In 2023, heavy rains in the Horn of Africa caused widespread flooding, displacing hundreds of thousands of people and causing huge damage, even though early climate forecasts warned of such an event.
Heavy rains in the Horn of Africa have left entire towns under water. In October and November 2023, heavy rains caused widespread flooding in Somalia, Ethiopia and Kenya. The floods follow the longest drought on record, which has left millions of people food insecure between 2020 and 2023. According to the United Nations Office for the Coordination of Humanitarian Affairs, flooding has killed more than 100 people and displaced more than 700,000 people since October 1.
Countries in the Horn of Africa typically have two rainy seasons: the "short rains" in October, November and December (OND) and the "long rains" in March, April and May (MAM). Rainfall in the "short rainy season" ending in mid-November was much heavier than in previous years. According to the Famine Early Warning Systems Network (FEWSNET), precipitation totals in southern and western Ethiopia, Somalia and Kenya have been between two and four times above average since October 1.
Excessive rainfall in the plateau areas of Ethiopia and Somalia in late October and early November caused the water level of the Shabelle River to rise until the river surged on November 11. Subsequent rains caused the river to overflow its banks in central Somalia, flooding surrounding areas, including the town of Beledweyne. Flooding in the town forced about 250,000 people, or 90% of the population, to leave their homes.
The picture above shows Beledven on November 15, 2023. For comparison, the image above shows the same area on September 12, 2023. The images, acquired by the Land Imager (OLI) on Landsat 8, use false color to highlight the presence of water, which appears blue.
The video below shows a wider view of the Shabelle River.
Continuing heavy rains also caused the Juba River in western Somalia to overflow, inundating farmland and roads in the town of Luke. In Bardere, a bridge was washed away, cutting off access to the town.
As early as July 2023, researchers at the University of California, Santa Barbara's Climate Hazards Center used climate models to provide early warnings for rainfall and flooding in the Horn of Africa during the OND "short rain" season. The Climate Hazards Center provides rainfall data and forecasts to FEWSNET, a project supported by the U.S. Agency for International Development (USAID) in partnership with several other agencies, including NASA.
At the time, sea surface temperature patterns in the Indian and Pacific oceans were forecast to bring unusually high rainfall to East Africa. The positive Indian Ocean Dipole (IOD) is characterized by warmer than normal sea surface temperatures in the western Indian Ocean and cooler than normal temperatures in the eastern equatorial Indian Ocean, typically favoring the development of a moist OND in eastern Africa. El Niño (warmer than normal sea surface temperatures in the central and eastern tropical Pacific) also tends to amplify the effects of positive IOD. These two forces have been linked to floods in East Africa and droughts and fires in Australia.
"I think our forecasts are a good example of how concern about climate hazards is increasing over time," said Chris Funk, director of the Climate Hazards Center. "In July, we predicted strong El Niño and IOD threatening East Africa. In September, our forecasts became more concerning. Then in October, we noticed a large increase in the intensity of the IOD, and at the same time, rapid cooling over the eastern Indian Ocean led us to predict an extremely wet season."
Abnormally high rainfall since October has eased long-term drought conditions in the Horn of Africa. But it could also lead to cholera outbreaks, an increase in pests and diseases of crops and livestock, and the loss of life that has already occurred.
Researchers at the Climate Hazards Center note that this year's IOD intensity looks similar to that seen in late 2019, when an IOD event caused abnormal rainfall, flooding and displacement in the Horn of Africa. The unusually wet soil that year also led to an outbreak of desert locusts (Schistocercagregaria) in early 2020, which invaded and destroyed crops on at least 70,000 hectares (173,000 acres) of land in Kenya.
"Since the second half of 2016, the eastern Horn of Africa has had an almost uninterrupted series of very wet or very dry rainy seasons," Funk said. "The Climate Hazards Center is leveraging recent advances in climate modeling - which can predict these droughts and heavy rains months in advance - in an effort to connect these predictions to better inform risk management, agricultural and livestock management practices."