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approximately 6,700 cfs, or the 12 year recurrence flood. The deposit is composed of fine-grained alluvium, and is overgrown by thick, mature stands of Russian olive, tamarisk and willow, with a cottonwood gallery forest. Some vegetation show signs of being buried in alluvium. These are characteristics similar to the cottonwood terrace identified elsewhere in the Green River Basin (Allred 1997, Grams 1997, Orchard and Schmidt 1998). The cottonwood terrace was abandoned in the Green River system in the late 1920s during a regional drought which caused a significant decrease in annual peak flood magnitudes (Orchard and Schmidt 1998). Discharge records do not exist for the White River during the period between 1906 and 1922, and it is unclear if the same decrease in flood magnitudes that occurred in the Green River system also occurred in the White River basin. However, because of similarity of the cottonwood terrace in the Green River system and the terrace described here in the White River basin, we hypothesize that the two surfaces are equivalent, and were abandoned around the same time in the late 1920s or early 1930s. This terrace was probably last inundated in 1965. We termed the intermediate surface as the low terrace. The low terrace is just above the elevation of the active flood plain and is lower in elevation than the cottonwood terrace. This surface begins to be inundated at approximately 5,700 cfs, or by thesevenyear recurrence flood. We believe that the abandonment of this surface coincided with the significant decrease in flood magnitudes which occurred in the mid- 1960s in the White River Basin. Unlike the active flood plain, the low terrace contains mature woody riparian species such as tamarisk, Russian olive and willow (Figure A-14). This terrace is underlain by horizontally bedded, fine-grained alluvium well stabilized by thick, abundant riparian vegetation. This surface typically terminates abruptly aLa 0.5 m 20