Storm / wave induced erosion and flooding

The Lower Perdido Islands – Bird, Robinson and Walker Islands – are located in the Perdido Pass, in Orange Beach. The area is a popular destination, attracting many visitors due to its blue-green water and diverse wildlife, which, however, leads to erosion from boat wakes and marine debris. Its popularity impacts these wildlife habitats, including the seagrasses, marsh and forests which provide habitat for nesting birds and nurseries for local fish. Therefore, the Nature Conservancy, the City of Orange Beach, Moffatt & Nichol, and Olsen Associates Inc. started working together in 2017 to create a conservation management plan for the Perdido Islands, as well as develop some restoration initiatives to support this critical habitat for the future [1,3]. This Lower Perdido Islands' restoration project is part of a larger Perdido Bay Watershed restoration plan [2]

Located southeast of Bayou La Batre, Coffee Island is a barrier island that provides a buffering capacity for shorelines in Mobile County [5]. Since 1950, the shoreline on the island has been eroding. In response, the Nature Conservancy has put in a ‘’living shoreline’’ construction in 2010 to reduce wave energy and decrease erosion the island has been facing [1]. A ‘’living shoreline’’, ‘’refers to the use of nature-based techniques and materials such as oyster shells, reef blocks, bagged shells, live shellfish, and plants to help protect eroding shorelines’’ [2]. While the living shorelines constructed in 2010 still provide habitat benefits, these efforts no longer protect the shoreline from erosion. This in turn threatens not only the island's buffering capacity, but also the integrity of the marsh on the island [5]. Therefore, the Nature Conservancy has secured funding for a second project on the island, the Coffee Island Restoration project (in 2023) that aims to implement a (longer) 5,000-foot living shoreline breakwater, including the use of ‘’super sacks’’ – a specific kind of sediment barriers functioning as dikes – to protect the coastline while enhancing habitat [4, 6]

To reduce the risk of urban flooding, the city of Seville, through its metropolitan water company Emasesa, established several "sustainable urban drainage systems". One of the pilot locations is on the Avenida de las Ascociaciones de Vecinos, where a rain garden complemented by an infiltration zone was established. The main aim of the project is to reduce the risk of flooding, but the system can also improve the urban landscape by offering green space, preventing desertification and reducing pollutants carried by runoff [Ref. 1-4]. After implementation, the project was shown to be effective during heavy rain [Ref. 5]. The system can store up to 34 m2 of water and reduce flow rates to the sewage network by 69 % and the total runoff to sewage by 93 % [Ref. 3-5]. The project was initiated and led by Emamesa, while two different companies were employed to design and construct the system [Ref. 1, 2, 6, 7]. The total budget of the project, which also included some renovations of grey infrastructure along the street, was 165000 EUR [Ref. 1].

The Waliwa project, launched in 2017 by the municipality of Sainte-Luce, is a collaborative effort dedicated to restoring marine biodiversity, enhancing the ecological balance of the bay area, revitalizing the local ecosystem and supporting sustainable economic activities. By focusing on marine biodiversity conservation, Waliwa addresses several critical environmental challenges. The project helps mitigate coastline erosion, support the blue economy through artisanal fishing and tourism, and foster an environmentally friendly culture among the local community.
So far, the Waliwa project has implemented three initiatives: it restored the Gros Raisin backshore to address erosion and provide nesting sea turtles with protected space (Ref 4). The project also intervened to restore the Pont Café pond, which was covered in Salvinia Molesta, preventing the intake of oxygen and hampering its role as a water filter, habitat for species and flood regulator .
Furthermore, the project has conducted studies and raised awareness about the challenges posed by wastewater management on the health of municipal water bodies. Through these efforts, Waliwa is working to create a more sustainable and resilient marine environment for future generations. (Ref 4, 5, 6; 12)

