Section 18 Default Changes

This chapter lists default changes between major releases. For a full list of changes (not only default changes) between versions since the 2023-03-AF release, see the TUFLOW Classic/HPC Changelog. For versions 2023-03-AF and prior, see the relevant release notes in the TUFLOW Downloads Archive.

18.1 2025.0 Release

Table 18.1 outlines the changes made to the default settings for the 2025.0 release and lists commands to revert the settings to those used by the prior major release group (2023-03). All default settings can be reverted to the prior release by using the command, “Defaults == Pre 2025”. For more information on changes, see the TUFLOW Classic/HPC Changelog.

Table 18.1: **Default Changes in the 2025.0 Release and Backward Compatibility to 2023-03**
Description	Backward Compatibility Command
Reset all defaults to that used by the 2023-03 release.	Defaults == PRE 2025
The format of a TIN written when the WRITE TIN command is used with Z Shapes or write TIN commands was changed. The new default (2DM) writes the TIN using the SMS 2DM mesh format, which can be read in by QGIS and SMS. The previous default (SMS TIN) wrote a TIN that could only be read by SMS.	TIN Output Format == SMS TIN
The default value for the HPC HQ Boundary Filter Constant has been set to 5. This can provide improved stability for HQ boundaries. For backwards compatibility, set this to 1. See Section 8.3.2.2.	HPC HQ Boundary Filter Constant == 1
Internally, HPC multiplies the Nu, Nc, Nd control number limits by a dynamic control factor. Method A considers that a high control number step has occurred if any of Nu, Nc, Nd has exceeded the dynamic control number limits (i.e. after the dynamic control factor has been applied) by the 20% margin. Method B (the 2025.0 default) applies the test using the original static limits (i.e. before the dynamic control factor has been applied). For more information see Section 3.5.4.	HPC Timestep Approach == Method A
A CHECK option has been added to the HPC DP Check command and set as the new default. This downgrades the previous default from ERROR. For more information see Section 13.4.2.2.	HPC DP Check == ERROR

18.2 2023-03 Release

Table 18.2 outlines the changes made to the default settings for the 2023-03 release and lists commands to revert the settings to those used by the prior major release group (2020-10). All default settings can be reverted to the prior release by using the command, “Defaults == Pre 2023”. For more information on changes, see the 2023-03 Release Notes.

Table 18.2: **Default Changes in the 2023-03 Release and Backward Compatibility to 2020-10**
Description of Change	2023-03 Release Notes	Backward Compatibility Command
Change to quadtree handling of inertial parallel to boundary	Section 6.4	Quadtree BC Parallel Inertia Approach == Method A
Upper limiting Manning’s n in Wu turbulence calculation	Section 5.7.1	Viscosity Coefficient == \(\langle\)C3D, C2D, 99\(\rangle\)
Duplicate Materials IDs	Section 2.7.2	No specific command - Defaults == Pre 2023
Duplicate Soil IDs	Section 2.7.3	No specific command - Defaults == Pre 2023
Duplicate SA Boundaries	Section 6.10.2	No specific command - Defaults == Pre 2023
HPC Weir Approach	Section 5.2	HPC Weir Approach == Method A
HPC SX Momentum	Section 5.2	HPC SX Momentum Approach == Method A
HPC Boundary Approach	Section 6.6	HPC Boundary Approach == Method B
Initial Moisture and Green-Ampt infiltration	Section 2.3.9	No specific command - Defaults == Pre 2023
2d_bc QT Point Boundaries (Classic/HPC) Unsupported	Section 6.7	No specific command - Defaults == Pre 2023
2d_bc HQ Point Boundaries (Classic/HPC/Quadtree) Unsupported	Section 6.8	No specific command - Defaults == Pre 2023
SGS Approach	Section 2.2.2	SGS Approach == Method B
SGS Depth Output	Section 2.2.1	SGS Depth Output == Exact
Mapping of partially wet SGS cells	Section 2.2.1	SGS Map Extent Full == h
High Resolution raster output interpolation method	Section 2.2.5	HR Interpolation Approach == Method A
High resolution thin breaklines	Section 2.2.6	HR Thin Z Line Output Adjustment == OFF

