Flood protection

St Inez creek was an ecologically functional tidal waterbody in Panaji, Goa. Panaji has been identified as one of the most vulnerable coastal cities from floods due to the predicted sea-level rise. St Inez creek is one of the very important freshwater bodies in the city because of its cultural, social and biodiversity value. Recently, the ecological functionality of the creek was severely compromised through a combination of natural degradation and anthropogenic influences, which includes sedimentation, collapsed embankments, eutrophication, weed growth, pollution, the release of raw sewerage from neighbouring informal settlements and dumping of construction debris. The current intervention is about the restoration of the creek to conserve the urban nature and ecological systems and to increase the resilience of the city. [1, 2]

Touted as a long-term solution to flooding of Mandaue City, establishment of a mangrove eco-park has begun, having received funding from the Department of Budget and Management (DBM) (Ref. 1). Through establishment of mangroves, the eco-park will "perform a significant role in shoreline protection, acting as a buffer against strong winds and waves", which is considered particularly important in light of the anticipated effects of climate change (Ref. 6).

A total 17-hectare plot is to be rehabilitated, as identified in the Mandaue City Government's Comprehensive Land Use Plan (Ref. 3). At present, it is unclear whether nature-based solutions (including mangrove restoration) are to be implemented across the entire 17ha of the site, but initial efforts have been focused on the restoration of a 5-ha section of mangrove forest (Ref. 2). Due to the lack of data on how exactly the remainder of the 17-ha area will be restored, the total NBS area for this project has only been recorded as 5-ha (5000m2) within this case study, rather than the entire 17,000m2 which is encompassed within the site.

The site is situated at the outfall of the Butuanon River which frequently overtops as a result of heavy rain and has been considered "biologically dead" since 1992 (Ref. 7). The site itself comprises a former dumpsite which had been "left derelict and filled with piles of trash", hence in addition to reducing flood risk, its rehabilitation will serve as green space in which "the residents of Mandaue City [can] gather and enjoy a breath of fresh air" (Ref. 2). The eco-park is considered to bring the added benefit of filtering water as it enters the Mactan Channel, in addition to reducing greenhouse gas emissions through carbon dioxide absorption (Refs. 1 & 6).

The Porsuk Stream divides the city of Eskişehir into two with a green corridor running along the shores of the stream. The Porsuk Stream served provisioning services and acted as a recreational area in the first half of the 20th century, however with increased industrial activities discharging untreated wastewater into the river, rapid urbanisation in the city and other settlements, and increased fertilisers and pesticides in the groundwater originated from agricultural practices (upstream of the Porsuk River), it became highly polluted and its ecosystem degraded severely (1,2,4,5). The Organization for Security and Cooperation in Europe (OSCE) identified the stream as one of the highly dangerous rivers in terms of pollution and health, where no living beings except viruses live (1).
Within the framework of the 'Eskişehir Urban Development Project' the 'Natural Disaster Loss Reduction Project (Porsuk Project)' has been initiated focusing on the ecological restoration of the stream, improving water quality, increasing the resilience of the city against natural disasters (as earthquakes and floods) while also reestablishing the stream's environmental and social role in the city (1). A network of natural infrastructure was created along the Porsuk by expanding public green spaces and link the entire corridor with a sustainable public transport network. (4,5)

One of Valdivia's (in South Chile) southern peripheral neighbourhoods reaches the river of Angachilla which in time led to the creation of an urban wetland, a beautiful and large urban nature reserve of the city of Valdivia. The city of Valdivia is inserted in an extensive network of rivers and coastal wetlands, which penetrate the city through estuaries, hualves and meadows. The Angachilla estuary wetland is one of the most important, connecting the southern sector of the city with the Valdivia River estuary.
These urban wetlands provide important ecosystem functions that directly benefit citizens. Since 2007, the residents of Villa Claro de Luna (neighbourhood) together with various social organisations have worked on the recovery of the Angachilla Wetland, a natural space of great ecological and social value located in the city of Valdivia. Actions included carrying out cleaning, restoration and environmental education activities to recover a place that, abandoned and without any protection from the authorities, was converted into a clandestine garbage dump. (1,2,3)

