment samples...... 18 APPENDIX 4: ...... 20 Photographs taken during survey...... 20

LIST OF FIGURES

Figure 1. Location of study area...... 5

Figure 2. Geologic map of study area...... 6 3

Figure 3. Beach profiles and approximate slope angles measured in Faga beach ..... 11

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ACKNOWLEDGEMENT

This project is funded by the Ministry of Science and Technology, Government of Republic of Korea and undertaken by the Korea Institute of Geology, Mining and Materials (KIGAM) at the request of the government of Samoa through the SOPAC.

The authors appreciate the cooperation of the SOPAC Technical Secretariat and the Meteorology Division of the Ministry of Agriculture, Forests, Fisheries and Meteorology of Samoa during the whole survey period. Special thanks should be given to Mr. A. Simpson, Dr. R. Howorth and Mr. R. Smith for arranging the survey in Fiji, and to Mr. L. Talia for his sincere discussion and kind guidance during the whole survey period in Savai’i Island. We would also record here our acknowledgement to Lala, Sunita, Tatia and all the other secretaries of the SOPAC office. 5

INTRODUCTION

As technical assistance to the 1998 SOPAC work program, a twelve-day survey project was undertaken from 30th, July, 1998 to 10th, Aug., 1998 in the island Savai’i, Samoa. The SOPAC work program in this area is mainly focused on understanding the shoreline movements and establishing sound coastal zone management data for fundamental protection of the important existing infrastructure. The detailed objectives of the program are as follows (Dr. R. Howorth, pers. com.; See Appendix 1. SOPAC DRAFT TASK PROFILE);

1. Establishment of the features of the coastal environment and active coastal processes including historical shoreline positions, 2. Identification of the areas where infrastructure may be under threat, 3. Identification of any potential areas for future aggregate assessment, 4. Compilation of coastal morphology data of the coastline from Salelologa to Pu’apu’a in Savai’i island, Samoa, to evaluate coastal processes, and assess any potential hazards, especially erosion.

This report is a preliminary result to partially fulfill the above-mentioned objectives after undertaking a ground-check and mapping the coastline features at a scale of 1:25 000 with available aerial photographs.

STUDY AREA

The study area is geographically located between Salelologa village and Pu’apu’a village (13° 34¢ S – 13° 44¢ S) in Savai’i Island, Samoa (Fig. 1). This area is the most populated in Savai’i (Ward and Ashcroft, 1998) and has experienced heavy damage by the cyclones Ofa and Val in Feb., 1990 and Dec., 1991, respectively (Ward and Ashcroft, 1998; Elmqvist et al., 1998). According to the geologic map of Savai’i (New Zealand Geological Survey, 1958; (Fig. 2) the whole study area is covered with middle to late Pleistocene volcanics except the small areas around the wharf in Salelologa and around Lesolo Point, which are composed of the Holocene Puapua volcanics. From Mt. Asi to Pu’apu’a village, Holocene Tafagamanu sand strips composed of coral sands are distributed along coastline about 1½ m above sea level. Small creeks, inland springs and lithified sands near the sea level can be noticed at several locations.

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Fig. 2. Geologic map of study area (by the courtesy of SOPAC GIS archive; modified from New Zealand Geological Survey, 1958)

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MATERIALS AND METHODS

Before starting the survey, a list of aerial photographs taken of the study area and relevant reports and information were acquired from the SOPAC archive. Geologic map (1:100 000 scale) and topographic maps (1:20 000) were also copied for using in the field.

At the Department of Lands and Survey in , Western Samoa, aerial photographs taken in 1990 (New Zealand Mapping; scale 1:15 000; SN 7815, Nos 311, 313, 315, 320, 322, 324, 326) were available with some transparent papers.

During the whole field survey period, ground-check was performed to assure the correct interpretation of any features seen on the photographs. Any morphologic feature which indicates coastal erosion was logged on the maps at the same time. Man-made structures like sea walls, groins, bathing pools, wharves, etc., were also logged on the maps.

For semi-quantitatively evaluating the difference of beach slopes across groins in Faga beach (between Cape and Malae village), six beach profiles were acquired with solid sticks and a tape ruler.

