A woman in a construction vest carrying a bucket alongside a river surrounded by trees.

project

Green-Gray Infrastructure Accelerator for Climate and Water Resilience

The Green-Gray Infrastructure Accelerator equips city leaders, communities, and partners to rapidly scale nature-based solutions (NBS) and green-gray infrastructure (GGI) in cities and watersheds. NBS leverages forests, wetlands, and mangroves to reduce climate risks, while GGI combines these systems with traditional infrastructure like levees, retention ponds, and water treatment plants to boost resilience.

Challenge

Cities across sub-Saharan Africa face escalating climate risks — droughts, extreme heat, and frequent floods — that threaten public health, livelihoods, and economies. By 2050, the share of urban residents in Africa facing at least eight days a year over 35 degrees C will rise from 66% to 85%, worsening heat-related illnesses and reducing worker productivity. Meanwhile, land-use changes are accelerating biodiversity loss, weakening essential ecosystem services.

With sub-Saharan Africa’s urban population expected to double by 2050, cities must address infrastructure gaps to protect vulnerable communities and ensure a climate-resilient future. This will be especially critical for the 60% of the region’s urban population that live in informal settlements, as they are particularly susceptible to climate risks.

Research by the World Resources Institute (WRI) and the World Bank, with contributions from the African Development Bank, analyzed almost 300 NBS and GGI projects across SSA. The report finds that, while the number of projects has steadily increased since 2012, only 16% of these projects focus on urban resilience. Given the significant climate and socio-economic benefits observed from these projects, cities need to urgently scale NBS to address infrastructure and climate needs.

Opportunity

Cities are integrating GGI — natural systems like forests and wetlands with traditional infrastructure such as retention ponds and seawalls — to tackle climate challenges more effectively. This hybrid approach enhances urban cooling, flood protection, coastal resilience, and drainage, offering more durable, cost-efficient solutions than gray infrastructure alone.

Greater political support and investment in GGI can help African cities close infrastructure gaps, boost climate resilience, and create green jobs. Scaling GGI also improves water security, reduces flooding, and strengthens social equity by empowering vulnerable communities. The GGI Accelerator drives this vision forward.

Project Description

The GGI Accelerator provides resources, innovative approaches, and strategic engagement with communities, governments, and investors to overcome barriers to NBS adoption in SSA cities. It helps cities become more livable, equitable, and climate-resilient by offering technical assistance across project development—from feasibility to financing and pilot implementation to scale.

With an initial cohort of 11 cities in seven countries, the GGI Accelerator fosters a supportive policy and financing environment, delivers climate resilience benefits, and scales successful models. Through peer learning, project development webinars, and investor roundtables, it equips cities to advance bankable projects, emphasizing gender equity and social inclusion (GESI) and robust monitoring, evaluation, and learning (MEL) for long-term impact across five key areas of support:

Policy Guidance & Institutional Development: We support cities to institutionalize NBS and GGI through equitable strategies and policies, improved regulations, and alignment with climate and water resilience goals. Regionally tailored research and access to technical experts raise awareness about NBS’ climate and socioeconomic benefits and drive buy-in from governments, donors, and communities.
Project Development & Implementation: We provide guidance on NBS and GGI through strategic risk and opportunity assessments, and gender and social equity (GESI)-responsive participatory planning. Cities receive technical assistance on locally appropriate NBS species selection; establishing enabling conditions to advance projects towards feasibility; community and stakeholder outreach; and monitoring, evaluation, and learning (MEL) systems.
Funding, Finance, & Economic Analysis: We connect cities with funders and investors, develop business cases, and support financial structures to facilitate transactions, improve project bankability, and unlock sustainable funding. We also host investor roundtables to develop innovative financial approaches and accelerate investment.
Peer Learning & Capacity Building: We facilitate peer-to-peer learning exchanges where cities share best practices, foster collaboration, and strengthen technical skills for planning, implementation, and maintenance.
Communication & Stakeholder Engagement: We enhance visibility and build momentum for NBS and GGI adoption through outreach to policymakers, communities, and investors, helping cities secure critical buy-in and scale impactful solutions.

Our Cities

The GGI Accelerator works with the following cities: Addis Ababa and Dire Dawa, Ethiopia; Kigali and Musanze, Rwanda; Johannesburg and Gqeberha, South Africa; Bukavu and Uvira, the Democratic Republic of Congo; Nairobi, Kenya; Kumasi, Ghana; and Brazzaville, the Republic of Congo.

The cities fall into three categories based on their stage of engagement: four Pioneering Cities (Johannesburg, Kigali, Dire Dawa, Bukavu) are implementing NBS pilot projects and exploring financing strategies for replication; two Advancing Cities (Addis Ababa, Nairobi) are institutionalizing GGI policies and preparing bankable projects; and five Emerging Cities (Brazzaville, Gqeberha, Kumasi, Musanze, Uvira) are building awareness, developing urban greening strategies, and conducting early-stage data analysis to integrate NBS into city planning.

Highlights from these cities include:

Johannesburg, South Africa: Indigenous plant rehabilitation in the Jukskei River catchment will reduce flood risk and solid waste pollution, mitigate urban heat, and enhance water security and livelihoods for 1.2 million residents in Alexandra Township.
Gqeberha, South Africa: Kromme Basin restoration will enhance water security and biodiversity, integrating hydrological modeling and stakeholder-driven solutions.
Addis Ababa, Ethiopia: A watershed investment program will offer a cost-effective approach to restore the Gefersa Catchment, enhancing water security for over 300,000 city residents.
Dire Dawa, Ethiopia: Dechatu River catchment restoration will benefit over 200,000 people in flood-prone areas and provide employment for 4,000.
Kigali, Rwanda: Restoration in the Nyabarongo River watershed will reduce flood risks and soil erosion, benefiting nearly 1 million residents.
Musanze, Rwanda: A new urban green space policy with dedicated financing will enhance biodiversity, air quality, and climate adaptation for 150,000 residents.
Bukavu, DRC: Ruzizi Basin restoration will mitigate flooding, enhance energy security, and protect hydropower for Rwanda, Burundi, and DRC.
Uvira, DRC: Restoration of water bodies and degraded landscapes will mitigate erosion and flood risks while expanding urban green spaces to improve public health and resilience.
Nairobi, Kenya: Restoration of the Nairobi River will catalyze a green economy, reduce flooding, and mitigate urban heat.
Brazzaville, Republic of Congo: NBS will be embedded into urban policy to strengthen flood resilience and expand urban greening, culminating in a formal plan for pilot project implementation.
Kumasi, Ghana: A first-ever urban greening policy will integrate NBS into city planning, securing long-term investment and sustainable green space management.