South Pacific Islands: Annual rainy season to occur across the region through at least April 30 /update 1

Event

The annual rainy season will run through April, bringing an elevated threat of heavy rainfall, strong winds, flooding, and landslides/mudslides to Fiji, New Caledonia, Solomon Islands, Tonga, and Vanuatu. Meteorological agencies may issue weather warnings in response to the rainy season, particularly if extreme rainfall, severe thunderstorms, or strong winds are forecast.

Hazardous Conditions
Heavy downpours, flooding, and landslides could affect business, transport, and utility services in many areas. Localized disruptions could persist well after hazardous events have concluded; floodwaters may take days to subside, and debris from mudslides may take weeks to be cleared. The risk of flooding is highest in low-lying communities near waterbodies in recognized floodplains. Rivers could flood during periods of intense rainfall. Fiji and Vanuatu have several rivers, including the Jordan, Lololima, and Sarakata rivers in Vanuatu and the Ba, Dreketi, Nadi, Nanuku, Navua, Rewa, and Sigatoka rivers in Fiji. The Solomon Islands and New Caledonia have several rivers and lakes, including the Lunga, Matanijau, and Tenaru rivers and Lake Tegano in the Solomon Islands and the Diahot and Dumbea rivers and Yate Lake in New Caledonia. Tonga does not have any rivers but Niuatoputapu and 'Eua islands contain creeks. Flash floods, which can occur with little to no warning, often pose a threat to communities downstream of major rivers or dams in the event of structural failure. Urban flooding is possible in areas with poorly maintained or inadequate drainage systems, while storm surges may trigger flooding in coastal areas. Landslides and mudslides are possible in hilly and mountainous areas.

Tropical systems, including tropical depressions and cyclones, may pose additional threats during the rainy season. Tropical systems usually prolong or aggravate disruptions already caused by heavy rainfall.

Transport
Floodwaters and debris flows may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around affected areas, especially in rural areas, where infrastructure is already of a poor standard. Ponding on road surfaces could cause hazardous driving conditions on regional highways. Authorities could temporarily close some low-lying routes that become inundated by floodwaters.

Severe weather could also exacerbate transport disruptions in areas already hard-hit by the coronavirus disease (COVID-19) pandemic, particularly resulting in air, land, and maritime freight shipment delays. Significant downpours could trigger flight delays and cancellations at any domestic and international airports that are continuing to operate. Authorities may temporarily suspend port operations if strong winds trigger hazardous sea conditions.

Localized business disruptions may occur; some businesses might not operate at full capacity because of flood damage to facilities, possible evacuations, and some employees' inability to reach work sites.

Health
The threat of disease outbreaks is elevated during the rainy season. Backflow from drains that have mixed with floodwaters can become trapped in open areas when inundations recede. These stagnant pools often become a breeding ground for mosquitoes and bacteria, increasing the incidence of insect- and waterborne diseases. Exposure to contaminated water from inundated industrial sites, sewer systems, and septic tanks also poses a significant health threat.

Advice

Monitor local media for updates and advisories on weather conditions. Confirm all transport reservations (air, ground, and maritime) prior to travel. Make allowances for possible supply chain disruptions throughout the rainy season, particularly in areas affected by flooding and or/landslide events.

Avoid low-lying areas near streams, rivers, and other bodies of water, such as reservoirs and coastlines, due to the threat of flooding. Do not drive on flooded roads. Exercise caution in elevated terrain due to the threat of landslides and mudslides. Charge battery-powered devices when electricity is available; restrict the use of cellphones to emergencies only during periods of severe weather. Take precautions against insect- and waterborne diseases. Keep any necessary medications in a waterproof container.

Resources

Fiji Meteorological Service
Meteo Nouvelle-Caledonie
Solomon Islands Meteorological Service
Vanuatu Meteorology and Geo-hazards Department