TUFLOW BC Advice - Revision history

Emilie Nielsen: /* I wish to use a PO line to monitor the flow exiting a model. Should I snap the PO line to the downstream boundary for this purpose? */

2026-04-08T05:35:07Z

I wish to use a PO line to monitor the flow exiting a model. Should I snap the PO line to the downstream boundary for this purpose?

← Older revision		Revision as of 15:35, 8 April 2026
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	==I wish to use a PO line to monitor the flow exiting a model. Should I snap the PO line to the downstream boundary for this purpose?==		==I wish to use a PO line to monitor the flow exiting a model. Should I snap the PO line to the downstream boundary for this purpose?==
	Plot Output (PO) Q lines report model flow results for water crossing the digitised line. Computationally, TUFLOW transposes the digitised PO line to the closest adjacent cell face for the output calculation. In addition to this, TUFLOW requires an active 2D cell on either side (upstream and downstream) of the cell face for the calculation. Collectively, these requirements are necessary for accurate flow calculations irrespective of the orientation of the PO line relative to the cell alignment.<br>		Plot Output (PO) Q lines report model flow results for water crossing the digitised line. Computationally, TUFLOW transposes the digitised PO line to the closest adjacent cell face for the output calculation. In addition to this, TUFLOW requires an active 2D cell on either side (upstream and downstream) of the cell face for the calculation. Collectively, these requirements are necessary for accurate flow calculations irrespective of the orientation of the PO line relative to the cell alignment.<br>
	It is best practice to snap 2D boundary condition lines, such as HT, QT and HQ, to the extent of the 2D code active area polygon at an orientation roughly perpendicular to the expected flow direction. This model design requirement means the 2D boundary condition lines are located along the outermost 2D cells in a model. Snapping a 2D PO line to the 2D boundary condition may align segments of the Plot Output (PO) Q result inspection line along the outermost cell faces of the model. This does not comply with TUFLOW’s requirement for an active 2D cell on either side of the Plot Output (PO) Q result inspection line. As a result, snapping a 2D PO line to the 2D boundary condition line may underestimate the flow exiting a model. For this reason, Plot Output (PO) Q lines should NOT be snapped to 2D boundary condition lines. The PO line should be defined immediately upstream of the downstream boundary. Use the po_check and grd_check files to review the PO line location to ensure there are active cells each side of the PO line.		It is best practice to snap 2D boundary condition lines, such as HT, QT and HQ, to the extent of the 2D code active area polygon at an orientation roughly perpendicular to the expected flow direction. This model design requirement means the 2D boundary condition lines are located along the outermost 2D cells in a model. Snapping a 2D PO line to the 2D boundary condition may align segments of the Plot Output (PO) Q result inspection line along the outermost cell faces of the model. This does not comply with TUFLOW’s requirement for an active 2D cell on either side of the Plot Output (PO) Q result inspection line. As a result, snapping a 2D PO line to the 2D boundary condition line may underestimate the flow exiting a model. For this reason, Plot Output (PO) Q lines should NOT be snapped to 2D boundary condition lines. The PO line should be defined immediately upstream of the downstream boundary. Use the [[Check_Files_2d_PO\|po_check]] and [[Check_Files_2d_grd\|grd_check]] files to review the PO line location to ensure there are active cells each side of the PO line.

			The image below shows a downstream 2d_bc boundary condition line (HQ) in purple, snapped to the edge of the 2d_code polygon. A 2d_po line (blue arrow) has been digitised just upstream of the boundary. The [[Check_Files_2d_PO\|po_check]] and [[Check_Files_2d_grd\|grd_check]] files have been loaded in to confirm that there is an active 2D cell on either side of the 2d_po line. <br>
			<br>
			[[File:BC_advice_01.png]]

