Least cost path analysis of early maritime movement on the Pacific Northwest Coast

Abstract

In this paper, we present a new method for modeling past maritime movement events using least cost path analysis. Nontraditional measures of movement cost, including cultural, environmental, and physiological variables, were calculated. Using multiple cost-weighting scenarios, spatial resolutions, and different considerations of overland travel, movement routes were predicted for five Pacific Northwest Coast study areas. This work uses a new application of least cost path analysis to seascapes and marine movement and the results have led to a better understanding of migration during the Late Pleistocene and Holocene. The resulting routes were systematically analyzed and compared to determine which produced the results most likely to predict high-use coastal movement corridors. We found that modeling scenarios where culturally derived costs of movement were highly weighted and in which overland travel was very costly produced the best predictions of possible past movement events. These models show that predicted routes cluster in distinct patterns which are influenced by the geography of the seascape through which the movement event is taking place and that areas of high traffic are most likely to be located immediately offshore and to the south of islands as well as in the spaces between landmasses. This knowledge increases our ability to predict the location of drowned sites on the Northwest Coast and is important in contemporary archaeology because it can help locate new sites in a landscape that has radically changed over the last 20,000 years. GIS analysis can reveal new sites hidden by changing sea levels, which may not be easily located using traditional forms of site prospection. Accurate modeling of maritime movement opens many coastal areas to increased archaeological exploration and has the potential for the discovery of new sites in drowned locations.