18.3 2020-10 Release

Table 18.3 outlines the changes made to the default settings for the 2020-10 release and lists commands to revert the settings to those used by the prior major release group (2020-01). All default settings can be reverted to the prior release by using the command, “Defaults == Pre 2020-10”. For more information on changes, see the 2020-10 Release Notes.

Table 18.3: **Default Changes in the 2020-10 Release and Backward Compatibility to 2020-01**
Description of Change	2020-10 Release Notes	Backward Compatibility Command
Timestepping change	Section 6.3.8	No backward compatibility setting.
Quadtree only Wu turbulence fix	Section 6.3.7	No backward compatibility setting.
Quadtree only thick z-shapes and boundaries fix	Section 3.1.8	No backward compatibility setting.
Vector output at dry Z points	Section 7.11.12	Map Output Vector Dry Zpts == ON
Map cutoff for vector output values	Section 7.11.13	Map Cutoff Vector == OFF
Support for Classic style HQ curve	Section 6.7	HPC HQ Boundary Approach == CELL
Relative filepaths for GIS workspaces	Section 7.10.4	GIS Project Path Format == ABSOLUTE

18.4 2020-01 Release

Table 18.4 outlines the changes made to the default settings for the 2020-01 release and lists commands to revert the settings to those used by the prior major release group (2018-03). All default settings can be reverted to the prior release by using the command, “Defaults == Pre 2020-01”. For more information on changes, see the 2020-01 Release Notes.

Table 18.4: **Default Changes in the 2020-01 Release and Backward Compatibility to 2018-03**
Description of Change	2020-01 Release Notes	Backward Compatibility Command
Turbulence scheme changed	Section 5.1	Viscosity Formulation == Smagorinsky
Improvement to dry wall treament for eddy viscosity	Section 5.2.3	Viscosity Approach == Method A
Flow depth used for bed friction calculation	Section 5.3	HPC Mannings Depth Approach == Method A
Improvement to HPC water level boundaries	Section 6.1	HPC Boundary Approach == Method A

18.5 2018-03 Release

Table 18.5 outlines the changes made to the default settings for the 2018-03 release and lists commands to revert the settings to those used by the prior major release group (2017-09). There is no “Defaults == Pre 2018” command provided for the 2018-03 release. For more information on changes, see the 2018-03 Release Notes.

Table 18.5: **Default Changes in the 2018-03 Release and Backward Compatibility to 2017-09**
Description of Change	2018-03 Release Notes	Backward Compatibility Command
For TUFLOW HPC an enhancement to the extrapolation of Pit curves to provide consistency with Classic was implemented.	Section 2.1.4	Pit Default Extrapolate Q Curve == OFF
The treatment of unconnected pits, which previously would trigger an ERROR, has changed to apply these pits as a virtual pipe pit that discharges water directly out of the model.	Section 2.1.5	Pit No 1D Connection == ERROR
Advanced index feature added to significantly improve 1D/2D model simulation speeds.	Section 4.1	Index 1D2D Links == OFF

18.6 2017-09 Release

Table 18.6 outlines the changes made to the default settings for the 2017-09 release and lists commands to revert the setting to those used by the prior major release group (2016-03). All default settings can be reverted to the prior release by using the command, “Defaults == Pre 2017”. For more information on changes, see the 2017-09 Release Notes.