	== Can TUFLOW model a waterfall? ==		== Can TUFLOW model a waterfall? ==

Pavlina Monhartova at 01:27, 3 September 2025

2025-09-03T01:27:44Z

← Older revision		Revision as of 11:27, 3 September 2025
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	Plot Output (PO) Q lines report model flow results for water crossing the digitised line. Computationally, TUFLOW transposes the digitised PO line to the closest adjacent cell face for the output calculation. In addition to this, TUFLOW requires an active 2D cell on either side (upstream and downstream) of the cell face for the calculation. Collectively, these requirements are necessary for accurate flow calculations irrespective of the orientation of the PO line relative to the cell alignment.<br>		Plot Output (PO) Q lines report model flow results for water crossing the digitised line. Computationally, TUFLOW transposes the digitised PO line to the closest adjacent cell face for the output calculation. In addition to this, TUFLOW requires an active 2D cell on either side (upstream and downstream) of the cell face for the calculation. Collectively, these requirements are necessary for accurate flow calculations irrespective of the orientation of the PO line relative to the cell alignment.<br>
	It is best practice to snap 2D boundary condition lines, such as HT, QT and HQ, to the extent of the 2D code active area polygon at an orientation roughly perpendicular to the expected flow direction. This model design requirement means the 2D boundary condition lines are located along the outermost 2D cells in a model. Snapping a 2D PO line to the 2D boundary condition may align segments of the Plot Output (PO) Q result inspection line along the outermost cell faces of the model. This does not comply with TUFLOW’s requirement for an active 2D cell on either side of the Plot Output (PO) Q result inspection line. As a result, snapping a 2D PO line to the 2D boundary condition line may underestimate the flow exiting a model. For this reason, Plot Output (PO) Q lines should NOT be snapped to 2D boundary condition lines. The PO line should be defined immediately upstream of the downstream boundary. Use the po_check and grd_check files to review the PO line location to ensure there are active cells each side of the PO line.		It is best practice to snap 2D boundary condition lines, such as HT, QT and HQ, to the extent of the 2D code active area polygon at an orientation roughly perpendicular to the expected flow direction. This model design requirement means the 2D boundary condition lines are located along the outermost 2D cells in a model. Snapping a 2D PO line to the 2D boundary condition may align segments of the Plot Output (PO) Q result inspection line along the outermost cell faces of the model. This does not comply with TUFLOW’s requirement for an active 2D cell on either side of the Plot Output (PO) Q result inspection line. As a result, snapping a 2D PO line to the 2D boundary condition line may underestimate the flow exiting a model. For this reason, Plot Output (PO) Q lines should NOT be snapped to 2D boundary condition lines. The PO line should be defined immediately upstream of the downstream boundary. Use the po_check and grd_check files to review the PO line location to ensure there are active cells each side of the PO line.


	== Can TUFLOW model a waterfall? ==		== Can TUFLOW model a waterfall? ==

Pavlina Monhartova at 01:27, 3 September 2025

2025-09-03T01:27:24Z

← Older revision		Revision as of 11:27, 3 September 2025
Line 11:		Line 11:
	It is best practice to snap 2D boundary condition lines, such as HT, QT and HQ, to the extent of the 2D code active area polygon at an orientation roughly perpendicular to the expected flow direction. This model design requirement means the 2D boundary condition lines are located along the outermost 2D cells in a model. Snapping a 2D PO line to the 2D boundary condition may align segments of the Plot Output (PO) Q result inspection line along the outermost cell faces of the model. This does not comply with TUFLOW’s requirement for an active 2D cell on either side of the Plot Output (PO) Q result inspection line. As a result, snapping a 2D PO line to the 2D boundary condition line may underestimate the flow exiting a model. For this reason, Plot Output (PO) Q lines should NOT be snapped to 2D boundary condition lines. The PO line should be defined immediately upstream of the downstream boundary. Use the po_check and grd_check files to review the PO line location to ensure there are active cells each side of the PO line.		It is best practice to snap 2D boundary condition lines, such as HT, QT and HQ, to the extent of the 2D code active area polygon at an orientation roughly perpendicular to the expected flow direction. This model design requirement means the 2D boundary condition lines are located along the outermost 2D cells in a model. Snapping a 2D PO line to the 2D boundary condition may align segments of the Plot Output (PO) Q result inspection line along the outermost cell faces of the model. This does not comply with TUFLOW’s requirement for an active 2D cell on either side of the Plot Output (PO) Q result inspection line. As a result, snapping a 2D PO line to the 2D boundary condition line may underestimate the flow exiting a model. For this reason, Plot Output (PO) Q lines should NOT be snapped to 2D boundary condition lines. The PO line should be defined immediately upstream of the downstream boundary. Use the po_check and grd_check files to review the PO line location to ensure there are active cells each side of the PO line.


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	== Can TUFLOW model a waterfall? ==		== Can TUFLOW model a waterfall? ==
	Yes, TUFLOW can model waterfalls, but it requires careful handling of supercritical flow conditions.		Yes, TUFLOW can model waterfalls, but it requires careful handling of supercritical flow conditions.

