TUFLOW HR Output - Revision history

Emilie Nielsen: /* Introduction */

2026-02-27T06:07:06Z

Introduction

← Older revision		Revision as of 16:07, 27 February 2026
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	:* High-resolution depth output: The depth is the difference between the interpolated water level and the sub-grid elevation. This is shown in the image on the right.<br>		:* High-resolution depth output: The depth is the difference between the interpolated water level and the sub-grid elevation. This is shown in the image on the right.<br>
	<br>		<br>
	[[File:~~Sgs_std_output~~.~~png~~\|~~360px~~]] [[File:~~Sgs_hr_output~~.~~png~~\|~~360px~~]]		[[File:SGS__standard_output_01.jpg\|400px]] [[File:SGS_HR_output_01.jpg\|400px]]

	The advantage of the HR output is that it can retain the sub-grid detail of the terrain information even at a coarse cell size. As compared in the example below, the HR depth output shows a clear flow path even at a 100m grid. However, nicer depth output does not mean reliable hydraulic result. In fact, the 100m cell size is too coarse to produce reliable/converged hydraulic results for any real-world flood model. It's is strongly recommended that the model convergence/benchmarking tests are conducted based on the standard map output. The HR output should be used for presentation purpose only.		The advantage of the HR output is that it can retain the sub-grid detail of the terrain information even at a coarse cell size. As compared in the example below, the HR depth output shows a clear flow path even at a 100m grid. However, nicer depth output does not mean reliable hydraulic result. In fact, the 100m cell size is too coarse to produce reliable/converged hydraulic results for any real-world flood model. It's is strongly recommended that the model convergence/benchmarking tests are conducted based on the standard map output. The HR output should be used for presentation purpose only.

Anne.Kolega: /* Showing Face Elevations in _DEM_Z_HR Check File */

2026-02-03T01:21:02Z

Showing Face Elevations in _DEM_Z_HR Check File

← Older revision		Revision as of 11:21, 3 February 2026
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	{{Tips Navigation		{{Tips Navigation
	\|uplink=[[ ~~TUFLOW 1D Channels and Hydraulic Structures~~ \| Back to ~~1D Channels and~~ ~~Hydraulic~~ ~~Structures~~]]		\|uplink=[[ TUFLOW_Output_Discussion \| Back to TUFLOW Output Discussion]]
	}}		}}

Emilie Nielsen: /* Introduction */

2026-01-29T03:17:13Z

Introduction

← Older revision		Revision as of 13:17, 29 January 2026
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	Example models with high-resolution outputs are available in the <u>[[TUFLOW_Example_Models\|TUFLOW Example Models]]</u> dataset.		Example models with high-resolution outputs are available in the <u>[[TUFLOW_Example_Models\|TUFLOW Example Models]]</u> dataset.

	For the HR output, the water level at each HR output location is interpolated from the computed 2D water levels. ~~The~~ ~~depth~~ is ~~the~~ ~~difference~~ ~~between~~ ~~the interpolated water level and the sub-grid elevation~~. ~~This differs from the standard~~ depth output ~~which calculates the depths at cell centres and corners first, then interpolates the depths to the standard output grid locations (default~~ is ~~half~~ ~~the~~ ~~cell size). The difference between the~~ standard ~~(left)~~ and HR ~~(right) depth interpolation processes is illustrated below.~~		For the HR output, the water level at each HR output location is interpolated from the computed 2D water levels (see <u>[[#Water_Level_Interpolation_Methods\|Water Level Interpolation Methods]]</u> for details). The depth output is calculated differently for standard and high-resolution outputs:
			:* Standard depth output: The depth is calculated at cell centres and corners first, then interpolated to the standard output grid locations (default is half the cell size). This is shown in the image on the left.

			:* High-resolution depth output: The depth is the difference between the interpolated water level and the sub-grid elevation. This is shown in the image on the right.<br>
			<br>
	[[File:Sgs_std_output.png\|360px]] [[File:Sgs_hr_output.png\|360px]]		[[File:Sgs_std_output.png\|360px]] [[File:Sgs_hr_output.png\|360px]]

Emilie Nielsen at 01:58, 29 January 2026

2026-01-29T01:58:45Z

← Older revision		Revision as of 11:58, 29 January 2026
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	Example models with high-resolution outputs are available in the <u>[[TUFLOW_Example_Models\|TUFLOW Example Models]]</u> dataset.		Example models with high-resolution outputs are available in the <u>[[TUFLOW_Example_Models\|TUFLOW Example Models]]</u> dataset.

