Datasets / Forecasting the Impact of Storm Waves and Sea-Level Rise on Midway Atoll and Laysan Island within the Papahanaumokuakea Marine National Monument - A Comparison of Passive Versus Dynamic Inundation Models


Forecasting the Impact of Storm Waves and Sea-Level Rise on Midway Atoll and Laysan Island within the Papahanaumokuakea Marine National Monument - A Comparison of Passive Versus Dynamic Inundation Models

Published By US Fish and Wildlife Service, Department of the Interior

Issued over 9 years ago

US
beta

Summary

Type of release
a one-off release of a single dataset

Data Licence
Not Applicable

Content Licence
Creative Commons CCZero

Verification
automatically awarded

Description

Two inundation events in 2011 underscored the potential for elevated water levels to damage infrastructure and affect terrestrial ecosystems on the lowlying Northwestern Hawaiian Islands in the Papahnaumokukea Marine National Monument. The goal of this study was to compare passive bathtub inundation models based on geographic information systems GIS to those that include dynamic water levels caused by waveinduced setup and runup for two endmember island morphologies: Midway, a classic atoll with islands on the shallow 28 m atoll rim and a deep, central lagoon; and Laysan, which is characterized by a deep 2030 m atoll rim and an island at the center of the atoll. Vulnerability to elevated water levels was assessed using hindcast wind and wave data to drive coupled physicsbased numerical wave, current, and waterlevel models for the atolls. The resulting model data were then used to compute runup elevations using a parametric runup equation under both present conditions and future sealevelrise scenarios. In both geomorphologies, wave heights and wavelengths adjacent to the island shorelines increased more than three times and four times, respectively, with increasing values of sealevel rise, as more deepwater wave energy could propagate over the atoll rim and larger winddriven waves could develop on the atoll. Although these increases in water depth resulted in decreased setup along the islands shorelines, the larger wave heights and longer wavelengths due to sealevel rise increased the resulting waveinduced runup. Runup values were spatially heterogeneous and dependent on the direction of incident wave direction, bathymetry, and island configuration. Island inundation was modeled to increase substantially when wavedriven effects were included, suggesting that inundation and impacts to infrastructure and terrestrial habitats will occur at lower values of predicted sealevel rise, and thus sooner in the 21st century, than suggested by passive GISbased bathtub inundation models. Lastly, observations and the modeling results suggest that classic atolls with islands on a shallow atoll rim are more susceptible to the combined effects of sealevel rise and wavedriven inundation than atolls characterized by a deep atoll rim.