Palaeohydrologic analysis of Holocene flood slack-water sediments.

Estimates of the frequency and discharge of large floods can be refined and extended over the past 10 000 years through the study of slack-water sediments deposited in bedrock canyons and gorges. Slack-water deposits are typically fine-grained sand and silt that accumulate during major floods in protected areas where current velocity is reduced, such as in back-flooded tributary mouths, at channel expansions, and downstream from bedrock spurs. Relatively narrow bedrock canyons in arid, savanna, and semi-arid regions provide excellent areas for estimating flood discharges from the elevation of slack-water deposits. The accumulation and preservation of slack-water sediment sequences appear to be controlled by tributary-mainstream junction morphology and by tributary drainage basin efficiency. -from Authors