Technical Report #188. Marrack, L. and P. O'Grady. 2014. Predicting impacts of sea level rise for cultural and natural resources in five National Park units on the Island of Hawai'i. 40 pp.

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ABSTRACT:

Various climate change models predict that global sea levels will rise up to 1.9 m by 2100. Sea level rise and changes in storm run up during large surf events will affect nearshore habitats, cultural resources, water resources and infra-structure worldwide. Tide gauges on the island of Hawaii have shown an average sea level rise of 3.5 mm/yr over recent decades and future accelerated rates are expected. The Ala Kahakai National Historic Trail includes an approximately 280 km portion of prehistoric trail on or parallel to the Hawai'i Island shoreline and passes through numerous significant cultural and biological resources including resources within four national parks (Kaloko-Honokohau National Historical Park, Pu'ukohola Heiau National Historical Site, Pu'uhonua O Honaunau National Historical Park, and Hawai'i Volcanoes National Park), all of which will be impacted by sea level rise. Incorporating detailed elevation data and sea level rise predictions in the early stages of planning could lessen impacts and aid in long term management of the trail. In this project, investigators at University of California, Berkeley collaborated with National Park Service staff to model the effects of future sea level rise on present cultural and natural resources within the Ala Kahakai National Historic Trail corridor. Specifically, LiDAR  and other existing spatial data were used to create high resolution Digital Elevation Models. Then a Geographic Information System (GIS) was used to create visualizations of resource inundation likely to occur by the year 2100 using a range of more conservative to more extreme sea-level rise predictions. Spatial analysis was also used to determine areas where particular habitats such as anchialine pools, fishponds, and wetlands will most likely occur in 2100 so that these future habitats can be protected. The inundation models are conservative because they do not include projections of wave run-up during storms, erosion, or groundwater elevations above sea level. Additionally, comparisons of LiDAR points to National Geodetic Survey Benchmarks indicates LiDAR elevations are offset by an average of + 0.25 m. Correction of this error in DEMs resulted in greater inundation at each sea level rise scenario compared to the models without the correction. Final sea level rise scenarios incorporate corrections for the offset. Detailed elevation data and model results for the NPS units are provided in a GIS geodatabase format for trail planning, park management and resource protection within the ALKA corridor.