From 1998-2002 Argentina went through an economic depression, which began after the Russian and Brazilian financial crises, caused widespread unemployment, riots, the fall of the government, and a default on the country's foreign debt. Rosario, the third-most populous city in the country, was not a stranger to the crisis' effects as many of its inhabitants were now living under the poverty line. Coupled with this, climate change was heating up the city and making rainfall more erratic, leading to both flooding in Rosario and fires in the nearby river delta. To tackle urban inequality and climate change the Municipality of Rosario developed a program called "Urban Agriculture Program" which aims to give low-income residents access to underutilized and abandoned public and private land to cultivate food. Over the years, the municipality evolved the program into a cornerstone of its inclusive climate action planning. (1)

The Orbital Forest of Tirana is an innovative urban forest that as a green belt forms a natural growth boundary for the City. Tirana has experienced rapid development in the past decades that led to population growth challenging municipal services and infrastructure, while climate change also posed extensive pressures to the urban area with intense flooding, precipitation, urban heat and degrading environment (1, 4). The Orbital Forest is a ring on the periphery of the City that connects 14,000 ha of Tirana’s parks, agricultural fields, and forests, maintaining the ecosystem and supporting biodiversity. (3, 4) The NBS aims to increase urban greenery through the plantation of 2 million trees that fit well to the existing ecosystem while also creating a natural boundary to halt urban sprawl (1,4,5). The afforestation of the Orbital Forest has been done through the “Donate a Tree For Tirana” campaign started in 2017 where citizens, businesses and international organisations can plant a tree adding to the green belt. As of 2021, more than 440,700 trees in the framework of the "Donate a Tree" campaign are also bringing urban nature closer to residents (3).

Kaysone experiences severe flooding events on an annual basis due to its location to the banks of Mekong river, as well as periodic storms, and past responses to these threats have focused on the Savanxay Market and the Southern Flood Gate, but with limited success (Ref. 1). This intervention focuses on the development of an integrated adaptation plan for the area around the market and adjacent to the Mekong canal. This plan includes NBS-specific components considering how the market's parking area provides an important opportunity for bioengineering and green cover, and that there is "an opportunity to use adjoining land as a constructed wetland and park for recreation, flood retention and storm water treatment" (Ref. 1). The adaptation plan comprises seven points overall, focusing on wastewater recycling, walking paths, proper drainage and green space in addition to an educational component related to climate change and its impacts (Ref. 1).

Climate change has become the day-to-day struggle for this nation - an island nation that faces serious sea-level rise implications should the problem remain uncurbed. The impacts seen are related to rising temperature, sea-level rise (coastal erosion), and changes in rainfall (flooding). To reduce the vulnerability of the population of two regions next to its capital (Victoria), the Ministry of Environment and Energy of Seychelles initiated in 2012 a project aiming at improving the quality of life for the people of Seychelles and restore coastal zones as well as the ecological habitat related to them through nature-based solutions. The project will reduce these vulnerabilities by spearheading ecosystem-based adaptation as climate change risk management—restoring ecosystem functionality, and enhancing ecosystem resilience and sustainable watershed and coastal processes, in order to secure critical water provisioning and flood attenuation. (1)

A multi-purpose green belt (12 km in length of Batticaloa Municipal Corporation coast) was established to protect the lagoon and coastal areas, restore mangrove ecosystems and improve coastal biodiversity. The project comes under activity 1.3 of the overarching project Climate Resilient Action Plans for Coastal Urban Areas in Sri Lanka (CCSL). The project focuses on the most urgent and immediate needs of the Sri Lankan coastal cities in adapting to climate change, and mitigating risks and the severity of impacts through Disaster Risk Management (DRM). The green belt plantation was done with Casuarinas plantation in 400 ha (out of which 75% by Mandru and 25% by the Forest Department), mangrove forest redesigning and protection of the existing vegetation. [1, 2, 6]

Hatirjheel area development project is a wetland restoration project that explores the possibility of reintroducing water edge elements into the city of Dhaka. The project includes both engineered infrastructure and NbS. The restored jheel (wetland) and Begunbari khal have improved storm-water management of Dhaka and made aquatic biodiversity better. It also increased green and open space in the busy capital. The intended objective of the project was to create a bridge between the densely developed old part of the city on the south and the new organised north part of the city. Spreading over 311 acres, this project has endeavoured towards improving connectivity between major urban corridors as well as acting as a retention pond to mitigate the flash flood-prone densely populated part of the area. [1,2]