East Africa’s Urban Flooding Epidemic: The Promise of Urban Reforestation to Unblock the Region’s Drain

A REPORT about East Africa’s flooding epidemic.

Abstract

Flooding in East Africa has resulted in very high avoidable casualties. It is caused both by natural factors like climate and landscape, as well as infrastructural shortcomings. The floods weaken existing infrastructure, causing even more susceptibility to flooding in the future. Concurrently, climate change exacerbates the magnitude of naturally occurring and cyclical floods.  

This report highlights the benefits of urban reforestation as a potential method for flood prevention and water management, overall relieving strain on existing water management systems and enhancing urban resilience, at a much smaller expense to East African governments than other infrastructure improvement projects.  

Case studies in Ethiopia show that urban reforestation minimises the impacts of urban flooding while also addressing food insecurity and unemployment. Urban reforestation also has beneficial impacts on weather and air quality in cities, while improving civilian well-being and mental health. Policies designating the use of unoccupied public land for reforestation purposes could make urban reforestation a pragmatic, widespread practice. Urban reforestation thus poses a sustainable solution to mitigate water management challenges as East Africa increasingly looks to curb endemic flooding in the region.  

Introduction

East Africa routinely experiences flooding due to the region’s geographical features and climate. In Kenya, low-lying arid and semi-arid areas frequently experience flash flooding. Though many floods are caused by seasonal phenomena like the El Niño rains, visiting the region annually with particular vigour every three to seven years, flooding has been exacerbated by climate change which has seen erratic dry spells and heavy monsoons plague the East African region for the past two decades. 

Recently, floods have wreaked havoc to a degree that supersedes historical levels. Heavy rains have occurred far more frequently than the expected cycle. The 2022 El Niño rains were the worst seen in the region in the last 70 years, with the situation only worsening in subsequent years. 2024 has seen particularly devastating floods sweep across the region; in April and May, floods killed 267, injured 188 and displaced 281,835 in Kenya, with 75 missing. This is a dramatic increase from the already astounding casualties of the country’s 2019 floods, during which over 100 died and 18,000 were displaced.  

Floods are particularly brutal in urban areas. Large portions of the urban population live in informal settlements. In Rwanda, for example, 61.3% of the urban population lives in informal settlements, with other nations in the region following similar patterns. Within informal settlements, water management infrastructure – like pipes, tunnels and drainage ditches – is rare, if at all present, and housing tends to be temporary leaving residents inevitably vulnerable to flooding catastrophes. 2024’s floods, for example, caused devastating damage in Nairobi’s Mathare slums, with 23,000 households displaced and countless individuals losing their livelihoods and all their belongings. 

Currently, East African cities lack sufficient infrastructure to manage flooding. Urban flooding occurs when stormwater cannot infiltrate the ground due to the prevalence of impervious surfaces such as concrete sidewalks and stone-lined drainage ditches. Many East African cities were planned and built primarily with colonial interests in mind, with little attention paid to water drainage, especially in the inevitable event of future expansion. In Dar Es Salaam, for example, road drainage systems were designed mainly to divert water away from European-dominated areas of the city, with the main objective being the prevention of water-borne diseases like malaria. Little attention was paid to where diverted water would accumulate, and little has been done in the decades since independence to develop water management systems to support current drainage needs. In addition, the underlying problem of many cities, like Kenya’s capital, Nairobi, being built on large networks of underground rivers whose banks routinely flood, adds a layer of difficulty to the already significant challenge of water management in East African cities. 

While the reconstruction of drainage systems in East African cities is a necessary objective, there exist other solutions to flooding that are less demanding and disruptive for governments and residents alike – urban reforestation being one such solution. Urban reforestation, a key facet of broader urban forestry, is the practice of introducing trees and vegetation to urban spaces which traditionally lack plant life. Many cities practice small-scale versions of this, lining motorways with trees or maintaining dense tree cover in certain sections of recreational parks. 

Urban reforestation is incredibly versatile and can range from small potted trees on balconies or rooftops to entire forests within the confines of cities such as Nairobi’s Karura Forest. With the population of East African cities forecast to continue to grow rapidly – urban residential growth is projected to increase to 58% by 2030 – sustainable water management solutions like urban reforestation must be implemented to allow East African cities to withstand future weather catastrophes.  

Methodology

This report employs a secondary research approach comprising a literature review, case study analyses, and data syntheses to evaluate urban reforestation as a flood mitigation strategy. This method is well suited for exploring trends, relationships and conducting comparative analyses on different countries within the region. It is also effective in leveraging data fragmentation across government departments, NGOs and private sector players to compile comprehensive and cohesive insights. Sources were selected for their relevance, credibility, and ability to contribute meaningful insights to the research topic. Sources included academic journals, industry reports, and government and public data to ensure a range of viewpoints.  

The report begins by assessing the necessity of green drainage infrastructure by reviewing the causes and impacts of urban flooding with mixed methods, combining quantitative and qualitative data from reputable sources such as The World Future Council’s Future Policy, a reliable source for policy case studies. This, in addition to an evaluation of current flood management practices in Kenya, Uganda, Rwanda and Tanzania, were used to paint a picture of how prepared East Africa is for the predicted increase of climate change-induced hydrological extremes.  

To evaluate the possible effectiveness of urban reforestation in combatting unpredictable and severe flooding, an environmental, social and governance (ESG) analysis was employed to weigh the benefits and challenges of this strategy. Data was sourced from all relevant fields, such as the biological field to consider which environmental factors are most relevant for East Africa, and governmental sources to gauge the effects of existing and potential policies.  

Lastly, a recommended action plan was assembled by combining the scientific, historical, and legal knowledge amassed throughout the report. However, limitations of this methodology can be rooted in the use of secondary research, which inherently relies on preexisting data, allowing for potential bias from certain sources, and some data sources being outdated or not fully reflecting recent developments, and limited sources.  

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