Direct Rainfall (Rain on Grid) Modelling Guidance - Revision history

Anne.Kolega: /* What is the best approach for modelling buildings in rain on grid model? */ i.e.

2026-04-02T01:48:20Z

What is the best approach for modelling buildings in rain on grid model?: i.e.

← Older revision		Revision as of 11:48, 2 April 2026
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	:::* Retain the model design described above, with subsequent post-processing of the mapped results before reporting. Either, delete the model result where there is overlap with the building footprint, or overlay the building footprint polygon objects over/above the result dataset in the GIS Map Layout (hiding the flood model result within the building footprints).		:::* Retain the model design described above, with subsequent post-processing of the mapped results before reporting. Either, delete the model result where there is overlap with the building footprint, or overlay the 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 under-estimate 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: This removes the rainfall from the model that would otherwise fall on the buildings. This approach will under-estimate 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 represent the rainfall that would be falling on the building using <font color="blue"><tt>Read GIS SA RF</tt></font> inflow boundaries. To do this, digitise a 2d_sa_rf polygon for each building (with a buffer of one of more 2D cells) where the building footprint has been excluded from the direct rainfall region. The 2d_sa_rf input will convert the input rainfall hyetograph to flow, deposited initially on the lowest 2D cell, then for subsequent timesteps distributed over all wet cells, within the 2d_sa_rf regions (ie. on the ground surrounding the building). Refer to TUFLOW <u>[[TUFLOW_Example_Models#Boundary_Condition_Options \| Example model EG03_014.tcf]]</u> for a demonstration of this inflow boundary condition configuration.		:::* Exclude buildings from the rainfall polygon and represent the rainfall that would be falling on the building using <font color="blue"><tt>Read GIS SA RF</tt></font> inflow boundaries. To do this, digitise a 2d_sa_rf polygon for each building (with a buffer of one of more 2D cells) where the building footprint has been excluded from the direct rainfall region. The 2d_sa_rf input will convert the input rainfall hyetograph to flow, deposited initially on the lowest 2D cell, then for subsequent timesteps distributed over all wet cells, within the 2d_sa_rf regions (i.e. on the ground surrounding the building). Refer to TUFLOW <u>[[TUFLOW_Example_Models#Boundary_Condition_Options \| Example model EG03_014.tcf]]</u> for a demonstration of this inflow boundary condition configuration.
	:::* Exclude buildings from the rainfall polygon and represent the rainfall that would fall on the building using <font color="blue"><tt>Read GIS SA RF PITS</tt></font> inflow boundaries. This approach is similar to the previous method, although instead of directing the inflow to the ground surrounding the building, it is directed into the sub-surface drainage (underground pipe) system. To implement this approach every 2d_sa_rf polygon must encompass at least one 1D pit. If multiple 1D pits are within a single 2d_sa_rf region, the flow from the polygon is split equally between the 1D pits. The pits can be snapped to a 1D node, connected via the pit-search distance or via an x-connector, to allow captured by the pit to enter a 1D representation of the sub-surface drainage system. Refer to TUFLOW <u>[[TUFLOW_Example_Models#Multiple_Domain_Model_Design \| Example model EG15_000.tcf]]</u> for a demonstration of this inflow boundary condition option.		:::* Exclude buildings from the rainfall polygon and represent the rainfall that would fall on the building using <font color="blue"><tt>Read GIS SA RF PITS</tt></font> inflow boundaries. This approach is similar to the previous method, although instead of directing the inflow to the ground surrounding the building, it is directed into the sub-surface drainage (underground pipe) system. To implement this approach every 2d_sa_rf polygon must encompass at least one 1D pit. If multiple 1D pits are within a single 2d_sa_rf region, the flow from the polygon is split equally between the 1D pits. The pits can be snapped to a 1D node, connected via the pit-search distance or via an x-connector, to allow captured by the pit to enter a 1D representation of the sub-surface drainage system. Refer to TUFLOW <u>[[TUFLOW_Example_Models#Multiple_Domain_Model_Design \| Example model EG15_000.tcf]]</u> for a demonstration of this inflow boundary condition option.

Anne.Kolega: /* What is the best approach for modelling buildings in rain on grid model? */ e.g.

2026-04-01T22:18:02Z

What is the best approach for modelling buildings in rain on grid model?: e.g.

