HPC Impact Assessment Guidance: Difference between revisions

If the modeller suspects the model is producing artificial impacts, the base case and design case models should be run with a reduced Control Number Factor. To reduce the likelihood of varying timesteps in the base case and design case model runs, applying a CN factor of 0.8 is recommended for all model runs in a Flood Impact Assessment. It would not be unreasonable to reduce this factor as low as 0.5 if the modelled results presented signs of artificially modelled impacts. To define the CN Factor the following command can be implemented in the TUFLOW Control File (TCF).<br>

 

 

If there is no difference observed in the modelled impacts, as shown below, when running the models at a CN factor of 0.8 and 0.5, then it is unlikely that the timestep is the cause of any artificial impacts.