ABSTRACT
This chapter presents a field and laboratory approach for better understanding human-environment interactions in past agricultural societies in semi-arid environments. The field approach aims at studying the formation and evolution of anthropic landscapes based on a geomorphic approach to fluvial dynamics, combined with the geoarchaeological study of irrigation systems, considered as anthropic and environmental structures, and connected agricultural fields. To frame these dynamics chronologically and provide a more precise description of environmental and social dynamics (e.g., dynamics of deposition, flooding events, vegetation cover, fire regime, slash and burn, manuring), systematic sampling for chronology and soil analysis (micromorphology) is conducted in these three connected environments. The selection, description, and quantification of markers in soil thin sections allows for the statistical classification of past dynamics, interpreted based on historical or current references. The multiplication of local studies is key to documenting large-scale socioenvironmental dynamics, which can then be juxtaposed with climatic, archeological, and demographic data. This approach is illustrated through the socioenvironmental study of the hydrosystem of the Salt River in the semi-arid Phoenix Basin (Arizona) and the Hohokam irrigated agrosystem. This case study demonstrates how the field and micromorphological study of two irrigation canals and intertwined fluvial deposits at the headgates of one of the largest canal systems, Canal System 1, in use from the seventh to the fifteenth century A.D., provides vital information about past water management and land use as well as fluvial regime and climate change.
