Direct Rainfall (Rain on Grid) Modelling Guidance: Difference between revisions
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:::* Retain the model design described above, though post process the results before reporting. Either delete the model result where there is overlap with the building footprint, or overlay building footprint polygon objects over/above the result dataset in the GIS Map Layout (hiding the flood model result within the building footprints).
:::* Exclude buildings from the rainfall polygon: This removes the rainfall from the model that would otherwise fall on the buildings. This approach will underestimate the amount of rainfall entering the model. If the collective building footprint area is negligible in comparison to the entire model, this approach may be acceptable.
:::* Exclude buildings from the rainfall polygon and suppliment the exclusion using <font color="blue"><tt>Read GIS SA RF</tt></font> inflow boundaries. Digitise a 2d_sa_rf polygon for each building (with a buffer of one of more cell length) where the building footprint has been excluded from the direct rainfall region. The sa_rf input will convert the input rainfall hyetograph into flow volume, depositing the water to the lowest 2D cell withni the 2d_sa_rf regions (ie. on the ground surrounding the house). Refer to TUFLOW <u>[[TUFLOW_Example_Models#Boundary_Condition_Options | example model EG03_005.tcf]]</u> for a demonstration of this inflow boundary condition option.
#* Most rainfall that falls on buildings collects on the roof and through gutters and downpipes finds its way directly into the sub-surface drainage system. In such case, <font color="blue"><tt>Read GIS SA RF PITS</tt></font> command can be used to feed the water directly into the pits. Every 2d_sa_rf polygon needs to have at least one 1D pit within to automatically deposit the flow. If multiple pits are present, the flow from the polygon splits equally.
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