Uncertainty of wave runup prediction on coral reef-fringed coasts using SWASH model

Liu, Ye; Liao, Zhiling; Fang, Kezhao; Li, Shaowu

doi:10.1016/j.oceaneng.2021.110094

“…The low frequency swash (𝑆 𝐿𝐹 ) component increases with rising sea level at a smaller rate than 𝑆 𝑖𝑛𝑐 , suggesting that the LF energy is primarily set by nonlinear interactions of the shoaling swell. Uncertainty in modeled 𝑅 2% is not estimated, but Liu et al (2021) 38 found that laboratory measurements of 𝑅 2% on a fringing reef bathymetry matched SWASH estimates to within one standard deviation of model ensemble results. The effects of sea level rise on coastal flood risk at Faga'itua are twofold.…”

Section: Resultsmentioning

confidence: 99%

Rising Sea Levels and the Increase of Shoreline Wave Energy at American Samoa

Barnes,

Becker,

Tagarino

et al. 2024

Preprint

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American Samoa is experiencing rapid relative sea level rise due to increases in global sea level and significant post-2009 earthquake land subsidence, endangering homes and critical infrastructure. Wave and water-level observations collected over a fringing reef at Faga‘itua Bay, American Samoa, in 2017 reveal depth-limited shoreline sea-swell wave heights over the range of conditions sampled. Using field data to calibrate a one-dimensional, phase-resolving nonhydrostatic wave model (SWASH), we examine the influence of water level on wave heights over the reef for a range of current and future sea levels. Assuming a fixed reef bathymetry, model results predict rising sea levels will escalate nearshore extreme water levels that are dominated by an increase in nearshore sea-swell wave heights. Model results provide insight into how and at what reef depths rising sea levels reduce reef capacity to dissipate wave energy, compounding shoreline threats. This study aims to bring increased attention to the immediate threats to American Samoa’s way of life, and to demonstrate the utility of SWASH for extrapolating wave transformation to future sea level.

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“…The low frequency swash (𝑆𝑆 𝐿𝐿𝐿𝐿 ) component increases with rising sea level at a smaller rate than 𝑆𝑆 𝑖𝑖𝑚𝑚𝑖𝑖 , suggesting that the LF energy is primarily set by nonlinear interactions of the shoaling swell. Uncertainty in modeled 𝑅𝑅 2% is not estimated, but Liu et al ( 2021) 38 found that laboratory measurements of 𝑅𝑅 2% on a fringing reef bathymetry matched SWASH estimates to within one standard deviation of model ensemble results. The effects of SLR on coastal flood risk at Faga'itua are twofold.…”

Section: Resultsmentioning

confidence: 99%

Rising Sea Levels and the Increase of Shoreline Wave Energy at American Samoa

Barnes,

Becker,

Tagarino

et al. 2024

Preprint

0

View full text Add to dashboard Cite

American Samoa is experiencing rapid relative sea level rise due to increases in global sea level and significant post-2009 earthquake land subsidence, endangering homes and critical infrastructure. Wave and water-level observations collected over a fringing reef at Faga‘itua Bay, American Samoa, in 2017 reveal depth-limited shoreline sea-swell wave heights over the range of conditions sampled. Using field data to calibrate a one-dimensional, phase-resolving nonhydrostatic wave model (SWASH), we examine the influence of water level on wave heights over the reef for a range of current and future sea levels. Assuming a fixed reef bathymetry, model results predict rising sea levels will escalate nearshore extreme water levels that are dominated by an increase in nearshore sea-swell wave heights. Model results provide insight into how and at what reef depths rising sea levels reduce reef capacity to dissipate wave energy, compounding shoreline threats. This study aims to bring increased attention to the immediate threats to American Samoa’s way of life, and to demonstrate the utility of SWASH for extrapolating wave transformation to future sea level.

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“…Empirical runup and overtopping estimates based on offshore ocean conditions and bathymetry and topography are well established (e.g., Franklin & Torres‐Freyermuth, 2022; Gouldby et al., 2014; Liu et al., 2023; Merrifield et al., 2014; Stockdon et al., 2006). These formulations are widely used in coastal hazard, coastal engineering, and flood forecasting applications (e.g., Almar et al., 2021; Gouldby et al., 2014; Merrifield et al., 2021; Stockdon et al., 2023; Vitousek et al., 2017; Vousdoukas et al., 2018, 2023).…”

Section: Methodsmentioning

confidence: 99%

A National‐Scale Coastal Flood Hazard Assessment for the Atoll Nation of Tuvalu

Wandres,

Espejo,

Sovea

et al. 2024

Earth's Future

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Atoll nations such as Tuvalu are considered to be amongst those most vulnerable to the effects of climate change. Here we present a national‐scale coastal flood hazard assessment for Tuvalu based on high‐resolution Light Detection and Ranging (LiDAR) topography and bathymetry. We follow a fully probabilistic approach, considering sea level anomalies, tides, and extreme wave conditions from a mixed climate (i.e., from distant extra‐tropical storms and local tropical cyclones). Nearshore processes such as wave setup and runup are also accounted for. Hazard maps were calculated for the present sea level, as well as for sea level rise projections corresponding to different shared socioeconomic pathways (SSP2 4.5 and SSP5 8.5) and time horizons (2060 and 2100). With a mean elevation of 1.55 m above mean sea level (1.37 m above mean high water spring) >25% of land area is inundated once every 5 years and >50% of land area floods once every 100 years nationally. Results indicate that present day 1‐in‐50 years floods (>45% of land area flooded) will occur more than once every 5 years by 2060 (annual exceedance probability >20%), even under the moderate SSP2 4.5 sea level rise projections. Results of this study highlight the pressing need for ambitious and large‐scale adaptation solutions which are commensurate with projected sea level rise and marine hazard impacts. The methodologies presented in this paper can easily be applied to other low‐lying islands in the tropical Pacific, where mixed climates (i.e., regular and TC conditions) and non‐linear nearshore processes dominate extreme water levels and flooding.

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Uncertainty of wave runup prediction on coral reef-fringed coasts using SWASH model

Cited by 19 publications

References 43 publications

Rising Sea Levels and the Increase of Shoreline Wave Energy at American Samoa

Rising Sea Levels and the Increase of Shoreline Wave Energy at American Samoa

Rising Sea Levels and the Increase of Shoreline Wave Energy at American Samoa

A National‐Scale Coastal Flood Hazard Assessment for the Atoll Nation of Tuvalu

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