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Direct Rainfall (Rain on Grid) Modelling Guidance: Difference between revisions

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== What is the best approach for modelling buildings in rain on grid model? ==
There are numerous different industry standard ways to represent buildings in a direct rainfall model. <u>[https://downloads.tuflow.com/_archive/Australian_Rainfall_Runoff_Project_15_Subproject_report_buildings_final.pdf | Australian Rainfall and Runoff Guideline, Project 15 (Representation of buildings in 2D Numerical Flood Models)]</u> discusses some of the available options. Common TUFLOw modelling approaches are summarised below:
# Using depth varying Manning's n, apply a low value (n = 0.02) at shallow depth ( d < 0.03m) and a high value (>0.1 3) to the building areafootprint:
#* This is a very common and easy to implement option. The low Manning's n aims to mimic the quick runoff response associated with drainage from the roof. The higher Manning's n aims to represent the losses associated with deeper floodwater impacting the side of teh house.
#* This is a very common and quick to setup approach that significantly slows down water passing through the buildings.
# Raise the building footprint elevation withusing TUFLOW's topographic updatesupdate features:
#* Raising elevationthe eliminatesmodel watertopography creates an obstruction to flow. It prevents floodwater from passing through buildings (as is the buildingscase with the Manning's n approach), however as rainfall is assigned to all active cells, it will be falling on top of the buildings and from there to the ground.
#* With bigger rainfall, this might create a waterfall like output around the buildings.
# Exclude buildings from rainfall polygon:
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