	For the HR output, the water level at each HR output location is interpolated from the computed 2D water levels. The depth is the difference between the interpolated water level and the sub-grid elevation. This differs from the standard depth output which calculates the depths at cell centres and corners first, then interpolates the depths to the standard output grid locations (default is half the cell size). The difference between the interpolation processes is illustrated below.		For the HR output, the water level at each HR output location is interpolated from the computed 2D water levels. The depth is the difference between the interpolated water level and the sub-grid elevation. This differs from the standard depth output which calculates the depths at cell centres and corners first, then interpolates the depths to the standard output grid locations (default is half the cell size). The difference between the standard (left) and HR (right) depth interpolation processes is illustrated below.

	[[File:Sgs_std_output.png\|360px]] [[File:Sgs_hr_output.png\|360px]]		[[File:Sgs_std_output.png\|360px]] [[File:Sgs_hr_output.png\|360px]]

Emilie Nielsen: /* Water Level Interpolation Methods */

2026-01-29T01:34:40Z

Water Level Interpolation Methods

← Older revision		Revision as of 11:34, 29 January 2026
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	Note that when these two methods are applied, the interpolated corner water level is biased to the non-sheet flow cells, and consequently, sheet flow cells may appear as “dry” cells. The improved approach takes into account that the sheet flow water level is currently under development.		Note that when these two methods are applied, the interpolated corner water level is biased to the non-sheet flow cells, and consequently, sheet flow cells may appear as “dry” cells. The improved approach takes into account that the sheet flow water level is currently under development.

	Whilst Methods B and C can substantially improve the water surface mapping of SGS models using direct rainfall (rain-on-grid), there will always be inaccuracies with mapping at a higher resolution than the 2D cell resolution due to interpolation and extrapolation. Regardless of the software, the greater the ratio of 2D cell size to the high-resolution DEM cell size, the greater the potential for mapping inaccuracies. Should better mapping accuracy be required, reducing the 2D cell size to compute the spatial variation in water surface and velocities more accurately is by far the best course of action.		Whilst Methods B and C can substantially improve the water surface mapping of SGS models using direct rainfall (rain-on-grid), there will always be inaccuracies with mapping at a higher resolution than the 2D cell resolution due to interpolation and extrapolation. Regardless of the software, the greater the ratio of 2D cell size to the high-resolution DEM cell size, the greater the potential for mapping inaccuracies. Should better mapping accuracy be required, reducing the 2D cell size to compute the spatial variation in water surface and velocities more accurately is by far the best course of action.

	Please also note that it is not necessary to use these options for non-rainfall on grid models.

	=Interpolation near Thin Breaklines =		=Interpolation near Thin Breaklines =

Emilie Nielsen: /* Introduction */

2026-01-29T01:18:43Z

Introduction

← Older revision		Revision as of 11:18, 29 January 2026
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	=Introduction=		=Introduction=
	High-Resolution (HR) Grid/Raster Map Outputs was first introduced in TUFLOW 2020-10-AB release. When an SGS model uses “<font color="blue"><tt>SGS Approach </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>Method C</tt></font>”, the sampled elevations are retained at the end of the geometry processing. These sub-grid elevations include topography modifiers such as breaklines, and they allow a high-resolution elevation check file to be written and used for high-resolution depth map outputs. Currently, ASC, FLT and TIF raster formats are supported.		High-Resolution (HR) Grid/Raster Map Outputs was first introduced in TUFLOW 2020-10-AB release. When an SGS model uses “<font color="blue"><tt>SGS Approach </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>Method C</tt></font>”, the sampled elevations are retained at the end of the geometry processing. These sub-grid elevations include topography modifiers such as breaklines, and they allow a high-resolution elevation check file to be written and used for high-resolution depth map outputs. Currently, ASC, FLT and TIF raster formats are supported.

