Investigating the use of alluvial fan volume to represent fan size in morphometric studies

Studies of the morphometric properties of alluvial fans have predominantly used a two-dimensional planimetric area to represent fan size even though fans are three-dimensional sediment deposits, but the validity of this substitution has been questioned. Volumes of fans in nonsubsiding settings were estimated with the objective of investigating the relationship between fan volume and fan area. A simple geometric approach was developed so that volumes of noncoalescent fans could be estimated with measurements from topographic maps. Data were collected from two study areas with humid, temperate climates: the Bow Valley in Alberta, Canada, and the Absaroka Range in Wyoming, USA. Because these landscapes were glaciated, the fans are of paraglacial origin and are not related to contemporaneous tectonic subsidence. Using functional relation analysis, results indicate that the proportional power-law relationship between fan volume and fan area is not significantly different from 1:1 in both study areas. Morphometric relationships between fans and drainage basins are also examined, with fan volume and cumulative sediment yield employed as variables.