Flood protection

The renovation of the "Marechal Humberto Delgado" Square focused on transforming the area into a more pedestrian-friendly and sustainable urban space. The project included reorganising the traffic system, creating a new urban green square, requalifying the bus terminal, enhancing the integration of different transport modes and improving pedestrian access (Ref 1). Key features of the intervention were the introduction of cycle paths, wider sidewalks, green spaces with 200 new trees, and recreational facilities such as a children's playground and water features (Ref 2). The project also addressed critical infrastructural needs, including constructing a rainwater collector as part of Lisbon's General Drainage Plan to mitigate the city's frequent flooding issues (Ref 3). The renovation, completed in 2024, was part of the 'A Square in Every Neighborhood' program, emphasizing community involvement and sustainable urban development (Ref 3).

Salines Beach, a popular destination for over a million visitors annually (Ref 9), is facing severe erosion due to rising sea levels and poor coastal management. Since 1995, the beach has lost more than 20 meters in width. This loss has been worsened by vehicle traffic and the introduction of coconut trees in the 1950s, which reduced the native root systems that once helped to stabilize the coast (Ref 5). Now, the encroaching sea threatens to swallow the road that runs along the beach.
In response, the Salines Conservation Committee—comprised of concerned community members and environmental groups—has been advocating for urgent action to halt the erosion. They have called for a renaturalization of the area through the replanting of endemic species and restrictions on car traffic, both aimed at restoring the beach’s natural resilience.
When part of the road collapsed in July 2022, the committee took immediate action, organizing community-based interventions. These efforts included blocking traffic, raising public awareness, and planting over 60 endemic plants in the damaged area. The aim was to reestablish a root network capable of anchoring the coastline and capturing shifting sands (Ref 1; 2). The intervention was described as "a response to the urgent need to rebuild the root network, an ecological engineering solution recognized as the most effective method for retaining beach sand and slowing coastal erosion" (Ref 2; 1). The intervention on this section of the coast was first completed, then discarded by the municipality of Sainte-Anne (Ref 2). Regional and National agencies are currently undertaking the restoration works but it is unclear the stage of completion (See Ref 3).

The Gårda pilot rain garden has been constructed as part of the research project Innovative Rain Gardens at Chalmers University of Technology in Gothenburg. In addition to causing flooding, runoff rain water in urban environments can be contaminated with microplastics, organic pollutants and metals which can spread into the natural environment. Yet, most of the storm water in urban environments is not treated. The purpose of the Innovative Rain Gardens project is to research the ability of a pilot rain garden to treat such pollution. The project acknowledges the function of a rain garden to prevent flooding, but in this study only the pollution treatment potential is investigated. The pilot rain garden was constructed next to the E6 highway in central Gothenburg [Ref. 1-4]. It includes several different bioretention filters where selected plants are grown in filters containing different materials such as biochar, ash and soil [Ref. 2, 3]. Results so far show that the use of rain gardens can significantly reduce pollution. However, further research is needed to determine the long term function of the bioretention filters and the potential of scaling up the NBS. The project is funded by the Swedish Research Council for Sustainable Development (Formas), IMMERSE - Implementing Measures for Sustainable Estuaries, an Interreg project supported by the North Sea Programme of the European Regional Development Fund of the European Union, and COWIfonden (private foundation) [Ref. 1-3].

The Juan Angola River is an urban channel included in the system of rivers and channels of Cartagena, and it connects the Ciénaga de la Virgen wetland and the Bay of Cartagena, facing similar issues as the Cienaga de la Virgen such as illegal occupation of its shores, illegal waste dumping, deforestation of mangroves, and pollution. The recovery plan for the Juan Angola River is led by the EPA Cartagena (Environmental Protection Agency), with the support of other institutions, aiming to restore the Juan Angola’s ecosystem. This includes targeting the mangrove forest, dredging the natural channel, and delineating buffer zones with urban infrastructure to create public recreational spaces. The activities involve relocating people illegalling cupping informal settlements from the river shore, moving an existing bridge (the Benjamín Herrera bridge) which obstructs the current, recovering the low tide and riverbed areas, building pedestrian paths, clean the riverbank, recover mangrove areas and establish programs of education and environmental awareness (ref 1 and 2).

The Tres Rios Ecosystem Restoration Project is an ambitious initiative aimed at revitalizing a seven-mile stretch of the Salt and Gila Rivers in Phoenix, Arizona. The Tres Rios Environmental Restoration project involves the rehabilitation of nearly 700 acres in and around the Salt River, restoring a vital wetland and riparian habitat. Initially conceived in 1993 to tackle water quality issues and improve flood control, the project gained significant traction in the 2000s through a partnership between the City of Phoenix and the U.S. Army Corps of Engineers (USACE). Funding was structured with 65 percent from the USACE and 35 percent from the City of Phoenix and the Sub-Regional Operating Group Members, including Scottsdale, Tempe, Glendale, and Mesa.
The Tres Rios project encompasses habitat restoration, flood control, and recreational development, with the primary objectives being to restore a degraded ecosystem, enhance water quality, and provide new recreational spaces. Construction involved relocating 1.6 million cubic yards of earth to shape three large wetland zones and two deep-water retention basins. Additionally, 18,000 feet of underground water lines and 600 feet of 84-inch fiberglass effluent pipelines were installed. To establish a thriving wetland habitat, the project coordinated the planting of over 300,000 aquatic and terrestrial plants.
Habitat restoration efforts re-establish native vegetation and create wetland areas that support local biodiversity. The lush and scenic Tres Rios is now home to more than 150 different species of birds and animals like muskrats, raccoons, skunks, coyotes, bobcats, and beavers. By using treated wastewater to sustain the ecosystem, the project reduces dependency on natural water sources, thereby helping to mitigate water scarcity. The Tres Rios Ecosystem Restoration Project serves as a model for sustainable urban ecological initiatives, combining environmental health with community benefits. (1-8, 10-13)

