Abstract

The physiography of stream systems on the north and south slopes of the Uinta Mountains reflects broad differences in physical conditions on the two sides of the range. Variations in bedrock geology, stream gradients, and the extent and style of Late Pleistocene glaciations, have produced a different collection of stream planforms and alluvial landforms on the opposite slopes. However, both slopes of the range experience similar hydrometeorological conditions, producing broadly similar stream hydrology across the range. The entire range receives the majority of its annual precipitation from winter frontal storms from the North Pacific Ocean, resulting in the bulk of annual stream discharge occurring during the months of winter snowmelt. Accordingly, the magnitude of modern floods is closely correlated to the size of snowpack that accumulates in winter and the rate at which it melts in spring. Recent research investigating the fluvial geomorphology of the Uintas has focused on stream channel responses to sediment transportation, particularly on the lower Duchesne and Green Rivers. Additional work in the sub-alpine Uintas has evaluated a range of responses of fluvial systems to climatic and land-use changes over the past several millennia. Alluvial sediments in select sites on the north slope of the range record the effects of logging during the 19th and 20th Centuries. Tree-ring data have been used to reconstruct streamflow in the southern Uintas for the past ~350 years, and the reconstruction suggests that annual streamflow during this period experienced significant variability over decadal and centennial timescales. Based on this, the sub-alpine Uintas apparently experienced prolonged drought conditions through the peak of the Little Ice Age in the western United States.