Nature-Based Solutions Help African Cities Fight Floods

When torrential rains hit Kinshasa in April 2025, the city of 20 million came to a standstill. Floodwaters submerged more than half the city as the Ndjili River and smaller streams overflowed, quickly overwhelming the city’s drainage capacity. Lives were lost and thousands displaced, with more than 1,000 homes destroyed.

Those living in shanties at the city’s periphery were particularly hard hit. Kinshasa is Africa’s third-largest city and one of its fastest-growing. Urban planners simply can’t keep up as the city’s borders push farther and farther into the hinterlands.

It’s a common situation. Across many African cities, urban expansion — and the roads, buildings and concrete that come with it — is paving over natural spaces and leaving people more vulnerable to the consequences of extreme weather. Less green space means trapped heat, increased storm runoff and dirtier air. Climate change is worsening these challenges. Research shows that by 2100, up to 950 million urban Africans could be exposed to extreme heat waves intensified by the urban heat island effect. Floods and heavy rainfall are increasingly destroying homes and disrupting transport and other essential services.

Built infrastructure like seawalls, dams and reservoirs is both expensive and insufficient to keep pace with ever-more-extreme weather. That’s why cities are rethinking what counts as infrastructure.

Many are expanding their definition to include wetland parks, rain gardens, urban forests and other “nature-based solutions.” From 2012 to 2022, the number of nature-based infrastructure projects in Africa grew about 15% every year.

From green corridors and urban parks to restored wetlands and watersheds, four African cities show how integrating nature can be one of communities’ strongest defenses against climate change.

Green Corridors Help Clear Addis Ababa’s Air  

The population in Addis Ababa, Ethiopia, is growing fast. Official estimates put the city’s growth rate at 3.7% per year. As a result, the city is seeing a rapid expansion of concrete and asphalt for streets and housing — materials that trap heat.  

At their hottest, the city’s busiest neighborhoods — Merkato Market, Jacros and Ayer Tena, in particular — now register temperatures of more than 40 degrees C. Rising heat, paired with Addis Ababa’s daily motor traffic, worsens air quality: data from 2021 to 2023 puts Addis Ababa’s average PM2.5 index at around 27.5, more than five times the WHO’s recommended limit.  

But things have started to change since Addis Ababa introduced green corridors in 2024.  

The city implemented linear strips of greenery on its biggest thoroughfares, linking urban parks, riversides, public plazas and landscaped open spaces into a connected system. Since 2024, the city has upgraded more than 58 kilometers of roadsides and riverbanks, re-greening an area more than 10 times the size of Central Park in New York City. Many of these green corridors hold new bicycle lanes and dedicated walkways, improving both walkability and reducing traffic.

Today, Addis Ababa’s PM2.5 levels are 4.6 points lower than they were in 2023. With technical guidance from WRI, the city has reintroduced 80 indigenous tree species, setting Addis Ababa on a path to recover its biodiversity. And by 2030, when new trees have matured, green corridors are expected to deliver cooling benefits.  

To help spread these benefits across the rest of the city, WRI is piloting a new rapid assessment tool to identify priority areas where nature can reduce heat, mitigate floods or restore biodiversity.

Restoring Lost Wetlands in Kigali

Kigali, the capital of Rwanda, sits within a basin of 37 wetlands covering more than 10% of its surface area. They’re important for absorbing rainwater in the steeply sloped city — especially as climate change intensifies heavy rainfall. The city’s low-lying districts are particular at risk of recurrent flash floods.

Yet wetlands’ intrinsic value has historically gone unrecognized in Kigali. Encroachment from informal settlements, agriculture, sand mining, brick-making and unregulated industrial activity had, by the mid-2010s, destroyed many of the city’s wetlands, compromising their ability to prevent floods and pollution.  

Today, these low-lying areas are being restored as hydrological hotspots.  

Kigali’s Nyandungu Eco-Park, a 121-hectare site comprising both restored wetland and forest, opened in 2022 across from Kigali International Airport. It contains 13 catchment ponds, solid waste traps, a 10-hectare lake and more than 60 kilometers of walking and cycling paths. The National Environmental Protection Authority is also restoring the neighboring wetlands of Gikondo and Kibumba, creating what the World Bank has described as “the largest citywide urban wetland rehabilitation programme in Africa.”