← Older revision		Revision as of 08:18, 2 April 2026
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	# Using depth-varying Manning's ''n'' over the area of the building footprint, with the application of a lower value (''n'' = 0.02) at shallow depths (d < 0.03m) and a higher value (''n'' > 0.3) at a more significant depths (d > 0.1m):		# Using depth-varying Manning's ''n'' over the area of the building footprint, with the application of a lower value (''n'' = 0.02) at shallow depths (d < 0.03m) and a higher value (''n'' > 0.3) at a more significant depths (d > 0.1m):
	#* This is a very common and easy to implement option. The low Manning's ''n'' value aims to mimic the quick runoff response associated with drainage from the roof. The higher Manning's ''n'' value aims to represent the losses associated with deeper floodwater impacting the side of the building.		#* This is a very common and easy to implement option. The low Manning's ''n'' value aims to mimic the quick runoff response associated with drainage from the roof. The higher Manning's ''n'' value aims to represent the losses associated with deeper floodwater impacting the side of the building.
	# Raise the building footprint elevation using TUFLOW's topographic update features (eg. <font color="blue"><tt>Read GIS Z Shape</tt></font>):		# Raise the building footprint elevation using TUFLOW's topographic update features (e.g. <font color="blue"><tt>Read GIS Z Shape</tt></font>):
	#* Raising the model topography creates an obstruction to flow. It prevents floodwater from passing through buildings (as is the case with the Manning's ''n'' approach)		#* Raising the model topography creates an obstruction to flow. It prevents floodwater from passing through buildings (as is the case with the Manning's ''n'' approach)
	#* The application of rainfall on top of the building can however produce some undesirable results that require further consideration. Those being, water falling from the building roof to the ground can require a reduced model timestep to maintain model stability which can slow the simulation speed. Also, depending on the Map Cutoff Depth assumptions, water may be present in the results on the building rooftops. This may not be desired for mapping purposes. There are a variety of options available to resolve these issues:		#* The application of rainfall on top of the building can however produce some undesirable results that require further consideration. Those being, water falling from the building roof to the ground can require a reduced model timestep to maintain model stability which can slow the simulation speed. Also, depending on the Map Cutoff Depth assumptions, water may be present in the results on the building rooftops. This may not be desired for mapping purposes. There are a variety of options available to resolve these issues:

Abigail.lillo: /* What is the best approach for modelling buildings in rain on grid model? */

2025-03-13T05:35:45Z

What is the best approach for modelling buildings in rain on grid model?

