Alluvial Fans in the Italian Alps: Sedimentary Facies and Processes

  1. I. Peter Martini4,
  2. Victor R. Baker5 and
  3. Guillermina Garzón6
  1. A. Moscariello1,
  2. L. Marchi2,
  3. F. Maraga3 and
  4. G. Mortara3

Published Online: 17 MAR 2009

DOI: 10.1002/9781444304299.ch9

Flood and Megaflood Processes and Deposits: Recent and Ancient Examples

Flood and Megaflood Processes and Deposits: Recent and Ancient Examples

How to Cite

Moscariello, A., Marchi, L., Maraga, F. and Mortara, G. (2002) Alluvial Fans in the Italian Alps: Sedimentary Facies and Processes, in Flood and Megaflood Processes and Deposits: Recent and Ancient Examples (eds I. P. Martini, V. R. Baker and G. Garzón), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304299.ch9

Editor Information

  1. 4

    Department of Land Resource Science, University of Guelph, Guelph, Ontario, Canada

  2. 5

    Department of Hydrology and Water Resources, University of Arizona, Tucson, AZ 85721–0011, USA

  3. 6

    Dpto de Geodinámica, Fac. de Geología, Universidad of Complutense, 28040 Madrid, Spain

Author Information

  1. 1

    Godwin Institute of Quaternary Research, University of Cambridge, UK

  2. 2

    Research Institute for Prevention of Geological and Hydrological Hazard, Italian National Research Council, Padua, Italy

  3. 3

    Research Institute for Prevention of Geological and Hydrological Hazard, Italian National Research Council, Turin, Italy

Publication History

  1. Published Online: 17 MAR 2009
  2. Published Print: 10 FEB 2002

ISBN Information

Print ISBN: 9780632064045

Online ISBN: 9781444304299

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Keywords:

  • alluvial fans in Italian Alps - sedimentary facies and processes;
  • geology, geomorphology and climate;
  • geomorphology;
  • texture of alluvial fan deposits;
  • lithological control on fan processes and sediments;
  • fan-related hazards;
  • fan activity and climate

Summary

Sediment gravity flows are very common sedimentary processes in the Alpine region and are often characterized by rapid deposition of large amounts of material. Hazard evaluation in such mountainous areas depends on proper identification of the dominant sedimentary processes, interpreted both from modern and ancient sedimentary facies and their distribution. Three main groups of alluvial fans, characterized by different dominant sedimentary processes, have been distinguished on the basis of lithological characteristics of the catchment area. The dominant catchment lithologies are:

1 massive and/or crudely stratified carbonate rocks (dolomite and massive limestones);

2 fine-grained sedimentary and metamorphic rocks (schists, calc-schists, mica schists, slate, phyllites and quartzites);

3 massive crystalline rocks (granites, granodiorites).

Their main characteristics are illustrated by three case studies concerning large debris-flow events that occurred in the recent past. The comparison of sediment texture and grain-size distribution indicates that important differences in the sedimentological features of debris flows are generated by the three different rock types in the catchments. Colluvium lithology strongly controls the grain-size distribution of the debris available on the catchment that is mobilized, transported and accumulated on the fan during catastrophic flood events. The proportion of fine-grained particles (clay and fine silt) within the colluvium plays a key role in controlling the dominant primary sedimentary processes. The study of 23 flood events over the past 30 yr indicates that the catchments of group 1 and 2 fans produce large amounts of clay and fine silt, which typically can lead to the generation of cohesive sediment gravity flows. Group 3 fan catchments produce colluvium free of clay and fine silt that can be mobilized and transported by water flow processes, and which in extreme flood events usually are associated with non-cohesive sediment gravity flows.