These two cities show how nature-based solutions address climate hazards like urban flooding

Globally, more than 40% of the world’s population lives within 100 kilometres of a coastline and more than 600 million people (10% of the global population) live at elevations of 10 metres or less above sea level. Human civilizations have long relied on waterways for commerce, food and transport.

However, the uncertainty of climate change underscores the need for nature-based interventions to help cities thrive amidst changing flood pulses and adapt to climate hazards.

Some cities are already harnessing their natural endowments to adapt for the future. Through natural systems and sustainable infrastructure, cities can enhance their resilience, protect ecosystems and improve the quality of life for their inhabitants.

The following sections outline how two cities, which depend on integrated urban water systems, are advancing essential urban interventions to ensure positive impacts on both people and nature.

Bangkok in Thailand, a delta city often referred to as the “City of Three Waters,” faces increased flood vulnerability due to its unique hydro-ecological landscapes shaped by rivers, rainfall and the sea.

Despite being an area of naturally flood-prone areas, factors such as heavy urbanization on floodplains and a shift from water-based to land-based development inevitably increase the severity of floods.

Additionally, land subsidence and severe coastal erosion from resource extraction, infrastructure load and mangrove deforestation derive in larger impacts and a “sinking city”.

Addressing scenarios of water-based urbanization is essential for the city’s holistic growth and survival. Groundwater management regulations in Thailand from the 1970s, including the 1977 Groundwater Act, initially helped control groundwater use and laid the groundwork for nature-positive action.

However, with growing climate challenges, these measures alone are insufficient.

Bangkok has pioneered several blue-green infrastructure and adaptive reuse projects, integrating existing grey infrastructure to enhance nature and the city’s interaction with ecosystem services.

The city of Belém do Pará, in Brazil, is a community deeply connected to the riverine ecosystem – culturally and economically.

The city is living proof of urban efforts to rehabilitate urban watersheds and, in consequence, reduce inland flooding, enhance soil filtration capacity and ensure socioeconomic benefits such as a reduction in crime rates and improved socioeconomic conditions for citizens.

The city hosts more than 1.5 million inhabitants settled alongside the five rivers that span the city.

Over time, urban developments in the riverbanks and watershed lands have been driven by grey interventions and landfilling. As a result, flooding risks have increased and the need to reform infrastructure and improve community engagement with the water systems has become central in Belém’s urban planning.

The local government, in partnership with the Federal Government of Brazil and international cooperation agencies, has begun the implementation of two projects to re-inventing waterfronts and watersheds to recover water quality and enhance the living standards of more than 70% of Belém’s inhabitants:

The combination of policies, ecology and landscape architecture is a key element of water-based urbanism. A key to success from Belém and Bangkok has been building strong public-private-community partnerships to complement government initiatives and realize this critical yet achievable transition to cities in harmony with nature and their rivers.

This article is part of "Nature Positive: Leaders’ Insights for the Transition in Cities," a collection of articles by the Global Commission on Nature-Positive Cities offering a range of strategies and practical solutions adaptable to diverse urban environments and supporting a shift towards nature-positive city developments.

Nature-Positive Cities is an initiative by the World Economic Forum, in collaboration with Oliver Wyman.