As necessary, rock and surface sediments were sampled to collect additional data for further studies after visual examination of grain texture and mineralogical composition. Sampling locations were logged in the topographic map or measured with latitude and longitude by using a Trimble TM GPS receiver.

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RESULTS

1. Mapping the coastal morphology

After the survey in Samoa, brief results were reported and discussed in the SOPAC office in Fiji with interpreted aerial photographs and logged data. In the office of KIGAM, interpreted aerial photographs were compiled together with the logged features, and schematically drawn with CorelDraw program (Appendix 2; CorelTM v.8.0). The topographic map (1:20 000) was also referred to when combining and positioning the mapped areas.

The final output is a digitized map of 1:25 000 scale in .DXF file format for SOPAC GIS database by using AutoCADTM. The following is a detailed description of each coastal area ;

Salelologa to Safua The field survey was started from Salelologa wharf. Sea walls and underlying exposed basement rocks prevail in this area.

The sea walls consist mainly of basaltic rocks of up to 2.0-m diameter with slopes of mostly 30 to 35 degrees (max. 70 degrees). The rocks still look fresh and angular. Black basaltic sand and shell fragments were found around the sea walls, which looks to have originated from the infilling materials of the sea walls. Basement rocks could mostly be seen under the sea walls. In Vai’afai village, active reclamation is being done inside the bay.

Sandy mud or muddy sand (the grain sizes are not yet analyzed) dominates surface sediments along the coastal area with some gravel with rare boulders. According to a resident living near the public library, the boulders seen around the coast in village have been moved up landward during storm periods from the outer shore zone. The prevailing wind direction in this area could be inferred from the coconut trees leaning toward the land area, especially in the Salelavalu area.

Fresh water seepage or springs and swimming pools are found at Foua, Iva and Vaisa’ulu villages. In the Iva village a resident said they had a disagreement with the neighboring families on the application of the fresh-water spring. Because of this the area around that spring is being ignored and wasted by both families as just a rubbish ground now (Appendix 4. top).

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No sea wall was found, and one seems to be needed at the headland from to Papaloa. In the other areas the local residents have built sea walls, which might be vulnerable to future meteorological impacts.

Safua to Eve’eve Sea wall protection could be seen along most of the coastline. Mangrove plantation is developed around Vaitolo village. Two groins approximately 10 meters long and a swimming pool were found in Lealaoali’i village. In Aeauli, sand beach and mud flats have developed around the reclaimed area which was used as a car maintenance shop. Southward from the reclaimed area in Eve’eve gravelly sand beach and muddy sand flat are developed. Gravels are subround to subangular and show bimodality in size. Local sea walls and reclaimed area could be the possible sources for them. Muddy sand flat consists of black terrigenous pebbly fine sand and white calcareous material.

Eve’eve to Fogapoa A retreating wave-cut sea cliff was found around Mt. Asi in village. Seaward from the sea cliff a locally gravel-paved pebbly sand beach is developed. The sand is composed of black terrigenous and white calcareous materials. Gravels are mostly coral fragments up to 50-cm in diameter. Some ripples are found on the pebbly sand beach.

Fogapoa to Si’ufaga Around the cape Tuasivi no well-constructed sea wall was found, only some small and fragile ones, built too low, for the Tuasivi hospital and the Tuasivi school. Erosion seems predominant although this area is being used functions important to the local residents. In addition, according to our attache and a teacher in the school, an old benchmark was almost submerged, which might indicate a local sea-level change.

Si’ufaga to Sa’asa’ai White sand beaches with ‘foe’ plantation in the supratidal area are developed along the whole coast line. In the aerial photographs taken in 1990 the sand covers the whole backshore across the road to several tens of meters, deposited by the cyclone Ofa (see Appendix 2 for the areal distribution). Lithified sands (beach rock) are also seen in the intertidal zone. In Si’ufaga some indication of erosion and shoreline retreat were found 250 m south from the groin (Appendix 4. middle and bottom). To evaluate any differential wave influence in this area by the wharf, six beach profiles were measured across the beach after the beach was divided into northern

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Sa’asa’ai to Pu’apu’a (Lesolo Point) Well-constructed sea walls and white sand beaches were mapped. In Samile and Asaga and at Leato Point, bridges were constructed over the creeks originating from the coastal swamps. The spits developed at the mouths of those creeks could indicate the local direction of the longshore current.

