Relative effects on a low-volume road system of landslides resulting from episodic storms in northern Idaho

Transportation Research Record
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In late November to early December 1995 and February 1996, northern Idaho was hit by heavy rains on a deep snowpack, resulting in two flood and landslide events of historic magnitude. Each of these storms was larger than the previous significant storm, which occurred in January 1974. A study was initiated by the U.S. Department of Agriculture Forest Service to survey and study the effects of the resultant landslides on the Clearwater National Forest, including the effects on the aquatic ecosystem. The results of this study were compared with the estimated average natural sediment resulting from landslides to evaluate the incremental impacts of these recent episodic landslides. They were also compared with the results of a study conducted on the landslides resulting from the January 1974 storm to determine if the landscape was responding more severely to large storms as a result of Forest Service management activities over the past 21 years. The general results of this study indicate that, of the Forest Service management activities, roads are the major contributor; however, they contribute less sediment than natural landslides. The total resultant sediment appears to be within the transport capacity of the aquatic system, and the landslide response in 1974 was similar to the 1995-1996 response. The results of the aquatic ecosystem study were generally mixed, with some habitat parameters indicating degradation, some unchanged, and some improved as a result of the flooding or flooding with landslide sediment.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Relative effects on a low-volume road system of landslides resulting from episodic storms in northern Idaho
Series title Transportation Research Record
Volume 2
Issue 1652
Year Published 1999
Language English
Publisher National Research Council
Publisher location Washington, DC, United States
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Transportation Research Record
First page 235
Last page 243
Conference Title Proceedings of the 1999 7th International Conference on Low-Volume Roads
Conference Location Baton Rouge, LA, USA
Conference Date 23 May 1999 through 26 May 1999