HR: 16:45h
AN: H54A-04 [Abstracts]
TI: Experiences in 2D Numerical Modeling of River Bifurcations
AU: Mosselman, E
EM: erik.mosselman@wldelft.nl
AF: WL | Delft Hydraulics, P.O. Box 177, Delft, 2600 MH, Netherlands
AU: Mosselman, E
EM: erik.mosselman@wldelft.nl
AF: Delft University of Technology, Stevinweg 1, Delft, 2628 CN, Netherlands
AU: * Sloff, K
EM: kees.sloff@wldelft.nl
AF: WL | Delft Hydraulics, P.O. Box 177, Delft, 2600 MH, Netherlands
AU: * Sloff, K
EM: kees.sloff@wldelft.nl
AF: Delft University of Technology, Stevinweg 1, Delft, 2628 CN, Netherlands
AU: Jagers, B
EM: bert.jagers@wldelft.nl
AF: WL | Delft Hydraulics, P.O. Box 177, Delft, 2600 MH, Netherlands
AB:
We present our experiences with morphological computations using a 2D depth-averaged finite-difference model
for river bifurcations. These computations reveal new details of the importance of a proper computational gid and
a proper representation of transport processes of graded sediment. The basic structure of the computational
grid, irrespective of fine-tuning, determines the possibility to reproduce flow separation at sharp bank angles as
well as the errors due to grid distortion in the key area of the bifurcation. Inclusion of floodplain flows requires that
the grid at the bifurcation be split into subgrids with corresponding domain decomposition techniques to solve
the equations. Application to the Rhine bifurcation at Pannerden casts doubt on the common wisdom that the
active-layer thickness for graded sediment is equal to half the dune height, or somewhat larger due to sporadic
deeper troughs. A larger active layer must be adopted on larger time scales, because the thickness depends on
all kinds of local bed level fluctuations generated by discharge variations. Examples are the sand waves
generated by fast changes due to the flooding of floodplains, and the stage-dependent variations of the
transverse bed slope in river bends.
DE: 0545 Modeling (4255)
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 1862 Sediment transport (4558)
SC: Hydrology [H]
MN: 2007 Fall Meeting