37 Geomorphology and Surface Processes of Tectonically Active Regions

Wednesday, 7 September 2011
11:00 AM - 3:40 PM
A 017

LITHOLOGIC AND GLACIALLY-CONDITIONED CONTROLS ON DEBRIS-FLOW SEDIMENT FLUX IN ALTO ADIGE, ITALY

Paper number: 37-3
Program: Theme Sessions
Time: 11:40 AM – 11:55 AM

Authors

Abstract

Debris flows are efficient processes of sediment transfer from slope base to alluvial fans in mountain drainage basins. To advance current understanding of debris-flow sediment dynamics at the regional scale we analyze a historical (1998-2009) database of debris flows in 82 selected basins of the Alto Adige Province, north-eastern Italy. By combining historical information on event-based debris-flow volumetric deposition, high-resolution (LiDAR-derived) digital topography, and mapping of Quaternary sediment stores we are able to (i) characterize the principal topographic conditions at which debris-flow initiation, transportation, and deposition operate; (ii) detail debris-flow sedimentary signatures across spatial scales; and (iii) link debris-flow sediment flux to morphometry, lithologic variability, and sediment availability. We show that basin-wide specific yield obeys a negative scaling relation with basin area, which in turn is strongly controlled by dominant bedrock geology and abundance of Quaternary deposits. When the event-based sediment flux is subsumed across spatial scales, a more complex sedimentary signature is apparent, regardless of sediment availability. We hypothesize that this signature is characteristic of most debris-flow dominated settings.