AN AERIAL GEOARCHAEOLOGICAL SURVEY OF THE LAIE PIER, OAHU, HAWAII, U.S.A. USING UAVS

Laie, Hawaii, is a small village on the windward side of the north shore of the Hawaiian island of Oahu. In 1868 the area of Laie was turned into a large sugar plantation. In order to get the stacks of raw sugar and molasses to Honolulu for shipment overseas, a warehouse and small pier, with a crane, was built on the beach, today called “Pounders Beach,” on the southeastern corner of the village in 1887 (although possibly as early as 1881). The pier was built extending from the berm of the beach out over the Pleistocene, fringing reef platform and marine terrace. At this location a deep channel extends through the reef and approaches close to shore, allowing for the approach of small steamships.

Although not definitively recorded, the pier was likely abandoned sometime between 1899 and 1907, when the Oahu Railroad was extended to Laie. Today all that remains of the pier, above sea-level, are the iron, vertical support struts that held up the pier platform. Below sea-level there are a few large pieces of coral-encrusted debris scattered in an area around the struts. Little to no documentation of the pier since its abandonment has taken place, although it is a valuable historical artifact for the area, as well as a possible reference structure for changes to the local beach and sea level. Although clearly visible from the ground, the structure itself does not appear on USGS topographic maps and is nearly invisible from normal air photos and Google Earth. In order to better understand the changes that have occurred to the beach in and around the pier since its abandonment, as well as to document the history of the pier itself, small UAVs (DJI Phantom II and III with GoPro cameras attached) were used to obtain high-resolution images of the beach and pier layout. This images were corrected for the fisheye-distortion caused by the GoPro lenses. The aerial views are much clearer than previously available aerial photographs and clearly show the outline of the pier and its alignment and layout. The images are now being used as base photomaps for documenting debris fields, dominant current and sand flow direction, as well as a better understanding of the overall relationship between the pier and the reef channel. The UAVs were invaluable as inexpensive aerial platforms for collecting aerial photographs for such a small-scale structure.