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| Titel |
Qualitative and quantitative study on drainage networks at laboratory scale |
| VerfasserIn |
G. Oliveto, D. Palma, A. Di Domenico |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250030600
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| Zusammenfassung |
| Although simulated drainage networks at the laboratory scale would represent highly-simplified
models of natural drainages, they would provide a significant contribute to the comprehension
of the complex dynamics governing the fluvial systems. Laboratory experiments
also give the advantage to detect transient growth phases shedding some light on
the knowledge of temporal and spatial landform evolution. Perhaps, pioneering
laboratory experiments on drainage network evolution were carried out in 1977
at REF (Rainfall Erosion Facility) of Colorado State University by Schumm and
co-workers.
This study deals with an analysis of physical experiments simulating the evolution and the
development of drainage networks. To this purpose, some experiments were carried out at
University of Basilicata by using a 1.5 m by 1.5 m box-basin-simulator with an outlet incised
in the middle of the downslope-end side. The experimental landscape was made of a weakly
cohesive soil mainly constituted by clay and silt. A system of microsprinklers generated an
almost uniform artificial precipitation. Simulations were performed at a constant rainfall
rate with intensity of 100 mm/h. In total four experiments were carried out. Three
of those were conducted by ensuring consistent initial conditions except for the
initial landscape planar slope of 9%, 5%, and 0.6%, respectively. The remaining
experiment was performed with a landscape slope of 9% again, but with the (surface)
base-level coinciding with the base of the outlet (i.e. streams could not erode below the
base-level).
Despite the central outlet constraint, the generated stream system for the 9% plane
exhibited trellis-like drainage patterns with many short tributaries joining the main stream at
nearly right angles. For the 5% experiment still sub-parallel drainage patterns were formed
but mainly in the centre of the watershed. Channels were clearly shallower than those
of the 9% experiment. For the gentler slope of 0.6% dendritic drainage patterns
developed with tributaries entering the main channel at acute angles (less than 90Ë
).
Digital elevation models (DEM) of the evolving landscape were achieved through
detailed soil surveys with a laser pointer or a laser scanner. Then, the drainage networks were
extracted from the DEMs by using the D8 algorithm.
Based on the data collected, the scaling properties of the simulated networks are
analysed and compared with those of natural basins. Findings are provided mainly in
terms of Hortonian laws, fractal dimensions and informational entropy. Scaling
properties and space filling tendencies are discussed and peculiar differences between
quasi-equilibrium and transient stages are also highlighted. Experimental evidences are
also provided on the interaction between the base-level and growing mechanisms. |
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