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Earth Surface Dynamics An interactive open-access journal of the European Geosciences Union

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Earth Surf. Dynam., 5, 585-603, 2017
https://doi.org/10.5194/esurf-5-585-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
25 Sep 2017
Large-scale coastal and fluvial models constrain the late Holocene evolution of the Ebro Delta
Jaap H. Nienhuis1,2,3, Andrew D. Ashton2, Albert J. Kettner4, and Liviu Giosan2 1Earth, Atmospheric and Planetary Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
2Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
3Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, FL 32306, USA
4Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309, USA
Abstract. The distinctive plan-view shape of the Ebro Delta coast reveals a rich morphologic history. The degree to which the form and depositional history of the Ebro and other deltas represent autogenic (internal) dynamics or allogenic (external) forcing remains a prominent challenge for paleo-environmental reconstructions. Here we use simple coastal and fluvial morphodynamic models to quantify paleo-environmental changes affecting the Ebro Delta over the late Holocene. Our findings show that these models are able to broadly reproduce the Ebro Delta morphology, with simple fluvial and wave climate histories. Based on numerical model experiments and the preserved and modern shape of the Ebro Delta plain, we estimate that a phase of rapid shoreline progradation began approximately 2100 years BP, requiring approximately a doubling in coarse-grained fluvial sediment supply to the delta. River profile simulations suggest that an instantaneous and sustained increase in coarse-grained sediment supply to the delta requires a combined increase in both flood discharge and sediment supply from the drainage basin. The persistence of rapid delta progradation throughout the last 2100 years suggests an anthropogenic control on sediment supply and flood intensity. Using proxy records of the North Atlantic Oscillation, we do not find evidence that changes in wave climate aided this delta expansion. Our findings highlight how scenario-based investigations of deltaic systems using simple models can assist first-order quantitative paleo-environmental reconstructions, elucidating the effects of past human influence and climate change, and allowing a better understanding of the future of deltaic landforms.

Citation: Nienhuis, J. H., Ashton, A. D., Kettner, A. J., and Giosan, L.: Large-scale coastal and fluvial models constrain the late Holocene evolution of the Ebro Delta, Earth Surf. Dynam., 5, 585-603, https://doi.org/10.5194/esurf-5-585-2017, 2017.
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Short summary
The Ebro Delta in Spain has a distinctive coastline shape, the origin of which has been debated. Here we show with two simple models, one of the Ebro River and one of its delta, that is it possible to reproduce this distinctive shape under constant sediment supply, wave climate, and sea-level conditions. We also find that the majority of the delta grew in the last 2000 years, when a great increase in sediment supply from the Ebro River allowed it to accelerate its growth.
The Ebro Delta in Spain has a distinctive coastline shape, the origin of which has been debated....
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