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Intense rainfall in mid- and late April causes widespread floods in East Africa and Yemen

  • Seasonal Monitor
  • East Africa
  • May 5, 2020
Intense rainfall in mid- and late April causes widespread floods in East Africa and Yemen

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  • Mensagens-chave
  • Forecast
  • Partner
    • Seasonal rains intensified across East Africa in the past week, resulting in widespread floods that caused human fatalities and displacement, as well as crop damage and loss of household assets in parts of Kenya, Uganda, Ethiopia, Somalia, Burundi, and Yemen.

    • The on-going exceptional seasonal rains are mostly attributed to sustained warmer-than-normal Indian Ocean, coupled with favorable atmospheric conditions over much of East of Africa.

    • Cropping and rangeland conditions remain generally favorable in response to the seasonal rains, despite the adverse impacts of flooding in parts of the region. However, localized damage from desert locust has been reported in Belg-cropping areas of Ethiopia, southeastern South Sudan, and northeastern Uganda and there is a high risk of localized damage in eastern and central Kenya and northwestern Somalia.

    • The rainfall forecast indicates an increased likelihood for continued moderate to locally very heavy rains in most parts of the region in coming week, with heightened risks of flash floods in flood prone areas. However, rainfall intensity is expected to subside in mid-May.

    Torrential rainfall from mid- to late April marked the full establishment of the Belg rains in Ethiopia and Gu rains in Somalia, as well as the mid-point of the March to May long rains season in Kenya, Uganda, southeastern South Sudan, Rwanda, and Burundi. Rainfall was heaviest from April 11th to 20th in Ethiopia, southern Somalia, Kenya, Uganda, Burundi, and coastal Tanzania, where satellite-derived anomalies were in excess of 50-200 millimeters (mm) (Figure 1). In many areas, the heavy rains alleviated the rainfall deficits that were previously observed in early April and cumulative seasonal totals are well above average (Figure 2). However, cumulative rainfall deficits are recorded in localized areas of western Ethiopia, southern South Sudan, and western Uganda.

    The heavy rains during the period of April 11-20 were ranked among the wettest on the 40-year record in several areas: central Kenya; central Ethiopia; the Mandera triangle area of Kenya, Ethiopia and Somalia; parts of coastal Kenya and Tanzania; and parts of central and western Yemen. Regionally, flash floods and riverine floods have caused human fatalities and displaced tens of thousands of households, in addition to causing property and infrastructure damage and flooding cropland. In Kenya, available reports indicate that more than 116 people have died and 40,000 people have been displaced. In Uganda, 200 people have been displaced near Lake Victoria and Lake Kyoga; an additional 140,000 people are at risk of being displaced due to flash floods. In Ethiopia, flash floods occurred in Diredawa and in two localities of SNNPR (Gamo and South Omo zones), where loss of human lives and property were also confirmed by various local sources. In Yemen, OCHA estimates nearly 150,000 people have been affected by flooding in 13 governorates since mid-April, including in Marib, Sana’a, Hajjah, Aden, Lahj, Abyan, Taizz, and Shabwah, in addition to 4,625 households affected by floods in late March, including in Al Dhale’e and Hadramaut governorates. In Somalia, floods occurred along the Juba river basin in southern Somalia due to above-average rainfall locally and in the river catchments of the Ethiopian highlands, especially in Gedo region. Early reports from FAO/SWALIM indicate loss of both property and recently planted crops. Flash floods also occurred in northeastern Somalia, resulting in the death of six people. In Burundi, flash floods, landslides, and river floods have affected nearly 30,000 people.

    Further, recent observations of Lake Victoria water levels by the Lake Victoria Basin Commission (LVBC) and complemented by NASA/Poseidon satellite-based observations (NASA/POSEIDON Lake Levels) depict unprecedented lake water levels. Current levels are the highest on the historical 60-year local record, superseding the comparable lake levels recorded during the 1997/98 extreme El Niño event. Already, there are media reports of flooded islands within the Lake, forcing the relocation of 1,000 people.