			Example models with high-resolution outputs are available in the <u>[[TUFLOW_Example_Models\|TUFLOW Example Models]]</u> dataset.

	For the HR output, the water level at each HR output location is interpolated from the computed 2D water levels. The depth is the difference between the interpolated water level and the sub-grid elevation. This differs from the standard depth output which calculates the depths at cell centres and corners first, then interpolates the depths to the standard output grid locations (default is half the cell size). The difference between the interpolation processes is illustrated below.		For the HR output, the water level at each HR output location is interpolated from the computed 2D water levels. The depth is the difference between the interpolated water level and the sub-grid elevation. This differs from the standard depth output which calculates the depths at cell centres and corners first, then interpolates the depths to the standard output grid locations (default is half the cell size). The difference between the interpolation processes is illustrated below.

Emilie Nielsen: /* Interpolation near Thin Breaklines */

2026-01-29T01:15:14Z

Interpolation near Thin Breaklines

← Older revision		Revision as of 11:15, 29 January 2026
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	=Interpolation near Thin Breaklines =		=Interpolation near Thin Breaklines =
	Thin breaklines are often used to define hydraulic controls, such as levees and road embankments. These controls often experience upstream controlled weir flow, where the water levels on the two sides of the breakline can be considerably different. Retaining just one water level (upstream, downstream or average) at output points along the breakline may result in unsatisfactory water level map output as illustrated in the two figures below. This issue becomes more profound the larger the 2D cell size.		Thin breaklines are often used to define hydraulic controls, such as levees and road embankments. These controls often experience upstream controlled weir flow, where the water levels on the two sides of the breakline can be considerably different. Retaining just one water level (upstream, downstream or average) at output points along the breakline may result in unsatisfactory water level map output as illustrated in the two figures below. This issue becomes more profound the larger the 2D cell size.
		⚫	: '''Note:''' This feature only works for thin breaklines in Z Shape (2d_zsh) layers. Thick/wide breaklines raise more than 1 row of cell centres and 2 rows of cell faces, and thus do not experience this HR interpolation issue.

	[[File:breakline_h_intp_output.png\|480px]]<br>		[[File:breakline_h_intp_output.png\|480px]]<br>
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	[[File:HR_thin_brk_on.png\|480px]] [[File:HR_thin_brk_on_adj.png\|480px]]<br>		[[File:HR_thin_brk_on.png\|480px]] [[File:HR_thin_brk_on_adj.png\|480px]]<br>
	'''HR Thin Z Line Output Adjustment == ON CELL SIDES (left) and ON ALIGNMENT (right)'''		'''HR Thin Z Line Output Adjustment == ON CELL SIDES (left) and ON ALIGNMENT (right)'''

⚫	Note: ~~this~~ feature ~~(at present)~~ only works for thin breaklines in Z Shape (2d_zsh) layers. Thick/wide breaklines raise more than 1 row of cell centres and 2 rows of cell faces, and thus do not experience this HR interpolation issue.

	=Showing Face Elevations in _DEM_Z_HR Check File =		=Showing Face Elevations in _DEM_Z_HR Check File =

Emilie Nielsen: /* Showing Face Elevations in _DEM_Z_HR Check File */

2026-01-29T01:11:22Z

Showing Face Elevations in _DEM_Z_HR Check File

← Older revision		Revision as of 11:11, 29 January 2026
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	<font color="blue"><tt>HR Grid Output Use Face Elevations </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>{ON} \| OFF</tt></font>		<font color="blue"><tt>HR Grid Output Use Face Elevations </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>{ON} \| OFF</tt></font>

	* ~~“ON”~~ (default): ~~use~~ face elevations in [[Check_Files_2d_DEM_Z_HR \| _DEM_Z_HR]] check file. This option accurately shows the cell faces where water can be hydraulically blocked. However, when cell faces are angled with the thin breakline, this can create 'pockets' of lower elevations in the check file that do not exist in reality.		* ON (default): Use face elevations in [[Check_Files_2d_DEM_Z_HR \| _DEM_Z_HR]] check file. This option accurately shows the cell faces where water can be hydraulically blocked. However, when cell faces are angled with the thin breakline, this can create 'pockets' of lower elevations in the check file that do not exist in reality.
	* ~~“OFF”~~: Face elevations are not used in [[Check_Files_2d_DEM_Z_HR \| _DEM_Z_HR]] check file. This is an useful option for report writing, as 'clean' high-resolution DEM images can be generated reflecting all geometry updates except for the Thin Breakline updates at cell faces.		* OFF: Face elevations are not used in [[Check_Files_2d_DEM_Z_HR \| _DEM_Z_HR]] check file. This is an useful option for report writing, as 'clean' high-resolution DEM images can be generated reflecting all geometry updates except for the Thin Breakline updates at cell faces.