← Older revision		Revision as of 15:35, 13 March 2025
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	:::* Retain the model design described above, with subsequent post-processing of the mapped results before reporting. Either, delete the model result where there is overlap with the building footprint, or overlay the building footprint polygon objects over/above the result dataset in the GIS Map Layout (hiding the flood model result within the building footprints).		:::* Retain the model design described above, with subsequent post-processing of the mapped results before reporting. Either, delete the model result where there is overlap with the building footprint, or overlay the 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 under-estimate 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: This removes the rainfall from the model that would otherwise fall on the buildings. This approach will under-estimate 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 represent the rainfall that would be falling on the building using <font color="blue"><tt>Read GIS SA RF</tt></font> inflow boundaries. To do this, digitise a 2d_sa_rf polygon for each building (with a buffer of one of more 2D cells) where the building footprint has been excluded from the direct rainfall region. The 2d_sa_rf input will convert the input rainfall hyetograph to flow, deposited initially on the lowest 2D cell, then for subsequent timesteps distributed over all wet cells, within the 2d_sa_rf regions (ie. on the ground surrounding the building). 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~~.		:::* Exclude buildings from the rainfall polygon and represent the rainfall that would be falling on the building using <font color="blue"><tt>Read GIS SA RF</tt></font> inflow boundaries. To do this, digitise a 2d_sa_rf polygon for each building (with a buffer of one of more 2D cells) where the building footprint has been excluded from the direct rainfall region. The 2d_sa_rf input will convert the input rainfall hyetograph to flow, deposited initially on the lowest 2D cell, then for subsequent timesteps distributed over all wet cells, within the 2d_sa_rf regions (ie. on the ground surrounding the building). Refer to TUFLOW <u>[[TUFLOW_Example_Models#Boundary_Condition_Options \| Example model EG03_014.tcf]]</u> for a demonstration of this inflow boundary condition configuration.
	:::* Exclude buildings from the rainfall polygon and represent the rainfall that would fall on the building using <font color="blue"><tt>Read GIS SA RF PITS</tt></font> inflow boundaries. This approach is similar to the previous method, although instead of directing the inflow to the ground surrounding the building, it is directed into the sub-surface drainage (underground pipe) system. To implement this approach every 2d_sa_rf polygon must encompass at least one 1D pit. If multiple 1D pits are within a single 2d_sa_rf region, the flow from the polygon is split equally between the 1D pits. The pits can be snapped to a 1D node, connected via the pit-search distance or via an x-connector, to allow captured by the pit to enter a 1D representation of the sub-surface drainage system. Refer to TUFLOW <u>[[TUFLOW_Example_Models#Multiple_Domain_Model_Design \| Example model EG15_000.tcf]]</u> for a demonstration of this inflow boundary condition option.		:::* Exclude buildings from the rainfall polygon and represent the rainfall that would fall on the building using <font color="blue"><tt>Read GIS SA RF PITS</tt></font> inflow boundaries. This approach is similar to the previous method, although instead of directing the inflow to the ground surrounding the building, it is directed into the sub-surface drainage (underground pipe) system. To implement this approach every 2d_sa_rf polygon must encompass at least one 1D pit. If multiple 1D pits are within a single 2d_sa_rf region, the flow from the polygon is split equally between the 1D pits. The pits can be snapped to a 1D node, connected via the pit-search distance or via an x-connector, to allow captured by the pit to enter a 1D representation of the sub-surface drainage system. Refer to TUFLOW <u>[[TUFLOW_Example_Models#Multiple_Domain_Model_Design \| Example model EG15_000.tcf]]</u> for a demonstration of this inflow boundary condition option.

Pavlina Monhartova: /* What is the best approach for modelling buildings in rain on grid model? */

2024-08-23T03:16:53Z

What is the best approach for modelling buildings in rain on grid model?

← Older revision		Revision as of 13:16, 23 August 2024
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	:::* Exclude buildings from the rainfall polygon: This removes the rainfall from the model that would otherwise fall on the buildings. This approach will under-estimate 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: This removes the rainfall from the model that would otherwise fall on the buildings. This approach will under-estimate 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 represent the rainfall that would be falling on the building using <font color="blue"><tt>Read GIS SA RF</tt></font> inflow boundaries. To do this, digitise a 2d_sa_rf polygon for each building (with a buffer of one of more 2D cells) where the building footprint has been excluded from the direct rainfall region. The 2d_sa_rf input will convert the input rainfall hyetograph to flow, deposited initially on the lowest 2D cell, then for subsequent timesteps distributed over all wet cells, within the 2d_sa_rf regions (ie. on the ground surrounding the building). 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.		:::* Exclude buildings from the rainfall polygon and represent the rainfall that would be falling on the building using <font color="blue"><tt>Read GIS SA RF</tt></font> inflow boundaries. To do this, digitise a 2d_sa_rf polygon for each building (with a buffer of one of more 2D cells) where the building footprint has been excluded from the direct rainfall region. The 2d_sa_rf input will convert the input rainfall hyetograph to flow, deposited initially on the lowest 2D cell, then for subsequent timesteps distributed over all wet cells, within the 2d_sa_rf regions (ie. on the ground surrounding the building). 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.
	:::* Exclude buildings from the rainfall polygon and represent the rainfall that would fall on the building using <font color="blue"><tt>Read GIS SA RF PITS</tt></font> inflow boundaries. This approach is similar to the previous method, although instead of directing the inflow to the ground surrounding the building, it is directed into the sub-surface drainage (underground pipe) system. To implement this approach every 2d_sa_rf polygon must encompass at least one 1D pit. If multiple 1D pits are within a single 2d_sa_rf region, the flow from the polygon is split equally between the 1D pits. The pits can be snapped to a 1D node, connected via the pit-search distance or via an x-connector, to allow captured by the pit to enter a 1D representation of the sub-surface drainage system.		:::* Exclude buildings from the rainfall polygon and represent the rainfall that would fall on the building using <font color="blue"><tt>Read GIS SA RF PITS</tt></font> inflow boundaries. This approach is similar to the previous method, although instead of directing the inflow to the ground surrounding the building, it is directed into the sub-surface drainage (underground pipe) system. To implement this approach every 2d_sa_rf polygon must encompass at least one 1D pit. If multiple 1D pits are within a single 2d_sa_rf region, the flow from the polygon is split equally between the 1D pits. The pits can be snapped to a 1D node, connected via the pit-search distance or via an x-connector, to allow captured by the pit to enter a 1D representation of the sub-surface drainage system. Refer to TUFLOW <u>[[TUFLOW_Example_Models#Multiple_Domain_Model_Design \| Example model EG15_000.tcf]]</u> for a demonstration of this inflow boundary condition option.