The Dublin Urban Rivers LIFE (DURL) project incorporates two interconnected wetlands in Griffeen Park as part of its broader initiative to improve water quality, natural water management and aquatic biodiversity in urban areas. These wetlands were specifically designed as a natural sewage system to treat wastewater from the surrounding areas, addressing a significant environmental issue known as "domestic misconnection." Domestic misconnection occurs when household appliances, such as washing machines, dishwashers, and kitchen sinks, are incorrectly linked to surface water drains rather than the sewage system. This leads to untreated wastewater being directly discharged into local waterways, contributing to contamination.
In the River Griffeen catchment, which includes approximately 12,000 dwellings and associated infrastructure, domestic misconnections are a considerable threat to water quality. The DURL project focuses on identifying and rectifying these misconnected appliances to ensure that wastewater is properly treated before entering the river. This process will not only improve water quality but will also provide flood alleviation and support healthier aquatic ecosystems in the area.
The project is aligned with broader environmental policies, including the River Basin Management Plan 2022-2027, the Water Framework Directive, the Climate Change Action Plan, the Floods Directive, and the draft Biodiversity Plan. One of the key strategies is to use a Geographic Information System (GIS) to streamline inspections for domestic misconnections, making the process faster and more cost-effective.
The constructed wetlands in Griffeen Park, with a standing water depth of approximately 30 cm, are planted with a variety of native Irish species. These wetlands offer a natural, sustainable solution to wastewater treatment, with the potential for similar applications across Europe. (Ref. 2, 4)

The Three Mile Creek Greenway Trail project aims to transform the existing creek into a valuable community asset by developing a multi-use greenway trail (Ref 1). This greenway will connect various parts of the city through walking and biking paths, linking neighbourhoods, parks, and commercial districts while providing access to unique natural areas (Ref 2). The creek having been adandonned for decades (Ref 5), the initiative seeks to turn 3 Mile Creek (3MC) into a vibrant natural corridor that fosters recreation, education, and economic activities (Ref 1, Ref 2). The project aims also at reducing pollutants in the waterway, restoring natural stream channels, and maintaining flood protection (Ref 1).
The 3MC Greenway Trail is expected to become a key feature of Mobile's urban landscape, offering numerous benefits. These include enhancing community health, both mental and physical (Ref 2), and stimulating the local economy by increasing property values, tax revenues, and opportunities for recreation-related businesses and job development (Ref 2). Additionally, the trail will improve community connectivity by linking neighbourhoods, parks, and schools, thereby fostering a stronger sense of community and better access to public spaces (Ref 2). Lastly, the project will contribute to environmental restoration through stormwater management, pollution reduction, and natural habitat preservation (Ref 2).
The greenway is part of a plan to restore the health of the Three Mile Creek watershed and is the first major piece of a long-term Mobile Greenway Initiative (MGI) (Ref 4).

The Mziuri Park in the center of Tbilisi and adjacent to the city's zoo was heavily impacted by floods and landslides that occured in June 2015 in Georgia. As a result, many of its facilities were destroyed, necessating the redevelopment of the site (Ref. 1,2). In 2017, the Georgian government initiated the Urban Reconstruction and Development (GURAD) Project with funding from the European Investment Bank (EIB) under the 100 million € framework loan. The park's reconstuction is one of multiple projects under the natural disaster recovery component of the GUARD Fund (Ref. 1,2). As of 2020, the park has been fully redeveloped catering to the needs of diverse groups, but especially youth and children with a number of different sports, cultural and recreational areas (Ref. 3,4). Importantly, construction was carried out under consideration of spatial adaptation measures for people with disabilities and with a renewed drainage system to mitigate the effects of future floods (Ref. 1). The park is now again one of the most important recreational areas in Tbilisi (Ref. 3).

The mangrove area of Morne Cabri, located in the municipality of Le Lamentin and sharing the bay of Fort-deFrance, is the largest mangrove area in Martinique. Since 2011, the municipality has led efforts to understand and better manage the area (Ref 1). The natural regeneration of the mangrove is threatened by fresh water run-off (from waste and rainwater), invasive species and pollution. However, it is an important protection against extreme weather events, operates as a carbon sink for the island and provides recreational activities (Ref 1). The municipality has led several initiatives supported by volunteers, local businesses, national subsidies and private donations (See: Ref 2, 3, 4, 11).

Birmingham faces several immediate risks due to climate change, including heatwaves, water shortages from droughts, floods, and extreme weather (Ref 11). To address these challenges, Birmingham City Council has set a goal to reduce carbon emissions by 60% by 2027. As part of this effort, the new Birmingham Library project, initiated by the council, includes a rooftop garden designed to contribute to this target (Ref 3). The library was designed by the Dutch firm Mecanoo Architecten, with a design process spanning from 2008 to 2012 (Ref 5). The two outdoor rooftop gardens, located on levels 3 and 7, were completed in 2013 (Ref 1). These gardens provide green spaces in the city center, enhance water management through rainwater harvesting, serve as educational facilities for sustainable food innovation, and create natural habitats for wildlife (Ref 1, 3, 4, 6). Their contributions helped the library achieve a BREEAM 'Excellent' rating and have garnered various awards (Ref 1, 10). The new library aligns with Birmingham City Council's Big City Plan to regenerate the city center, with the green roof gardens playing a key role (Ref 4).