The rains we should not forget

DAR ES SALAAM: AS the country prepares for what meteorologists warn could become one of the strongest El Niño events on record, Tanzania’s history tells a bigger story.

The country has suffered devastating floods for decades. Some came during El Niño years. Others did not.

From Dar es Salaam’s overflowing Msimbazi River to the Lake Victoria Basin, from Tanga’s washed-away bridges to the southern highlands battered by torrential rains, the same places keep appearing in the country’s flood history.

The pattern points to more than one climate event. It shows how geography, weather systems and human activities keep exposing the same communities whenever heavy rain falls.

According to Tanzania Meteorological Authority (TMA) Director General, Dr Ladislaus Chang’a, the country has experienced major El Niño episodes in 1982/83, 1997/98, 2015/16 and 2023/24.

He said Pacific Ocean temperatures have already risen by more than 2.2 degrees Celsius and could exceed 3 degrees Celsius later this year.

Climate experts, however, say El Niño is only part of the story. Some of Tanzania’s worst floods happened during non-El Niño years. They were driven by the Indian Ocean Dipole, regional weather systems and local atmospheric conditions.

The same places keep flooding

According to TMA climate status report issued annually, Tanzania’s flood history follows a familiar pattern, the northern coast, including Dar es Salaam, Coast and Tanga regions, appears repeatedly because of moisture from the Indian Ocean.

The Lake Victoria Basin, covering Kagera, Mwanza, Geita, Shinyanga, Simiyu and Mara, faces repeated flooding because of moisture from the Congo Basin and equatorial weather systems.

The southern highlands, including Mbeya, Songwe, Morogoro and Iringa Regions, receive heavy rain when moist air rises over mountains.

Low-lying areas such as Igunga in Tabora face another problem. Their clay soils retain water for long periods, making flooding worse. Instead of isolated disasters, these events form a recurring national pattern.

2011: Dar es Salaam overwhelmed

The year 2011 showed that devastating floods do not require El Niño. According to TMA’s Climate Status Report, extreme rainfall caused widespread destruction across several regions.

The first warning came in May, when Tukuyu recorded 232 millimetres of rain in a single day. The worst came in December of the same year.

Dar es Salaam received 60 millimetres on December 19, 156.4 millimetres on December 20 and another 43.8 millimetres on December 21.

Within three days, large parts of the city were under water. Floods swept through the Msimbazi flood plain. Roads became impassable. Bridges disappeared beneath fast-moving water. The TMA report showed that 43 people died, many others went missing and thousands lost their homes.

The disaster spread beyond the city. Above-normal rainfall also affected the Lake Victoria Basin and southern Tanzania.

TMA linked the floods to unusual warming over northern Australia, stronger westerly winds and warming in the western Indian Ocean, which pushed moist air towards Tanzania.

2018: The threat spread nationwide

By 2018, flooding had become a nationwide story. TMA recorded floods across the northeastern highlands, northern coast, central Tanzania and the Lake Victoria Basin.

March was particularly severe. Rainfall reached twice the long-term average across the north-eastern highlands. At least 20 people died, with Dar es Salaam recording the highest number of casualties. Between April 13 and 15, another major flood struck the commercial capital and 14 people died.

Schools closed for two days. Roads became impassable. The swollen Msimbazi River swept away nine houses, leaving more than 600 families homeless.

The disruption reached Zanzibar, where floods damaged roads and inundated more than 120 houses. The year brought other tragedies, six students died after a thunderstorm in Geita Region.

Sumbawanga District later recorded deaths, injuries and hundreds of destroyed rural houses. The events showed that different regions faced different threats urban floods, river floods and severe storms.

2019: Destruction intensified

The year 2019 represented a new level of extreme weather impacts, characterised by what TMA described as a quite a number of devastating extreme weather events, particularly heavy rains associated with significant flooding.

In October, several meteorological stations in the northern coast and northeastern highlands recorded rainfall five to ten times their long-term October averages.

The strong Indian Ocean Dipole phenomena during October through December was linked to above-normal rainfall over most regions in both bimodal and unimodal rainfall regimes.