The Swedish Geotechnical Institute, a government agency, and the county administrative boards in Västra Götaland and Scania are running a project which tests methods to prevent erosion of coastal salt meadows. Erosion risks destroying unique ecosystems, and the aim is to develop cost-efficient, nature-based mitigation methods that can be replicated in other sites with similar problems. The project is part of an EU-funded Interreg North Sea project called MAinstreaming NAture BAsed Solutions through COASTal systems (MANABAS COAST), which involves other countries in the region [Ref. 1, 5]. Four different salt meadows are included in the Swedish part of the project. The sites are called pilot areas and are meant to test and showcase NBS to inform policy and develop methods that can be used in larger scales in the future. One of the sites is located at Glose in Kungälv municipality within the Gothenburg FUA [Ref. 2-4]. Here, the biodiversity of a salt meadow used for grazing and the adjacent coastal waters are threatened by erosion. According to a new management plan, NBS such as natural barriers will be implemented to break waves and halt erosion, preserving the ecosystems, improving water quality and ensuring the land continued use as a pasture for grazing cattle [Ref. 4].

The Far West Detroit neighborhood faces significant challenges with its aging infrastructure. The neighborhood’s stormwater and sewer systems are combined into a single system that is only capable of handling a limited volume. During heavy rain events, the system's capacity is exceeded, causing excess stormwater and untreated sewage to overflow into the Rouge River, which negatively impacts the environment (Ref. 1).
Detroit is investing $40 million in a transformative stormwater management system in the Far West neighborhood near Rouge Park. Described by the Detroit Water and Sewerage Department as the largest project of its kind, it will redirect 98 million gallons of rainwater and snowmelt into two new detention basins and a renovated sewer system. The new wastewater system is expected to significantly reduce water volumes in Detroit’s combined sewer system during heavy rainfall and to provide flood relief for approximately 1,200 homes that have experienced flooding in recent years. This expansion, informed by community feedback, marks one of the city's most notable investments in green infrastructure to improve its overextended wastewater management system.
The project has been planned through extensive studies and community coordination since 2016, with construction set to occur in three phases, extending through 2026. Crews broke ground on the South Basin, North Basin, and sewer overhaul in July 2022, and progress is reportedly on track. In addition to the basins, the stormwater management initiative includes neighborhood improvements to enhance recreational opportunities for residents and visitors alike. Planned enhancements in Rouge Park will introduce wetland spaces with native flora, creating greener, more inviting areas in the community for residents to enjoy (Ref. 2).

The Fenkell Stormwater Project in the Brightmoor neighborhood of Detroit is an initiative led by the Detroit Water and Sewerage Department (DWSD) to mitigate the impact of heavy rain events on the local sewer system. By transforming 92 Detroit Land Bank Authority (DLBA) parcels into 24 bioretention gardens, the project aims to significantly reduce street flooding and basement backups in the area. These gardens, spread across approximately 50 acres of mostly vacant land, utilize permeable soils and landscaping techniques to absorb excess rainfall, which helps prevent the overloading of the city’s combined sewer system. This is particularly important in reducing combined sewer overflows (CSOs), which occur when the system's capacity is exceeded during heavy rains, leading to untreated stormwater and sewage being discharged into the Rouge River.
The project is expected to manage and treat about nine million gallons of stormwater annually, making a significant impact on both the neighborhood’s infrastructure and the environment. In addition to the bioretention gardens, the project includes the partial removal of Blackstone Street between Keeler and Midland streets to further enhance stormwater management.
Community engagement has been a critical component of the project, with residents of Brightmoor and Minock Park participating in meetings to share their preferences for the types of trees, plantings, and other features. The DWSD will maintain the gardens under its Green Stormwater Infrastructure (GSI) program, which already includes 19 other similar projects across the city. The project is currently in the construction phase and is expected to be completed by the end of 2024, modernizing Brightmoor’s stormwater infrastructure and providing long-term environmental and community benefits.
(Ref.1-3)

