Ground Level at Couplings to Nodes

When coupling nodes from the 1D network to 2D overland, one ground level is specified for the network and another one is specified in the 2D domain file. These two values should normally be consistent, but due to differences of source data sets and accuracies, some discrepancies may arise.

When coupling manholes / junctions, their ground level is automatically adjusted during the simulation, and replaced by the ground level defined in the 2D domain, in order to ensure consistency and avoid volume errors. Modified ground levels will be reported in the simulation log file. But this can lead to errors when starting the simulation, especially when the discrepancy is high: in that case, it can happen that the modified ground level in the node becomes lower than its invert level, which is not allowed and therefore the simulation will not start. For this reason, it is worth checking the consistency of ground levels in the network and in the 2D domain.

This can e.g. be achieved using user-defined columns, like this:

• Create a new user-defined column in the nodes editor to store the ground level from the 2D domain file
• Use the Interpolation and Assignment Tool to assign the ground level from the 2D domain file to this new column
• Create another user-defined column in the nodes editor and use the 'Field calculator' to compute the difference between the ground level defined in the node and the ground level assigned from the 2D domain file
• You can finally use this column with differences to sort the nodes by differences, select or zoom in to troublesome nodes, show differences as labels on the map, etc.

Note

When the 'Location in 2D domain' of the coupling is defined by a polygon, the node is coupled to all elements / cells from the 2D domain which have their centroid within the polygon. The resulting ground level obtained from the 2D domain (and applied to the node) is then the average level from all the coupled elements / cells.