User Forum of Software BASEMENT

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Registered: 2024-03-07

Posts: 1

Modelling of bridges with hq-relation

Hello,

I am using Basement v2.8.2 to carry out hydraulic analyses on a stream with a trapezoidal cross-section. I am currently trying to integrate a bridge into my model. For this purpose, I have cut out the area of the bridge from my existing mesh and defined StringDefs at the upper and lower edge of the cutout over the entire width of the watercourse. The bridge is to be derived later using an hq-relation derived from the bridge geometry. I am currently using an hq-relation that I obtained from a reference simulation without bridges. The results of the reference simulation and the hq-relation should therefore be similar. Unfortunately, this is not the case. I always get the following message as soon as the water level rises and new elements along the embankments get wet:

WARNING -> Mass conservation is not guaranteed! Negative water depth in element
   #27812 (slope = 0.705888).
       missing volume to compensate the overdraft: 0.00276294

The problem does not occur if I define the stringdef only via the channel bottom, but this changes the simulation results significantly compared to the reference simulation.

I have already increased the minumum_water_depth from 0.05 to 0.1 (Hydraulics - Parameters), which has reduced the number of messages, but has not solved the problem.

Do you have any tips on what I need to change to correct the error?

Thank you very much!