Sea Level Rise Triggering Widespread Coastal Hardening and Environmental Destruction on Hawaiian Shores

Abstract

In Hawaiʻi, protecting beach resources reinforces a high quality of life for residents, is critical to its tourism-based economy, and preserves an important ecosystem that is crucial for a number of endangered native species. However, narrowing and loss due to shoreline hardening continues to threaten Hawaiian beaches. Additionally, as sea level rise accelerates erosion, there may also be an acceleration of shoreline hardening across the state. Thus, modeling future beach vulnerability to hardening provides important data for developing resource management plans. We model future erosion for 0, 0.17, 0.32, 0.6, and 0.98 meters of sea level rise on the island of Oʻahu. Results show sea level rise of only 0.32 m triggers a cascade of seawall applications and that after 0.98 m of sea level rise, 49% of the shoreline could potentially harden if widespread hardening is allowed, risking sensitive beach resources. We conclude that current and near-term sea level rise, not future sea level rise, poses the greatest threat to critical habitat. We also conclude that existing coastal management does not effectively protect beaches threatened with hardening, and there is an immediate need for new policy development.