Africa: Annual rainy season likely to cause increased flood threat and localized disruptions across southern regions through March

Event

Southern Africa will experience periods of heavy rainfall during the annual rainy season through March. Affected countries include Angola, Zambia, Zimbabwe, Botswana, Namibia, South Africa, Lesotho, and Eswatini.

There are a few areas where the rainy season is unlikely to have a major impact, including the Northern and Western Cape provinces of South Africa, the desert regions of western Namibia, and the Makgadikgadi Pan Desert of Botswana.

The heavy rainfall period will increase the risk of flooding and landslides. Meteorological agencies throughout southern Africa may issue weather warnings, particularly if extreme rainfall, severe thunderstorms, or strong winds are forecast.

Flood-prone areas

Communities with poor or a lack of stormwater drainage systems may experience urban flooding during significant rainfall, while areal flooding threatens sites near rivers and streams - particularly those within recognized floodplains. Deadly flash flooding is possible following torrential downpours, especially in vulnerable communities near the edge of watercourses.

Floodwater ponding events might persist in low-lying areas over the coming weeks and months. Even relatively low amounts of precipitation can trigger flood events in locations where dry, compacted soil cannot absorb runoff. Landslides and mudslides could occur in hilly or mountainous areas, including the Drakensburg (South Africa, Lesotho, and Eswatini) and Witwatersrand mountain ranges (South Africa and Botswana).

Transport

Floodwaters and debris flows will likely 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 will cause hazardous driving conditions on regional highways. Authorities will probably temporarily close some low-lying routes that become inundated by floodwaters.

Severe weather will likely trigger flight delays and cancellations at domestic and international airports. Authorities will probably temporarily suspend port operations or close beaches if strong winds trigger hazardous sea conditions. Flooding will likely block regional rail lines; freight and passenger train delays and cancellations are likely in areas with heavy rainfall and potential track inundation.

Localized business disruptions are probable; 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

There is an increased threat of disease outbreaks during the rainy season. Backflow from drains 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) before 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

Botswana Meteorological Service
Eswatini Meteorological Service
Namibia Meteorological Service
South Africa Weather Service
Zambia Meteorological Department
Zimbabwe Meteorological Services Department