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United States Department of Agriculture

Agricultural Research Service

Title: The Sensitivity of Snowmelt Processes to Climate Conditions and Forest Cover During Rain-on-Snow: a Study of the 1996 Pacific Northwest Flood

Authors
item Marks, Daniel
item Kimball, John - UNIVERSITY OF MONTANA
item Tingey, David - EPA - CORVALLIS OR
item Link, Tim - OREGON STATE UNIVERSITY

Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 1, 1998
Publication Date: N/A

Interpretive Summary: A warm, very wet Pacific storm caused major flooding in the Pacific Northwest during February 1996. Rapid melting of the mountain snowcover contributed to this flooding. An energy balance snowmelt model is used to simulate snowmelt processes during this event in the Central Cascade mountains of Oregon. Data from paired open and forested experimental sites at locations at and just below the Pacific Crest were used to drive snowcover down to elevations as low as 500m in the Oregon Cascades. At the start of the storm, the depth of the snowcover at the high site (1142m) was 1.97m with snow water equivalent (SWE) of 425mm, while at the mid site (968m) the snowcover was 1.14m with SWE of 264mm. During the 5-6 day period of the storm the high site received 349mm of rain, lost 291mm of SWE, and generated 640mm of runoff, leaving only 0.22m of snow on the ground. The mid site received 410mm of rain, lost 264mm of water to melt, and generated 674mm of runoff, completely depleting the snowcover. Simulations at adjacent forested sites showed significantly less snowmelt during the event. The snowcover under the mature forest at the high site lost only 44mm of SWE during the event, generating 396mm of runoff, and leaving 0.69m of snow. The model accurately simulated both depth and SWE during the development of the snowcover prior to the storm, and the depletion of the snowcover during the event. ...

Technical Abstract: A warm, very wet Pacific storm caused major flooding in the Pacific Northwest during February 1996. Rapid melting of the mountain snowcover contributed to this flooding. An energy balance snowmelt model is used to simulate snowmelt processes during this event in the Central Cascade mountains of Oregon. Data from paired open and forested experimental sites at locations at and just below the Pacific Crest were used to drive snowcover down to elevations as low as 500m in the Oregon Cascades. At the start of the storm, the depth of the snowcover at the high site (1142m) was 1.97m with snow water equivalent (SWE) of 425mm, while at the mid site (968m) the snowcover was 1.14m with SWE of 264mm. During the 5-6 day period of the storm the high site received 349mm of rain, lost 291mm of SWE, and generated 640mm of runoff, leaving only 0.22m of snow on the ground. The mid site received 410mm of rain, lost 264mm of water to melt, and generated 674mm of runoff, completely depleting the snowcover. Simulations at adjacent forested sites showed significantly less snowmelt during the event. The snowcover under the mature forest at the high site lost only 44mm of SWE during the event, generating 396mm of runoff, and leaving 0.69m of snow. The model accurately simulated both depth and SWE during the development of the snowcover prior to the storm, and the depletion of the snowcover during the event. ...

Last Modified: 10/30/2014
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