Abrar.Alttahir: /* Can TUFLOW model a waterfall? */

2025-02-06T06:32:54Z

Can TUFLOW model a waterfall?

← Older revision		Revision as of 16:32, 6 February 2025
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	It is best practice to snap 2D boundary condition lines, such as HT, QT and HQ, to the extent of the 2D code active area polygon at an orientation roughly perpendicular to the expected flow direction. This model design requirement means the 2D boundary condition lines are located along the outermost 2D cells in a model. Snapping a 2D PO line to the 2D boundary condition may align segments of the Plot Output (PO) Q result inspection line along the outermost cell faces of the model. This does not comply with TUFLOW’s requirement for an active 2D cell on either side of the Plot Output (PO) Q result inspection line. As a result, snapping a 2D PO line to the 2D boundary condition line may underestimate the flow exiting a model. For this reason, Plot Output (PO) Q lines should NOT be snapped to 2D boundary condition lines. The PO line should be defined immediately upstream of the downstream boundary. Use the po_check and grd_check files to review the PO line location to ensure there are active cells each side of the PO line.		It is best practice to snap 2D boundary condition lines, such as HT, QT and HQ, to the extent of the 2D code active area polygon at an orientation roughly perpendicular to the expected flow direction. This model design requirement means the 2D boundary condition lines are located along the outermost 2D cells in a model. Snapping a 2D PO line to the 2D boundary condition may align segments of the Plot Output (PO) Q result inspection line along the outermost cell faces of the model. This does not comply with TUFLOW’s requirement for an active 2D cell on either side of the Plot Output (PO) Q result inspection line. As a result, snapping a 2D PO line to the 2D boundary condition line may underestimate the flow exiting a model. For this reason, Plot Output (PO) Q lines should NOT be snapped to 2D boundary condition lines. The PO line should be defined immediately upstream of the downstream boundary. Use the po_check and grd_check files to review the PO line location to ensure there are active cells each side of the PO line.

			<span style="color:#FF0000">
			<font size = 18>Page Under Construction</font>
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	== Can TUFLOW model a waterfall? ==		== Can TUFLOW model a waterfall? ==
	Yes, TUFLOW can model waterfalls, but it requires careful handling of supercritical flow conditions.		Yes, TUFLOW can model waterfalls, but it requires careful handling of supercritical flow conditions.

Abrar.Alttahir at 05:40, 6 February 2025

2025-02-06T05:40:06Z

← Older revision		Revision as of 15:40, 6 February 2025
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	* [[TUFLOW_2D2D_BC_Advice\| Multiple Domain 2D/2D Boundary Configuration Guidance]]		* [[TUFLOW_2D2D_BC_Advice\| Multiple Domain 2D/2D Boundary Configuration Guidance]]
	* [[TUFLOW_1D2D_Boundary_Configuration_Guidance\| 1D/2D Boundary Configuration Guidance (SX and HX)]]		* [[TUFLOW_1D2D_Boundary_Configuration_Guidance\| 1D/2D Boundary Configuration Guidance (SX and HX)]]
	<br>

