Atoll Reclamation, an Option? Robert Smith, Geoscience Division PC

Transcription

1 Atoll Reclamation, an Option? Robert Smith, Geoscience Division PC 1

2 Atoll Provinces of the Tropical Pacific Ocean Numbers vary for atolls globally E.H Bryan jnr reported some 400 atolls From Dickinson 2009 published in GSA 2

3 Typical Atoll Issues Land shortage and scarcity, Increasing land tenure problems (disputes on ownership, boundaries, and leases), Increased demand for shelter and housing, Increasing numbers of urban squatters and emergence of urban poor, Groundwater and lagoon pollution through leaching of sewage and other waste, ad hoc garbage and waste disposal Increasing environmental degradation Contamination of fish from human excrement, 3

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5 Vulnerabilities with respect to climate variability and change Rising mean sea level is only one of several potential effects of changing global climate. Other factors that will affect the coasts of islands in atoll settings include: Changing storm patterns (e.g. cyclone frequency and distribution), wind patterns, Sea-surface temperature (SST). Impacts on sediment supply coral and other species. Changes in rainfall that effect rainwater harvesting Changes in rainfall that impact ground water recharge 5

6 Global average sea level versus Regional sea level. Global average sea level is affected by changes in net ocean heat content and land based ice melt which are strongly influenced by warming trends. Regional sea level variations largely result from changes in wind patterns and ocean circulation that are components of natural climate variability. Source :Pages AGU publication 2016 Interglacials past 800,00 yrs 6

7 Regional sea level trends January monthly summary Federated States of Micronesia recorded its lowest monthly sea level on record, while monthly sea levels at many other stations fell to their lowest levels in 5 years. Sea level anomalies below -20 cm were observed at Federated States of Micronesia, Papua New Guinea, Solomon Islands and Tuvalu. April Small storm surges were observed at Vanuatu, Fiji and Tonga in early April, brought about by strong winds and low barometric pressure from Tropical Cyclone Zena. Tropical Cyclone Amos caused a small surge at Samoa on 23 rd April April 2016 Sea levels remained lower than normal at many stations in connection with the El Niño, with monthly anomalies around -30 cm at Solomon Islands and lower than -10 cm at PNG, Kiribati, Nauru and Tuvalu. Sea levels at Marshall Islands and FSM were near normal for this time of year. Source: Climate and Ocean support programme in the Pacific monthly reports. Pacific Sea Level Monitoring Project BOM 7

8 Source: Climate and Ocean support programme in the Pacific monthly reports. Pacific Sea Level Monitoring Project BOM 8

9 Coastal Protection and Reclamation Extensive sections of the ocean and lagoon shoreline have been modified by construction of sorts This is partly in response to erosion threats and partly in the process of reclaiming land a valuable commodity traditionally Infrastructure under threat from coastal erosion e.g. hospital, schools Studies to date show 90% of the coastline is under some form of attack Majuro Ebye Tarawa Betio-Bairiki causeway

10 So why Reclamation? Lets consider possible options with respect to the aforementioned issues Do nothing Coastal protection of existing islands expensive, no new land Migration cultural ties make leaving very difficult Decentralisation Reclamation - new land water resources engineered water table reduces population pressure for accommodation can lead to improved economic opportunities community recreational space (ncd s) 10

11 Maldives 26 Atolls along a 860km long chain north south in the Indian Ocean with some 1,190 low lying coral islands. Administratively divided into 20 atolls -358 islands inhabited, capital being Male Population 341,000 (2014) Tourism receipts in 2014 $ 2.6 billion US 11

12 Male and Hulhumale Hulhumale Hulhumale : mid 1990s, the idea of creating an artificial island from an existing lagoon for a futuristic urban city which would accommodate the excessive population of the central region was born Male Scale bar 3km Phase I of Hulhumalé reclamation, 188 hectares, began on 16th October 1997 and was completed by June , Hulhumalé Phase I has reached a population of 30,000, which is the halfway mark of the target population of 60,000 Phase II of the Hulhumalé project, consisting of 240 hectares, is targeting a total population of 100,000. Male and Hulhumale

