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Volume 377
Proc. IAHS, 377, 41-50, 2018
https://doi.org/10.5194/piahs-377-41-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Proc. IAHS, 377, 41-50, 2018
https://doi.org/10.5194/piahs-377-41-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

  16 Apr 2018

16 Apr 2018

Morphodynamic change analysis of bedforms in the Lower Orinoco River, Venezuela

Santiago Paul Yepez1, Alain Laraque1, Carlo Gualtieri2, Frédéric Christophoul1, Claudio Marchan3, Bartolo Castellanos4, Jose Manuel Azocar5, Jose Luis Lopez4, and Juan Alfonso5 Santiago Paul Yepez et al.
  • 1GET, UMR CNRS/IRD/UPS – UMR 5563 du CNRS, UMR234 de l'IRD, 31400 Toulouse, France
  • 2University of Napoli Federico II, 80138 Napoli, Italy
  • 3Centro de Sismología, Universidad de Oriente 6101, Venezuela
  • 4IMF – UCV Instituto de Mecánica de Fluidos, Caracas 1041-A, Venezuela
  • 5COEA, Instituto Venezolano de Investigaciones Científicas (IVIC), Caracas 1020-A, Venezuela

Abstract. The Orinoco River has the third largest discharge in the world, with an annual mean flow of 37600m3 s−1 at its outlet to the Atlantic Ocean. Due to the presence of the Guiana Shield on the right bank, the lower reach of the Orinoco has a plan form characterized by contraction and expansion zones. Typical 1–1.5km wide narrow reaches are followed by 7–8km wide reaches. A complex pattern of bed aggradation and degradation processes takes place during the annual hydrological regime. A series of Acoustic Doppler Current Profiler (ADCP) transects were collected on an expansion channel in the Orinoco River, specifically over a fluvial island, representative of the lower Orinoco. In this study, temporal series of bathymetric cartography obtained by ADCP profiles combined with Differential Global Position System (DGPS) measurements (with dual-frequency), were used to recover the local displacement of bed forms in this island. The principal aims of this analysis were: (1) to understand the dynamics and evolution of sand waves and bars at this section and (2) to quantify the volume (erosion vs. accretion) of a mid-channel bar with dunes by applying DEM of Difference (DoD) maps on time series of bathymetric data. This required sampling with ADCP transects during the months of: May 2016; November 2016 and April 2017. Each bathymetric transect was measured twice, 1 day apart and on the same trajectory obtained by a GPS receptor. The spatial analysis of these ADCP transects is presented as a novel tool in the acquisition of time series of bathymetry for a relatively deep section ( ∼ 20m) and under variable flow conditions.

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Enhancing knowledge of the role of morphological changes (volume) with this new methodology is an opportunity to gain better understanding of river bed sediment transport. This type of study will support dredging projects in the Orinoco River to maintain navigability, which will contribute to the management of this important river basin.
Enhancing knowledge of the role of morphological changes (volume) with this new methodology is...
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