 |
| Titel |
Bedload transport rates estimated in two gravel bed streams from NW Spain |
| VerfasserIn |
D. Vázquez-Tarrío, R. Menéndez-Duarte, J. Crespo, M. Fernandez |
| Konferenz |
EGU General Assembly 2012
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250059299
|
|
|
|
|
|
| Zusammenfassung |
| The rivers located in the northern side of Cantabrian Mountain Range (a mountain range
which runs parallel to North-western Spanish coast) drain to the Gulf of Biscay, saving a
difference of height of roughly 2,000 m in a short path. The climate is Atlantic, with annual
rainfall averages around 1,100 mm. The hydrological regime of the main channel is pluvial,
with maximum winter discharges and a relatively regular water discharge along the whole
year. These facts give place to rivers with a high gradient and with an important contribution
of coarse bedload transport to its sedimentary dynamics. In the present work, bedload
transport rates were estimated in two gravel bed streams through the use of tracer stones.
These two gravel bed streams are a part of the drainage network of Narcea River
basin.
Narcea River drainage basin has got a catchment surface of 1,800 Km2. Lithology of the
basin comprises a diversity of Paleozoic sedimentary rocks (mainly siliciclastic lithologies:
quartzarenites, shales and slates) and the vegetation cover shows an alternation of bush areas
(mainly heather), beech and oak forests and pastures. An important extension of the basin is
represented by headwater channels, with highly-coarse bed sediment, very irregular
hydrologic regimes and the occurrence of periodic debris-flow like mass movements. By its
side, higher order channels are mainly alluvial reaches with cobble and gravel beds.
These reaches develop floodplains, generally with little areal extension and limited
spatial continuity (except in the lower parts of the basin). In this work, two gravel
bed streams from this basin were selected for estimating bedload transport rates,
the Pigüeña river and the Coto river. The both are tributaries of the main Narcea
river.
Bedload transport rates were estimated through the use of tracer stones. This technique
consists on feeding channel bed with tagged stones and measuring its travel distances after
flood events capable of moving bed sediment. Here, the tracer stones were taken directly from
the channel bed on the study sites. Tracer stones were tagged by two means: painting clasts
and inserting magnets inside the stones (using a drill and filling the void with epoxy resin).
Tracer stones were fed directly over the bed surface of two side channel bars placed in the
study reaches. Tracer clasts were deposited following a straight line transverse to the main
flow direction.
Six flood episodes with ability to carry sediment were studied (three for each study site).
Then, the first bedload transport rates, for rivers placed in the Northern Cantabrian range,
have been estimated. Bedload transport rates of 0,01 to 0,1 Kg/m•s have been measured.
These transport rates lay inside the same range of values to those rates compiled from
scientific literature in other gravel bed rivers. The measured bedload transport rates
are relatively low, indicating a low-transport regime for the Narcea River basin. |
|
|
|
|
|
|