A series of slow moving storms with prolonged rains that saturated the soils of south-central Oahu culminated on New Years Day of 1988 in severe runoff and hillside erosion, resulting in catastrophic damage to stream flood mitigation channels, homes, and roads in Aina Haina and Niu Valleys. Click to enlarge The largest waves reach Oahu in winter. Along the north shore, it is common to see wave heights between 15-20 feet annually from winter swell. Often, winter north and northeast swells wrap around Makapuu Point and generate waves at Sandy Beach that are as high as the largest summer surf found there. Trade wind waves can be high, but because of their shorter wavelengths, they have less energy than north and south swell.
South swells tend to have less energy and longer wave periods than winter swells.
Hurricane generated waves have exceeded 15 feet along east Oahu and 10 feet on Oahu's southern shores. Combined with storm surge and high tides, hurricane waves can overwash coastal roads and properties, as they did along the Kaaawa and Kaneohe coasts during Hurricane Fernanda in 1993 and along the Honolulu and Waianae coasts during Hurricane Iniki in 1992. Fletcher, Charles, Eric Grossman, Bruce Richmond. Atlas of Natural Hazards in the Hawaiian Coastal Zone.