Damping of ship-induced primary waves in groyne fields

Numerical modelling of flow over sharp-crested rectangular contracted weir

Weirs are flow control structures that can be used for flow diversion purposes. They are classified according to section geometry or their length in the flow direction. For sharp-crested rectangular weirs, Rehbock [1] derived stage-discharge equations. In contracted geometries, streamlines curve at the approach flow leading to variations in flow...

Experimental study on bed-material transport over entrance sills at longitudinal training walls

Bed-material transport over entrance sills at longitudinal training walls

Groynes have been replaced by longitudinal training walls in an 11-km long pilot project to optimize training of the river Waal in the Netherlands. These train­ ing walls improve navigability, reduce flood levels, create a sheltered second channel with more favourable ecological conditions, and decrease the erosive action on the river bed that...

The Effect of Small Density Differences at River Confluences

Remarkable 3D flow structures occur at river confluences with small density differences due to differences in sediment concentration or temperature. We explain these by comparing numerical simulations for an idealized confluence with aerial photographs of several river confluences where color differences express the pattern of density...

On the stability of river bifurcations created by longitudinal training walls: Numerical investigation

To maintain a navigable channel and improve high-flow conveyance, engineers have recently proposed constructing longitudinal training walls as an alternative to the traditional transverse groynes. However, previous work has shown that the system of parallel channels created by a longitudinal training wall might be unstable in rivers with...

Flow patterns around longitudinal training dams

With the intention to reduce the negative  effects of ongoing bed erosion, as well as to  improve several other river functions such as  protection against floods, provision of safe and  efficient navigation and ecology, a ‘pilot project  longitudinal training dams’ was initiated. The  training dams have recently...

The effect of small density differences at large confluences

Confluences are fascinating elements in river systems. The merging of tributary rivers produces complex hydrodynamics that can play an important role in sediment transport problems, ecological studies or the routing of a pollutant. If the two merging rivers originate from different regions they can have different characteristics. One such a...

Sediment transport over sills at longitudinal training dams with unaligned main flow

Longitudinal training dams (LTDs) are  constructed in the River Waal in the  Netherlands. They are aligned parallel to the  river shore and divide the river into a main and  side channel. The existing groynes are  removed yielding more discharge capacity at  high flows. The side channel creates possibly a ...

Riverbank protection removal to enhance habitat diversity through bar formation

Over the past centuries natural river banks have been transformed into banks with artificial revetments or sheet piles to protect them from erosion. Important river features for flora and fauna have disappeared and the ecological quality of the river reduced dramatically. Recently, the importance of the ecological function of rivers has been...

Experimental and numerical evidence for intrinsic nonmigrating bars in alluvial channels

Experimental and numerical evidence for intrinsic nonmigrating bars in alluvial channels

Alternate bars in straight alluvial channels are migrating or nonmigrating. The currently accepted view is that they are nonmigrating if the width-to-depth ratio is at the value of resonance or if the bars are forced by a persistent local perturbation. We carried out 2-D numerical computations and a long-duration mobile-bed flume experiment to...