Regulation of built environment

Sri Lanka faces multiple natural hazards, including tropical storms, flash floods, and landslides. As the country's urban population has grown, development projects have encroached on wetlands, compromising their natural flood protection, air and water purification, and carbon storage capabilities. Additionally, hilly regions are at risk of landslides, particularly during the monsoon season, posing significant threats to vulnerable communities (4).
To address these challenges, the World Bank and the Sri Lankan government collaborated on the Metro Colombo Urban Development Project. This initiative focused on nature-based solutions (NBS) as cost-effective and sustainable approaches to risk management (4). By strengthening natural processes and ecosystem services, the project aimed to mitigate hazards such as floods, erosion, and landslides (4). Technical assessments by the World Bank highlighted the importance of wetlands in flood protection, leading to efforts to protect and restore 20 square kilometres of freshwater lakes, wetlands, and swamps (1, 4).
The project supported the Sri Lankan government in reducing flooding in the Colombo Water Basin and enhanced local authorities' capacity to manage infrastructure and services. It prioritised metropolitan investments to mitigate the physical and socioeconomic impacts of flooding and aimed to build long-term capacity for urban management and local service delivery (6).

The project focused on implementing multilayer blue-green roofs in four Italian cities—Cagliari, Palermo, Perugia, and Viterbo—as part of a broader European initiative to address climate change impacts in urban environments (1,3). Spearheaded by a collaboration between multiple Italian universities and the Dutch company Metropolder, the project began in 2019 (1,3). The primary goal is to enhance urban resilience by integrating green infrastructure capable of mitigating climate-related urban hazards such as flooding and heat waves, which are increasingly severe due to climate change and urbanisation (2,3).
The multilayer blue-green roofs combine the ecological benefits of traditional green roofs with an added water storage layer, allowing them to retain rainfall and manage runoff effectively (2,3). This dual function helps reduce pluvial flooding and the urban heat island effect, while also improving thermal insulation in buildings (2,3). Each installation was planted with low-maintenance, climate-adapted vegetation, and equipped with sensors to monitor ecohydrological and thermal performance over several years (1,3). These roofs are capable of retaining up to 100% of rainfall from significant events, thereby easing the burden on urban drainage systems and contributing to climate adaptation in Mediterranean cities (2,4).

The City of Mobile has developed and implemented a Storm Water Management Program (SWMP) as required by the regulations of the Environmental Protection Agency (Ref 1). Flooding is a significant issue in Mobile, occurring frequently throughout the town (Ref 3). The SWMP aims to protect water quality and prevent harmful pollutants in stormwater runoff from entering the Municipal Separate Storm Sewer System (MS4) area (Ref 1). Stormwater runoff refers to rainfall that does not seep into the ground but instead flows over yards, streets, parking lots, and buildings, eventually entering the storm sewer system, which directs it into creeks, rivers, bays, and the Gulf of Mexico (Ref 1). Stormwater can collect pollutants such as trash, debris, sediment, heavy metals, oils, and hazardous household materials. Additionally, development increases impervious surfaces, leading to more stormwater runoff (Ref 2).

Rapid urbanization and a population density of 6,247 people per km² have placed significant stress on Nairobi's natural resources (Ref 1). The 40-km long Nairobi River Basin, originating from the Ondiri Swamp, serves as a vital water source for the city (Ref 1, 2). However, it has suffered severe pollution from untreated sewage, solid waste, industrial contaminants, plastics, and agricultural runoff (Ref 1, 3). This degradation has had a serious impact on the ecosystem, local residents, and biodiversity (Ref 3).

To address these issues, the Nairobi River Basin Programme (NRBP), sponsored by UNEP, was launched in 1999 (Ref 4). Since then, government and non-state actors have worked together on solid waste management, riparian restoration, and wastewater control (Ref 1). The program was implemented in two phases: Phase I (2003–2006) and Phase II (2006–2009), involving stakeholders from the government, private sector, and civil society (Ref 1, 4, 5). Despite these efforts, a study from 2017 found significant tree removal along the river, and between 1988 and 2014, encroachment into the 30-meter riparian buffer zone dramatically increased, particularly between 2010 and 2014, further degrading the river’s health (Ref 1).

The Loma del Marión recovery project in Cartagena, Colombia, is a community-driven initiative supported by EPA Cartagena that focuses on restoring and conserving the remaining 1.2 hectares of tropical dry forest. Initially covering 33 hectares, the area has suffered degradation due to illegal encroachments, deforestation, and waste burning. The project has included planting over 3,000 plants and fostering community involvement in environmental conservation (ref 1). The main goals are to restore the ecosystem by reforesting native species, preventing landslide risks, and developing an ecopark that will serve as an educational and recreational space. Planned facilities include a library for learning about local flora and fauna, hiking trails, and a community garden to enhance local food security (ref 1,4). A notable educational initiative in the project is the formation of "Vigías del Ambiente" (Environmental Watchers), a group of 40 youths from the Red Nacional Jóvenes de Ambiente, supported by EPA Cartagena and CDKN. This initiative educates young people on climate change, conservation, and waste management through workshops and activities (ref 2, 3). In addition, the EPA is leading detailed studies of the tropical dry forest to identify and protect endemic species (ref 5). The project has resulted in significant environmental and social benefits, such as planting thousands of trees, boosting community engagement in conservation, and establishing youth groups dedicated to sustainable development and climate action (ref 3, 5).

