Differing Max Velocities in RAS Mapper

[leelum1]

I’ve found that when a model is run for a different amount of simulation days (both past the peak flow), different max velocity results maps are computed, although I would expect them to be the same since the max velocities would be associated with the peak flows. So in the first screenshot the model was run for 5 days and you can see the patch of high velocity were there are velocities of over 1000. I ran the same exact model for 1 day (peak flow occurs around 16:00) and the second screenshot shows the max velocity layer from that run where the high velocities are now under 10.

When I pan through the time steps in the 5 day simulation the high velocities do not appear. Can anybody explain to me how RAS calculates these max velocities and suggest why I would be getting different results?

[cameron]

The max velocity does not always occur at the peak flow. It could occur right when a cell is starting to get wet with shallow flow or it could be due to an instability. Your first figure looks like an instability.

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