Storm surge and sea level rise (SLR) are affecting coastal communities, properties, and ecosystems. While coastal ecosystems, such as wetlands and marshes, have the capacity to reduce the impacts of storm surge and coastal flooding, the increasing rate of SLR can induce the transformation and migration of these natural habitats. In this study, we combined coastal storm surge modeling and economic analysis to evaluate the role of natural habitats in coastal flood protection. We focused on a selected cross-section of three coastal counties in New Jersey adjacent to the Jacques Cousteau National Estuarine Research Reserve (JCNERR) that is protected by wetlands and marshes. The coupled coastal hydrodynamic and wave models, ADCIRC+SWAN, were applied to simulate flooding from historical and synthetic storms in the Mid-Atlantic US for current and future SLR scenarios. The Sea Level Affecting Marshes Model (SLAMM) was used to project the potential migration and habitat transformation in coastal marshes due to SLR in the year 2050. Furthermore, a counterfactual land cover approach, in which marshes are converted to open water in the model, was implemented for each storm scenario in the present and the future to estimate the amount of flooding that is avoided due to the presence of natural habitats and the subsequent reduction in residential property damage. The results indicate that this salt marshes can reduce up to 14% of both the flood depth and property damage during relatively low intensity storm events, demonstrating the efficacy of natural flood protection for recurrent storm events. Monetarily, this translates to the avoidance of up to $13.1 and $32.1 million in residential property damage in the selected coastal counties during the '50-year storm' simulation and hurricane Sandy under current sea level conditions, and in the year '2050 SLR scenario', respectively. This research suggests that protecting and preserving natural habitats can contribute to enhance coastal resilience.

The increasing rate of sea level rise (SLR) poses a major threat to coastal lands and natural resources, especially affecting natural preserves and protected areas along the coast. These impacts are likely to exacerbate when combined with storm surges. It is also expected that SLR will cause spatial reduction and migration of coastal wetland and marsh ecosystems, which are common in the natural preserves. This study evaluates the potential impacts of SLR and marsh migration on the hydrodynamics and waves conditions inside natural protected areas during storm surge. The study focused on four protected areas located in different areas of the Chesapeake Bay representing different hydrodynamic regimes. Historical and synthetic storms are simulated using a coupled storm surge (ADCIRC) and wave (SWAN) model for the Bay region for current condition and future scenarios. The future scenarios include different rates of local SLR projections (0.48 m, 0.97 m, 1.68 m, and 2.31 m) and potential land use changes due to SLR driven marsh migration, which is discretized in the selected preserve areas in a coarse scale. The results showed a linear increase of maximum water depth with respect to SLR inside the protected areas. However, the inundation extent, the maximum wave heights, and the current velocities inside the coastal protected areas showed a non-linear relationship with SLR, indicating that the combined impacts of storm surge, SLR, and marsh migration depend on multiple factors such as storm track, intensity, local topography, and locations of coastal protected areas. Furthermore, the impacts of SLR were significantly greater after a 1 m threshold of rise, suggesting the presence of a critical limit for conservation strategies.intensification over the next century [10,11], the combined effects of storm surge and SLR are likely to increase flood impacts in coastal areas [12].Furthermore, SLR is most likely to exacerbate the impacts of storm surge by amplifying the total inundated area and maximum water levels [12][13][14][15]. Higher surge elevations, along with increasing wave heights driven by SLR [16], may result in increased tidal current and changes in shorelines [17]. The gradual shoreline recession will also reduce the wave energy dampening and increase the long-term erosion rates [18]. This will largely affect coastal wetlands and salt marshes containing plants and vegetation that can only withstand within a limited tidal range, salinity [19,20], and elevation range to mean sea level [21]. The sustainability of these natural habitats depends on the accretion rate at which they are vertically rising with respect to the rate of SLR [22]. If the water elevation is rising at a faster rate than the marsh is able to build in order to sustain vegetation, the marsh will begin to migrate inland [23]. Although some tidal wetlands are capable of vertical movement with small changes in sea level [20,24], higher increase in SLR will cause submergence and landward movement of marshes across the coastal landscape [24,25]. The i...

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Bangladesh is regarded as one of the most climate-vulnerable regions in South Asia due to its unique geographical location and socio-economic conditions. Natural disasters, changing temperatures, precipitation, and sea level rise have affected agricultural production, infrastructure, and livelihoods in the country. To face these challenges, nature-based solutions (NbS) can address climate change adaptation, protection and management of natural ecosystems, and biodiversity conservation. For example, in Bangladesh, coastal mangroves can protect communities from storm surge and sea level rise, forests in hilly regions can prevent landslides, and green spaces in urban areas can reduce heat stress and promote the well-being of inhabitants. However, effective design, implementation, and upscaling of NbS requires support from national policies and plans. This study reviews relevant Bangladeshi national policies from the past three decades to investigate NbS as a potential framework to address climate change and societal challenges in the country. We systematically analyzed twenty policy documents across three sectors: national development; disaster management and climate change; and environment and forest. Our study found growing emphasis on preservation, protection, and management of natural ecosystems in the national policies. However, our analysis showed that among the twenty policies, nineteen of them have no direct mention of NbS terminology. Instead, the policies include various strategies and terminologies that fall under the NbS umbrella, such as ecosystem-based adaptation, ecosystem services, and green and eco-building. However, these policies are still widely missing specific implementation guidelines, robust financial support, and institutional mechanisms for monitoring and evaluating NbS initiatives in Bangladesh. We recommend several policy actions to facilitate effective and inclusive NbS interventions in Bangladesh: enhance inter-ministry cooperation; develop national funding support; develop a national promotional campaign; pursue evidence-based research and capacity-building activities; and involve youth, marginalized people, and women. These actions can optimize the benefits of NbS to enhance the country’s resilience against climate change and foster sustainable development.

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