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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Sediment management and morphodynamics : Numerical modelling of river dunes in the waal under extreme floods
Numerical modelling of river dunes in the waal under extreme floods
Author : SANJAY GIRI(1), SATOMI YAMAGUCHI(2), MOHAMED NABI(1), JONATHAN NELSON(3) & YASUYUKI SHIMIZU(4)
ABSTRACT
This The Waal branch of Rhine system is considered to be an important fairway. The flood events and extensive
navigation cause significant morphological changes, which create difficulties for safe and efficient navigation particularly
during low water period. Therefore, it is important to predict the bed level changes, particularly evolution of bed forms
during the flood event including both the high water and low water periods. Besides this, it is also important to
understand the bed form evolution process and resulting flow resistance during extreme floods in order to quantify their
effect on water levels.
Many attempts have been made to improve both understanding and predictive capability of bed form evolution, transition
and associated resistance under varying flow conditions. The interaction among the flow-field, bed forms and sediment
transport is quite complex and difficult to capture in simple models. A number of our recent studies have made some
noticeable efforts to numerically replicate the dune formation and evolution processes. A morphodynamic model was
been developed that successfully reproduces fluid and bed form dynamics in a coupled manner under arbitrary steady or
unsteady flow condition.
This study is the continuation of our previous efforts, in which we have attempted to replicate the flow and bed form
evolution process under a couple of synthetic (extreme) flood scenarios in the river Waal. Within the scope of this study,
at first, we have analyzed the observed data during moderate floods in the Waal. The bed level data were measured
during a moderate flood event in 1997. A vertical two-dimensional morphodynamic model with a free-surface flow
condition, which includes equilibrium, non-equilibrium bed load as well as suspended sediment transport modules, has
been used to replicate the flow and bed form evolution processes under extreme flood conditions. The boundary
condition (unit discharge and water levels) for vertical two-dimensional model was extracted from a calibrated onedimensional
hydrodynamic model SOBEK, developed for the Rhine branches. A preliminary result shows that bed forms
are present even during extreme flood condition. This study reveals the capability of a numerical model, which can be
applied to predict real-world river dunes and drag evolution with hysteresis effects in physics based manner.
File Size : 829,555 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Sediment management and morphodynamics
Date Published : 19/08/2015
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