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| Titel |
Controls on the distribution and geometry of postglacial bedrock channels |
| VerfasserIn |
K. Whitbread, J. Jansen, P. Bishop |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250064026
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| Zusammenfassung |
| In postglacial rivers of the northwest Scottish Highlands, reach-scale channel slopes remain
strongly controlled by glacially-conditioned valley-floor slopes 14.0-11.7 kyr after
deglaciation. The inherited slopes, together with glacially-conditioned sediment flux, control
the distribution of bedrock channels, and therefore fluvial erosion, in these rivers.
Declining paraglacial sediment flux lowers the critical slope for the alluvial to bedrock
channel transition resulting in a long-term increase in the proportion of bedrock
channels.
Bedrock channel cross-sectional geometry is strongly hydraulically scaled despite
variable bedrock lithologies, but differences in scaling relationships for coarse-grained
alluvial and bedrock channels suggest that transport-limited and detachment-limited erosion
processes produce characteristic differences in channel form. The development of
hydraulically-scaled channel geometry indicates that most bedrock channels in the northwest
Scottish Highlands have achieved a stable cross-section configuration (i.e. w/d ratio), and that
this stability is achieved where postglacial bedrock incision has progressed to ~1.5 times the
bankfull equivalent flow depth.
The findings indicate that in post-orogenic, postglacial terrains bedrock channel
cross-sections adjust on timescales of 104 years whereas full adjustment of channel slope
takes considerably longer. |
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