2. Beach Profiling

From reference points (mainly the landward boundary of the foe vegetation) beach profiles were measured at selected intervals (Fig. 3). The values of height and distance were plotted and the average slopes of the beach were calculated assuming that the measured lines were perpendicular to the coastline and that the beach has no slope change along the measured lines. The local height changes due to the lithified sand were neglected.

3. Surface Sampling

The samples collected during the field survey were compiled and listed to hand over to the SOPAC archive (Appendix 3) for further analysis.

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Fig. 3. Beach profiles and approximate slope angles measured in Faga beach. Surface sampling sites were noted as A1, A2, etc. (see Appendix 2).

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DISCUSSION AND CONCLUSION

1. Features indicating shoreline erosion resulting from the cyclones and normal waves were noticed in many locations along the coast. The northeastern part of the study area (from Cape Tuasive to Pu’apu’a) appears to be experiencing more severe erosion than the southeastern part (from Saleleloga to Cape Tuasivi). Long- term meteorological and oceanographic studies are required to quantitatively evaluate the amount of erosion and the main processes that cause the difference between the two areas.

2. The sizes of the sea-wall materials seem too small considering the prevailing wind and the resultant wave energy. According to one of the local residents, the rock materials were easily moved in storm wave condition even after the cyclones Ofa and Val had swept the study area. Most sea-wall construction is being done by the local residents with their own budget, which explains the small size and amount of the building materials. Government-based constructions are recommended in severely eroded as well as newly reclaimed areas.

3. A dispute between adjacent families about using fresh-water seepage near their territorial boundary was noticed, which finally resulted in mutual negligence of that boundary area (one family wanted to use it for a swimming pool, whereas the other wanted to leave it as it has been. Meanwhile, the area was being wasted by rubbish as a dumping ground). An intermediary to be able to settle that kind of family dispute would be needed to avoid spoiling that kind of area.

4. Pollution by rubbish seems to prevail along the whole survey area. The local residents living along the coast are throwing plastic, home appliances, household tools and any other kind of waste away without any concern. Public enlightenment is required.

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REFERENCES

Elmqvist, T., P. A. Cox, E. D. Pierson and W. E. Rainey (ed.), 1998. The Rain Forest and the Flying Foxes – An introduction to the rain forest preserves on Savai’i, Samoa. Published by Fa’asao Savai’i, The Conservation Society, Saleleloga, Savai’i Samoa, 127pp.

New Zealand Geological Survey, 1958. Savai’i (1:100,000). Published by the Department of Scientific and Industrial Research.

Rearic, D. M., 1990. Survey of cyclone Ofa damage to the northern coast of , Samoa. SOPAC Technical Report 104, 37pp.

Ward, R. G. and P. Ashcroft, 1998. Samoa: Mapping the Diversity. Institute of Pacific Studies, University of the South Pacific, Apia and National University of Samoa, Samoa, 145pp.

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APPENDICES

Appendix 1:

SOPAC draft Task Profile Coastal Morphology Mapping Salelologa to Pu’apua on the island of Savai’i, Samoa.

Background : The lack of understanding of shoreline movements both historical and current often impact on important, and existing infrastructure resulting in a bandaid approach to cure rather than prevention. For sound coastal zone management data in the form of maps reflecting coastal process help enormously in decision making with respect to existing and future development.

Objectives: · Establish features of the coastal environment and active coastal processes including historic shoreline positions. · Identify areas where infrastructure maybe under threat. · Identify potential resources areas for future aggregate assessment. · Compile coastal morphology data of the coastline from Saleologa to Pu’apua, Savai’I, Samoa.

Work Plan: · Collect relevant data and information available to SOPAC, including list of relevant SOPAC reports and air photographs of key sites. · Undertake field survey and mapping at a scale of 1:25,000 to evaluate coastal processes, and assess potential hazards especially erosion. · Compilation of results into digital format for GIS implementation.

