Channel and Perennial Flow Initiation in Headwater Streams: Management Implications of Variability in Source-Area Size |
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Authors: | Kristin L Jaeger David R Montgomery Susan M Bolton |
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Institution: | (1) College of Forest Resources, University of Washington, P.O. Box 352100, Seattle, WA 98195-2100, USA;(2) Present address: Department of Geosciences, Colorado State University, 322 Natural Resources Building, Fort Collins, CO 80523, USA;(3) Earth & Space Sciences, University of Washington, P.O. Box 351310, Seattle, WA 98195-1310, USA;(4) College of Forest Resources, University of Washington, P.O. Box 352100, Seattle, WA 98195-2100, USA |
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Abstract: | Despite increasing attention to management of headwater streams as sources of water, sediment, and wood to downstream rivers,
the extent of headwater channels and perennial flow remain poorly known and inaccurately depicted on topographic maps and
in digital hydrographic data. This study reports field mapping of channel head and perennial flow initiation locations in
forested landscapes underlain by sandstone and basalt lithologies in Washington State, USA. Contributing source areas were
delineated for each feature using a digital elevation model (DEM) as well as a Global Positioning System device in the field.
Systematic source area–slope relationships described in other landscapes were not evident for channel heads in either lithology.
In addition, substantial variability in DEM-derived source area sizes relative to field-delineated source areas indicates
that in this area, identification of an area–slope relationship, should one even exist, would be difficult. However, channel
heads and stream heads, here defined as the start of perennial flow, appear to be co-located within both of the lithologies,
which together with lateral expansion and contraction of surface water around channel heads on a seasonal cycle in the basalt
lithology, suggest a controlling influence of bedrock springs for that location. While management strategies for determining
locations of channel heads and perennial flow initiation in comparable areas could assign standard source area sizes based
on limited field data collection within that landscape, field-mapped source areas that support perennial flow are much smaller
than recognized by current Washington State regulations. |
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Keywords: | Headwater streams Channel initiation Perennial initiation Source area sizes Seasonal flow characteristics Forest hydrology |
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