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23/03/2011 12:11:39

I have created an existing model which is running successfully, but shows significant out of bank flow. I am now trying to model a flood relief / bifurcation channel that will split from the reach before rejoining further downstream. Can anyone provide guidance on the best way to model this? Is an abstraction unit necessary? I have tried modelling the channel using a spill unit connected to a junction, but the model runs dry in a steady run (error E1023). I have attached the .dat file. Thanks very much for any help. Charles


24/03/2011 07:59:32

Hi Charles Looking at your model, it appears that the invert of the bypass channel is significantly lower than that of the main channel, this is why the channel is going dry. Your schematisation looks sensible and similar to that I've used in the past for a high level bypass. I would investigate whether the model is representative of the river as invert levels suggest that the majority of flow is carried by the bypass channel, is this correct? If you are happy with the representation, then the easiest way to keep the channel "wet" is to add a sweetener flow to the head of the dry channel and an abstraction (ABS) downstream to remove the flow. If you are happy with this arrangement, ABS units can be used with logical rules so that flow is only added when require (e.g. at low flow). Hope this helps. Adam


24/03/2011 10:10:06

Thanks for your help Adam, I tweaked the schematisation and added a 'sweetener' flow - now working fine.

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