Alluvial fans are prominent depositional landforms created where steep high power channels enter a zone of reduced stream power and serve as a transitional environment between a degrading upland area and adjacent lowland (Harvey 1997). Typically, they range in scale from axial lengths of tens of meters to tens of kilometres. They are usually cone-shaped forms with surface slopes radiating away from an apex, located at the point where the feeder channel enters the fan. Their morphology resembles a cone segment with constant or slightly concave slopes that typically range from less than 25 degrees at the head, or apex, of the fan to less than a degree at the terminus, or toe. Three main factors are considered to be necessary for optimal alluvial fan development, including topography conducive to the formation of such landforms; sediment availability and production in the drainage basin; and a medium or mechanism for transporting sediment from the drainage basin to the site of fan construction (Blair and Mc Pherson 1994). Processes responsible for fan evolution and configuration include primary processes which deliver sediment to the fan, secondary processes which rework the sediment on the fan, stabilization processes that involve surface modification, and finally dissection processes that may erode the fan surface. On the basis of the primary processes, fans can be classified into debris flow and fluvially dominant fans. These processes are catchment controlled and depend on the water—sediment mix fed to the fan. The dominant primary processes are expressed by the sediment comprising the fan and by the surface morphology. These depositional landforms occur in any climatic environment, including desert mountain regions, arctic, alpine, humid temperate, and even humid tropical environments. Alluvial fans are subaerial features, however if they extend into water, like the fans of the study area, they are known as fan deltas.
Document Type: Research Article
Publication date: January 1, 2011
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Natural Environment and Culture in the Mediterranean Region II The Mediterranean Basin is the largest of the five Mediterranean-climate regions, and one of the largest archipelagos in the world. The basin is located at the intersection of two major landmasses, Eurasia and Africa; and has around five thousand islands, which contribute much to its high diversity and spectacular scenery. This volume continues the analysis of the changes and impacts experienced by the native flora and fauna of the Basin first expounded in 'Natural Environment and Culture in the Mediterranean Region'.