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I have set up a triple coupling model to evaluate the sediment transport characteristics in coastal environment for a site that includes a couple of tidal channels. The general magnitude and pattern on the tidal flat seems reasonable using Bijker or Soulsby-van rijn equations. However,
It appears that that these wave-induced sand transport formula overestimate the bedload transport in the river/tidal channel (see figure). I have tried to run the model without the wave effect and have similar finding. Does anyone have encountered similar issues or know any paper that I can look up?

Thanks.

Edwin

Hi,

From this image it is impossible to see how big the bedload trasnport is. However, the erosion deposition suggests that the model is smearing out the slopes in the bathymetry (erosion on the sides of the channel and in particular on any outcrops in the channel that then causes deposition in the deeper parts of the channel. This is to be expected unless you proved differences in grain size/ erodibility. The model is correcting for the differences between reality and the model parameters.

Take the resulting bathymetry from this run as the initial bathymetry for a new run. This should have less erosion/deposition around the edges.

Something else I can;t see from the figure. Have you included enough of the inlet/estuary for the model to allow for the tidal flow in and out of the inlet to maintain the tidal channel. If the inlet/estuary is too small the tidal channel will infill.

Note that in general, the coupled system tends to deepen tidal channels too much.

Hi Michel,

Thanks. I have run the model for a couple of days and used that resulting bathymetry as the initial condition. I will let the model run a bit longer and use that bathymetry as initial condition.

The problem that I noticed is that continuous deposition of sediment from one node to the neighbouring node. Due to the coarse mesh length (about 25 m) and relatively flat region, the slope or slide effect have limited impact on sediment transport and I ended up getting various localized high spots on the flat building up. This resulted in tidal flows that do not match the field observation.

I didn't show the entire mesh. The model extends another 35 km inland.

Edwin