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* HPC is an explicit finite volume scheme which is mass conserving to numerical precision.
* The HPC scheme uses 4th order time integration, which means the simulation completes in fewer time steps compared to 1st or 2nd order time integration schemes.
==I am running existing and developed case and see differences away from the model changes. Why?==
Any geometry changes between models, no matter how small, will affect results, sometimes to a greater degree than that occurring in the area of change. For example, a few millimetres increase in water level can determine whether or not overtopping of an embankment occurs, and this can consequently cause even larger impacts on the downstream side of the embankment. Furthermore, these changes can be compounded by subsequent changes in timestepping when using the adaptive timestepping option (the default in TUFLOW HPC), especially at fringes of the flood extent, where cells are constantly wetting and drying. Modellers and reviewers should be judicious and pragmatic when assessing which impacts are real and which are numerical noise.<br>
Suggestions:
* Use the latest TUFLOW HPC release available.
* Check that cell size is appropriate to the modelling exercise.
* Use depth varying manning's n (lower manning's n for shallow water depths), specifically for direct rainfall models.
* Set appropriate <font color="blue"><tt>Map Cutoff Depth </tt></font> for the modelling task. e.g. direct rainfall models might have higher values to avoid undesirable noise on the wet/dry interface.
==Why seemingly identical models can produce non-identical results?==
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