Studying Prehistoric Dryland Agricultural Systems in Central Arizona through Aerial LiDAR, Pedology, Hydrology, and Paleobotany

Statistical Research Inc. (SRI) conducted phased data recovery at two large dryland agricultural fields and associated Hohokam habitation sites along U.S. Highway 60 in central Arizona. The agricultural fields consisted of cross channel and contour rock alignments and rock piles covering many acres within and outside of a newly proposed highway right-of-way along Queen Creek. Nearby were small, seasonal habitation sites occupied between AD 400 and 1350. Aerial 3-Dimensional Laser Range Finding (LiDAR) was used to map the fields, construct 10 cm digital elevation models, and examine field slope, aspect, and drainage patterns. Drainage patterns before and after field construction were then modeled to compare natural versus human-modified field topography and hydrology, and to infer the aboriginal aims of field construction. Field function was further examined with soil moisture and chemistry studies to characterize anthropogenic soil signatures, and pollen and flotation analysis to identify cultivars and cultigens. Contrary to expectations, this detailed functional study found little evidence for agave cultivation, which has been the primary cultivar found in other dryland fields of central Arizona. The Queen Creek fields were built prior to the large-scale production of agave in central Arizona. Although agave occurs naturally nearby, these fields were used for a mix of crops, including maize, native cacti, and possibly even cotton and helped sustain a series of intermittently occupied farmsteads and hamlets.