Madagascar: Heavy rainfall and further flooding forecast nationwide through Jan. 23 /update 1

Event

Following rounds of heavy rainfall, further flooding is forecast across Madagascar through at least Jan. 23. Additional rainfall is likely in the coming days as part of the country's rainy season, which could exacerbate flooding in the area. Madagascar's General Directorate of Meteorology has warned of heavy rainfall of more than 10 cm (4 inches) per day over Analanjirofo, Atsinanana, Boeny, Diana, Sofia, and Vatovavy regions. Flooding and landslides are possible. Red (the highest level on a four-tier scale) warnings are in place for Ambatolampy, Andramasina, Anosibe An’ala, Antanambao Manampotsy, Marolambo, Marovoay, Mahajanga I, Mahajanga II, Mahanoro, Mitsinjo, Nosy-Varika, and Vatomandry districts. Yellow (second-lowest level on a four-tier scale) warnings are in place over Ambanja, Ambilobe, Analalava, Antsiranana, Antsohihy, East Fenerive, Mananara Avaratra, Moramanga, Soanierana Ivongo, Toamasina I, Toamasina II, and Vavatenina districts as well as Nosy-Be and Sainte Marie islands, Maroantsetra Town, Port Berger City, and Brickaville Commune. Water levels of the Sisaony River have dropped, reducing the flood risk. Officials could update and possibly extend the coverage of the relevant weather alerts over the coming days.

As of Jan. 21, reports indicate widespread damage, including collapsed houses and bridges, damaged infrastructure, and inundated farmland, in Antananarivo City and surrounding areas. At least 11 people have died in the Analamanga Region following landslides and flooding caused by heavy rainfall. Around 9,000 people have also been evacuated, more than 3,400 houses flooded, and 11 houses destroyed. Evacuations shelters are located at the Ankorondrano and Mahamasina indoor gymnasiums as well as at Amboditanimena.

Hazardous Conditions
Sustained heavy rainfall could trigger flooding in low-lying communities near rivers, streams, and creeks. Urban flooding is also possible in developed areas with easily overwhelmed or a lack of stormwater drainage systems. Sites located downstream of large reservoirs or rivers may be subject to flash flooding after relatively short periods of intense rainfall. Landslides cannot be discounted in hilly or mountainous areas, especially where heavy rainfall has saturated the soil.

Authorities could issue mandatory evacuation orders for flood-prone communities over the coming days. Disruptions to electricity and telecommunications services are possible where significant flooding or landslides impact utility networks.

Transport
Floodwaters and debris flows may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around affected areas. 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 trigger flight delays and cancellations at regional airports, including - but not limited to - those serving Antananarivo (TNR). Authorities may temporarily suspend port operations or close beach fronts along the Mozambique Channel and the Indian Ocean if strong winds trigger hazardous sea conditions. Flooding could block regional rail lines; freight and passenger train delays and cancellations are likely in areas that see heavy rainfall and potential track inundation.

Localized business disruptions may occur in low-lying areas; 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
Although a secondary concern, the threat of disease outbreaks cannot be discounted in the coming days and weeks. Backflow from drains that has 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 weather updates and related advisories. Confirm all transport reservations and business appointments prior to travel. Make allowances for localized travel delays, as well as potential supply chain disruptions, where flooding has been forecast. Do not drive on flooded roads. Charge battery-powered devices in case prolonged electricity outages occur.

Resources

Madagascar General Directorate of Meteorology (French)