Searched for: author:"Chavarrias Borras, V."
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Chavarrias Borras, V. (author)
doctoral thesis 2019
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Chavarrias Borras, V. (author), Stecca, Guglielmo (author), Siviglia, Annunziato (author), Blom, A. (author)
A notable drawback in mixed-size sediment morphodynamic modeling is the fact that the most commonly used mathematical model in this field (i.e., the active layer model Hirano, 1971) can be ill-posed under certain circumstances. Under these conditions the model loses its predictive capabilities, as negligible perturbations in the initial or...
journal article 2019
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Chavarrias Borras, V. (author), Arkesteijn, L. (author), Blom, A. (author)
The active layer model (Hirano, 1971) is frequently used for modeling mixed-size sediment river morphodynamic processes. It assumes that all the dynamics of the bed surface are captured by a homogeneous top layer that interacts with the flow. Although successful in reproducing a wide range of phenomena, it has two problems: (1) It may become...
journal article 2019
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Arkesteijn, L. (author), Blom, A. (author), Czapiga, Matthew J. (author), Chavarrias Borras, V. (author), Labeur, R.J. (author)
An engineered alluvial river (i.e., a fixed-width channel) has constrained planform but is free to adjust channel slope and bed surface texture. These features are subject to controls: the hydrograph, sediment flux, and downstream base level. If the controls are sustained (or change slowly relative to the timescale of channel response), the...
journal article 2019
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Chavarrias Borras, V. (author), Schielen, Ralph (author), Ottevanger, Willem (author), Blom, A. (author)
A two-dimensional model describing river morphodynamic processes under mixed-size sediment conditions is analysed with respect to its well posedness. Well posedness guarantees the existence of a unique solution continuously depending on the problem data. When a model becomes ill posed, infinitesimal perturbations to a solution grow infinitely...
journal article 2019
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Chavarrias Borras, V. (author), Stecca, Guglielmo (author), Labeur, R.J. (author), Blom, A. (author)
The mixed-size character of sediment is a necessary property to ex- plain physical phenomena such as downstream fining or the presence of armor layers. The active layer model was developed to model mixed-size sediment in river morphodynamics. This model assumes that the topmost part of the bed, the active layer, has no vertical stratification...
journal article 2018
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Chavarrias Borras, V. (author), Stecca, G. (author), Blom, A. (author)
In this paper we analyze the Hirano active layer model used in mixed sediment river morphodynamics concerning its ill-posedness. Ill-posedness causes the solution to be unstable to short-wave perturbations. This implies that the solution presents spurious oscillations, the amplitude of which depends on the domain discretization. Ill-posedness...
journal article 2018
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Chavarrias Borras, V. (author), Blom, A. (author), Orru, C. (author), Martín-Vide, Juan Pedro (author), Viparelli, Enrica (author)
Laboratory experiments were conducted on a sand-gravel Gilbert delta to gain insight on its dynamics under varying base level. Base level rise results in intensified aggradation over the topset, as well as a decrease in topset slope and topset surface coarsening, the signals of which migrate in an upstream direction. Preferential deposition...
journal article 2018
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Blom, A. (author), Chavarrias Borras, V. (author), Ferguson, Robert I. (author), Viparelli, Enrica (author)
Downstream fining of bed sediment in alluvial rivers is usually gradual, but often an abrupt decrease in characteristic grain size occurs from about 10 to 1 mm, i.e., a gravel-sand transition (GST) or gravel front. Here we present an analytical model of GST migration that explicitly accounts for gravel and sand transport and deposition in the...
journal article 2017
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Blom, A. (author), Arkesteijn, E.C.M.M. (author), Chavarrias Borras, V. (author), Viparelli, Enrica (author)
journal article 2017
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Chavarrias Borras, V. (author), Ottevanger, W. (author), Labeur, R.J. (author), Blom, A. (author)
The set of equations used in modelling river  morphodynamics needs to be (at least) wellposed  to be representative of the real natural  phenomenon. As we deal with a time dependent  process the solution needs to be wave-like to be  well-posed. In other words, the solution must  have a domain of dependence and of...
abstract 2017
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Orru, C. (author), Blom, A. (author), Chavarrias Borras, V. (author), Ferrara, V (author), Stecca, G. (author)
We present a new image analysis technique for measuring the grain size distribution (texture) of the bed surface during flow in a laboratory experiment. A camera and a floating device are connected to a carriage used to take images of the bed surface over the entire flume length. The image analysis technique, which is based on color segmentation...
journal article 2016
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Blom, A. (author), Viparelli, Enrica (author), Chavarrias Borras, V. (author)
There has been quite some debate on the relative importance of particle abrasion and grain size selective transport regarding the river profile form and the associated grain size trends in a graded alluvial stream. Here we present new theoretical equations for the graded alluvial river profile that account for the effects of particle abrasion...
journal article 2016
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Orru, C. (author), Chavarrias Borras, V. (author), Ferrara, V. (author), Stecca, G. (author), Blom, A. (author)
A flume experiment was conducted to examine the evolution of a sand-gravel reach under a lack of sediment supply. A bed composed of a bimodal sediment mixture was installed with a uniform slope and an gradual fining pattern. At the upstream end of the flume the initial bed consisted of 100% gravel, which decreased stepwise (10% steps) in...
conference paper 2015
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Chavarrias Borras, V. (author), Orru, C. (author), Viparelli, E. (author), Vide, J.P.M. (author), Blom, J.C. (author)
conference paper 2014
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Orru, C. (author), Chavarrias Borras, V. (author), Uijttewaal, W.S.J. (author), Blom, A. (author)
Measurements of spatial and temporal changes in the grain-size distribution of the bed surface and substrate are crucial to improving the modelling of sediment transport and associated grain-size selective processes. We present three complementary techniques to determine such variations in the grain-size distribution of the bed surface in sand...
journal article 2014
Searched for: author:"Chavarrias Borras, V."
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