However, this was not the only period of concern as significant events also occurred during April and May. Tanga Region experienced particularly severe impacts in October, with at least 20 deaths attributed to heavy rainfall, including flooded rivers and destroyed bridges.

Extreme rainfall events documented included Morogoro recording 77.6 millimeters on January 15, causing floods at Dumila Bridge and Mtwara recording 177.6 millimeters over just two days on February 7 and 8.

According to the TMA report, the human stories behind these statistics paint a picture of recurring trauma. Over 100 residents fled their flooded homes following heavy rainfall in Arusha district on April 29.

The destruction of properties and infrastructure was reported in various locations, including roads connecting Arusha with neighbouring districts and regions.

Between May 5 and 12, heavy rainfall over northeastern parts of the country, including Zanzibar, Dar es Salaam, Pemba and Coast regions, caused serious flooding.

In Dar es Salaam, at least five people died and several houses were flooded, displacing over 1,000 households and destroying more than 1,500 residences and infrastructure. In Zanzibar, three people were injured and over 2,000 houses were flooded and destroyed.

Public transport was shut down in Dar es Salaam’s Jangwani area due to the flooded Msimbazi River, schools were closed across Dar es Salaam, Unguja, and Pemba islands and social and economic activities were delayed or completely closed for over six hours.

Perhaps the most devastating single event of 2019 occurred in Handeni district, where approximately 29 people lost their lives due to severe floods. Most victims were swept away by flood waters or killed by falling debris as houses collapsed under the impact of the downpour.

The heavy rain brought economic activities, including transport, communication and power services, to a complete standstill. The infrastructure damage was staggering as up to 15 bridges managed by the Tanzania Rural and Urban Roads Agency (TARURA) were damaged.

The Tanzania National Roads Agency (TANROADS) also suffered significant damage, including a portion of the Dar es Salaam-Arusha Road and the Korogwe-HandeniMkata section.

The Mandera Bridge between Korogwe and Segera was swept away, forcing the closure of the Dar es Salaam-Arusha highway on October 26. According to TMA, the scale of the disaster left more than 2,000 bus passengers and motorists stranded at Mandera.

Approximately 40 houses were damaged, 70 were surrounded by water and more than 300 families were left without shelter. Hundreds of hectares of agricultural fields were flooded and crops were destroyed.

TMA attributed the Handeni flood to heavy rains that hit the neighbouring upstream districts of Kilindi, Kiteto and Simanjiro, where many seasonal rivers cutting through Handeni originated.

The year concluded with another devastating event on December 16 and 17, when heavy rains brought businesses and transport to a standstill in Dar es Salaam.

Most businesses remained closed throughout the day as transport to the city centre was suspended after most roads were submerged by flash floods.

ALSO READ: El Niño rains demand action before disaster

Why the same regions remain vulnerable

Climate Researcher of Saint Augustine University of Tanzania (SAUT), Mr Ngogo Mang’enyi said geography explains much of the recurring pattern.

He said the coast receives huge amounts of moisture from the Indian Ocean. When ocean temperatures rise, evaporation increases.

Moist air then moves inland and produces heavy rainfall. Mr Mang’enyi said the Lake Victoria Basin follows another pattern.

Moisture from the Congo Basin combines with strong equatorial heating to produce repeated heavy rain across Kagera, Mwanza and neighbouring regions. The southern highlands experience heavy rainfall when moist air rises over mountains and cools.

“This phenomenon explains why these regions frequently experience heavy rainfall events,” Mr Mang’enyi said.

He added, “Low-lying flood plains face another challenge because clay soils hold water longer. Flooding therefore lasts even after the rain stops”.

Human activity worsens the risk

Geography explains where floods occur, human activity often determines how destructive they become. Population growth has pushed settlements into floodprone areas, construction has blocked natural drainage channels and trees that once slowed runoff have disappeared.

“When rainfall occurs, water no longer follows its natural course, instead, it enters human settlements and causes damage,” Mr Mang’enyi said.

He said poor planning has made the problem worse, communities continue building too close to waterways, leaving little room for rivers to expand safely.