	[[File:HR_Z_Use_Face_Elevations_ON.PNG\|480px]] [[File:HR_Z_Use_Face_Elevations_OFF.PNG\|480px]]<br>		[[File:HR_Z_Use_Face_Elevations_ON.PNG\|480px]] [[File:HR_Z_Use_Face_Elevations_OFF.PNG\|480px]]<br>

Emilie Nielsen: /* Interpolation near Thin Breakline */

2026-01-29T01:10:08Z

Interpolation near Thin Breakline

Emilie Nielsen: /* Water Level Interpolation Methods */

2026-01-29T01:07:19Z

Water Level Interpolation Methods

← Older revision		Revision as of 11:11, 29 January 2026
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	<font color="blue"><tt>HR Grid Output Use Face Elevations </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>{ON} \| OFF</tt></font>		<font color="blue"><tt>HR Grid Output Use Face Elevations </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>{ON} \| OFF</tt></font>

	* ~~“ON”~~ (default): ~~use~~ face elevations in [[Check_Files_2d_DEM_Z_HR \| _DEM_Z_HR]] check file. This option accurately shows the cell faces where water can be hydraulically blocked. However, when cell faces are angled with the thin breakline, this can create 'pockets' of lower elevations in the check file that do not exist in reality.		* ON (default): Use face elevations in [[Check_Files_2d_DEM_Z_HR \| _DEM_Z_HR]] check file. This option accurately shows the cell faces where water can be hydraulically blocked. However, when cell faces are angled with the thin breakline, this can create 'pockets' of lower elevations in the check file that do not exist in reality.
	* ~~“OFF”~~: Face elevations are not used in [[Check_Files_2d_DEM_Z_HR \| _DEM_Z_HR]] check file. This is an useful option for report writing, as 'clean' high-resolution DEM images can be generated reflecting all geometry updates except for the Thin Breakline updates at cell faces.		* OFF: Face elevations are not used in [[Check_Files_2d_DEM_Z_HR \| _DEM_Z_HR]] check file. This is an useful option for report writing, as 'clean' high-resolution DEM images can be generated reflecting all geometry updates except for the Thin Breakline updates at cell faces.

	[[File:HR_Z_Use_Face_Elevations_ON.PNG\|480px]] [[File:HR_Z_Use_Face_Elevations_OFF.PNG\|480px]]<br>		[[File:HR_Z_Use_Face_Elevations_ON.PNG\|480px]] [[File:HR_Z_Use_Face_Elevations_OFF.PNG\|480px]]<br>

← Older revision		Revision as of 11:10, 29 January 2026
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	Please also note that it is not necessary to use these options for non-rainfall on grid models.		Please also note that it is not necessary to use these options for non-rainfall on grid models.

	=Interpolation near Thin ~~Breakline~~ =		=Interpolation near Thin Breaklines =
	Thin breaklines are often used to define hydraulic controls, such as levees and road embankments. These controls often experience upstream controlled weir flow, where the water levels on the two sides of the breakline can be considerably different. Retaining just one water level (upstream, downstream or average) at output points along the breakline may result in unsatisfactory water level map output as illustrated in the two figures below. This issue becomes more profound the larger the 2D cell size.		Thin breaklines are often used to define hydraulic controls, such as levees and road embankments. These controls often experience upstream controlled weir flow, where the water levels on the two sides of the breakline can be considerably different. Retaining just one water level (upstream, downstream or average) at output points along the breakline may result in unsatisfactory water level map output as illustrated in the two figures below. This issue becomes more profound the larger the 2D cell size.

