Nature-based solutions: An optimal approach for flood risk reduction

NBSs include widening of natural flood plains, protecting and expanding wetlands, restoring oyster and coral reefs, and investing in urban green spaces that reduce run-off

Floods are among the most damaging natural disasters in terms of threat to human lives and economic costs. The frequency and intensity of flooding are expected to increase globally (IPCC). Flood is one of the most devastating disasters in Bangladesh (World Disasters Report 2018). Recent pictures of flood loss and damage indicate that the conventional approaches (i.e., built infrastructure) of flood management is mostly failed to protect the people’s lives, resources, and livelihoods. It is, therefore, high time to take “more” concerted efforts to adopt and mainstream an integrated and/or hybrid measure to reduce flood risks.

Realising the limitations of infrastructure-based options and increased understandings on the role of ecosystems, nature-based solutions (NBSs) for flood management have been received much attention to academicians, practitioners, and policymakers. NBSs strategically conserves or restores nature (sometimes called “green infrastructure”) while supports conventionally built infrastructure systems (“gray infrastructure”) can reduce disaster risk and produce more resilient and lower-cost services.

NBSs include widening of natural flood plains, protecting and expanding wetlands, restoring oyster and coral reefs, and investing in urban green spaces that reduce run-off. NBSs provide an optimal opportunity to better integrate the agendas of climate action, flood risk reduction, and biodiversity conservation into a coherent and holistic approach.

Recent advances on NBSs for flood risk reduction are noticeable. The World Bank publishes a flagship report on “Implementing Nature-based Flood Protection,” and the World Wildlife Fund (WWF) produces comprehensive “Flood Green Guide.” The Sendai Framework on Disaster Risk Reduction, the Paris Agreement on Climate Change and the SDGs endorses NBSs for flood management.

Mounting evidence demonstrates that NBSs are often successful and cost-effective. Vietnam has implemented a widespread mangrove restoration project integrated with dike systems to reduce coastal flooding—which ultimately saved US$215 million. In the United States, natural wetlands have moderated damages from Hurricane Sandy by an estimated $625 million. China’s “Sponge Cities” programme—a typical example of NBSs—in 30 pilot cities is integrating vast amounts of green space into urban design to prevent surface flooding. Practical Action Asia sought to collect evidence of examples using NBSs for flood risk reduction in South Asia and convenes a platform for regional knowledge exchange and learning.

Flood risk management approaches include non-structural (e.g., land use planning and flood monitoring strategy) and structural in the form of nature-based (soft) solutions (e.g., wetland restoration and retention ponds) and grey (hard) solutions (e.g., dam and reservoirs). To effectively reduce flood risk, it is recommended first to apply non-structural solutions and then consider structural solutions by prioritising NBSs whenever possible as part of an integrated approach.

NBSs can be combined with grey solutions referring as well to hybrid solutions (e.g., dikes with ecosystem restoration). In the case of no other options, then grey solutions can be deployed.

At a larger scale, NBSs planning requires several things. First, NBSs for flood management should start with a system-wide analysis of the local socio-economic, environmental, and institutional conditions. Pertinent questions have to be addressed, such as how the physical landscape of water bodies influence the human and infrastructure at various spatial scales? What would be the time scale of establishing NBSs? And how stakeholders’ purposes would be served through NBSs?

Second, assessing the risks and benefits of possible NBSs should be conducted, covering risk reduction benefits as well as social and environmental effects. Key factors include understanding the three elements of (local) risk: hazard, exposure, and vulnerability; and the future changes in risk as a consequence of climatic, socio-economic, and institutional reforms.

Third, setting standardised performance evaluation, i.e., NBSs are necessitated to be tested, designed, and evaluated quantitatively. The purpose of this evaluation is three-fold: measuring the effectiveness of NBSs in reducing hazard/exposure, minimising uncertainties in design, and making a comparison with conventional engineering interventions.

And, fourth, NBSs planning requires adaptive management that likely emphasise a robust monitoring, evaluation, knowledge generation, flexible decision-making, and learning.

Implementation and upscaling NBSs hinge on many issues. First, “improving the knowledge base,” this can be enhanced through empowered participation of diverse stakeholders, including (political) leaders and addressing information and research gaps. Research shows the impacts of NBS are well understood, but their cost-effectiveness and the sustained delivery of different benefits is often unclear. Hence, NBSs application needs to be based less on generalised assumptions and better assessed and explicitly designed for local applications.

Second, “leveraging financing”—NBSs do not necessarily require additional financial resources but usually involve redirecting and making more effective use of existing financing. At this stage, the current budget of water resource management is enough to enabling uptake of NBSs.

Third, “enabling the regulatory and legal environment” is critical to NBSs implementation for flood risks reduction, since the current regulatory and legal environments for flood management are developed largely with grey-infrastructure approaches in mind. For instance, in China, the implementation of the ‘sponge city’ concept is fully backed by suitable rules, regulations, and policy framework.

Fourth, “strengthening institutional scaffoldings” to enhance intersectoral collaboration, harmonise policies across multiple agendas, and institutionalise adaptive management (and governance). Likewise, institutions have to be capacitated to increase cooperation between landscape planners, ecologists, green infrastructure specialists, and engineers to make them useful and successful.

In sum, the Bangladesh economy continues to grow at an impressive rate, which is sometimes thwarted by natural disasters—flood. Mainstreaming NBSs in flood management can be heralded as a transformational change in urban flood governance to address the daunting challenges of flooding.

