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Spatially Varying 2D Water Level Boundary

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I am having problems setting up a water level boundary and would be very grateful if anyone could offer some assistance.

I am trying to vary a 2D water level boundary as described in section 4.10.7 in the Tuflow manual (last paragraph on the page). I have water level time series at 5 points located along a river bank and I want Tuflow to interpolate the water level in between these points and apply it to the 2D domain.

I have digitised a 2D HX line along the edge of the river bank and created a 1d_bc file which consists of 5 points to represent the locations at which I have the hydrographs (the 1d bc points are snapped to vertices of the 2d HX line). The 2d_bc file also includes CN points to connect the 1d_bc HT to the 2d_bc HX lines. I have created a 1d nwk which simply consists of nodes to snap the 1d_bc HT points to.

I have been playing around with this for a while and keep getting various errors such as ‘ERROR – invalid channels per node count’ or similar. Basically I think that I am not setting up the 1d network correctly. The model I have is purely 2d i.e. I just want to model the flow from the river onto the floodplain using the water level boundaries. However I seem to have to create a 1d network to get Tuflow to interpolate between by hydrograph points - which I don't really want to do and this is causing problems.

Any assistance would be much appreciated, apologies if I haven’t explained the problem very well!

Thanks

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Tom

Try using a 2d QT boundary instead of a 2d HX. I think you can still use the 1d BC point to assisgn your time series and the 2d QT boundary will interpolate these time series and apply theese flows along the 2d QT boundary.

I have not try this before but at the User workshop yesterday this was mentioned. Hope it helps ans sorry if it does not work.

Regards

David

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Tom, you have set this up correctly, but you will need a "dummy" 1D channel (the ERROR message you are getting is a hangover from having to specify at least one 1D channel - will look into having this requirement removed).

The easiest way to have a dummy 1D channel is to digitise a channel in your 1d_nwk layer (anywhere you like and not snapped to any of your 1D nodes), make it a weir (W Channel_Type), set Use_Chan_Stor... to "T" and enter a value for the Width attribute. This should remove the error you are presently getting.

You may also have to assign dummy storage to the 1D nodes at your five 1D HT locations. The size of this storage does not influence the computations (because the water level is set by the HT value so no mass-balance calcs occur at the node), but it is a requirement that every 1D node has non-zero storage (so as to prevent a divide by zero). The easiest way to do this is to enter a non-zero positive value in the Length_or_ANA attribute. This will automatically create a 1D nodal area (NA) table of constant surface area. Suggest entering 99999 so as to indicate this is a dummy value. You may also have to set the Downstream Invert attribute to below your lowest HT value. I'll make a note to look into making this process somewhat less annoying!

If you continue to have problems, please get back to me. I've also made a note to expand the text in the manual to include the above.

Cheers

Bill

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Very handy to find this remedy on the Forum at 8.30PM on a Sunday night. I kind of figured it was telling me I needed channels but I was going to add one channel for each node, something I knew I'd never done in the past (because I'd always previously had a 1D channel network) and something which was going to be onerous for my 60 inflows.

Cheers

Tina

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