	== What is the recommended cell wet/dry depth for direct rainfall models? ==		== What is the recommended cell wet/dry depth for direct rainfall models? ==

Abigail.lillo: /* What is the best approach for modelling buildings in rain on grid model? */

2024-08-13T11:45:18Z

What is the best approach for modelling buildings in rain on grid model?

← Older revision		Revision as of 21:45, 13 August 2024
Line 57:		Line 57:
	:::* Exclude buildings from the rainfall polygon: This removes the rainfall from the model that would otherwise fall on the buildings. This approach will under-estimate 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: This removes the rainfall from the model that would otherwise fall on the buildings. This approach will under-estimate 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 represent the rainfall that would be falling on the building using <font color="blue"><tt>Read GIS SA RF</tt></font> inflow boundaries. To do this, digitise a 2d_sa_rf polygon for each building (with a buffer of one of more 2D cells) where the building footprint has been excluded from the direct rainfall region. The 2d_sa_rf input will convert the input rainfall hyetograph to flow, deposited initially on the lowest 2D cell, then for subsequent timesteps distributed over all wet cells, within the 2d_sa_rf regions (ie. on the ground surrounding the building). 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.		:::* Exclude buildings from the rainfall polygon and represent the rainfall that would be falling on the building using <font color="blue"><tt>Read GIS SA RF</tt></font> inflow boundaries. To do this, digitise a 2d_sa_rf polygon for each building (with a buffer of one of more 2D cells) where the building footprint has been excluded from the direct rainfall region. The 2d_sa_rf input will convert the input rainfall hyetograph to flow, deposited initially on the lowest 2D cell, then for subsequent timesteps distributed over all wet cells, within the 2d_sa_rf regions (ie. on the ground surrounding the building). 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.
	:::* Exclude buildings from the rainfall polygon and represent the rainfall that would fall on the building using <font color="blue"><tt>Read GIS SA RF PITS</tt></font> inflow boundaries. This approach is similar to the previous method, although instead of directing the inflow to the ground surrounding the building, it is directed into the sub-surface drainage (underground pipe) system. To implement this approach every 2d_sa_rf polygon must encompass at least one 1D pit. If multiple 1D pits are within a single ~~2d_rf_sa~~ region, the flow from the polygon is split equally between the 1D pits. The pits can be snapped to a 1D node, connected via the pit-search distance or via an x-connector, to allow captured by the pit to enter a 1D representation of the sub-surface drainage system.		:::* Exclude buildings from the rainfall polygon and represent the rainfall that would fall on the building using <font color="blue"><tt>Read GIS SA RF PITS</tt></font> inflow boundaries. This approach is similar to the previous method, although instead of directing the inflow to the ground surrounding the building, it is directed into the sub-surface drainage (underground pipe) system. To implement this approach every 2d_sa_rf polygon must encompass at least one 1D pit. If multiple 1D pits are within a single 2d_sa_rf region, the flow from the polygon is split equally between the 1D pits. The pits can be snapped to a 1D node, connected via the pit-search distance or via an x-connector, to allow captured by the pit to enter a 1D representation of the sub-surface drainage system.