13 Atoll reclamation Haa Dhaalu Atoll-Kulhudhuffushi Island Geographical Atoll name Thiladhunmathi Atoll Kulhudhuffushi 2001 Kulhudhuffushi 2006 Kulhudhuffushi 2014 Population 8224 Length 2.9km Width 1.8km Original island 200 hectares MTCC added 9 hectares Boskalis International bv 28 hectares Cost NZ$10m Newly reclaimed land to be used for residential, commercial or industrial and social facilities 13

14 Vilufushi Island Thaa Atoll Maldives The project aim was to create a safer and larger island for the Vilufu-shi residents, who were temporarily evacuated to Buruni island, as well as for the population of some other smaller nearby islands. The project involved in increasing the level of a part of the existing island and the reclamation of a part of the surrounding shallow reef flats, to provide extra land for residential purposes. The surface of the island was increased from 16ha to 62 ha and raised an additional 1.4 m above MSL. In addition, construction of about 2000 m. of revetment around the is-land at 2.4 m above MSL, and a new fishing harbour. The harbour will include 350 m. of breakwater and 350 m. of quay wall. The required amount of sand dredged was1.1 million m3. Dredging was completed in 5 weeks. Equipment used included a medium sized cutter suction dredger, a pipeline system and various bulldozers and wheel loaders. 14

15 Vilufushi Island

16 Tarawa Atoll Centred at 173 E and 1 25 N Shallow with an average depth of 7m, large tidal flats Total land area about 3100 hectares ( 31km 2 ) Lagoon km 2. Of the total country population 48.7% reside in South Tarawa (2010 census in %) Projected by ,000 South Tarawa in 2010, 3184 persons per km 2 source content/uploads/2013/01/6_south-tarawa-revised pdf 16

17 Tarawa Atoll Issues Failing Infrastructure - Water and Sanitation Sand and gravel extraction Planning and Urban Development Population pressures are exacerbated by the very limited land resources, of the 1521 Ha some 300 Ha are fish ponds in Temaiku Narrow island widths and land scarcity small changes in coastline become very significant. 17

18 Previous land reclamation projects in Tarawa Temiaku Blight 1968 a senior agricultural officer Mr R.T.Hubbard mooted the idea of closing off Temaiku Bight to reclaim tidal lagoonal tidal flats an area 300Ha. This worked commenced in Betio wharf and container yard 1998 The new Parliament location

19 Options for reclamation 36 Ha -1.5 million m3 ht +3m Temaiku area -247 Ha 19

20 Republic of the Marshall Islands Kwajalein Majuro 20

21 Ebeye

22 South end of Ebeye island showing the USCG Loran station first established here in 1950 and decommissioned 31 Dec 1977 Source Lagoon reef flat West East Lagoon shoreline West Infrastructure remains? Sand spit Shoreline features indicating that erosion persisted earlier than Beach rock exposed

23 N Lagoon East Peace Park Fuel tanks Seawall and fence line of Power plant Remnant toe of coastline?? Beach rock Borrow-pits Ocean

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26 Reclaim areas 43 Ha 26

27 Funafuti Atoll 1943 Tuvalu 27

28 Represented 8% of island Required 250, 000 m3 Work required included: Sediment type Resources identification within specs of dredging parameters UXO surveys for potential hazards 28

29 Borrow pit 2 29

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32 1Ha 109Ha 32

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34 Conclusions Significant uncertainties remain, particularly related to the magnitude and rate of the ice-sheet contribution for the 21st century and beyond, the regional distribution of sea level rise, and the regional changes in storm frequency and intensity ( a closing comment in chapter of IPCC Chp 13 WGAR15) PI leaders need to act now Once developed, the potential for agricultural and recreational development on par with larger islands can be realised. Increase in STATE Land Ownership Increased base value to a potential tourism market Development of community recreational facilties (ncd s) Strengthening planning and urban Management Increased resilience and sustainability Engineered water lenses leading to sustainability in water resources possible 34

35 Vinaka Picture courtesy of Peter Olivier Calibre Consulting 35