Geomorphic Analysis of Deep Coral Habitat in the Kaiwi Channel, Hawaiian Islands

The Kaiwi Channel is located between the Hawaiian Islands of O’hau and Moloka’i. In 2014, the University of Hawaii ALOHA Program surveyed the channel and the area to its north off the southeastern coast of O’ahu. Sonar data were acquired aboard the R/V Falkor with Kongsberg EM302 and EM710 multibeam echosounders, and bathymetry and backscatter data were post-processed using CARIS HIPS and SIPS 9.0 software. The Kaiwi Channel is 42 km wide with a maximum depth of 700 m. Its western margin exhibits a steep slope, whereas the eastern margin’s more gradual slope contains an array of small submarine canyons with relief as much as 500 m. Using backscatter, hard substrate areas were found in a large area of the channel’s eastern floor extending 2.0 km along the channel axis at depths between 300 and 500 m. Overlays of backscatter intensity with bathymetry and slope maps provide a means to estimate the area’s seafloor character and identify possible deep coral and other benthic habitats.