Airborne lidar survey of irrigated agricultural landscapes: an application of the slope contrast method

Irrigated agriculture was central to the economies of many of the world’s best known complex societies. New high-resolution digital elevation models (DEM) derived from remotely sensed lidar data give archaeologists the opportunity to study field systems at a scale not previously possible. Here we describe a method called slope contrast mapping that takes advantage of the dissimilarity between artificial and natural slopes to identify and map discrete features. We use this relatively simple method in our own research to identify complexes of agricultural terraces in the North Kohala district, Hawai’i Island. It has also proved useful for mapping the natural landscape, specifically the extent of flat land between valleys suited for irrigated agriculture.