USGS/Cascades Volcano Observatory, Vancouver, Washington
REPORT:
Channel Geometry and Hydrologic Data for Six Eruption-Affected Tributaries of
the Lewis River, Mount St. Helens, Washington, Water Years 1983-84
--
Holly A. Martinson, Hazel E. Hammond, William W. Mast, and Patrice D. Mango,
1986,
Channel Geometry and Hydrologic Data for Six Eruption-Affected Tributaries of
the Lewis River, Mount St. Helens, Washington, Water Years 1983-84:
U.S. Geological Survey Open-File Report 85-631
Abstract
The May 18, 1980, eruption of Mount St. Helens generated a lateral blast,
lahars, and tephra deposits that altered the tributary channels in the Lewis
River drainage basin. In order to assess potential flood hazards, study channel
adjustments, and construct a sediment budget for the perturbed drainages on the
northeast, east, and southeast flanks of the volcano, channel cross sections
were monumented and surveyed on Pine Creek, Muddy River, and Smith Creek during
September and October of 1980. Additional cross sections were monumented on
Swift Creek, Bean Creek, and Clearwater Creek during the summer of 1981. This
network of about 80 channel cross sections have been surveyed more frequently,
after periods of higher flow. The repetitive cross-section surveys provide
measurements of bank erosion or accretion and of channel erosion or aggradation.
Longitudinal stream profiles were surveyed periodically for selected short
reaches of channel. Corresponding map views constructed from aerial photographs
together with the longitudinal profiles provide a means for assessing channel
profile and planform stability and for applying changes measured at channel
cross sections to longer reaches of channel for sediment-budget computations.
This report presents plots of channel cross-section profiles, longitudinal
stream profiles, and channel planform maps constructed from the survey data
collected during water years 1983-84.
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02/28/01, Lyn Topinka