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Forest roads and geomorphic process interactions, Cascade Range, Oregon
Author(s) -
Wemple Beverley C.,
Swanson Frederick J.,
Jones Julia A.
Publication year - 2001
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/1096-9837(200102)26:2<191::aid-esp175>3.0.co;2-u
Subject(s) - mass wasting , fluvial , bedrock , storm , geology , debris flow , sediment , sedimentary depositional environment , hydrology (agriculture) , debris , mass movement , landslide , sediment transport , sedimentation , structural basin , rockfall , physical geography , geomorphology , oceanography , geography , geotechnical engineering
A major flood in February 1996 triggered more than 100 geomorphic features affecting forest roads in a 181 km 2 study area in the western Cascade Range, Oregon. Eight types of features, including mass movements and fluvial features, were mapped, measured and analysed using geographic information systems and sediment budgets for the road network. Although roads functioned as both production and depositional sites for mass movements and fluvial processes, the net effect of roads was an increase in basin‐wide sediment production. Debris slides from mobilized road fills were the dominant process of sediment production from roads. Road‐related sedimentation features were concentrated in a portion of the study area that experienced a rain‐on‐snow event during the storm and was characterized by the oldest roads and steep slopes underlain by unstable, highly weathered bedrock. The downslope increase in frequency of features and volumes of sediment produced, combined with the downslope increase in relative frequency of fluvial over mass‐wasting processes, suggests that during an extreme storm event, a road network may have major impacts on stream channels far removed from initiation sites. Overall this study indicated that the nature of geomorphic processes influenced by roads is strongly conditioned by road location and construction practices, basin geology and storm characteristics. Published in 2001 by John Wiley & Sons, Ltd.