408 research outputs found
Explicit computation of dynamic bed form roughness for operational flood modelling using a time-lag approach
Adapting the Coleman et al. (2005) time-lag approach for application under unsteady discharge
Fresh Sounds (Book Review)
Reviewed Title: Fresh Sounds, by Betty Pulkingham and Jeanne Harper, William B. Eerdmans Publishing Company, Grand Rapids, Michigan, 192 pages
Presentatie van onzekerheden in riviermodellen aan beleidsmakers
In het waterbeheer in Nederland wordt gebruik gemaakt van numerieke\ud
modellen voor, onder andere, het voorspellen van hoogwaterstanden.\ud
Deze modellen zijn gebaseerd op de waterbewegingvergelijkingen.\ud
De resultaten van deze modellen worden in veel gevallen\ud
deterministisch verondersteld. Numerieke modellen zijn echter altijd\ud
onzeker. Bij de afdeling Waterbeheer wordt onderzoek gedaan naar de\ud
kwantificering van deze onzekerheden. Hierbij kijken we hoe nauwkeurig\ud
de waterstanden in de Nederlandse rivieren worden voorspeld.\ud
Kwantificering van de onzekerheid in de waterstanden zorgt voor een\ud
betere onderbouwing van maatregelen die worden genomen om overstromingen\ud
te beperken (zie figuur 1). In dit artikel gaan we in op hoe\ud
de onzekerheden in modelresultaten gecommuniceerd kunnen worden\ud
naar de besluitvormers. Dit afstudeeronderzoek van Lea Goedhart\ud
is gedaan als onderdeel van het promotieonderzoek van Jord Warmink\ud
naar de onzekerheid in riviermodellen en is uitgevoerd in samenwerking\ud
met HydroLogic
Hydrodynamic modelling with unstructured grid using D-Flow-FM: case study Afferden-Deest
Accurate predictions of water levels play an important role in the management of flood safety. Nowadays, it has become common practice to use multi-dimensional numerical hydrodynamic models for such purposes. Currently, two model types are the standard tools in the Netherlands, namely WAQUA/TRIWAQ (Rijkswaterstaat, 2012) and Delft3D (Deltares, 2014). WAQUA and Delft3D are both based on a structured curvilinear grid, which can follow large-scale topographical changes and uses similar grid resolution throughout the entire computational domain. Drawbacks of the structured curvilinear grid approach are that elevation jumps in the river's topography may lead to unrealistic staircase representations in the model, and the inner bends of meandering rivers gridlines may become focussed to unnecessarily small grid cells (Kernkamp et al., 2011). To improve on these issues, Deltares is developing the unstructured-grid-based hydrodynamic model Flexible Mesh (also referred to as “D-Flow-FM”). The unstructured grid approach enables the user to use a spatially variable grid resolution. By combining curvilinear grid cells with triangular grid cells, the modeller can increase grid resolution on the locations where, because of local topographical variations, it is most desired. In this study, modelling results of Flexible Mesh and WAQUA are presented for a selected river reach near Afferden-Deest and benefits of local grid refinements in Flexible Mesh are demonstrated
Evolution of bed form height and length during a discharge wave
This research focusses on modeling the evolution of bed form during a discharge wave for application in operational flood forecasting. The objective of this research was to analyze and predict the bed form evolution during a discharge wave in a flume experiment. We analyzed the data of a flume experiment and show that dune length is determined by development of secondary bed forms during the receding limb of the discharge wave. Secondly, three models were compared to predict the bed form evolution: an equilibrium model, a time-lag model and the physically-based, numerical model of Paarlberg et al. (2010). We show some preliminary results and show that the numerical model seems promising for modeling bed form evolution for operational flood forecasting
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