Client: Samoa Government

Proposed Schedule: Study duration foreseen 2.5 weeks starting no earlier than mid-July

Suva- Briefing at SOPAC (2 days) Samoa-Field Mapping (10 days) Suva- Debriefing and Interim Report Completion (2 days)

Resource Requirements: Databases, GIS capabilities mapping and plotting.

SOPAC Personnel: Support from Coastal and ITU Units as necessary.

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Agency Personnel: Mr. Sung-Pil Kim, Korea Institute of Geology Mining and Materials (KIGAM)

Funding Sources: KIGAM

Proposed output: · Coastal morphology map of coast Saleologa to Pu’apu’a with accompanying notes. · Digital representation of coastal morphology mapping for GIS.

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Appendix 2:

Map of coastal morphology of Savai’i Island (from Salelologa to Pu’apu’a)

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Appendix 3:

List of rock specimen and surface sediment samples

No. Sample Name on the Bag Location Remarks

- Rock Specimens near Saleleloga (from basement black, scoraceous

outcrop)

#1 98.AUG. 4 Saleleloga subtidal (low tide) Near MM public library (Saleleloga) 1:20,000

fine shore deposit topographic map

#2 98-8-04 Salelavalu fine sand subtidal Savai’i Timber in Salelavalu ²

#3 98.8.5 sand bar at Mt. Asi Channel sand bar ²

between Mt. Asi & Leloa Is. In Fatausi

#4 98. 8. 5 Aeauli (Car Maintenance Shop) Aeauli ²

southern sand beach

#5 98. 8. 5 Aeauli (Car Maintenance Shop) Aeauli ² southern sand beach

#6 98. 8. 5 Aeauli (Car Maintenance Shop) Aeauli ² northern mudflat with gravel

#7 98. 8. 5 beside funeral Vaimaga ² sand beach

#8 98. 8. 5 Vaimaga beside funeral Vaimaga ² muddy sand with gravel

#9 98. 8. 5 Fatausi junction Fatausi ² sand beach

#A1 98. 8. 6 Faga beach #A1 13° 39¢ 55² S / 172° 10¢ 44² W GPS (WGS-84)

at transect line A upper beach

#A2 98. 8. 6 Faga beach #A2 ² ² at transect line A lower beach

#B1 98. 8. 6 Faga beach #B1 13° 39¢ 44² S / 172° 10¢ 51² W ² at transect line B upper beach

#B2 98. 8. 6 Faga beach #B2 ² ² at transect line B lower beach

#C1 98. 8. 6 Faga beach #C1 13° 39¢ 35² S / 172° 10¢ 58² W ² at transect line C back shore

#C2 98. 8. 6 Faga beach #C2 ² ² at transect line C lower beach

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No. Sample Name on the Bag Location Remarks

- Rock Specimens near Saleleloga (from basement black, scoraceous

outcrop)

#D1 98. 8. 7 Faga beach #D1 13° 39¢ 28² S / 172° 11¢ 04² W ² at transect line D backshore

#D2 98. 8. 7 Faga beach #D2 ² ² at transect line D upper beach

#D3 98. 8. 7 Faga beach #D3 ² ² at transect line D backshore

#E1 98. 8. 7 Faga beach #E1 Lu’ua village backshore across road ² at transect line E Backshore

#E2 98. 8. 7 Faga beach #E2 ² ² at transect line E upper beach

#E3 98. 8. 7 Faga beach #E3 ² ² at transect line E lower beach

#F1 98. 8. 7 Faga beach #F1 Malae village ² at transect line E 100m from road junction & seawall

backshore

#F2 98. 8. 7 Faga beach #F2 ² ² at transect line E upper beach

#F3 98. 8. 7 Faga beach #F3 ² ² at transect line E lower beach

#10 98. 8. 8 Lano beach Asaga

spit at Asaga

#11 98. 8. 8 Pu’apu’a

Pu’apu’a beach (H. W. L.)

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Appendix 4:

Photographs taken during survey.

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