The Green and Blue Axis (Eixo Verde e Azul, EVA) is an inter-municipal green corridor project connecting the municipalities of Sintra, Oeiras, and Amadora through a 15-kilometre green ecological axis along the Jamor River (Ref 2). It aims to renaturalize the river, improve water quality, and control flooding while promoting sustainable mobility through pedestrian and cycling routes (Ref 5). The project also enhances public access to green spaces and cultural heritage sites, such as the Queluz National Palace (Ref 6). EVA supports the Lisbon Metropolitan Area’s regional strategy for climate change adaptation, risk prevention, and low-carbon economy (Ref 4). Funded by the European Regional Development Fund and municipal budgets, the project has an overall investment of €11 million (Ref 1). EVA exemplifies inter-municipal cooperation, overcoming policy conflicts to achieve shared environmental, social, and economic goals, making it a model for integrated territorial development (Ref 4). The project’s long-term impact includes reduced carbon footprint and increased territorial cohesion.

The project to redevelop Archipelagos Square in Cagliari aims to transform this key urban space, which serves as a gateway between the city and its coastal areas, into a more functional and aesthetically pleasing environment. Currently, the area lacks cohesive design, leading to unregulated use and its transformation into an informal parking lot. The redevelopment will address these issues by enhancing the pedestrian experience and reducing vehicular traffic. Improvements in public comfort and safety will include better rainwater drainage, the removal of architectural barriers, and the creation of accessible pathways for all.
This project emphasizes environmental sustainability and the preservation of the local landscape. Key interventions include revitalizing green spaces, safeguarding native vegetation, and removing invasive species. Integrating walking and cycling paths will improve connectivity between the city, Marina Piccola, and Poetto beach, fostering outdoor recreational activities. A designated eco-system filter will recreate the natural dune environment, blending pedestrian areas with the surrounding landscape.
Funded by the Fondo Sviluppo e Coesione (FSC), the project has a total budget of 3 million euros, with construction lasting 10 months starting in October 2023. The redevelopment reflects the broader goals of Cagliari’s administration to promote sustainable urban mobility and improve the public realm, contributing to the city's vision of becoming a hub for nautical sports while enhancing the overall quality of life for residents and visitors (Refs. 1, 2, 3 & 4).

Lima is the capital of the region with the lowest coverage of green spaces. According to the World Health Organisation (WHO), a city should have at least 9m2 of green space per inhabitant. Lima is just over 3m2 square metres, which means a deficit of almost 60 million square metres. In this context, actions from the public and private sectors are essential to add this type of space to the city. In response to this need, Grupo Centenario carried out a green project on one of its plots of land in San Isidro, where real estate projects will be developed (1, 2, 3, 4).
A square was built with a green area with wild and low-consumption species, knocking down the walls that surrounded the land for years, turning it into a place for everyone to see and use (1, 2, 3, 4). The Choquehuanca Square was built to contribute to the community and make it a better place to live. It is located on a plot of land that was previously enclosed by walls, converting it into an area of 3,945 m2 with a green space that occupies 70% of the square (1, 2, 3). This is a temporary project, as the green space was opened while projects are being developed on this land (1, 2, 3).

The "EnRútate por el Ambiente" initiative is a collaborative strategy implemented in Cartagena through a partnership between Ecopetrol, EPA Cartagena, and the Cartagena Refinery. The initiative aims to promote sustainable community development in neighborhoods adjacent to the refinery by addressing key environmental challenges such as pollution and the degradation of water bodies and green spaces. Its overarching objective is to improve quality of life through the promotion of sustainable practices and environmental stewardship (ref 5).
The strategy is structured around three programs. The first component focuses on the management of public spaces for recreation and environmental care. The second, Guardians of the Channels, seeks to empower local residents as promoters of water body conservation within their communities. The third program promotes the engagement of all community members, including schools and educational institutions, through participatory environmental initiatives (ref 1).

Terres Sainville is one of Fort-de-France's priority neighborhoods, known for the precarious living conditions of its residents and the prevalence of illicit activities. Many plots of land in the area have been abandoned and are used as informal dumpsites. In response, the City of Fort-de-France developed the "Jaden Lanmou" (Garden of Love) program, which aims to revitalize neglected spaces across the city’s 145 neighborhoods, Terres Sainville being one of them.
With support from the Terres Sainville town hall, neighborhood associations (such as the Terres Sainville Citizens' Council and local schools), and the Ypiranga Martinique association, the community has been working to transform these wastelands into shared gardens. Since 2021, Ypiranga has created 10 productive gardens, designing each based on the land's configuration, soil quality, and the preferences of local residents, including options for market gardening, medicinal plants, fruit trees, and above-ground containers (Ref 1; 7).
This initiative prioritizes the development of city-owned land and strategic transit sites, while also encouraging private landowners to maintain their abandoned plots or share them with the community. Additionally, the program seeks to enhance existing flowerbeds, create new ones, and incorporate artistic elements like street art and graffiti. Public meeting spaces are being developed to foster community interaction.
The city aims to involve residents by providing equipment, training, workshops, and advice on best practices. Ultimately, neighborhood representatives and residents will be responsible for maintaining these new communal spaces and ensuring they are respected (Ref 2).