Keeping up with the coast: quantifying shoreline change on Hawaiʻi Island
Rose Hart1, Ryan Perroy1, Charles Fletcher2, Steven Colbert1, Bethany Morrison3
1University of Hawai‘i at Hilo, Hilo, HI. 2University of Hawai‘i at Mānoa, Honolulu, HI. 3Hawai‘i County Planning Department, Hilo, HI

Track

IV. Putting Research into Practice for Thriving 'Åina

Abstract

Hawaiʻi Island, bounded by nearly 430 km of diverse and dynamic coastline under various levels of zoning and development, has never had a comprehensive assessment of coastal vulnerabilities or any systematic monitoring of long-term shoreline change rates to enforce sustainable coastal development. Consequently, Hawaiʻi Island's coastal communities are in a weak position for adapting to the potential impacts of sea-level rise (SLR), coastal erosion, and subsidence. To better predict and manage coastal vulnerabilities, this project quantifies shoreline change rates from the present and recent past for three different geomorphic coastal settings on Hawaiʻi Island. We use shoreline records from historic aerial photographs and three-dimensional datasets systematically collected from small unmanned aerial systems (sUAS) and other survey platforms, to quantify shoreline change at a calcareous beach (Hāpuna State Beach Park), a sea cliff (Honoliʻi Beach Park), and subsiding coastal lava field (Kapoho Tide Pools). These data are merged with SLR and subsidence projections using GIS to estimate and visualize impacts at our three sites. Results from this study can provide insights to the chronic, seasonal, and episodic coastal processes that threaten adjacent communities and resources along Hawaiʻi Island's coast and help Hawaiʻi County planners develop necessary adaptations to coastal management strategies.