Marine Atlas: Maximizing Benefits for Solomon Islands

STORMY TIMES: CYCLONES

Tropical cyclones pose direct and indirect threats to Solomon Islands, its people and its marine life. Marine and coastal habitats including mangroves, seagrasses and coral reefs play an important role in offering effective protection and therefore need to be sustainably managed and conserved.

Solomon Islands is less prone to cyclones than several of its Pacific Island neighbours to the east. However, the country still has a significant risk of cyclones, particularly in the east and south. On average, Solomon Islands receives 1–2 cyclones per season. The cyclones that affect Solomon Islands are often in the early stage of their life cycle, meaning they are usually relatively small. Nevertheless, they can cause serious dam- age to structures, crops, forests and local water supplies, and have caused loss of life in the past (Solomon Islands Government Meteorological Services Division, n.d.). Cyclones are monitored by the Solomon Islands Government Meteorological Ser- vices Division in Honiara and categorized according to the Australian and South Pacific Category System from category 1 (90 km/h gusts) to category 5 (280 km/h gusts). The cyclone season is considered to

run from the beginning of November to the end of April, but destructive cyclones can occur outside this period. The formation of cyclones in the region is strongly influenced by the El Niño–Southern Oscillation (ENSO; see also chapters “Go with the flow” and “Hotter and higher”). During El Niño years, cyclones are more likely to form between 6°S and 18°S and 170°E and 170°W. The highest density is centred over the south- ern and eastern part of Solomon Islands’ waters, where low-level relative vorticity, an upper-level divergent atmosphere and weak environmental wind shear are very conducive to genesis. During La Niña years, slightly fewer tropical cyclones form and the origin moves to the south of Solomon Islands (Chand and Walsh, 2009). El Niño brings a heightened risk of cyclones.

change and the frequency and intensity of cyclones in the region. Diamond et al. (2013) found a statistically significant increase in the number and intensity of cyclones in the period 1991–2010 compared with the period

1970–1990 in the tropical South-West Pacific. In Solomon Islands, it is estimated that the number of tropical cyclones will decrease by the end of the twenty-first century. However, those that do occur are expected to be more

intense or severe (MECDM, 2012). Rising SSTs are fuelling cyclones (see also chap- ters “Hotter and higher”) that are resulting in increasing damage, including to Solomon Islands’ valuable coastal habitats. At the same time, conserving habitats such as coral reefs and mangroves offers a very effective form of protection against storms. In this way, Solomon Islands can strengthen its defences against cyclones.

In the past decade, there has been increasing attention on the relationship between climate

Cyclone Namu

pecially along the island’s eastern side where entire villages were destroyed. On Guadalcanal Island, a village of 43 people had only five survivors and more than 75 per cent of the island’s plains were flooded. In addition, 22 per cent of homes on the island were either dam- aged or destroyed. Villages throughout the entire island group sustained severe damage. Overall, approximately 90,000 people—one third of the country’s pop- ulation—were reported homeless. Cy- clone Namu was responsible for at least 150 deaths, largely from flooding and landslides. Property damage and eco- nomic losses across Solomon Islands totalled US$25 million and US$100 million (1986 USD) respectively.

On May 15, 1986, a tropical depression formed within the monsoon trough. Located north of Solomon Islands, the storm steadily intensified while mean- dering. After briefly moving west, the storm attained category 2 intensity on May 18, moving through the country’s island chain the following day. Cyclone Namu had a peak intensity of 120 km/h. Although its wind speed was not par- ticularly high, the storm’s slow move- ments allowed for prolonged periods of heavy rainfall, resulting in significant flooding throughout Solomon Islands. The islands of Malaita and Guadalcanal experienced the worst damage. Rough seas and strong winds severely dam- aged Malaita Island’s coastal areas, es-

MAXIMIZING BENEFITS FOR SOLOMON ISLANDS

CLIMATE CHANGE THREATS

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