	== What is the recommended cell wet/dry depth for direct rainfall models? ==		== What is the recommended cell wet/dry depth for direct rainfall models? ==

Pavlina Monhartova: /* Rainfall Losses and Soil Infiltration */

2024-08-08T01:26:11Z

Rainfall Losses and Soil Infiltration

← Older revision		Revision as of 11:26, 8 August 2024
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	</ol>		</ol>

	Similarly, a variety of soil infiltration options are supported. The available options include, Initial / Continuing Infiltration, the Horton Infiltration method and the Green-Ampt Infiltration method. The following link provides ~~some future~~ discussion on the Green-Ampt method.		Similarly, a variety of soil infiltration options are supported. The available options include, Initial / Continuing Infiltration, the Horton Infiltration method and the Green-Ampt Infiltration method. The following link provides further discussion on the Green-Ampt method.
	* <u>[[Green-Ampt Infiltration Parameters \| Green-Ampt Infiltration Parameters]]</u>		* <u>[[Green-Ampt Infiltration Parameters \| Green-Ampt Infiltration Parameters]]</u>


	= Common Questions Answered (FAQ)=		= Common Questions Answered (FAQ)=

Abigail.lillo at 05:44, 17 July 2024

2024-07-17T05:44:29Z

← Older revision		Revision as of 15:44, 17 July 2024
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	* The single precision version of TUFLOW is recommended for direct rainfall models using HPC.		* The single precision version of TUFLOW is recommended for direct rainfall models using HPC.
	* The double precision version of TUFLOW is recommended for direct rainfall models using TUFLOW Classic.		* The double precision version of TUFLOW is recommended for direct rainfall models using TUFLOW Classic.

			= Rainfall Boundary Conditions=
			The following links provide boundary condition guidance for applying direct rainfall:
			* [[TUFLOW Rainfall Control File Examples]]
			* [[TUFLOW NetCDF Rainfall Format]]

	= Rainfall Losses and Soil Infiltration=		= Rainfall Losses and Soil Infiltration=

Abigail.lillo at 04:54, 10 January 2024

2024-01-10T04:54:53Z

← Older revision		Revision as of 14:54, 10 January 2024
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	= Direct Rainfall =		= Direct Rainfall =
	Please see <u>[https://www.tuflow.com/library/webinars/#feb2021_direct_rainfall Direct Rainfall (Rain on Grid) Webinar]</u>.<br>		Please see <u>[https://www.tuflow.com/library/webinars/#feb2021_direct_rainfall Direct Rainfall (Rain on Grid) Webinar]</u>.<br>

	<br>
			= TUFLOW Executable =
			* The single precision version of TUFLOW is recommended for direct rainfall models using HPC.
			* The double precision version of TUFLOW is recommended for direct rainfall models using TUFLOW Classic.

	= Rainfall Losses and Soil Infiltration=		= Rainfall Losses and Soil Infiltration=

Abigail.lillo at 02:01, 10 January 2024

2024-01-10T02:01:03Z

← Older revision		Revision as of 12:01, 10 January 2024
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	:::* Exclude buildings from the rainfall polygon and represent the rainfall that would be falling on the building using <font color="blue"><tt>Read GIS SA RF</tt></font> inflow boundaries. To do this, digitise a 2d_sa_rf polygon for each building (with a buffer of one of more 2D cells) where the building footprint has been excluded from the direct rainfall region. The 2d_sa_rf input will convert the input rainfall hyetograph to flow, deposited initially on the lowest 2D cell, then for subsequent timesteps distributed over all wet cells, within the 2d_sa_rf regions (ie. on the ground surrounding the building). 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.		:::* Exclude buildings from the rainfall polygon and represent the rainfall that would be falling on the building using <font color="blue"><tt>Read GIS SA RF</tt></font> inflow boundaries. To do this, digitise a 2d_sa_rf polygon for each building (with a buffer of one of more 2D cells) where the building footprint has been excluded from the direct rainfall region. The 2d_sa_rf input will convert the input rainfall hyetograph to flow, deposited initially on the lowest 2D cell, then for subsequent timesteps distributed over all wet cells, within the 2d_sa_rf regions (ie. on the ground surrounding the building). 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.
	:::* Exclude buildings from the rainfall polygon and represent the rainfall that would fall on the building using <font color="blue"><tt>Read GIS SA RF PITS</tt></font> inflow boundaries. This approach is similar to the previous method, although instead of directing the inflow to the ground surrounding the building, it is directed into the sub-surface drainage (underground pipe) system. To implement this approach every 2d_sa_rf polygon must encompass at least one 1D pit. If multiple 1D pits are within a single 2d_rf_sa region, the flow from the polygon is split equally between the 1D pits. The pits can be snapped to a 1D node, connected via the pit-search distance or via an x-connector, to allow captured by the pit to enter a 1D representation of the sub-surface drainage system.		:::* Exclude buildings from the rainfall polygon and represent the rainfall that would fall on the building using <font color="blue"><tt>Read GIS SA RF PITS</tt></font> inflow boundaries. This approach is similar to the previous method, although instead of directing the inflow to the ground surrounding the building, it is directed into the sub-surface drainage (underground pipe) system. To implement this approach every 2d_sa_rf polygon must encompass at least one 1D pit. If multiple 1D pits are within a single 2d_rf_sa region, the flow from the polygon is split equally between the 1D pits. The pits can be snapped to a 1D node, connected via the pit-search distance or via an x-connector, to allow captured by the pit to enter a 1D representation of the sub-surface drainage system.