	=Frequently Asked Questions (FAQ)=		=Frequently Asked Questions (FAQ)=
	==I wish to use a PO line to monitor the flow exiting a model. Should I snap the PO line to the downstream boundary for this purpose?==		==I wish to use a PO line to monitor the flow exiting a model. Should I snap the PO line to the downstream boundary for this purpose?==
	Plot Output (PO) Q lines report model flow results for water crossing the digitised line. Computationally, TUFLOW transposes the digitised PO line to the closest adjacent cell face for the output calculation. In addition to this, TUFLOW requires an active 2D cell on either side (upstream and downstream) of the cell face for the calculation. Collectively, these requirements are necessary for accurate flow calculations irrespective of the orientation of the PO line relative to the cell alignment.<br>		Plot Output (PO) Q lines report model flow results for water crossing the digitised line. Computationally, TUFLOW transposes the digitised PO line to the closest adjacent cell face for the output calculation. In addition to this, TUFLOW requires an active 2D cell on either side (upstream and downstream) of the cell face for the calculation. Collectively, these requirements are necessary for accurate flow calculations irrespective of the orientation of the PO line relative to the cell alignment.<br>
	It is best practice to snap 2D boundary condition lines, such as HT, QT and HQ, to the extent of the 2D code active area polygon at an orientation roughly perpendicular to the expected flow direction. This model design requirement means the 2D boundary condition lines are located along the outermost 2D cells in a model. Snapping a 2D PO line to the 2D boundary condition may align segments of the Plot Output (PO) Q result inspection line along the outermost cell faces of the model. This does not comply with TUFLOW’s requirement for an active 2D cell on either side of the Plot Output (PO) Q result inspection line. As a result, snapping a 2D PO line to the 2D boundary condition line may underestimate the flow exiting a model. For this reason, Plot Output (PO) Q lines should NOT be snapped to 2D boundary condition lines. The PO line should be defined immediately upstream of the downstream boundary. Use the po_check and grd_check files to review the PO line location to ensure there are active cells each side of the PO line.		It is best practice to snap 2D boundary condition lines, such as HT, QT and HQ, to the extent of the 2D code active area polygon at an orientation roughly perpendicular to the expected flow direction. This model design requirement means the 2D boundary condition lines are located along the outermost 2D cells in a model. Snapping a 2D PO line to the 2D boundary condition may align segments of the Plot Output (PO) Q result inspection line along the outermost cell faces of the model. This does not comply with TUFLOW’s requirement for an active 2D cell on either side of the Plot Output (PO) Q result inspection line. As a result, snapping a 2D PO line to the 2D boundary condition line may underestimate the flow exiting a model. For this reason, Plot Output (PO) Q lines should NOT be snapped to 2D boundary condition lines. The PO line should be defined immediately upstream of the downstream boundary. Use the po_check and grd_check files to review the PO line location to ensure there are active cells each side of the PO line.
	<br>

			== Can TUFLOW model a waterfall? ==
			Yes, TUFLOW can model waterfalls, but it requires careful handling of supercritical flow conditions.

			As water approaches a waterfall, it speeds up and transitions into free fall. To ensure realistic behaviour, the model must allow for this acceleration rather than imposing an artificial depth at the brink.

			Here are three suggested approaches in TUFLOW:

			# '''HQ (Water Level versus Flow) Boundary:''' Defining a custom HQ curve ensures the model correctly represents the flow acceleration before the waterfall.
			# '''Steep Slope HQ Boundary:''' Setting a higher slope value in the automatic HQ boundary can also generate supercritical conditions near the outlet.
			# '''2D HPC Weir:''' Modelling a small drop in 2D cell elevations with a weir structure can better reflect natural waterfall hydraulics.

			It is also recommended to run sensitivity tests with different boundary setups to check how the downstream conditions influence the model results.{{Tips Navigation
	{{Tips Navigation
	\|uplink=[[ TUFLOW_Modelling_Guidance \| Back to TUFLOW Modelling Guidance]]		\|uplink=[[ TUFLOW_Modelling_Guidance \| Back to TUFLOW Modelling Guidance]]
	}}		}}

Pavlina Monhartova: /* Does PO line snapped to the downstream boundary report the flow out of the model correctly? */

2023-10-03T02:22:38Z

Does PO line snapped to the downstream boundary report the flow out of the model correctly?

← Older revision		Revision as of 12:22, 3 October 2023
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	=Frequently Asked Questions (FAQ)=		=Frequently Asked Questions (FAQ)=
	==~~Does~~ PO line ~~snapped~~ to the ~~downstream~~ ~~boundary~~ ~~report~~ the ~~flow~~ ~~out~~ of the ~~model~~ ~~correctly~~?==		==I wish to use a PO line to monitor the flow exiting a model. Should I snap the PO line to the downstream boundary for this purpose?==
			Plot Output (PO) Q lines report model flow results for water crossing the digitised line. Computationally, TUFLOW transposes the digitised PO line to the closest adjacent cell face for the output calculation. In addition to this, TUFLOW requires an active 2D cell on either side (upstream and downstream) of the cell face for the calculation. Collectively, these requirements are necessary for accurate flow calculations irrespective of the orientation of the PO line relative to the cell alignment.<br>
	It might not report the flow correctly if the cell face recognised by the PO line doesn’t have an active cell on each side. There are two recommended approaches:<br>
			It is best practice to snap 2D boundary condition lines, such as HT, QT and HQ, to the extent of the 2D code active area polygon at an orientation roughly perpendicular to the expected flow direction. This model design requirement means the 2D boundary condition lines are located along the outermost 2D cells in a model. Snapping a 2D PO line to the 2D boundary condition may align segments of the Plot Output (PO) Q result inspection line along the outermost cell faces of the model. This does not comply with TUFLOW’s requirement for an active 2D cell on either side of the Plot Output (PO) Q result inspection line. As a result, snapping a 2D PO line to the 2D boundary condition line may underestimate the flow exiting a model. For this reason, Plot Output (PO) Q lines should NOT be snapped to 2D boundary condition lines. The PO line should be defined immediately upstream of the downstream boundary. Use the po_check and grd_check files to review the PO line location to ensure there are active cells each side of the PO line.
	* Move the PO line slightly upstream from the downstream boundary.
			<br>
	* Extend the model downstream preserving the same bed elevation slope conditions and keep the PO line at the original location of the downstream boundary.
	When using HT boundaries, the distance between the PO line and the boundary can be quite small making sure there are active cells each side of the PO line from the po_check file. The required distance between the PO line and HQ boundary is location specific. HQ boundaries should never be placed close to the area of interest. To confirm the distance assumption is acceptable, sensitivity testing might be conducted on the slope by ±10%. If the flow and water level results at the PO line remain unchanged irrespective of the slope, the downstream boundary location and configuration can be considered acceptable.<br>