Fairhope's Municipal Pier is a popular bayfront destination featuring a 1/4-mile pier, swimming areas, picnic spots, a landscaped rose garden, benches, restrooms, a marina, a restaurant, walking trails, and a duck pond. However, the area has been fragilized over the years. The beaches are absent and less prominent now, due in large measure to the presence of shoreline hardening (Ref 5), making the shoreline more vulnerable to climate hazards (Ref 5).
The main goal of the Working Waterfront and Greenspace Restoration Project is to introduce safe and user-friendly improvements to the 10-acre South Beach Park area, which encompasses the Municipal Pier (Ref 2). These upgrades aim to enhance the public's use and access of the waterfront, while ensuring the park's long-term resilience and sustainability (Ref 2). The new design tackles both the structural issues of the bulkhead/seawall and the overall aesthetics of the Fairhope Pier area (Ref 2).
Over the years, storms, particularly Hurricanes Sally and Zeta, have compromised the structural integrity of the anchoring hardware of the bulkhead/seawall, causing parts of the wall to shift. Additionally, water intrusion behind the wall has eroded the soil supporting the walkway in certain areas (Ref 2). Other important features include new handrails, decking, restroom facilities, and lights on the pier. The project will also add new stairs leading to the bluff, restore the fountain, and renovate the parking lot. A funicular lift will be installed at the bluff to enhance accessibility (Ref 5).
Pedestrian safety will be improved to meet the requirements of the Americans with Disabilities Act. Other enhancements include landscaping with new irrigation, and the construction of new sidewalks (Ref 2, Ref 4).

Martinique is a biodiversity hotspot, home to over 1,500 endemic plants, 70% of which are under threat from human activities. In response to these pressures, the Péyi Vert [Green Country] initiative was launched to plant endemic trees and strengthen the island's biodiversity. Beyond simply preserving species, these trees are crucial in maintaining healthy ecosystems, as they provide essential services such as carbon sequestration, shade, food for human consumption, soil decontamination, pollination, and protection against coastline erosion.
Launched in June 2020 by Entreprises et Environnement (EE), a not-for-profit business association representing 80 Martinican companies, the Péyi Vert initiative aims to plant 1 million native trees (either Martinican or Caribbean) over five years. It can be seen as a Martinique-wide strategy to adapt to and mitigate climate change. Péyi Vert facilitates connections between people who want to plant trees and Martinican companies that serve as financial sponsors. The initiative emphasizes conserving natural heritage by planting endangered species, as well as promoting native species that, while not necessarily threatened, provide valuable ecosystem services or contribute to biodiversity restoration.
Between 2020 and 2023, EE reported planting 50,000 trees (Refs 1, 4, 6, 7). Although individuals can make donations, Péyi Vert primarily seeks funding from companies looking to offset their carbon emissions or enhance their Corporate Social Responsibility (CSR). To achieve its goals, the initiative mainly collaborates with municipalities, companies, and farmers (Ref 3).

In the bay of Fort-de-France, mangroves cover nearly 1,300 hectares, representing about 70% of the total mangrove area in Martinique. This plant formation, characteristic of tropical marine environments, is essential for the ecological balance of the bay. Mangroves act as filters, purifying marine and river waters, protecting the coastline against erosion, and providing habitat for various marine flora and fauna.
However, this fragile ecosystem is threatened by wave-induced erosion, urbanization, the spread of invasive species, and pollution. In response to these challenges, the French Coastal Protection Agency (Conservatoire de l'espace littoral et des rivages lacustres, CELRL) and its partners have launched an initiative to restore several mangrove areas as part of the “Contrat de la Grande Baie de Martinique" which is a collaborative initiative aimed at the sustainable management and restoration of the coastal and marine environment of the Greater Bay of Martinique. This contract typically involves partnerships between various stakeholders, including government agencies, local municipalities, environmental organizations, and community groups. The project identified several sites totaling 3.81 hectares in the Greater Bay area that require reclamation.
The project aims to restore mangrove populations by creating favorable conditions through actions such as clearing invasive species and trash, followed by replanting with white, black, or red mangrove seedlings, depending on the environmental characteristics of each site. Additionally, the initiative seeks to engage the public and youth through volunteering days and awareness campaigns (Refs 1-9).