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	'''HR Thin Z Line Output Adjustment == OFF'''		'''HR Thin Z Line Output Adjustment == OFF'''

	A new HR output feature has been introduced to improve the water level interpolation along thin ~~breakline~~.		A new HR output feature has been introduced to improve the water level interpolation along thin breaklines.
	~~Any~~ further questions please email TUFLOW support: [mailto:support@tuflow.com?Subject=TUFLOW%201D%20gates%20help support@tuflow.com]		For any further questions please email TUFLOW support: [mailto:support@tuflow.com?Subject=TUFLOW%201D%20gates%20help support@tuflow.com]

	<font color="blue"><tt>HR Thin Z Line Output Adjustment </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>OFF \| {ON CELL SIDES} \| ON ALIGNMENT</tt></font>		<font color="blue"><tt>HR Thin Z Line Output Adjustment </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>OFF \| {ON CELL SIDES} \| ON ALIGNMENT</tt></font>

	* ~~“OFF”~~: does not apply any water level adjustment.		* OFF: does not apply any water level adjustment.
	* ~~“ON~~ CELL ~~SIDES”~~ (default): two water levels, rather than one, are stored at cell corners selected by thin breaklines. These water levels are used to interpolate HR water levels on either side of thin breaklines. This option produces a sudden drop in water level across the breakline as illustrated in the figure below, noting the sudden drop follows the 2D cell faces where the breakline is applied.		* ON CELL SIDES (default): two water levels, rather than one, are stored at cell corners selected by thin breaklines. These water levels are used to interpolate HR water levels on either side of thin breaklines. This option produces a sudden drop in water level across the breakline as illustrated in the figure below, noting the sudden drop follows the 2D cell faces where the breakline is applied.
	* ~~“ON~~ ~~ALIGNMENT”~~: As an extension to the “ON CELL SIDES” option, this method moves and aligns the 2D cell corner vertices to the original alignment of the breakline for producing HR water level and depth. The arrows in the figure below show how vertices of the TIN are moved to align with the breakline. This can produce substantially improved high-resolution mapping along thin breaklines with substantial drops in water levels, especially for larger 2D cell sizes. Note that the cell corners are NOT shifted for the hydraulic calculations.		* ON ALIGNMENT: As an extension to the “ON CELL SIDES” option, this method moves and aligns the 2D cell corner vertices to the original alignment of the breakline for producing HR water level and depth. The arrows in the figure below show how vertices of the TIN are moved to align with the breakline. This can produce substantially improved high-resolution mapping along thin breaklines with substantial drops in water levels, especially for larger 2D cell sizes. Note that the cell corners are NOT shifted for the hydraulic calculations.

	[[File:HR_thin_brk_on.png\|480px]] [[File:HR_thin_brk_on_adj.png\|480px]]<br>		[[File:HR_thin_brk_on.png\|480px]] [[File:HR_thin_brk_on_adj.png\|480px]]<br>
	'''HR Thin Z Line Output Adjustment == ON CELL SIDES (left) and ON ALIGNMENT (right)'''		'''HR Thin Z Line Output Adjustment == ON CELL SIDES (left) and ON ALIGNMENT (right)'''

	Note: this feature (at present) only works for thin breaklines in Z Shape (2d_zsh) layers. Thick/wide breaklines raise more than 1 ~~rows~~ of cell centres and 2 rows of cell faces, and thus do not experience ~~similar~~ HR interpolation issue.		Note: this feature (at present) only works for thin breaklines in Z Shape (2d_zsh) layers. Thick/wide breaklines raise more than 1 row of cell centres and 2 rows of cell faces, and thus do not experience this HR interpolation issue.