Pavlina Monhartova at 03:49, 29 September 2023

2023-09-29T03:49:08Z

← Older revision		Revision as of 13:49, 29 September 2023
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	=TUFLOW Boundary Condition Advice=
	The following links provide useful boundary condition guidance to TUFLOW users.		The following links provide useful boundary condition guidance to TUFLOW users.

Pavlina Monhartova at 03:48, 29 September 2023

2023-09-29T03:48:30Z

@@ Line 1: / Line 1: @@
 * [[TS1_File_Format | TS1 File Format]]
 * [[TUFLOW_NetCDF_Rainfall_Format|TUFLOW NetCDF Rainfall Format]]
@@ Line 5: / Line 8: @@
 * [[TUFLOW_1D2D_Boundary_Configuration_Guidance| 1D/2D Boundary Configuration Guidance (SX and HX)]]
 <br>
 {{Tips Navigation
 |uplink=[[ TUFLOW_Modelling_Guidance | Back to TUFLOW Modelling Guidance]]

ElizaCollison at 03:25, 4 October 2022

2022-10-04T03:25:32Z

← Older revision		Revision as of 13:25, 4 October 2022
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	* [[TUFLOW_Rainfall_Control_File_Examples \| TUFLOW Rainfall Control File Examples]]		* [[TUFLOW_Rainfall_Control_File_Examples \| TUFLOW Rainfall Control File Examples]]
	* [[TUFLOW_2D2D_BC_Advice\| Multiple Domain 2D/2D Boundary Configuration Guidance]]		* [[TUFLOW_2D2D_BC_Advice\| Multiple Domain 2D/2D Boundary Configuration Guidance]]
	* [[TUFLOW_Modelling_Webinars#1D.2F2D_Linking_Guidance \| Webinar: 1D/2D Linking Guidance]]
	* [[TUFLOW_1D2D_Boundary_Configuration_Guidance\| 1D/2D Boundary Configuration Guidance (SX and HX)]]		* [[TUFLOW_1D2D_Boundary_Configuration_Guidance\| 1D/2D Boundary Configuration Guidance (SX and HX)]]
	<br>		<br>

ElizaCollison at 03:21, 4 October 2022

2022-10-04T03:21:29Z

← Older revision		Revision as of 13:21, 4 October 2022
Line 4:		Line 4:
	* [[TUFLOW_2D2D_BC_Advice\| Multiple Domain 2D/2D Boundary Configuration Guidance]]		* [[TUFLOW_2D2D_BC_Advice\| Multiple Domain 2D/2D Boundary Configuration Guidance]]
	* [[TUFLOW_Modelling_Webinars#1D.2F2D_Linking_Guidance \| Webinar: 1D/2D Linking Guidance]]		* [[TUFLOW_Modelling_Webinars#1D.2F2D_Linking_Guidance \| Webinar: 1D/2D Linking Guidance]]
	* [[~~TUFLOW_1D2D_SX_Advice~~\| 1D/2D SX Boundary Configuration Guidance]]		* [[TUFLOW_1D2D_Boundary_Configuration_Guidance\| 1D/2D Boundary Configuration Guidance (SX and HX)]]
	<br>		<br>
	{{Tips Navigation		{{Tips Navigation