Identification and characterization of sand deposit distribution on Oahu fringing reefs, Hawaii

Abstract

Carbonate sand on the sea floor is an important component of the geology and ecology of nearshore fringing reefs on Oahu, Hawai'i. Sands also play a key role as a dynamic influence on bathymetry through their interplay with hydrologic environmental conditions. These sands are a product of direct sedimentation from nearshore and reef top organisms, and mechanical erosion of reefal carbonates, which are created, stored, and transported across the reef top environment. Thus sand distribution is a function of organic and mechanical production, hydrologic environment, reef ecology, geomorphology, and geology. My goal is to identify patterns of sand deposit distribution to better understand the role of sand within the coastal environment and how its presence is controlled by the same environment. This thesis is the product of combined work in remote sensing, data analysis, geology, reef ecology, and geomorphology, all aimed at improving understanding of carbonate sandy substrate on high volcanic islands. By studying sandy substrate in a local (Oahu, Hawaiʻi) setting, I have developed methods that can be exported to other marine settings. There are five chapters within this thesis. The first chapter is this general introduction. The second, third and fourth chapters are each manuscripts dealing with different portions of research on sand identification, classification, and analysis. The fifth chapter contains conclusions on how these avenues of research have aided in understanding sand distribution.