Table 18.6: **Default Changes in the 2017-09 Release and Backward Compatibility to 2016-03**
Description of Change	2017-09 Release Notes	Backward Compatibility Command
New SX boundaries defaults.	Section 4.5	Set Defaults == PRE 2017 if similar results are required to the 2016-03-AE release.
XF files are now being processed for boundaries.	Section 4.1	Set Defaults == PRE 2017 or use XF Files Boundaries == OFF if similar results are required to the 2016-03-AE release.
Regions in 2d_bc layers now applied as regions (previously only cell over region centroid selected).	Section 4.5.4	No backward compatible workaround provided.
Material IL and CL now applied to gridded rainfall (previously not applied).	Section 4.3	No backward compatible workaround provided.
SA regions now always select a 2D cell even if there are no cell centres falling within the region (previously a SA region would not select any cell if no cell centres fell within the region).	Section 4.4	No backward compatible workaround provided.
If using “Reveal 1D Nodes == ON”, “Time Series Output Interval == ” must be specified.	Section 9.2	No backward compatible workaround provided.

18.7 2016-03 Release

Table 18.7 outlines the changes made to the default settings for the 2016-03 release and lists commands to revert the setting to those used by the prior major release group (2013-12). All default settings can be reverted to the prior release by using the command, “Defaults == Pre 2016”. For more information on changes, see the 2016-03 Release Notes.

Table 18.7: **Default Changes in the 2016-03 Release and Backward Compatibility to 2013-12**
Description of Change	2016-03 Release Notes	Backward Compatibility Command
New operational 1D structure defaults.	Section 4	Set Defaults == PRE 2016 if similar results are required to the 2013-12-AC release.
Primary upstream and downstream 1D channels now correctly take into account bed slope.	Section 6	Set Defaults == PRE 2016 if similar results are required to the 2013-12-AC release.
A new layered 2D FC calculation method has been implemented.	Section 8	Set Layered FLC Default Approach == CUMULATE or use Defaults == PRE 2016 if similar results are required to the 2013-12-AC release.
The SX Flow Distribution Cutoff Depth has been raised to 0.005m from 0.0m.	Section 11	Set Defaults == PRE 2016 or use SX Flow Distribution Cutoff Depth == 0.0 if similar results are required to the 2013-12-AC release.
The “End After Maximum == ” tolerance has been increased to 0.001m from 0.0m.	Section 21	Set Defaults == PRE 2016 if similar results are required to the 2013-12-AC release.
A new ERROR message has been added to cross-check the 1D timestep is a multiple of the timestep for all 2D domains.	Section 49	Set Defaults == PRE 2016 if similar results are required to the 2013-12-AC release.
WARNING 2460 has been escalated to an ERROR and stricter command line syntax rules have been introduced (“=” will now return an ERROR message if TUFLOW is expecting “==”)	Section 50	Set Defaults == PRE 2016 if similar results are required to the 2013-12-AC release.
The treatment of the eddy viscosity term in the GPU Solver has been enhanced in the 2016-03-AD build with slightly improved results in areas of rapidly changing velocity patterns.	Section 145	Set GPU Viscosity Method == Method A or use Defaults == PRE 2016 to achieve the same results as Build 2013-12-AC and prior.

18.8 2013-12 Release

Table 18.8 outlines the changes made to the default settings for the 2013-12 release and lists commands to revert the setting to those used by the prior major release group (2012-05). All default settings can be reverted to the prior release by using the command, “Defaults == Pre 2013”. For more information on changes, see the 2013-12 Release Notes.