			== What is the recommended cell wet/dry depth for direct rainfall models? ==
			For models with SGS turned off, a reduced cell wet/dry depth of 0.0002m (0.0007ft) is recommended due to the substantial amount of shallow sheet flow. <br>
			If SGS is turned on, a reduced cell wet/dry depth is not necessary because the cell wet/dry calculation conducted on the SGS storage curve captures a greater change in depth. In the case, the default of 0.002m (0.007ft) may be sufficient; however, it should be reviewed and selected according to the magnitude of flooding depths.

	<br>		<br>

Tuflowduncan: /* What is the best approach for modelling buildings in rain on grid model? */

2023-12-20T14:40:42Z

What is the best approach for modelling buildings in rain on grid model?

← Older revision		Revision as of 00:40, 21 December 2023
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	#* Raising the model topography creates an obstruction to flow. It prevents floodwater from passing through buildings (as is the case with the Manning's ''n'' approach)		#* Raising the model topography creates an obstruction to flow. It prevents floodwater from passing through buildings (as is the case with the Manning's ''n'' approach)
	#* The application of rainfall on top of the building can however produce some undesirable results that require further consideration. Those being, water falling from the building roof to the ground can require a reduced model timestep to maintain model stability which can slow the simulation speed. Also, depending on the Map Cutoff Depth assumptions, water may be present in the results on the building rooftops. This may not be desired for mapping purposes. There are a variety of options available to resolve these issues:		#* The application of rainfall on top of the building can however produce some undesirable results that require further consideration. Those being, water falling from the building roof to the ground can require a reduced model timestep to maintain model stability which can slow the simulation speed. Also, depending on the Map Cutoff Depth assumptions, water may be present in the results on the building rooftops. This may not be desired for mapping purposes. There are a variety of options available to resolve these issues:
	:::* Retain the model design described above, with subsequent post processing of the results before reporting. Either, delete the model result where there is overlap with the building footprint, or overlay the building footprint polygon objects over/above the result dataset in the GIS Map Layout (hiding the flood model result within the building footprints).		:::* Retain the model design described above, with subsequent post-processing of the mapped results before reporting. Either, delete the model result where there is overlap with the building footprint, or overlay the 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 under-estimate 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: This removes the rainfall from the model that would otherwise fall on the buildings. This approach will under-estimate 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 represent the rainfall that would be falling on the building using <font color="blue"><tt>Read GIS SA RF</tt></font> inflow boundaries. To do this, digitise a 2d_sa_rf polygon for each building (with a buffer of one of more 2D cells) where the building footprint has been excluded from the direct rainfall region. The 2d_sa_rf input will convert the input rainfall hyetograph to flow, deposited initially on the lowest 2D cell, then for subsequent timesteps distributed over all wet cells, within the 2d_sa_rf regions (ie. on the ground surrounding the building). 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.		:::* Exclude buildings from the rainfall polygon and represent the rainfall that would be falling on the building using <font color="blue"><tt>Read GIS SA RF</tt></font> inflow boundaries. To do this, digitise a 2d_sa_rf polygon for each building (with a buffer of one of more 2D cells) where the building footprint has been excluded from the direct rainfall region. The 2d_sa_rf input will convert the input rainfall hyetograph to flow, deposited initially on the lowest 2D cell, then for subsequent timesteps distributed over all wet cells, within the 2d_sa_rf regions (ie. on the ground surrounding the building). 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.