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| Titel |
Integrating structural and functional connectivity to characterize sediment dynamics in a small Alpine catchment |
| VerfasserIn |
Marco Cavalli, Stefano Crema, Michiel Blok, Ana Lucía, Francesco Comiti, Lorenzo Marchi, Saskia Keesstra |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250134325
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| Publikation (Nr.) |
 EGU/EGU2016-15034.pdf |
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| Zusammenfassung |
| Sediment connectivity can be regarded as a descriptor of the internal linkages between
different landscape components within a catchment. The recent focus of the scientific
community on connectivity related topics, both concerning hydrological and sediment
connectivity, stresses the importance of understanding the main active pathways for a better
estimation of energy and matter transfer at catchment scale. This task can be addressed using
topography-based indices that analyse the linkages between landscape units. This approach to
characterize connectivity is known as structural connectivity. The main limitation of
structural connectivity is that it does not account for the processes driving sediment and
energy fluxes (i.e., functional connectivity).
In this work the integration between structural and functional approaches is proposed for
characterizing sediment connectivity in mountain catchments. The structural approach,
based on a topography-based sediment connectivity index, was used for assessing
hillslope-to-channel connectivity. Since field data on processes driving sediment transport
along the channel network are available, a functional approach has been devised to estimate
within-channel connectivity. An index of unit stream power computed from the hydraulic
properties of the channel (i.e., discharge, slope and channel width) has been compared with
the critical unit stream power computed from incipient motion thresholds derived from field
data to identify the cells of the Digital Terrain Model (DTM) in which sediment can be
mobilized under near-bankfull conditions. The index expressing the within-channel
connectivity is given by the length of the reaches consisting of contiguous cells that
exceed the critical unit stream power. During high-magnitude floods, when unit
stream power values exceed the threshold for incipient motion, channels experience
an increase in both hydrological and sediment connectivity. The proposed index
characterizes those sections of the channel network that are effectively connected
under near-bankfull conditions. The model has been developed and tested in a small
mountain catchment in the Italian Alps (Strimm catchment, 8.42 km2) in which a
high-resolution DTM and monitored discharge and sediment transport data are available.
The integration between structural and functional indices of sediment connectivity
has permitted characterizing the spatial pattern of sediment connectivity on the
hillslope and pointing out potential sites for sediment erosion, entrainment and
deposition along the main channel network. This combined approach represents a new
development of the index of connectivity considering sediment transport process along the
channel network, with the only limitation related to field data availability. However,
further testing is required to validate the index in order apply it to other catchments. |
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