Poor management of surface run-off in East Africa has come to the fore, with the onset of rains and a forecast of above normal rainfall in Kenya, Rwanda and Tanzania in the later part of October.
In Tanzania, 29 people were killed in floods in Tanga and Morogoro, as eight died in Kenya. A week of torrential rains in northeastern Ghana had also left 28 dead by Friday.
With the rains forecast to continue pounding Kenya, Rwanda and Tanzania intermittently up to February next year, there are fears of disease outbreaks, more deaths and other losses from inclement weather.
Meteorologists have attributed the heavy rainfall within equatorial countries to normal seasonal patterns and not the periodic phenomena el Nino.
“Nothing exceptional is happening. The inter-tropical convergence zone is moving from the north toward the Equator,” said Mathieu Mbati, senior forecaster at Meteor Rwanda, the country’s national meteorological authority.
The Meteor has forecast rainfall to increase by up to 20 millimetres per day to reach highs of between 350 millimeters and 410 millimeters in parts of Kirehe, Ngoma, Bugesera, Eastern Province and some parts of Nyanza, Gisagara districts in the southern province, before getting heavier in November.
It will be accompanied by thunderstorms and strong winds.
“It may increase soil vulnerability and lead to disasters,” Mr Mbati added.
Also Musanze, Gicumbi, Gakenke, Rulindo and Burera districts of Northen Province; Nyabihu, Rubavu, Rusizi, and Nyamasheke districts in the western province and Nyamagabe, Nyaruguru and Muhanga of the Southern Province will be the most affected by the short rains forecast at between 500 millimeters and 600 millimeters.
East African countries normally receive heavy rains during the short rain season of October to November due to a belt of low-pressure circling the earth and bringing together winds from the Northern and Southern hemispheres.
This natural occurrence, called the intertropical convergence zone, is repeated in April and May when the low pressure belt moves from the south towards the equator.
The weathermen in Kenya, however, offered another explanation. It said cooler moisture was being blown to the east African coast from Australia.
The occurrence known as the Indian Ocean Dipole was measured at 2.1 DMI (the DMI index is an indicator of the east-west temperature gradient) making it one of the strongest in decades.
“Strong winds will be blowing into our countries depositing a lot of moisture, hence a lot of rainfall,” said Ezekiel Muigai, a senior meteorologist at the National Meteorological Centre. However, this means dry spells and drought in Australia, Indonesia and Singapore.
In Tanzania, coastal towns of Tanga and Morogoro where deaths caused by flash floods have been reported are the most at risk.
“Based on the current and expected climate systems, there is an elevated chance of above normal to normal rains over most parts of unimodal Tanzania,” warned Tanzania’s meteorological authority director general Agnes Kijazi.
In the past week, parts of the capital Dar es Salaam, were cut off from the northern regions of Tanga, Kilimanjaro, and Arusha as well as Kenya and Uganda after bridges were submerged.
Flooding along major roads also forced the temporary closure of the Dar es Salaam Rapid Transit shuttle buses plying the Morogoro Road, a major highway in the city.
Dr Kijazi further said heavy rains are expected to cause floods with an outbreak of waterborne diseases, destruction of roads and homes, especially in areas with poor sewage systems.
In its outlook for September 2019 to April 2020, the Tanzania weatherman warned last week of continued heavy rains in 13 districts that could disrupt mining, agriculture and tourism.
Western, central, south western highlands, southern and the southern coast of Tanzania are forecast to have normal to above normal rainfall. Daily rainfall of up to 50 millimetre is expected but less likely to be destructive unless it falls consistently for several days.
Dr Kijazi said Tanzania had received 145 millimetres of rain since the season started at the end of September.
The Kenya Met Department also warned that convective clouds were sweeping through Tanzania and into the Kenyan Coast, causing high tides which fishermen should be weary of.
Flash floods are wreaking havoc in the northern Kenya district of Marsabit, and Kitui in the southeast and the low lying coastal areas, marooning homesteads and sweeping away infrastructure, vehicles and crops. The deaths in Kenya happened in Kitui and Garissa.
“We are likely to get more rain than the long-term average for the season especially in regions that have traditionally received less than average rainfall.
This is the season when you hear of trees falling on houses and rooftops being blown away,” said Mr Muigai of the National Meteorological Centre.
The rain that fell in Mombasa on Wednesday last week was measured at 118.3 millimetres. It caused flashfloods and damage to houses and marooning homes.
Dr Saji Hameed, one of the scientists who discovered the Indian Ocean Dipole (IOD) told a global weather publication,’’ The Weather Watchers’’ last month that there would be displacement of people, emergence of Rift Valley fever and other flood-related issues as those experienced during the strong IOD of 2006.
—Report by Pauline Kairu, Apolinari Tairu and Leonce Muvunyi.