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comprised of predominantly fine-grained alluvium that overlies cobbles and gravels. The . surface has been colonized by young vegetation such as horse tail grasses, and young tamarisk. This surface lacks mature. woody vegetation such as large tamarisk or Russian olive (Fig. 11). At least two other distinct flood plain-like surfaces exist adjacent to the White River within the detailed study site (Fig. 12). Figure 13 shows the longitudinal profile of these surfaces and surveys of actual river conditions of known discharges, and thalweg elevations. The highest elevation surface identified in this study is a terrace approximately 1 m above the active flood plain. It is inundated at discharges of approximately 190 m3/s (6700 W/s), or the 12-yr. 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 I 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. 20