Storms in an Ocean of Islands: Understanding the Contribution ofTropical Cyclones on Island Landscape Evolution

James P. Terry
Department of Geography, National University of Singapore, AS2, 1 Arts Link, Kent Ridge,
Singapore 117570; geojpt@nus.edu.sg

Although uncertainties remain, many scientists now believe that tropical Pacificregional climates may experience more frequent or sustained El Niño-like conditionsin the future, owing to global ocean warming. In consequence, there are potential
implications for changes to the current spatial patterns of tropical cyclone activity,with the possibility of increased storm intensities, shifts in mean positions of storm
genesis, and other potential variations in track behaviour, all of which may affect thevulnerability of South Pacific island communities to these extreme meteorologicalevents. In this talk, focus is directed towards examining several recent tropical
cyclones and the nature of their physical impacts on island landscapes. Fieldwork at
selected locations in Vanuatu, the Cook Islands and Fiji presents a range of studies
across different types of island settings (such as volcanic coasts, barrier reefs andlow-lying atoll islets) to elucidate some of the principal environmental changes felt.
Landscape effects of the following tropical cyclones are investigated in detail: TC
Ami which struck Vanua Levu Island in Fiji in January 2003, TC Percy thatdevastated Pukapuka Atoll in the Northern Cook Islands in March 2005 and TC Funathat traversed parts of northern Vanuatu in January 2008. Each of these storms hascaused long-lasting physiographic effects through the action of powerful waves,storm surge, mass movements and river floods. Off Vanua Levu’s northern coast,
coral boulder fields were emplaced on barrier reefs 8-25 km offshore due to reefedge damage. Examination of this coral detritus may provide clues on the siteselectivity of reef damage and the wave energy needed for clast production andentrainment. For the tiny coral islets of Pukapuka Atoll the major problem has beensaltwater contamination of the very limited existing groundwater resources, which
required approximately two years to recover. On Ambae Island in Vanuatu, waveinduced beach erosion has exacerbated shoreline retreat, threatening coastal forest,
agriculture and infrastructure development.
Yet, island landscapes can also benefit from the changes brought about by cyclonedriven geomorphic processes. Thick alluvial sediments deposited by floods onvalley floors provide rich soils for sugarcane production in Fiji, sustaining local

economies. Atoll islands are nourished by reef-derived debris during storms,increasing their longevity. Elsewhere, coastlines have experienced progradation
rather than erosion, depending on local physiographic controls.
A betterunderstanding of these and similar landscape responses to geomorphic processes
during storms therefore helps build up human resilience, which is an important formof adaptation to natural hazards for island communities.

Figure. Left: large coral boulder emplaced on the outer edge of the Great Sea Reef off the northern coastof Vanua Levu Island in Fiji by storm waves generated by cyclone Ami in January 2003. Right:
vegetation damage and shoreline retreat on Ambae Island in Vanuatu, after sediment mobilisation during
cyclone Funa in January 2008.