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Numerical modeling of hydrodynamic and sediment siltation due to typhoon in estuary channel regulation

Zhao H., Zhang Q., Xie M.

Polish Maritime Research

2015

S 1

61--66

Oujiang Estuary is a complex tidal estuary with many channels and shoals in the East China Sea, which was affected by typhoon frequently. The navigation channel of Wenzhou Port is located in the north branch of Oujiang Estuary, which happened serious sediment siltation in many times due to typhoon impact. The regulation is considered to decrease siltaion of the channel and protect shoals as well. According to the site survey data, the mathematic model is established and validated, which simulates the hydrodynamic, sediment transport and channel siltation due to typhoon in Oujiang Estuary. The channel regulation scenario is studied by the model simulation after analysis of the silation character. It indicates that the high concentration sediment from shoals north of channel is main sediment source caused siltation in the channel, which can be prevented into the channel by the regulation scenario and decrease siltation efficiently.

Wpływ regulacji koryta na warunki sedymentacji osadów na równinie zalewowej dolnego Dunajca

Liro M.

Przegląd Geologiczny

2012

Vol. 60, nr 7

380--386

In the last century the Dunajec channel in its lower river course was considerably transformed due to channelization works. The former multi-thread river channel was replaced by a single one, resulting in abandonment of side channels. Groynes were constructed on both main and side channel. Quick filling up of the inter-groyne basins reduced channel width and capacity. In the study area, a side channel with groynes was abandoned and filled up. The aim of this study was to reconstruct the rate and depositional conditions of the sediments infilling the abandoned channel. These sediments are 215-222 cm thick and were deposited at an average rate of 5-5.2 cm/year. Their sedimentary environment was inferred based on a C/M diagram. The depositional conditions in the abandoned channel were determined by two major factors: distance to the active channel and difference in elevation between depositional surface and active channel. Close to the active channel, 61% of sediment was deposited from suspension and 39% by traction current. At a distance of 200 m to the active channel, 100% of sediment was deposited from suspension, with 25% falling from pelagic suspension. At an early stage of infilling of abandoned channel, the depositional flows are more energetic and the deposition rate is higher than in the later stage. The investigated sediments are an example of accumulation induced by channelization works. The spatial distribution of these fine-grained, quickly deposited sediments is determined by the course of the abandoned channel.