The city’s restored wetlands are already helping to absorb stormwater and filter pollutants before they enter the region’s major river systems, the Nyabugogo and Nyabarongo. But those aren’t the only benefits. The Nyandungu pilot alone reintroduced 17,000 indigenous trees, supports more than 100 bird species and over 60 native plant species, and has created an estimated 4,000 green jobs, predominantly for youth and women.  

These returns have attracted further investment: Kigali and international partners have committed an additional $32 million to rehabilitate five interconnected wetlands across the city by 2026. Rwanda’s government is now looking to scale these solutions in other cities. Its Ministry of Infrastructure is developing a pipeline of bankable nature-based projects.

Removing Invasive Species Helps Revitalize Johannesburg’s Rivers 

In Johannesburg, invasive plants have degraded areas around the city’s Jukskei River. Pines, black wattle, eucalyptus, bugweed and other invasives monopolize nutrients and outcompete local flora.  

They also worsen flooding, especially in Johannesburg’s riverside informal settlements like Alexandra and Soweto. Invasive plants’ roots push out deeper-rooted indigenous species, destabilizing the soil around riverbanks. When rain hits these riverbanks, loose soil and sediment flow into the river, reducing its ability to absorb and slow floodwaters.  

Aggressive invasive roots also damage drainage pipes and culverts, multiplying flood impacts. Shifts in climate and rainfall patterns are further exacerbating the problem: as temperatures increase, invasives thrive, densify and spread.

Working with local communities, initiatives like WRI’s SUNCASA project are removing invasive plants to prevent flooding and loss of biodiversity while supporting livelihoods. So far, the project has cleared invasive plants from more than 133 hectares along the Jukskei’s riverbanks while creating more than 100 jobs in the process. Workers are also reintroducing indigenous species like African olive and white stinkwood. The trees’ sturdy roots will stabilize the Jukskei’s riverbanks, increase local biodiversity and reduce the impact of flooding.  

Johannesburg is also developing a Transformative Riverine Management Program, a framework and business model for investors and corporations to get involved in rehabilitating the city’s rivers, starting with the Jukskei. 

Watershed Restoration Tackles Dire Dawa’s Flooding at the Source 

Dire Dawa, Ethiopia’s flood risk begins upstream. Like other fast-growing secondary cities across Africa, the clearing of trees for farms and new settlements has left the surrounding watershed increasingly degraded.  As vegetation is lost, the landscape’s ability to slow and absorb rainfall disappears with it.  

During heavy rains, the Dechatu River surges down from the surrounding mountains with few trees or greenery to slow its path, flooding homes and killing people. The worst disaster occurred in 2006, when floods in the night cost the city hundreds of lives and millions of dollars in infrastructure damage. In 2020, more than 250 households were affected.

Dire Dawa has begun to look more closely at its watersheds to stop flooding at its source. Working with the SUNCASA project, local groups are restoring the city’s upstream landscapes by planting more than 1.2 million trees across the watershed. More trees can prevent floods, restore biodiversity and help recharge groundwater. By planting trees that are also fruit-bearing — avocados, mangoes and other crops that farmers can sell — these restoration efforts benefit both the landscape and household incomes.

The city is also establishing buffer zones to slow the flow of the river. By re-establishing grasses and ground cover to prevent erosion, shrubs to slow runoff, and trees to stabilize riverbanks and provide shade along the Dechatu River, these buffer zones help reduce the speed and sediment volume of flash floods.

Putting Nature at the Heart of Urban Planning

Taken together, these cases reflect a broader shift in how African cities approach urban planning. Nature-based solutions are gaining traction alongside more traditional built infrastructure, enhancing their effectiveness and durability. While a drain or a flood barrier addresses a single problem, nature-based solutions offer a way to address multiple challenges simultaneously. A restored wetland or a green corridor can tackle climate adaptation, biodiversity loss and social challenges such as unemployment and livability.

The timing of this shift matters. As African cities absorb a growing share of the world’s urban population, their development pathways carry global implications. Integrating nature into urban planning is a growth model more adaptive to uncertainty. For cities interested in these pathways, tools like the Strategic Nature-based Solutions Framework have already enabled cities like Addis Ababa and Kigali to identify flood risks, heat islands, water supply and biodiversity needs.

What is unfolding across Addis Ababa, Kigali, Johannesburg and Dire Dawa points to strong outlook for what happens when cities invest in landscapes that perform multiple functions: absorbing water, moderating heat, supporting livelihoods and shaping urban life for the better. This is how to build cities that can thrive in a changing climate.