Because of the difficulties faced by engineers, planners, and geomorphologists involved in the prediction of very large floods, the use of stratigraphic, morphologic, and pedalogic evidence for recognition of large floods in humid environments is helpful. Coarse gravel lenses in fine-grained alluvium, inverse grading, and clay balls are stratigraphic records of large floods, best preserved in valley reaches with wide cross sections. Alluvial fans and stepped or benched flood plains are landforms observed to form in lowlands following catastrophic floods. Mappable alluvial soils delineate only areas affected by moderate floods with recurrence intervals of less than 50 yr.

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