PREHISTORIC CANALS AS PALEOFLOOD RECORDS: CASE STUDIES FROM ARIZONA AND COASTAL PERU

Stratigraphic paleoflood records are typically derived from bedrock and alluvial reaches of rivers. Canals are anthropogenic extensions of rivers that may also contain relevant paleoflood information within their channel fill or where they intersect ephemeral drainages and form stratified pond deposits. Flood deposits associated with prehistoric canals provide insight into past climate and directly document the impact of flooding on ancient agricultural societies. I will provide examples of late Holocene (~3 ka to present) paleoflood information gained from large pre-Hispanic canals in the deserts of southern Arizona and north coastal Peru. Radiocarbon and luminescence-dated flood deposits in Arizona pre-Hispanic canals reveal individual flood events that can be compared with regional stratigraphic and dendrohydrological paleoflood records. Rhythmite-like pond deposits formed by the damming of ephemeral streams by large pre-Hispanic canals in Peru provide a proxy record of El Niño events along the northern coast. I will discuss preliminary results from the Chicama Valley concerning spatial and temporal variability in El Niño stratigraphic records associated with ephemeral streams dammed by the Ascope and Chicama-Moche Intervalley canals.