    The latest vegetation anomalies according to the eMODIS/Normalized Difference Vegetation Index show mixed vegetation conditions across the region (Figure 4). Better-than-normal conditions are observed in many areas that are currently receiving seasonal rainfall, including in many pastoral and agropastoral livelihood zones of the Horn. Some atypical dryness is observed in parts of eastern Ethiopia, southern Somalia, and northeastern Kenya, even though rainfall was above average in mid- to late-April and reports of desert locust are relatively low or absent in these areas. Persistent cloud cover, associated with ongoing rainfall and an increased likelihood of improving vegetation conditions, is also obscuring comprehensive views of surface vegetation conditions in some areas. Much of the dry or cloud-covered areas are likely to see improvement in vegetation conditions in the coming weeks as a result of the recent rains, apart from flood-inundated locations. Other drier-than-normal areas include northern Afar and Tigray regions of Ethiopia and northwestern South Sudan, which are in the dry season prior to the onset of the Kiremt and main rainfall seasons, respectively.

    Meteorological and environmental conditions remain conducive to Desert Locust breeding, with another generation anticipated to emerge in May and June. Although control efforts are ongoing and reducing locust populations, some delays in aerial spraying, training of ground control sprayers, and delivery of pesticides are being reported due to the impact of local and international travel and restrictions. The latest FAO/DLIS updates are indicative of northward migratory patterns of desert locusts with expected changes in low-level wind regimes from north-south to the current establishment of south-north monsoonal wind patterns. This has pushed locusts from some of the breeding areas in Somalia and Ethiopia northward up to Yemen.

    The following is a country-by-country update on recent seasonal progress to date:

    • In Somalia, heavy rainfall at the start of the Gu season in mid-April has resulted in floods in riverine areas, but the rains were broadly favorable for early crop planting in southern agropastoral regions. Currently, most crops in agropastoral areas have germinated and there are no recent reports of desert locust in these areas. Meanwhile, above-average rainfall in central and northern pastoral regions has maintained very good pasture and water availability. Desert locusts are consuming vegetation in the northwest, but so far the heavy rains have served to regenerate enough vegetation for livestock consumption. The main areas of concern for desert locust damage are Northwestern and Togdheer agropastoral livelihood zones, where planting is starting. Heavy rains within the Juba and Shabelle river basins caused floods in the lowlands of Middle Shabelle region (Jowhar and Balad Districts), Gedo (Bardhere district), Middle Juba (Sakow, Buale, Jilib districts), and Lower Juba (Jamame District). Field reports indicate that these floods destroyed some of the off-season crops and also constrained main planting activities. Flash floods were also reported in Burhkaba District (Bay region) and Qardho District (Bari region) and Hargeysa town.
    • In Ethiopia, the Belg rainfall season is now well established in the country, with mostly early to timely onset and above average to average rainfall performance. Recent heavy rains caused floods and landslides in Diredawa and Gamo and South Omo zones in SNNPR, with reported loss of human lives and extensive property damages. Based on current ground conditions, including damage caused by desert locust, slightly below-average Belg crop production is anticipated. Preliminary estimates from the government of Ethiopia indicate a possibility for about a ten percent reduction.
    • In Kenya, heavy rainfall caused loss of lives and displaced tens of thousands of households in in western Kenya and the Rift Valley as well as central, southeastern, and coastal strip areas. In Tana Riverine livelihood zone, river flooding destroyed more than 200 acres of maize, beans, green grams and vegetables that had been planted for the long rains season. In eastern and southern counties, early-planted crops are currently in the reproductive stage, but the majority of crops are either in the emergent to early vegetative stages. Desert locust control efforts are ongoing, but localized damage to short rains crops in Embu (Mbeere), Tharaka Nithi, Meru (Meru North), and Kitui counties, where crops are in the vegetative stages. Overall, pastoral conditions and livestock remain in good condition following prolonged seasonal rains with short-lived dry spell. With water resources and hydro-electric dams full, water is likely to be discharged into lower catchments areas of the Tana and Athi rivers, which may result in further floods. Lake Victoria’s record-high water levels are also posing a threat to local island and beach inhabitants.
    • In Sudan, typical sunny and dry conditions prevail across the country with near-average vegetation conditions. Dry conditions will persist until the onset of its main seasonal rains from June to September.
    • In South Sudan, southern and eastern regions of the country are benefitting from the first season rains. Cropping and vegetation conditions have significantly improved, especially in regions bordering southwestern Ethiopia, which experienced very early rainfall onset in February. However, the entry of several swarms of desert locust in the southeast in March/April pose a significant threat to first season crops in Magwi, Torit, Lopa/Lafon, Budi, and Ikotos counties of Eastern Equatoria. According to county-level agricultural departments and FAO field monitoring staff, desert locusts have damaged an estimated 10 percent of crops planted in Magwi county and 10 percent of crops in Lopa/Lafon.
    • In Uganda, the heavy rains have helped to ease or overcome early season deficits, though deficits persist in the western part of the country. Despite the deficits compared to the long-term average, cumulative rainfall has still been favorable for cropping conditions. In bimodal areas, planting and weeding are ongoing, with most crops in early vegetative to early flowering stages. In parts of Teso, Karamoja, and parts of Acholi and Lango sub-regions, some localized crop damage in April has been reported due to desert locusts. There is an increased likelihood for flash-floods over eastern and areas around the Lake Victoria basin and in some urban areas, due to their inherent poor drainage systems.
    • In Rwanda and Burundi, average to above average rainfall performance is support favorable production prospects in both Rwanda and Burundi overall. However, western and southern Burundi had exceptionally heavy torrential rains in mid- to late April that caused flash floods with adverse impacts in Cibitoke, Bubanza, and Bujumbura provinces.
    • In Tanzania, rainfall in northeastern coastal areas during mid-April was the wettest on record. The rest of the county has received near average to above average rainfall in April as the seasonal tropical rainfall system shifts northward into the equatorial sector of East Africa. Cropping conditions in bimodal northern regions are in very good condition and in early reproductive stages. These is increased likelihood for floods, especially over northeastern coastal regions in the forecast.
    • In Yemen, the latest field information, confirmed by satellite rainfall estimates are indicative of above average rainfall amounts over western and coastal areas of the country. As summarized above, UNOCHA reports indicate heavy torrential rains and floods adversely impacted the city of Aden and Lahj, Abyan, Taizz, Al Dhale’e, Shabwah and Hadramaut governorates.


