ʻŌiʻo to Punalau, Oʻahu

Kahuku Point is on the north shore of Oʻahu and forms the northern tip of the island. The  shoreline is composed mostly of exposed limestone shelf with ‘perched’ calcareous beach above  the water line. Beach rock is also prevalent. Kaihalulu Beach (transects 63-80) and Hanakaʻilio  Beach (transects 81 -98) are found in two bays between limestone headlands. Shoreline position  is highly variable at these beaches as limestone outcrops are intermittently exposed and buried by  shifting sands. The area is exposed to north and west swells during winter months and easterly  tradewind waves year-round. 

Long-term shoreline change rates (1949-2015) calculated for Kaihalulu Beach indicate moderate  rates of erosion, approaching -0.6 ft/yr near the middle of the beach. Historical shorelines show  that Kaihalulu has been less erosive since 1967. Shoreline data from the 1910 and 1932 T-sheets  were omitted from this area due to overall poor data quality.  

Long-term shoreline change rates (1928- 2015) for Hanakaʻilio Beach indicate that the beach has  been stable or accreted in the mid-portions and erosive on the east and west ends (approaching – 0.1 ft/yr). Plots of historical shoreline position show high variability at Hanakaʻilio. As a result,  long-term rates have high uncertainty at most transects at Hanakaʻilio Beach. Shoreline data  from the 1910 and 1932 T-sheets were omitted from this area due to overall poor data quality.  

A previous study by Hwang (1981)* found 77 ft of erosion to the water line from 1949-1967 at  Kaihalulu Beach (transect 2 in his study) but no significant change to the vegetation line. 

*Hwang, D. (1981) “Beach changes on Oʻahu as revealed by aerial photographs”, State of Hawaii, Department of  Planning and Economic Development. 

Last updated: July 2021

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