Kahana Valley, Hawai`i, a geomorphic artifact: A study of the interrelationships among geomorphic structures, natural processes, and ancient Hawaiian technology, land use, and settlement patterns

Archaeological, geomorphological, and botanical research was conducted in Kahana Valley, O'ahu, Hawai'i to test a model of early Hawaiian utilization of the physical environment and to explain the dynamics of human and environmental interactions in an island setting. The research considered how early Polynesian manipulation of the landscape necessitated concomitant modification of their culture.;Prior to undertaking this research, a model was developed which postulated that Polynesian swidden agriculture deforested the slopes of wet-windward valleys, thus altering the vegetation complexes from forests to grasslands. The denuded slopes were exposed to accelerated erosion of the virgin soils, and the transported materials were deposited on the landward portions of sand bars and dunes and in coastal lagoons and bays. The former marine environments became today's marshes and alluvial plains. The alteration of the marine ecosystem to a terrigenous ecosystem impacted and eventually destroyed the habitats of littoral fish and mollusks, both major Polynesian foods. At the same time, alluvial sediments suitable for agriculture were formed. The purpose of the study was to test the model through archaeological survey and excavations of the Kahana Valley flood plain. The subsequent investigation confirmed the validity of the postulated sequence of events.;A major finding of the research was that initial settlement of the Hawaiian Islands occurred sometime between ca 430-30 B.C., much earlier than that postulated by previous models. A second major finding was that the initial colonizers of Kahana Valley when faced with an "ecological crunch" brought about by their manipulation of the ecosystem did not remain within the valley originally chosen for settlement. Rather than invent or use previously known cultural patterns to "adapt" to the chosen settlement area, as has been previously postulated for Polynesian colonizers, the Kahana Valley initial settlers chose to abandon the valley as their adaptive strategy.;The significance of the research lies in its explanation of the dynamics of human and environmental interactions by examination of the interrelationships among the cultural and natural systems at a quantifiable and testable level.