    Moderate to locally very heavy rains are forecast to continue through May 5th (Figure 5). Areas of increased chances for heavy to very heavy rains are along the northeastern coastal regions of Tanzania into Kenya’s coastal strip. Meanwhile, much of East Africa is expected to remain generally wet, with widespread moderate to heavy rains and an increased likelihood for continued widespread floods in the region. Regions of elevated risks of flooding include the Tanzania/Kenya coastal strip and surrounding regions as well as the Lake Victoria basin and its surrounding regions in Uganda, Tanzania, and Kenya. However, isolated areas of southeastern, eastern, and northern Kenya are expected to be uncharacteristically sunny and dry during this period.

    Although the March to May seasonal rains are forecast to continue into mid-May, there is an increased likelihood that the intensity of rainfall will begin to subside slightly over northern Kenya and also over parts of southern and central Tanzania. Meanwhile, East Africa coastal regions are expected to maintain abnormally heavy rains at the peak of their seasonal rains, which often occurs in May. Lower rainfall intensity is also likely in parts of southern Somalia, mid-way through its April to June Gu season.

    Sustained moderate to very heavy rains for the next 1-2 weeks, are likely to result into continued well above average seasonal rainfall performance over much of East Africa. Early season agricultural production prospects look generally favorable, but, with anticipated varied levels of flood severity and their associated adverse impacts in most flood prone areas. Seasonal and permanent river levels will continue to inundate surrounding agricultural areas with expected crop and property losses.


    Figura 1

    Figure 1

    Fonte: FEWS NET/UCSB Climate Hazards Center

    Figura 2

    Figure 2

    Fonte: FEWS NET/USGS

    Figura 3

    Figure 3

    Fonte: FEWS NET/UCSB Climate Hazards Center

    Figura 4

    Figure 4

    Fonte: FEWS NET/USGS

    Figura 5

    Figure 5

    Fonte: NOAA/CPC

    FEWS NET’s Seasonal Monitor reports are produced for Central America and the Caribbean, West Africa, East Africa, Central Asia, and Somalia every 10-to-30 days during the region’s respective rainy season(s). Seasonal Monitors report updates on weather events (e.g., rainfall patterns) and associated impacts on ground conditions (e.g., cropping conditions, pasture and water availability), as well as the short-term rainfall forecast. Find more remote sensing information here.

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