Climate change adds another challenge. A warmer atmosphere holds more moisture. That increases the potential for more intense rainfall.

A lesson beyond El Niño

Speaking with ‘Daily News’, Saint Augustine University of Tanzania (SAUT) Climate researcher, Mr Ngongo Mang’enyi says geography plays a major role.

Mr Mang’enyi said Coastal areas, including Dar es Salaam, Coast, Tanga, Morogoro and Mbeya, are particularly vulnerable. These regions experience high atmospheric moisture derived from the Indian Ocean.

When ocean waters warm, whether through natural phenomena or climate change, evaporation increases, providing more moisture for rainfall.

Winds from the southwestern and southeastern directions carry this moisture-laden air from the Indian Ocean toward the Tanzanian coast, where it encounters cooler air and produces heavy rainfall.

He also said Lake Victoria and surrounding areas, including Kagera, Mwanza and Shinyanga, represent another hotspot.

These regions are influenced by moisture from the Congo Basin forests. Located near the equator, these areas receive intense solar radiation, increasing evaporation from the Congo Basin and directing moisture toward the Lake Victoria region.

The southern highlands, including Morogoro, Iringa, Songwe and Mbeya, experience heavy rainfall due to their elevation. Moist winds from the Indian Ocean rise when they encounter these highland areas, cooling and condensing to produce significant precipitation.

“This phenomenon explains why these regions frequently experience heavy rainfall events,” said Mr Mang’enyi.

Moreover, Lowland areas and flood plains such as Tabora and Igunga face distinct challenges. The type of soil determines vulnerability, as clay soils that retain water for extended periods can become waterlogged, affecting agriculture, homes and livestock.

Sandy soils, which drain more quickly, tend to be less affected. Mr Mang’enyi further emphasises that the recurring nature of flood events is not merely a natural phenomenon but is significantly influenced by human activities.

He said Population growth and associated development activities, including agriculture and construction, have led to the removal of natural vegetation, particularly trees and disrupted natural drainage patterns.

“When rainfall occurs, water no longer follows its natural course. Instead, it seeks alternative paths, often entering human settlements and causing damage. The inability of communities to plan effectively, failing to leave space for water to flow naturally, compounds the problem,” said Mr Mang’enyi.

He said climate change, driven largely by human activities including deforestation and industrialisation, is contributing to rising global temperatures.

Mr Mang’enyi said as the world approaches a 1.5-degree Celsius temperature increase above pre-industrial levels, a threshold the United Nations has warned we should not cross, atmospheric moisture increases, potentially leading to more intense rainfall events.

The historical record of extreme rainfall and flooding in Tanzania demonstrates the urgent need for comprehensive adaptation strategies.

While El Niño events will continue to pose significant threats, the broader pattern of extreme weather requires sustained attention and investment. The rains we should not forget serve as a powerful reminder that Tanzania’s vulnerability to extreme weather extends far beyond El Niño events.

The documented history of catastrophic rainfall and flooding in 2011, 2018, 2019 and throughout the decades reveals a pattern of recurring disaster that has taken thousands of lives, displaced countless communities and destroyed infrastructure critical to economic development.

Understanding this history is essential not as an exercise in cataloging past tragedies but as a foundation for building a more resilient future.

The geographic patterns identified including coastal areas, Lake Victoria basin, southern highlands and lowland regions, each present unique challenges that require tailored solutions.

Human activities, from deforestation to urban development, have exacerbated natural vulnerabilities and addressing these underlying causes must be part of any comprehensive strategy.

Climate change looms as an amplifying factor, potentially making extreme rainfall events more frequent and intense. As Tanzania faces the prospect of potentially recordbreaking El Niño conditions, the lessons from past rainfall events become even more urgent.

The country must prepare not only for the immediate threat but for the long-term challenge of living with extreme weather.

This requires sustained investment in infrastructure, early warning systems, community preparedness and environmental protection.

The rains we should not forget are not merely historical footnotes; they are warnings that must be heeded.

Tanzania’s future resilience depends on learning from these events and taking action to protect communities, livelihoods and the nation’s development progress from the devastating impacts of extreme rainfall and flooding