Record high rainfall leads to severe flooding in the northern sector

• In August, continued above-average rainfall (Figure 1) constituted the wettest of the 40-year historical record in parts of Sudan, Eritrea, and Ethiopia (Figure 2). In Greater Darfur and in the northeast of Sudan, this has resulted in the damage or destruction of homes, bridges, roads, and dams and caused displacement of over 170,000 people across 14 states. The collapse of the Arba’at Dam on August 25 has likely been the deadliest incident, with estimates of over 130 people killed. Overall, nearly 600,000 people have been affected.
• In Ethiopia, continued heavy rainfall and landslides in August in parts of Gambella, Afar, Amhara, Somali, Oromia, and South Ethiopia has led to over 300 deaths, displacement, and destruction or damage to cropland in localized areas. Overall, 800,000 people have been affected.   
• In South Sudan, flooding expanded further amid heavy rainfall, affecting 472,000 people in 26 counties as of the end of August. Continued high water levels in lakes upstream and an elevated release of water from the Jinja Dam are sustaining very high water levels in the Nile River, surpassing Alert and High thresholds in some locations.  
• Elsewhere in the region, namely parts of meher-producing Ethiopia, bimodal South Sudan, and unimodal Kenya and Uganda, the favorable rainfall conditions are expected to contribute to average to above-average crop production. Atypical rainfall occurred in the bimodal areas of Uganda during the typically dry July-August period. 
• The risks of further flooding in September remains relatively high in most parts of eastern, central, and western Sudan; northern South Sudan; western Ethiopia; and upper Shabelle River in Somalia due to the high river levels and continued heavy rains upstream.

Context: Between June and September, the following are the areas and names of the rainy seasons underway in parts of East Africa: kiremt rains (June to September) in western and northern Ethiopia; main rainy season (June to September) in the unimodal zones of South Sudan and Sudan; long rains in unimodal Uganda and Kenya; karan/karma rains (July to September) in northern pastoral areas of Ethiopia and Sitti and Fafan zones of Somalia; and second rains (July to November) in South Sudan bimodal zone. 

As of the end of August, cumulative rainfall in parts of Sudan, Eritrea, and Ethiopia indicated the wettest year of the historical 40-year record (Figure 2), which is leading to severe flooding in many areas (Figure 3). In Sudan, 15 states experienced severe flooding that resulted in deaths of over a hundred people, displacement of over 170,000, and significant damage and destruction to property and public infrastructure. In late August, surging waters from floods led to Arba’at Dam north of Port Sudan to burst its banks, causing over 130 deaths and many more missing, with massive damage along its path. In Ethiopia, flooding, mudslides and landslides have been reported throughout the season, claiming more than 300 lives and affecting more than 800,000 people. These incidents have been reported across almost all the Ethiopia regions, the latest ones in west Gambella, along Rib River in Amhara, Afder and Shabelle in Somali, and central parts of South and Central Ethiopia regions. In South Sudan, the inundated areas within the Sudd wetlands continue to increase due to the above-average rains in central and southeastern South Sudan. This is likely to increase even further given the continued rains forecasted for September and high river water levels. 

Across the western sector of the region, the unimodal cropping season is still underway in the Western Rift Valley areas of Kenya and in Karamoja in Uganda. Currently, crops are in favorable conditions across the region following average to above-average rainfall. The bimodal regions of Kenya, Uganda, Rwanda, Burundi, and Somalia have been harvested, while harvesting is ongoing in bimodal South Sudan. Harvests were average across Uganda, Rwanda, western Kenya, northeastern Burundi, and parts of southern Somalia, attributable to favorable rainfall despite dry spells and delayed rainfall onset in some areas. In contrast, southeastern, eastern, and coastal Kenya, as well as central Somalia, are experiencing below-average production due to the irregular temporal distribution and early to average cessation of rainfall.

Vegetation remains favorable for most regions apart from coastal Kenya, southern Somalia, and parts of the Somali region of Ethiopia according to the map of vegetation health (NDVI) as of the end of August (Figure 4). These areas of the Horn of Africa are of particular concern moving forward to the 2024 October–December rainy season given the forecasted transition from neutral ENSO conditions to La Niña, most likely by October 2024. La Niña is associated with below-average rainfall over the Horn as evidenced in the historic 2020-2023 La Niña-induced drought.

The September rainfall outlook, based on the NMME one-month forecast initialized in August (Figure 5), indicates continued above-average rainfall across the northern sector. However, the forecast show a neutral signal for central and northern Sudan as the rains start to shift southwards, which could offer a reprieve from flooding events. Ethiopia and South Sudan remain at high flood risk in the coming month, especially in central (including the Sudd wetlands) and southern South Sudan and western and southwestern Ethiopia.

The onset of the September–December rainfall season for the bimodal areas of the region, especially in most of Uganda, Rwanda, Burundi, and western Kenya, is likely to be on time.