Keith Katzer is the first to my knowledge to propose an extremely large flood significantly shaping Hohokam society this early in the Hohokam history. How did you determine the high levels of floods for the Salt?Ī: Jonathan Fuller (U of A thesis 1987) determined that a very large flood likely occurred around 900 CE based on flood deposits in Hohokam canals and the height of flood deposits in the Salt River canyon that appeared to have the same dating (slackwater analysis). Record levels on the Colorado River was 500,000 CFS. Q: The level of flooding on the Salt is extraordinary to me. Approximately every 14 years, floods of 100,000 cfs occurred, damaging earthen canals. Those floods destroyed weir dams and headgates. ![]() As a point of reference, before the construction of the Roosevelt and other dams along the Salt River, annual flooding was 8,000–12,000 cfs. The late Colonial/early Sedentary extremely large flood may have been as much as 400,000–450,000 cfs. The floodwaters extended two to three miles from the riverbed. If the 1891 flood provides insights for the extremely large flood, then it is conceivable that the Riverview and Scottsdale systems located their intakes where they did because the river had dramatically shifted its main channel.Ī: The peak of the 1891 flood (February 19 th) was 300,000 cubic feet per second or cfs. 900 CE), a flood deposit is found covering a canal. In a few cases, like the late Colonial/early Sedentary extremely large flood (ca. ![]() It is extremely difficult to separate individual flood or channel shift events in the depositional history of rivers, including the lower Salt. The archaeological record provides us with a general view of the past, so we rely on finding patterns or exceptional events. ![]() River aggrading, as it is called, appears to have been significant along the middle Gila River in the past, but is less well understood along the lower Salt. Q: Is there any evidence of that changing channels in the Salt River that may relate to how canals were constructed and maintained?Ī: The lower Salt River is known to have shifted parts of its main channel historically, because of flooding. Explore additional content related to The Flow of Water and Time: Irrigation Longevity and Social Change among the Lower Salt River Hohokam, Chris Caseldine’s November 10, 2020, Archaeology Café Online presentation.
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