Search

Developed barrier systems (barrier islands and spits) are lowering and narrowing with sea‐level rise (SLR) such that habitation will eventually become infeasible or prohibitively expensive for most communities in its current form. Before reaching this state, choices will be made to modify the natural and built environment to reduce relatively short‐term risk. These choices will likely vary substantially even along the same developed barrier system as these landscapes are rarely uniformly managed alongshore. Building on the results from a companion paper, here we use a new modeling framework to investigate the complexities in barrier system dynamics that emerge as a function of alongshore variability in management strategies, accelerations in SLR, and changes in storm intensity and frequency. Model results suggest that when connected through alongshore sediment transport, barriers with alongshore variable management strategies—here, the construction of dunes and wide beaches to protect either roadways or communities—evolve differently than they would in the absence of alongshore connections. Shoreline stabilization by communities in one location influences neighboring areas managed solely for roadways, inducing long‐term system‐wide lags in shoreline retreat. Conversely, when barrier segments managed for roadways are allowed to overwash, this induces shoreline curvature system‐wide, thus enhancing erosion on nearby stabilized segments. Feedbacks between dunes, storms, overwash flux, and alongshore sediment transport also affect outcomes of climate adaptation measures. In the case of partial, early abandonment of roadway management, we find that system‐wide transitions to less vulnerable landscape states are possible, even under accelerated SLR and increased storminess. Plain Language Summary: Because humans inhabit barrier islands and spits (collectively referred to as "barriers") these landscapes, that would otherwise naturally change shape in response to storms and sea‐level rise (SLR), are influenced by efforts to protect development with wide beaches and tall dunes. These features interfere with a process called overwash, which transports sand landward during storms, building barrier elevation relative to sea level. Here, we use a new model to better understand how these interactions influence the habitability of barriers over time. Our simulations show that different management decisions made for adjacent coastal segments affect each other in positive and negative ways. When communities nourish beaches, adjacent to segments managed for roadways, some nourished sand reaches the adjacent segments, reducing shoreline erosion there. Conversely, portions of barriers that are managed only for roadways allow some overwash to reach the barrier interior; this negatively affects neighboring communities by enhancing their shoreline erosion rates. We find that early abandonment of dune management along portions of barriers may prevent highly vulnerable future states, such as barrier drowning. As communities explore choices for climate adaptation, our findings reveal the importance of coordination among decision makers in adjacent communities to avoid undesirable outcomes. Key Points: When management strategies vary alongshore, their effects are coupled via alongshore sediment redistribution, influencing barrier evolutionBeach nourishment (along portions of barriers) induces system‐wide lags in shoreline retreat, even decades after nourishment practices ceaseMore overwash (due to lower dunes or increased storminess) can prolong habitability, but drives increased nourishment frequency elsewhere [ABSTRACT FROM AUTHOR]

Black, K.P.; Baba, M.; Mathew, J.; Kurian, N.P., and Ilic, A., 2021. Guidelines to prepare India's coast for climate change. Journal of Coastal Research, 37(6), 1117–1129. Coconut Creek (Florida), ISSN 0749-0208. India's first coastal protection guidelines for climate-change adaptation are described. The guidelines are holistic, recognizing the links between engineering, economic, physical, legal, social, environmental, and governmental intricacies. Robust protection solutions under climate change for millions of coastal residents may occur only when all these facets are improved within the complex regulatory, budgetary, and practical circumstances in India. Fifty-seven specific guidelines are presented in nine categories ranging from administrative to best-practice coastal protection. An "environmental softness ladder" that ranks coastal protection methods was developed as a scientific tool to guide policy development and project implementation. "Minimum floor level" for safe building was defined for each Indian coastal state using climate-change data produced for the study by Indian and international institutes. Beaches are more stable when the net sediment transport fluxes are close to neutral. "Grand schemes," which make large-scale changes to the coast rather than continuing with piecemeal localised works, are recommended. With diverse dynamics over a long coastline in India, the 4-year study engaged an exceptionally large number of experts, agencies, government bodies, development partners, and other stakeholders. [ABSTRACT FROM AUTHOR]

Tropical beaches provide coastal flood protection, income from tourism, and habitat for flagship species. They urgently need protection from erosion, which is being exacerbated by changing climate and coastal development. Traditional coastal engineering solutions are expensive, provide unstable temporary solutions, and often disrupt natural sediment transport. Instead, natural foreshore stabilization and nourishment may provide a sustainable and resilient long-term solution. Field flume and ecosystem process measurements, along with data from the literature, show that sediment stabilization by seagrass in combination with sediment-producing calcifying algae in the foreshore form an effective mechanism for maintaining tropical beaches worldwide. The long-term efficacy of this type of nature-based beach management is shown at a large scale by comparing vegetated and unvegetated coastal profiles. We argue that preserving and restoring vegetated beach foreshore ecosystems offers a viable, self-sustaining alternative to traditional engineering solutions, increasing the resilience of coastal areas to climate change. [ABSTRACT FROM AUTHOR]

This paper describes the application of coastal hydro-informatic modelling (using the TELEMAC Modelling System) to address management issues arising from projected hydrodynamical and morphological changes within a shallow, sandy estuarine environment. The model incorporates the complex interaction of ocean, terrestrial and atmospheric processes. The case study of the Dyfi Estuary, on the west coast of Wales, is highlighted here. As sea levels have risen locally and are predicted to rise further, a National Nature Reserve (Borth Bog), which has been reclaimed from tidal waters by embankments, will be at increasing risk from flooding episodes due to overtopping of these embankments at high tide. Present and predicted future tidal-fluvial scenarios have been modelled in the Dyfi Estuary in order to estimate the potential for flooding. In addition, areas of greatest velocity change and potential for sediment erosion/accretion have been identified. A further process that has been investigated is how salt marsh migration is affected by sea-level rise. This case study exemplifies some fundamental and complex physical processes inherent to estuaries, and shows how different management options can be assessed, before their implementation, through a modelling approach. [ABSTRACT FROM AUTHOR]

Fernández-Fernández, S.; Silva, P.A.; Ferreira, C.C., and Carracedo-García, P.E., 2020. Longshore sediment transport estimation at Areão Beach (NW Portugal) under climate change scenario. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. (Seville, Spain). Journal of Coastal Research, Special Issue No. 95, pp. 479-483. Coconut Creek (Florida), ISSN 0749-0208. The knowledge of longshore sediment transport is essential to understand coastal systems morphological evolution, and consequent erosion/accretion processes. This research is focused on Areão Beach, a groined sandy beach, located southwards of Aveiro Lagoon (NW Portugal). The high energetic wave climate and coastline orientation induce a substantial southward net sediment transport rate. Nevertheless, this transport is interrupted by coastal defense structures resulting in erosion problems downdrift. Future changes in wave and storm climate can alter current patterns of coastal erosion. This contribution aims to characterize the longshore sediment transport rate under a future wave climate scenario. The Delft3D-WAVE module propagated wave spectral data for historical and future, corresponding to climate change scenario RCP8.5. The hydrodynamic parameters (significant wave height, peak wave period and wave direction) were extracted at offshore Areão Beach and linear wave theory was applied to obtain significant wave height and wave direction at breaking point. Then, CERC empirical sediment transport formula re-evaluated in 2013 was used to estimate longshore sediment transport values. The results disclose a change in the magnitude of longshore sediment transport and an intensification of northwards transport in the future. These findings can contribute for an adequate decision-making regarding beach erosion management. [ABSTRACT FROM AUTHOR]