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II. INTRODUCTION A team of faculy and graduate students in the Department of Earth Resources at Colorado state University is presently studying flood sediments in the poudre River drainage basin. The basic objectives of this research are to: 1) reconstruct the magnitude and frequency of large floods occurring in the Poudre basin during the past several thousand years, 2) relate flood flow hydraulics to the configuration of channel and valley morphology, 3) relate flood occurrence to past climatic conditions in the basin, as recorded by various proxy indicators (pollen. lake sediments, packrat middens, tree rings, and fossil beetles), and 4) improve flood-frequency analyses for the Poudre basin by combining paleoflood data with standard systematic (gaged) discharge data. The first component of the research, which involved examining flood sediments in the lower reaches of poudre Canyon, was completed during autumn 1990-autumn 1991. This report summarizes the results of the first component, and briefly discusses our plans with respect to subsequent work. III. FIELD AREA The poudre River Canyon drains an area of 1060 mi2 in north- central Colorado, flowing north and then east from the continental Divide. The upper quarter of the Poudre drainage was glaciated during the Pleistocene, and the Horne Moraine marks the furthest extent of glacial ice. The basin is presently semiarid, and precipitation decreases from forty inches at the upper elevations to fourteen inches along the eastern base of the range. Vegetation in the Poudre basin varies from alpine tundra near the divide, down through spruce-fir forests and ponderosa pine forests, to the grasslands of the high plains. The Front Range portion of the basin lies primarily on precambrian igneous and metamorphic rocks. For the majority of its length, the river flows through the Colorado Front Range, in a steep, rocky channel confined by bedrock. The valley morphology of the canyon alternates between narrow bedrock gorges and wider reaches where alluvial terraces are preserved. The average gradients of these reaches, as obtained from 1:24,000 topographic maps, are 0.022 and 0.012, respectively. Both types of reaches preserve evidence of former mass movements, primarily debris flows, and of large floods. Meteorologic floods along the upper Poudre originate from snowmelt-runoff, rainfall-runoff, or a combination of the two.