HR: 14:25h
AN: H43H-04    [Abstracts]
TI: Travel Distance in Landscape Evolution Models
AU: * Kirkby, M J
EM: m.j.kirkby@leeds.ac.uk
AF: School of Geography, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, United Kingdom
AB: Models for the evolution of tectonically active steeplands are commonly constrained by two limitations, the dynamic interactions with valley floor width and the balance between supply and flux limited removal. This paper discusses the implications of using sediment travel distance to provide a transition between supply- and flux- limited models. Where travel distance is long relative to the region of interest, removal is essentially supply limited; and where short removal is flux limited. For most sites therefore, the coarsest debris is flux limited whereas fines are supply limited. Once a significant fraction of the removal is flux limited, then models must also consider the supply of sediment from the hillsides which is generally dominated by mass movement, interacting with regolith forming processes dynamically linked to gradient. To make use of travel distance as a model variable, there is a need to define it operationally. Most formulations tend to treat it as an event-scale measure, describing total travel distance during an entire event, and most measurements of marked tracers inevitably adopt the same approach. Such measurements provide distributions of travel distance, related to grain size, which commonly correspond well with gamma distributions, having a modal distance that moves away from zero as the tracer source is exhausted. However the total movement of a grain is built up from a number of individual bed or suspended load movements, and it is at this scale that travel distance might be related to sediment transport mechanics. Some analogy is made with storm or daily rainfall amounts, that are also gamma distributed, but for which much more detailed information is available on intensity variations within a storm, to suggest possible distributions that underlie the total event travel distance.
DE: 1815 Erosion
DE: 1825 Geomorphology: fluvial (1625)
DE: 1826 Geomorphology: hillslope (1625)
DE: 1847 Modeling
SC: Hydrology [H]
MN: 2007 Fall Meeting