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| Titel |
Implications of bedload sampling point on sediment budget assessment |
| VerfasserIn |
A. Rovira, J. P. Martín-Vide, C. Ibáñez |
| 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 |
250031612
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| Zusammenfassung |
| Past and present management of the Ebro catchment have altered water and sediment fluxes
of the lower Ebro River and its delta. The construction of the Mequinensa and Riba-Roja
dams during the 1960s disrupted the sediment transport continuity. As a result, the lower
Ebro River and its delta are facing a dramatic reduction in sediment delivery. As part of the
design of a sediment management plan, we constructed the sediment budget of the lowermost
Ebro river (85.530 km2) in order to evaluate the present sediment deficit and the required
restoration needs from the reservoirs. The sediment budget is based on bed load and
suspended sediment field measurements. Bed load and suspended sediment samples were
obtained at two different verticals; covering up to 50% of the total channel width. Special
attention has been paid on the importance of the sampling point, and its implications on the
sediment budget. Preliminary results indicate that approximately 130.000 tones
of sediment passed at the outlet basin in 2008; which represents a reduction in
sediment delivery up to 99% of its original yield (about 3 x 107 t/yr). Sediment was
transported in a proportion of 89% as suspended and 11% as bed load. In contrast, 40 km
upstream of the outlet basin, previous studies indicate that 40% of total load is
transported as bed load. That fact could be associated to the effect of dams, the
closer to the dams the higher the sediment deficit. In addition, results show that
when using data from two different verticals, the estimate of the total sediment
transported as bed load is one order of magnitude different (8.000 t versus 20.000 t).
Furthermore, bed material passing through the first vertical is composed by sand (53%) and
gravels (47%), while bed load at the second vertical is almost totally composed
by gravels. Both factors (crossectional location and bed load texture) have severe
implications on the assessment of the sediment budget; especially when results
are to be used for river management, restoration and sediment yield assessment. |
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