Trees, Snow and Flooding: An Investigation of Forest Canopy Effects on SnowAccumulation and Melt at the Plot and Watershed Scales in the Pacific Northwest

摘要

Concerns about the extent to which major Pacific Northwest floods over the lastdecade might have been exacerbated by logging have heightened the need for a better scientific understanding of the role of forest maturity on snow accumulation and melt. To address this need, a multi-scale field and modeling study of the effects of forest canopies on snow accumulation and melt was conducted. Over a three year period, weighing lysimeters and cut-tree experiments were used to measure the process controlling snow interception and its fate at a site in the Umpqua National Forest, OR (elevation 1200 m). Continuous observations of below-canopy snowpack evolution were made over the same period. Over the study period, approximately 60 percent of annual snowfall was intercepted by the canopy (up to a maximum of 40 mm water equivalent). Approximately 72 percent and 28 percent of the intercepted snow was removed as meltwater drip and large snow masses, respectively. Apparent average sublimation rates from the intercepted snow were less than 1 mm per day and totaled approximately 100 mm per winter season.