THE FLOOD CYCLE OF EPHEMERAL MOUNTAIN STREAMS IN THE SOUTHWESTERN UNITED STATES

ABSTRACT The flood cycle of an arroyo in southwestern United States exhibits three separate stages: 1) the flood stage, often turbulent and violent, and impossible to study as it occurs; 2) the immediate after-flood stage, exhibiting conspicuous and interesting patterns, of which some may be observed; and 3) the dry stage, an indefinite period which lasts until the next flood, during which stage some detailed mechanisms of transport patterns may be observed. From this dry stage, aided by schematic and fugitive impressions gained during the other two stages, systematic inferences may be drawn concerning the mechanisms involved in transport throughout the cycle. Schematic illustrations support the analysis and categorization of the several mechanisms and their transport-sedimentation activities in this paper. The flood stage thoroughly reworks the channels within a valley, rearranging the whole transport load of sediments. At the moment the flood begins to wane the heaviest elements of the whole load are dr...