	=Showing Face Elevations in _DEM_Z_HR Check File =		=Showing Face Elevations in _DEM_Z_HR Check File =

← Older revision		Revision as of 11:07, 29 January 2026
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	=Water Level Interpolation Methods=		=Water Level Interpolation Methods=
	Similar to the standard output, the HR output needs to interpolate cell centre water levels to cell corners. However, the interpolation methods for the standard output (<font color="blue"><tt>Map Output Corner Interpolation </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>Method C</tt></font>) can produce "bumpy" HR water level ~~output~~ in direct rainfall models with steep terrain, as the water level is linearly interpolated from the cell centres/corners, while the change of sub-grid elevations may not be linear. This often happens between fully wet cells and sheet flow cells, as illustrated below.		Similar to the standard output, the HR output needs to interpolate cell centre water levels to cell corners. However, the interpolation methods for the standard output (<font color="blue"><tt>Map Output Corner Interpolation </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>Method C</tt></font>) can produce "bumpy" HR water level outputs in direct rainfall models with steep terrain, as the water level is linearly interpolated from the cell centres/corners, while the change of sub-grid elevations may not be linear. This often happens between fully wet cells and sheet flow cells, as illustrated below.


	[[File:corner_h_intp_output.png\|480px]]		[[File:corner_h_intp_output.png\|480px]]


	In the HR water level output, these locations often have high water level with triangular shape.		In the HR water level output, these locations often have high water level with triangular shape.


	[[File:HR_Intp_A.png\|480px]]<br>		[[File:HR_Intp_A.png\|480px]]<br>
	'''HR Interpolation Approach ~~== Method A~~''' (~~Gray~~ lines show the triangulation TINs)		'''Method A HR Interpolation Approach''' (gray lines show the triangulation TINs)


	Two additional methods have been added for the HR corner water level interpolation:		Two additional methods have been added for the HR corner water level interpolation:
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	* Method C is the default option that applies the same sheet flow checks as the Method B. In addition, it also uses the number of wet SGS sampled points as a weighting that biases non-sheet flow cells that further improves the mapping to in-stream water levels.		* Method C is the default option that applies the same sheet flow checks as the Method B. In addition, it also uses the number of wet SGS sampled points as a weighting that biases non-sheet flow cells that further improves the mapping to in-stream water levels.

	The two images below present the high-resolution water level output at the same location, but with HR Interpolation Approach == Method B and ~~Method C~~. As can be seen, the water level along the narrow stream is “smoother”.		The two images below present the high-resolution water level output at the same location, but with <tt><font color=blue>HR Interpolation Approach </font><font color=red>==</font> Method B</tt> and <tt>MethodC</tt>. As can be seen, the water level along the narrow stream is “smoother”.


	[[File:HR_Intp_B.png\|480px]] [[File:HR_Intp_C.png\|480px]]<br>		[[File:HR_Intp_B.png\|480px]] [[File:HR_Intp_C.png\|480px]]<br>
	'''~~HR Interpolation Approach ==~~ Method B (left) and Method C (right)'''		'''Method B (left) and Method C (right) HR Interpolation Approach'''


	Note that when these two methods are applied, the interpolated corner water level is biased to the non-sheet flow cells, and consequently, sheet flow cells may appear as “dry” cells. The improved approach ~~that~~ takes into ~~the~~ account of the sheet flow water level is currently under development.		Note that when these two methods are applied, the interpolated corner water level is biased to the non-sheet flow cells, and consequently, sheet flow cells may appear as “dry” cells. The improved approach takes into account that the sheet flow water level is currently under development.

	Whilst Methods B and C can substantially improve the water surface mapping of SGS models using direct rainfall (rain-on-grid), there will always be inaccuracies with mapping at a higher resolution than the 2D cell resolution due to interpolation and extrapolation. Regardless of the software, the greater the ratio of 2D cell size to the high-resolution DEM cell size, the greater the potential for mapping inaccuracies. Should better mapping accuracy be required, reducing the 2D cell size to compute the spatial variation in water surface and velocities more accurately is, by far, the best course of action.		Whilst Methods B and C can substantially improve the water surface mapping of SGS models using direct rainfall (rain-on-grid), there will always be inaccuracies with mapping at a higher resolution than the 2D cell resolution due to interpolation and extrapolation. Regardless of the software, the greater the ratio of 2D cell size to the high-resolution DEM cell size, the greater the potential for mapping inaccuracies. Should better mapping accuracy be required, reducing the 2D cell size to compute the spatial variation in water surface and velocities more accurately is by far the best course of action.

	Please also note that it is not necessary to use these options for non-rainfall on grid models.		Please also note that it is not necessary to use these options for non-rainfall on grid models.