Ranjan Roy, Ph.D., is an Associate Professor in the Dept. of Agricultural Extension and Information System, Sher-e-Bangla Agricultural University, Email: [email protected]

 

 

Nature-based solutions: An optimal approach for flood risk reduction

NBSs include widening of natural flood plains, protecting and expanding wetlands, restoring oyster and coral reefs, and investing in urban green spaces that reduce run-off

Floods are among the most damaging natural disasters in terms of threat to human lives and economic costs. The frequency and intensity of flooding are expected to increase globally (IPCC). Flood is one of the most devastating disasters in Bangladesh (World Disasters Report 2018). Recent pictures of flood loss and damage indicate that the conventional approaches (i.e., built infrastructure) of flood management is mostly failed to protect the peoples lives, resources, and livelihoods. It is, therefore, high time to take more concerted efforts to adopt and mainstream an integrated and/or hybrid measure to reduce flood risks. Realising the limitations of infrastructure-based options and increased understandings on the role of ecosystems, nature-based solutions (NBSs) for flood management have been received much attention to academicians, practitioners, and policymakers. NBSs strategically conserves or restores nature (sometimes called green infrastructure) while supports conventionally built infrastructure systems (gray infrastructure) can reduce disaster risk and produce more resilient and lower-cost services. NBSs include widening of natural flood plains, protecting and expanding wetlands, restoring oyster and coral reefs, and investing in urban green spaces that reduce run-off. NBSs provide an optimal opportunity to better integrate the agendas of climate action, flood risk reduction, and biodiversity conservation into a coherent and holistic approach. Recent advances on NBSs for flood risk reduction are noticeable. The World Bank publishes a flagship report on Implementing Nature-based Flood Protection, and the World Wildlife Fund (WWF) produces comprehensive Flood Green Guide. The Sendai Framework on Disaster Risk Reduction, the Paris Agreement on Climate Change and the SDGs endorses NBSs for flood management. Mounting evidence demonstrates that NBSs are often successful and cost-effective. Vietnam has implemented a widespread mangrove restoration project integrated with dike systems to reduce coastal floodingwhich ultimately saved US$215 million. In the United States, natural wetlands have moderated damages from Hurricane Sandy by an estimated $625 million. Chinas Sponge Cities programmea typical example of NBSsin 30 pilot cities is integrating vast amounts of green space into urban design to prevent surface flooding. Practical Action Asia sought to collect evidence of examples using NBSs for flood risk reduction in South Asia and convenes a platform for regional knowledge exchange and learning. Flood risk management approaches include non-structural (e.g., land use planning and flood monitoring strategy) and structural in the form of nature-based (soft) solutions (e.g., wetland restoration and retention ponds) and grey (hard) solutions (e.g., dam and reservoirs). To effectively reduce flood risk, it is recommended first to apply non-structural solutions and then consider structural solutions by prioritising NBSs whenever possible as part of an integrated approach. NBSs can be combined with grey solutions referring as well to hybrid solutions (e.g., dikes with ecosystem restoration). In the case of no other options, then grey solutions can be deployed. At a larger scale, NBSs planning requires several things. First, NBSs for flood management should start with a system-wide analysis of the local socio-economic, environmental, and institutional conditions. Pertinent questions have to be addressed, such as how the physical landscape of water bodies influence the human and infrastructure at various spatial scales? What would be the time scale of establishing NBSs? And how stakeholders purposes would be served through NBSs? Second, assessing the risks and benefits of possible NBSs should be conducted, covering risk reduction benefits as well as social and environmental effects. Key factors include understanding the three elements of (local) risk: hazard, exposure, and vulnerability; and the future changes in risk as a consequence of climatic, socio-economic, and institutional reforms. Third, setting standardised performance evaluation, i.e., NBSs are necessitated to be tested, designed, and evaluated quantitatively. The purpose of this evaluation is three-fold: measuring the effectiveness of NBSs in reducing hazard/exposure, minimising uncertainties in design, and making a comparison with conventional engineering interventions. And, fourth, NBSs planning requires adaptive management that likely emphasise a robust monitoring, evaluation, knowledge generation, flexible decision-making, and learning. Implementation and upscaling NBSs hinge on many issues. First, improving the knowledge base, this can be enhanced through empowered participation of diverse stakeholders, including (political) leaders and addressing information and research gaps. Research shows the impacts of NBS are well understood, but their cost-effectiveness and the sustained delivery of different benefits is often unclear. Hence, NBSs application needs to be based less on generalised assumptions and better assessed and explicitly designed for local applications. Second, leveraging financingNBSs do not necessarily require additional financial resources but usually involve redirecting and making more effective use of existing financing. At this stage, the current budget of water resource management is enough to enabling uptake of NBSs. Third, enabling the regulatory and legal environment is critical to NBSs implementation for flood risks reduction, since the current regulatory and legal environments for flood management are developed largely with grey-infrastructure approaches in mind. For instance, in China, the implementation of the sponge city concept is fully backed by suitable rules, regulations, and policy framework. Fourth, strengthening institutional scaffoldings to enhance intersectoral collaboration, harmonise policies across multiple agendas, and institutionalise adaptive management (and governance). Likewise, institutions have to be capacitated to increase cooperation between landscape planners, ecologists, green infrastructure specialists, and engineers to make them useful and successful. In sum, the Bangladesh economy continues to grow at an impressive rate, which is sometimes thwarted by natural disastersflood. Mainstreaming NBSs in flood management can be heralded as a transformational change in urban flood governance to address the daunting challenges of flooding. Ranjan Roy, Ph.D., is an Associate Professor in the Dept. of Agricultural Extension and Information System, Sher-e-Bangla Agricultural University, Email: [email protected]