Searched for: author:"Blom, A."
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Ylla Arbos, C. (author), Blom, A. (author), Acevedo Goldaracena, F. (author), van Vuren, S (author), Schielen, R.M.J. (author)
The Rhine reach comprising the Niederrhein and the Upper Rhine Delta is characterized by a long history of engineering interventions. The area is densely populated and the Rhine, the main inland waterway in Europe, justifying the need for such measures. Interventions have had a strong impact on morphodynamic channel characteristics. We use bed...
conference paper 2020
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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), 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), 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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Schielen, Ralph M.J. (author), Blom, A. (author)
We derive an idealized model of a gravel-sand river bifurcation and analyze its stability properties. The model requires nodal point relations that describe the ratio of the supply of gravel and sand to the two downstream branches. The model predicts changes in bed elevation and bed surface gravel content in the two bifurcates under...
journal article 2018
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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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Siele, Meles (author), Blom, A. (author), Viparelli, Enrica (author)
In response to changes in the upstream controls (i.e., the water discharge, the sediment supply rate, and the calibre of the load), engineered alluvial channels adjust their bed slope and bed surface texture to establish a new equilibrium state. Here we present and discuss various causes of degradational response of engineered channels to...
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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Arkesteijn, E.C.M.M. (author), Labeur, R.J. (author), Blom, A. (author)
When rivers are forced by statistically invariant boundary conditions (i.e. an upstream water discharge, upstream sediment discharge and downstream base level that fluctuate around constant mean values), and are not subject to any forcing with a temporal trend (e.g. no uplift/subsidence, no sea-level rise), they tend to a morphodynamic...
abstract 2017
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van Denderen, R. Pepijn (author), Schielen, Ralph M.J. (author), Blom, A. (author), Hulscher, Suzanne J.M.H. (author), Kleinhans, Maarten G. (author)
Side channel construction is a common intervention applied to increase a river's conveyance capacity and to increase its ecological value. Past modelling efforts suggest two mechanisms affecting the morphodynamic change of a side channel: (1) a difference in channel slope between the side channel and the main channel and (2) bend flow just...
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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Emmanouil, A. (author), Blom, A. (author), Viparelli, Enrica (author), Frings, R. (author)
Sediment management measures are  becoming increasingly popular as they are  considered sustainable from both economic  and environmental point of view. For example,  aimed at counteracting river bed degradation,  sediment nourishments have been carried out  in the German reaches of the Rhine river while  a...
abstract 2017
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Tewolde, M.S. (author), Blom, A. (author), Frings, R. (author), Viparelli, Enrica (author)
The main objective of this research is to  improve our understanding of the relative  contribution of the causes of long-term bed  degradation in Rhine and other degrading  rivers. That is, the research is intended to  quantify past channel adjustment processes,  mainly bed degradation and bed surface  coarsening...
abstract 2017
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Stecca, G. (author), Siviglia, Annunziato (author), Blom, A. (author)
We present an accurate numerical approximation to the Saint-Venant-Hirano model for mixed-sediment morphodynamics in one space dimension. Our solution procedure originates from the fully-unsteady matrix-vector formulation developed in [54]. The principal part of the problem is solved by an explicit Finite Volume upwind method of the path...
journal article 2016
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Orrú, Clara (author), Blom, A. (author), Uijttewaal, W.S.J. (author)
Armor breakup and reformation was studied in a laboratory experiment using a trimodal mixture composed of a 1mm sand fraction and two gravel fractions (6 and 10mm). The initial bed was characterized by a stepwise downstream fining pattern (trimodal reach) and a downstream sand reach, and the experiment was conducted under conditions without...
journal article 2016
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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
Searched for: author:"Blom, A."
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