Introduction

The following section briefly describes the regional geologic setting and coastal historic sites of Pu‘ukoholā Heiau NHS and Kaloko-Honokōhau NHP.

The mandate of the National Park Service is to:

“...conserve the scenery and the natural and historic objects and the wild life therein and to provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for the enjoyment of future generations.”(The NPS Organic Act of 1916, 16 USC §1)

In addition, the mission of Kaloko-Honokōhau park enabling legislation is to perpetuate Hawaiian Culture and maintain/sustain fishponds and other cultural/recreational resources (beaches for canoe launching, ceremony, etc.). Coastal hazards including erosion, waves from large swell, hurricanes, tsunamis and sea-level rise threaten several National Parks and National Seashores on the United States coastline. To conserve such regions and allow for their enjoyment by future generations, it is important to assess the extent of coastal hazard vulnerability and manage such risks accordingly. This project details a coastal hazard analysis and assessment of Pu‘ukoholā Heiau NHS and Kaloko-Honokōhau NHP located on the Big Island of Hawai‘i.

Background

Pu‘ukoholā Heiau NHS (PUHE) and Kaloko-Honokōhau NHP (KAHO) contain several natural and cultural landmarks including ancient Hawaiian Heiau, loko i‘a and loko kuapā (fishponds), and coastal wetlands of intrinsic value (Figure 1). Coastal hazards threaten the preservation of these landmarks. Thus, the goal of this project is to assess the risk of coastal hazards to the parks. The coastal hazards under evaluation include coastal erosion, waves from large swell, sea-level rise, and tsunamis.

Park Locations

Figure1. Locations of Pu‘ukoholā Heiau NHS and Kaloko-Honokōhau NHP on the Big Island ofHawai‘i.

Geologic setting

Pu‘ukoholā Heiau NHS and Kaloko-Honokōhau NHP, located at the base of the Kohala and Hualalai volcanoes (respectively), were created by basaltic lava flows with ages dating approximately 400,000 years and less than 3,000 years (respectively). Both regions receive little rainfall 250-760 mm (10- 30 in) per year (Giambelluca, et al. 1986).

Pu‘ukoholā Heiau NHS, being the older of the two regions, has fewer basaltic lava outcrops and a better developed topsoil. The northern beach of Pu‘ukoholā Heiau NHS near the historic site of Pelekane has a significant patch of trees and vegetation due to a small intermittent stream extending up the Kohala mountains, which is also likely to have continuous groundwater input. The shorelines of Pu‘ukoholā Heiau NHS consist of embayed beaches of carbonate sand located on the northern and southern portions of the park. The beaches of the park are backed by dry grass and trees.

Unlike Pu‘ukoholā Heiau NHS, Kaloko-Honokōhau NHP has numerous basaltic lava outcrops, and little topsoil cover. Kaloko-Honokōhau NHP also contains more green vegetation and trees fed by significant groundwater input. The shorelines of Kaloko-Honokōhau NHP are mostly perched beaches of basaltic lava flows, which are heavily encroached by salt tolerant vegetation. The beach fronting the ‘Aimakapā Fishpond is the largest sandy beach of the park, with a width of about 32 m (105 ft) and a maximum height of 3 m (10 ft) above Mean Lower Low Water (MLLW). This beach is a natural barrier between the ‘Aimakapā Fishpond and the ocean.

Coastal historic sites

Our hazard assessment for the parks has found coastal historic sites to be at risk. At Pu‘ukoholā Heiau NHS, the beach at Pelekane Bay, as well as the remaining archeological sites, are threatened by coastal hazards.

The kuapā (seawall) at Kaloko Fishpond, the beach fronting the ‘Aimakapā Fishpond, and the archeological sites at the southern portion of the Kaloko-Honokōhau NHP including the ‘Ai‘ōpio Fishtrap and Pu`uoina Heiau are the historic sites and features that are at greatest risk to deterioration from coastal hazards. The Kaloko Fishpond is fronted by a seawall or kuapā that is approximately 9 m (30 ft) wide and a maximum height of 2 m (6.5 ft) above Mean Lower Low Water (MLLW). There are also a number of significant historic and cultural sites in the southern end (near the harbor entrance) of Kaloko-Honokōhau NHP, including ‘Ai‘ōpio Fishtrap, Pu‘uoina Heiau, and other significant archeological structures.