HR: 14:40h
AN: H42J-05    [PDF]
TI: Scaling and pattern of extreme geomorphic events in a mountain basin, Idaho, USA
AU: * Luce, C H
EM: cluce@fs.fed.us
AF: USDA Forest Service, Rocky Mountain Research Station, 316 E. Myrtle St., Boise, ID 83716 United States
AU: Rieman, B E
EM: brieman@fs.fed.us
AF: USDA Forest Service, Rocky Mountain Research Station, 316 E. Myrtle St., Boise, ID 83716 United States
AU: McKean, J A
EM: jmckean@fs.fed.us
AF: USDA Forest Service, Rocky Mountain Research Station, 316 E. Myrtle St., Boise, ID 83716 United States
AU: Dunham, J B
EM: @fs.fed.us
AF: USDA Forest Service, Rocky Mountain Research Station, 316 E. Myrtle St., Boise, ID 83716 United States
AU: King, J G
EM: jgking@fs.fed.us
AF: USDA Forest Service, Rocky Mountain Research Station, 316 E. Myrtle St., Boise, ID 83716 United States
AB: While extreme events are rare in individual streams or stream reaches, the occurrence of an extreme event somewhere within an ensemble of streams can be commonplace. The relationship between event frequency and magnitude for large units of analysis depends on the size of area considered and the spatial continuity of events. Some of the more extreme geomorphic events affect only a limited spatial area. Limitations to area relate to spatial extents of event triggers such as fires, thunderstorms, or rain-on-snow. Understanding the size of extreme events is important in approaching the frequency-magnitude relationships for larger analysis frames and clarifying the role of extreme events at different spatial scales. Sequential mapping of channel reorganizing events from aerial photography records dating back 40 years in the Boise River basin reveal important characteristics of severe disturbances in a spatial context. The most relevant to this discussion is that there is little coherence in extreme events beyond 10 km. Patterns of occurrence for fishes occupying these streams may reflect historic patterns of extinction and colonization following catastrophic disturbance. These patterns and recent data on apparent gene flow among streams suggest that scaling of ecological processes is concordant with the patterns of channel disturbance we have identified here. There is evidence that this scale relates more to the scale of driving storm events than to pre-existing land disturbances such as fire, logging, or grazing. One puzzle is that some areas seem more prone to multiple events than others, which may relate to underlying variation in lithology and exposure to weather. Lithology also constrains the temporal signature of extreme events. The spatial extent of events may serve as a valuable metric of event magnitude to gauge their ecological influence.
UR: http://www.fs.fed.us/rm/boise/
DE: 0400 Biogeosciences
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
SC: Hydrology [H]
MN: 2003 Fall Meeting