Case study on UH Hilo research of coastal erosion published in “U.S. Climate Resilience Toolkit”

The innovative research combines historic aerial photos, current drone imagery, and topographic surveys to discover coastal changes around Hawai‘i Island. The results of the study are informing policymakers who are crafting a new setback policy for coastal development.

Bethany walks on the rocky shore line.
Bethany Morrison from the Hawai‘i County planning department explores the coast of Ka‘ū during the UH Hilo research project on coastal erosion. Results of the findings are helping policymakers in long-range planning for the coastal zone. Photo by Ryan McClymont, USGS.

By Susan Enright

The results of a collaborative research project led by a graduate student at the University of Hawai‘i at Hilo have been published as a case study in the U.S. Climate Resilience Toolkit, a website where the public can find information and tools to understand and address climate risks. The website offers information from all across the United States federal government in one easy-to-use location. The case study also has been published regionally on the Pacific Islands Regional Climate Assessment (PIRCA) website.

The UH Hilo study examines shoreline migration—the rate that changes occur, gradually or suddenly—on Hawai‘i Island and is being used by county planners and policymakers to develop a more comprehensive and effective coastal development plan.

Scott Laursen
Scott Laursen

The published case study, “Reality Check: Collaborative Research Contributes to Real-Life Policy Decisions,” is co-authored by Scott Laursen, program specialist at the UH Pacific Islands Climate Adaptation Science Center. The center was established by the U.S. Department of the Interior in 2011 as a consortium hosted by UH Mānoa, UH Hilo, and the University of Guam.

The case study is co-authored by Bethany Morrison, a planner on land use with the County of Hawai‘i who collaborated on the research.

Bethany Morrison
Bethany Morrison

“We do not have adequate knowledge of Hawai‘i Island’s shoreline to be able to assess and adapt to the vulnerabilities from sea level rise and related hazards,” Morrison explains. “The goals of this project will help us to address these challenges. More specifically, Hawai‘i County will have a first phase of shoreline change rates and sea-level rise projections for three different types of shorelines.”

Laursen says that local managers such as Morrison, who work with regional land and seascapes, are also working within the social norms and values of the communities that utilize those ecosystems.

“Directly involving local professional networks within every stage of the scientific method roots research products within the place-based experiences of these natural and cultural resource managers,” Laursen explains in an email. “[This] increases the probability that these products will be utilized. Resource managers like Bethany can be thought of as ‘custodians of context’ throughout the research process, ensuring the immediate utility of research output.”

The innovative research in this particular project combines historic aerial photos, current drone imagery, and topographic surveys to discover coastal changes around Hawai’i Island. The results of the study are informing policymakers who are crafting a new setback policy for coastal development.

UH Hilo responds to an urgent request from the county

In 2016, responding to an urgent need to reevaluate set back policy in county code, planning experts in the County of Hawai‘i Office of Planning initiated a collaborative two-year research project funded by UH Hilo’s Manager Climate Corps, a program of the Pacific Islands Climate Adaptation Science Center. A research team was assembled, made up of Morrison and researchers from UH Hilo, to examine and quantify historic and contemporary rates of change along different types of shorelines on Hawai‘i Island, and then to model observed changes into the future through sea level rise impacts.

On the research team was UH Hilo graduate student Rose Hart—who had completed an undergraduate internship involving research on shoreline setback policies—who was the driving force behind the project. Also on the team was Ryan Perroy, associate professor of geography and director of UH Hilo’s Spatial Data Analysis and Visualization Labs. Perroy is an expert and award-winning researcher in innovative equipment and methods, notably in the use of drones to survey areas of the island to collect data on Rapid ‘Ōhi‘a Death and the recent lava flows in lower Puna.

Rose Hart and Ryan Perroy stand by Welsome sign to AAG conference.
Rose Hart and Ryan Perroy at the 2017 Association of America Geographers annual meeting in Boston, where Hart presented her shoreline research. Courtesy photo.
Students stands, guiding UAV up in the air.
Rose Hart guides an unmanned aerial vehicle. Courtesy photo, click to enlarge.

Hart, Perroy, and Morrison worked closely together to develop the detailed methodologies and field schedules. Over two years, the research team combined existing datasets (historic aerial photos) with new data (drone imagery collected by Hart and Perroy) along with topographic surveys to quantify past and present rates of coastal change. These data were then merged with sea level rise projections and other geospatial data to estimate future impacts along the coastline using a Geographic Information System platform.

Also collaborating on the project was Steve Colbert, chair and associate professor of marine science at UH Hilo, and Charles H. “Chip” Fletcher III, associate dean and professor at the School of Ocean and Earth Science and Technology at Mānoa.

Sharing the data

In May 2018, the research team presented their findings to the county planning department, which administers planning regulations for the entire island and provides technical advice to the mayor, planning commission and county council. Based on analyses at Hāpuna, Honoli‘i, and Kapoho, the team offered suggestions for how the county could use scientific data to create place-based setbacks. Predictive models that combined a designated shoreline setback distance, place-based shoreline erosion rates, and structural life expectancy were suggested for calculating setbacks for locations similar to Hāpuna and Honoli‘i. Conversely, elevation-based setbacks were suggested for low-lying coastal communities such as Kapoho.

Throughout the project, the research team worked directly with community members in each of the three study site locations. These interactions were particularly effective along the Hāmākua Coast. The project became so familiar to these communities that it was directly integrated into the Hāmākua Community Development Plan, which called for guidelines for a practical definition of “top of cliff,” a term in shoreline policy that has yet to be clearly defined. Developing common understandings is essential to monitoring and predicting erosion along unstable clifflines that can pose dramatic threats to community infrastructure.

Looking to the future and the uncertainty associated with climate change, the combined results of the completed study will be used to develop policies that are increasingly adaptive to present and future coastal change.

Read the full case study.


Story by Susan Enright, a public information specialist for the Office of the Chancellor and editor of UH Hilo Stories. She received her bachelor of arts in English and certificate in women’s studies from UH Hilo.

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