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Hi Tri,
Timestep is controlled by the amount of erosion and deposition that are being carried out - when there is more erosion (e.g. during a flood) the time step decreases.
The model has a pit filling alorithm to help with the hyraulics, and this can take a few hundred iterations to stabilise. SO I would recommend running it for 500 iterations or so.. Though there may be very little difference in the water surface between then and the beginning. Perhaps this is something you could check. Also experiment with increasing the sweep width (I mentioned this in a previous email) this should be set (approximately) to the number of cells wide the main channel is.
Tom
Dear Prof.,
I wonder if you are able to access your inbox.
I would like to ask if I want to achieve the water surface only, how many iterations the model should run. I am not sure I understand the time as well as the interation of the model.
Best regards,
--
Tri P.D. Van |
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 Tri (Tri) posted on Sunday, June 24, 2007 - 06:28 pm
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From Prof. Tom Coulthard
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Hello Tri,
On the figures, are the shaded values the water surface elevation (water surface + DEM elevation)? If so, you have water going up hill in several places!
I suspect this is due to water becoming trapped in the lower anabranch - it has no-where to drain to, so is just filling up. I think you need to have all of the DEM for this, so that this branch of the river drains through to the right hand side.
Tom
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The problem is with your DEM - you effectively create a trap for the water on the lower branch.
Otherwise, you could try increasing the init number of scans variable - Or try displaying the flow depth instead of the water surface..
Tom |
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