Coastal Natural and Nature-Based Features: International Guidelines for Flood Risk Management

Abstract

Natural and nature-based features (NNBF) have been used for more than 100 years as coastal protection infrastructure (e.g., beach nourishment projects). The application of NNBF has grown steadily in recent years with the goal of realizing both coastal engineering and environment and social co-benefits through projects that have the potential to adapt to the changing climate. Technical advancements in support of NNBF are increasingly the subject of peer-reviewed literature, and guidance has been published by numerous organizations to inform technical practice for specific types of nature-based solutions. The International Guidelines on Natural and Nature-Based Features for Flood Risk Management was recently published to provide a comprehensive guide that draws directly on the growing body of knowledge and practitioner experience from around the world to inform the process of conceptualizing, planning, designing, engineering, and operating NNBF. These Guidelines focus on the role of nature-based solutions and natural infrastructure (beaches, dunes, wetlands and plant systems, islands, reefs) as a part of coastal and riverine flood risk management. In addition to describing each of the NNBF types, their use, design, implementation, and maintenance, the guidelines describe general principles for employing NNBF, stakeholder engagement, monitoring, costs and benefits, and adaptive management. An overall systems approach is taken to planning and implementation of NNBF. The guidelines were developed to support decision-makers, project managers, and practitioners in conceptualizing, planning, designing, engineering, implementing, and maintaining sustainable systems for nature-based flood risk management. This paper summarizes key concepts and highlights challenges and areas of future research.

The impacts of tidal wetland loss and coastal development on storm surge damages to people and property: a Hurricane Ike case-study

“…This study shows that outer-lying barrier islands in Galveston Bay witnessed an increase in peak flood heights during H. Ike, due to the presence of back-barrier marsh wetlands functioning as semi-permeable barriers that slowed down or blocked the flow of the storm surge further inland. As wetlands become increasingly considered as alternatives within coastal defense portfolios 43 , it becomes essential to understand how these wetlands behave as barriers, and therefore, how they influence flood impacts on areas adjacent to these wetlands.…”

Greening the dike revetment with historic sod transplantation technique in a living lab

“…Managed realignment is the landward relocation of flood defences to restore nature on formerly reclaimed land (Esteves, 2014b;French, 2006). At managed realignment sites hybrid flood protection is provided by the flood risk reduction capacity of the restored foreshores complemented by the landward relocated flood defence (Bridges et al, 2021), that is, the (reinforced) existing or newly constructed realigned dike (van den Hoven et al, 2022). While managed realignment facilitates flood protection and nature restoration, we note managed realignment can result in trade-offs from a social perspective (Bax et al, 2023;Schuerch et al, 2022).…”

“…The required flood defence adaptation provides an opportunity to simultaneously tackle ecological challenges such as biodiversity loss (IPCC, 2022). Instead of traditional dike crest heightening, dikes can also be adapted by integrating vegetated foreshores to form a hybrid flood defence (Bridges et al, 2021). A foreshore is the sediment body fronting a dike on the waterside, for example a tidal flat or saltmarsh.…”

“…Flood risk infrastructure, such as dikes, has been built at places where natural features do not provide enough protection. Recently there has been an increasing focus on natural and nature‐based features that provide nature‐based flood protection (Bridges et al, 2022). For instance, on saltmarshes and mangroves that attenuate waves and reduce storm surges and high‐water levels (e.g., Hochard et al, 2021; Mazda et al, 2006; Möller et al, 2014; Willemsen et al, 2020).…”