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Coastal Landforms and Historical Shoreline Change on the West Coast of Hawai'i
Scientists from the U.S. Geological Survey (USGS)'s Coastal and Marine Geology Program have recently begun work with the National Park Service (NPS) to help create an inventory of geologic resources for two National Historical Parks (NHPs) and one National Historic Site (NHS) on the west coast of the Big Island of Hawai'i. Part of this effort involves making coastal-landform maps to be incorporated into a geographic information system (GIS) data layer. A long-term historical shoreline change analysis is also part of the inventory.
Above: (From left to right) Rick Gmirkin, NPS archeologist, explains to Tom Reiss and Cheryl Hapke how recent storm waves partly destroyed the Kaloko fishpond wall. In the background (inset) is one of the GPS receivers set up to record the position of a corner of the fishpond wall. |
In February 2004, a team of scientists from the USGS offices in Santa Cruz and Menlo Park, CA (Cheryl Hapke, Bruce Richmond, and Tom Reiss), conducted ground-based fieldwork at the three sites: Kaloko-Honokohau NHP, Pu'ukohola Heiau NHS, and Pu'uhonua O Honaunau NHP on Hawai'i's west coast. The purpose of the fieldwork was to collect ground-control points for photogrammetric processing of aerial photographs that will be used in the shoreline-change analysis, as well as to begin mapping coastal landforms in the parks.
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Above left: Bruce Richmond mapping an ephemeral flood-delta deposit at Pu'ukohola Heiau NHS. His equipment includes a GPS receiver and antenna in a backpack, used to accurately map the spatial distribution of coastal landforms in the field. [larger version]
Above right: A classic example of a perched beach at Pu'uhonua O Honaunau NHP. The long-term shoreline change photographic analysis will examine the migration of the shoreline reference feature (SRF), which is the seaward edge of the sand. [larger version]
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The first phase of the coastal landform mapping focused on identifying shoreline features. Large segments of all three of the parks' shorelines consist of a low-lying basalt terrace or bench overlain by carbonate sand and gravel beaches. These perched, or storm, beaches are typically active only during large-wave events. As luck would have it, the team arrived for their fieldwork during just such an event; however, access to many of the beaches was closed because of hazardous conditions. Although large-wave events are positive processes in terms of delivering sediment to the beaches, these events are also responsible for damage to many of the unique Hawaiian historic sites that dot the coast. An improved understanding of the processes that shape the parks' coast will help park personnel better manage park resources.
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Cheryl Hapke explains the long-term shoreline change project to park superintendent Daniel Kawaiaea at Pu'ukohola Heiau NHS, while keeping an eye on a GPS base station.
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For the aerial photographic analysis, five to six ground control points were collected in the vicinity of each of the three sites, using survey-grade Ashtech receivers and antennae. Tom Reiss set up a base station at the house we were renting (our neighbors were probably a bit perplexed), and team members occupied each ground-control point for approximately 45 minutes to collect global positioning system (GPS) data. All the ground control points were identified on existing aerial photographs before the fieldwork; they included such locations as intersections of paths, corners of cement blocks, and corners on the walls of fishponds (prehistoric enclosures built by Hawaiians for raising fish).
Future work will include additional offshore surveys to continue mapping of the coral reefs at Kaloko-Honokohau NHP and initiation of offshore mapping at both Pu'ukohola Heiau NHS and Pu'uhonua O Honaunau NHP. More detailed coastal landform mapping will also be conducted at all three parks.
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 May 2004
in this issue:
Cover story:
Geologic Resources of Hawai'i
 Study Notes Increased Disease in Marine Life
Cape Cod Natural History Conference
Tampa Bay Study's Annual Conference
Colonial Period Comes to Life
May Publications List
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U. S. Department of the Interior | U.S. Geological Survey
