UH Hilo to do post Iselle damage assessment and albizia mapping

Through remote sensing with satellite imagery and aerial imagery captured via unmanned aircraft, researchers will create albizia mapping of the altered landscape from Hurricane Iselle.

By Susan Enright.

Fallen Albizia trees at an intersection in Puna following Iselle.
Fallen albizia trees at an intersection in Puna following Iselle. The photo was taken by an unmanned aerial vehicle the day after the storm, giving researchers and emergency personnel a quick and accurate view of the damage. Photo by Nick Turner

Hawai‘i Island sustained immense damage when Tropical Cyclone Iselle–hours before classified as Hurricane Iselle–slammed into and then stalled over the coastal areas of Puna and Ka‘u on the night of Aug. 7, 2014. Dozens of homes are left damaged, the coast line and ecosystems of the area are still bathed in a toxic soup of chemicals and sewage sludge stirred up during the storm, and papaya farms are decimated.

One of the greatest impacts of the storm came from the hundreds of tall albizia trees that fell over and shattered throughout the districts, destroying power lines and blocking roads for days, and in some areas for weeks. Albizia is an invasive species that blankets much of the area hit by the storm.

Satellite Albizia mapping done in June 2014.
Satellite albizia mapping done in June 2014. Cartographer: Julie Gaertner. Click photo to see details.

Of great importance now, as the island scrambles to upright itself post Iselle, is risk assessment and mitigation efforts of the albizia.

This is where the Spatial Data Analysis and Visualization Lab (SDAV) at the University of Hawai‘i at Hilo will help with post Iselle efforts. Through remote sensing of damaged areas in Puna and Ka‘u using a combination of satellite imagery and aerial imagery acquired via unmanned aircraft, researchers will create albizia mapping of the altered and changed landscape from Iselle. This mapping is essential to planning for future storms and for eradication efforts by the county and state.

Nick Turner
Nick Turner

Nick Turner, a cyber computer programming analyst working on the project, says the addition of aerial imagery collected by unmanned aircraft will provide a low cost and effective way of increasing the accuracy of albizia classification in risk management. Turner, a specialist in building and flying unmanned aerial vehicles or UAV, started collecting sample aerial imagery in Puna via an unmanned aircraft the day after Iselle, and these images validate the improved image resolution for object detection and classification in a post disaster landscape.

“This imagery can also be used for damage assessments of roads, power lines, structures, and agriculture,” the project proposals states.

Mitigation maps showing high risk areas still prone to future storm damage that may impact homes, power infrastructure, and roads, will be identified with a recommended buffer zone. These maps will be intended for use by ground eradication teams working on albizia control. High-resolution imagery of power lines and roads will allow for identification of non-albizia trees that may threaten the power grid and transportation infrastructure in future storms.

The estimated mapping area is 400,000 acres in the Puna and Ka‘u districts of the island. Satellite imagery will be used to cover the entire affected area needing to be mapped, while imagery from unmanned aircraft will be used on targeted test site areas that require higher precision accuracy for albizia classification. A focus for unmanned aerial imagery will be on essential power and transportation infrastructure that may be vulnerable again to storm damage.

The project is scheduled to take 16 weeks.


About the author of this story: Susan Enright is a public information specialist in the Office of the Chancellor. She received her bachelor of arts in English and certificate in women’s studies from UH Hilo.

-UH Hilo Stories