Landscape Change and the Cultural Evolution of the Hohokam along the Middle Gila River and Other River Valleys in South-Central Arizona

Changes in river floodplain morphology can have devastating consequences for irrigation agriculturalists. Channel erosion occurred in the late nineteenth century, on the flood plain of the middle Gila River, Arizona and severely impacted the native Akimel O' odham (Pima) farmers. Prior to the Akimel O' odham, the prehistoric Hohokam also pursued irrigation agriculture along this river. Geoarchaeological investigations of the Gila River flood plain document a major period of channel cutting and widening sometime between A.D. 1020 to 1160. This channel erosion is coincident with the partial abandonment of large Hohokam villages and significant population rearrangements. It also marks the beginning of a major social reorganization when ball-courts were replaced by platform mounds as the social integrative structure and the Hohokam sphere of influence contracted. Other rivers utilized by the Hohokam—the Santa Cruz River, San Pedro River, and Tonto Creek-also experienced channel cutting between A.D. 1050 and 1150. Thus, a regional episode of channel erosion appears to have been a major factor that contributed to the reorganization seen in the Hohokam archaeological record. These synchronous landscape changes would have severely impacted Hohokam irrigation systems and food production capabilities. This undoubtedly created stresses within Hohokam society which in turn may have accelerated social, political, economic, ideological, and demographic changes that were already underway.