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Decadal-scale change of infiltration characteristics of a tephra-mantled hillslope at Mount St Helens, Washington

Hydrological Processes

By:
,
DOI: 10.1002/hyp.5863

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Abstract

The cataclysmic 1980 eruption of Mount St Helens radically reduced the infiltration characteristics of ???60 000 ha of rugged terrain and dramatically altered landscape hydrology. Two decades of erosional, biogenic, cryogenic, and anthropogenic activity have modified the infiltration characteristics of much of that devastated landscape and modulated the hydrological impact of the eruption. We assessed infiltration and runoff characteristics of a segment of hillslope thickly mantled with tephra, but now revegetated primarily with grasses and other plants, to evaluate hydrological modifications due to erosion and natural turbation. Eruptive disturbance reduced infiltration capacity of the hillslope by as much as 50-fold. Between 1980 and 2000, apparent infiltration capacities of plots on the hillslope increased as much as ten fold, but remain approximately three to five times less than the probable pre-eruption capacities. Common regional rainfall intensities and snowmelt rates presently produce little surface runoff; however, high-magnitude, low-frequency storms and unusually rapid snowmelt can still induce broad infiltration-excess overland flow. After 20 years, erosion and natural mechanical turbation have modulated, but not effaced, the hydrological perturbation caused by the cataclysmic eruption. Copyright ?? 2005 John Wiley & Sons, Ltd.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Decadal-scale change of infiltration characteristics of a tephra-mantled hillslope at Mount St Helens, Washington
Series title:
Hydrological Processes
DOI:
10.1002/hyp.5863
Volume
19
Issue:
18
Year Published:
2005
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
3621
Last page:
3630
Number of Pages:
10