Table 18.8: **Default Changes in the 2013-12 Release and Backward Compatibility to 2012-05**
Description of Change	2013-12 Release Notes	Backward Compatibility Command
For BW or IW channels that automatically insert a weir over the B or I channel, the weir width if not manually specified using the EN1 attribute is now based on the maximum width of the B or I channel, rather than the width at the channel’s invert.	Section 27	Structure Routines == ORIGINAL
“E” and “H” flags for RG, SG, SP and all new weirs set whether to use energy (E) or water surface (H) levels for the calculations.	Section 41	Structure Flow Levels == WATER
For W (weir) channels, “Weir Approach == METHOD A” has been reinstated as the default setting.	Section 68	Weir Approach == METHOD B
The approach for processing 2d_po flow lines has been reworked and will now not slow down a simulation if numerous 2d_po flow lines exist as was occurring with prior releases.	Section 1	PO Approach == METHOD A
Output 1D .csv files to a csv folder in a slightly new format that works with our new GIS 1D chart viewer.	Section 18	Time Series Output Format == PRE 2013
New interpolation/extrapolation methods to the 2D cell corners.	Section 5	Map Output Corner Interpolation == METHOD A
When the Maximum Courant Number is greater than zero, adaptive time-stepping is switched on. For the 4th order time solver a value of 1.0 (the new default) is recommended.	Section 1	Maximum Courant Number == 0.3 (only applies if GPU Solver == ON)
Tracks and outputs the maximums every timestep.	Section 1	Maximums and Minimums == OFF
Changes the default to “INCLUDE TIME” for restart files so filenames are time-stamped and written for each restart output time, and the files are placed in a folder called “trf”.	Section 64	Write Restart Filename == OVERWRITE
The default setting for Link 2D2D Approach has changed.	Section 68	Link 2D2D Approach == METHOD B

18.9 2012-05 Release

Table 18.9 outlines the changes made to the default settings for the 2012-05 release and lists commands to revert the setting to those used by the prior major release group (2011-09). All default settings can be reverted to the prior release by using the command, “Defaults == Pre 2012”. For more information on changes, see the 2012-05 Release Notes.

Table 18.9: **Default Changes in the 2012-05 Release and Backward Compatibility to 2011-09**
Description of Change	2012-05 Release Notes	Backward Compatibility Command
The approach to the sizing of automatic manholes and the application of losses has been enhanced.	Section 48	Manhole Approach == METHOD A
Uses an improved method for interpolating into the matrix for 1d_nwk M channels.	Section 91	M Channel Approach == METHOD A
Proportions SA inflows according to the depth of water. This feature also enhances SA inflows by applying an inflow in proportion to the depths of water of the wet cells contained within the SA polygon.	Section 7	SA Proportion to Depth == OFF
Enhanced wetting algorithm that provides significant improvement to inflows on steep areas (eg. direct rainfall models), whilst maintaining low mass error, greater stability and often larger timesteps.	Section 47	Wetting and Drying == ON (2012-05 default is Wetting and Drying == ON METHOD B)
The default viscosity coefficients have been changed to 0.5 Smagorinsky coefficient and 0.05m² /s constant.	Section 57	Viscosity Coefficient == 0.2, 0.1
Tracking of maximums and minimums every timestep for PO and LP output made available and set as default.	Section 27	Maximums and Minimums Time Series == OFF
Enhancement to automatic 2D HQ boundaries that if the consecutive flow values are the same.	Section 106	HQ Boundary Approach == METHOD A

18.10 2011-09 Release

Table 18.10 outlines the changes made to the default settings for the 2011-09 release and lists commands to revert the setting to those used by the prior major release group (2010-10). All default settings can be reverted to the prior release by using the command, “Defaults == Pre 2011”. For more information on changes, see the 2011-09 Release Notes.

Table 18.10: **Default Changes in the 2011-09 Release and Backward Compatibility to 2010-10**
Description of Change	2011-09 Release Notes	Backward Compatibility Command
The optimised compiler code is treated differently for Single Precision builds producing slightly different results (fractions of a mm) for some models.	Release Notes	No workaround.

18.11 2010-10 Release

Table 18.11 outlines the changes made to the default settings for the 2010-10 release and lists commands to revert the setting to those used by the prior major release group (2009-07). All default settings can be reverted to the prior release by using the command, “Defaults == Pre 2010”.

Table 18.11: **Default Changes in the 2010-10 Release and Backward Compatibility to 2009-07**
Description of Change	2010-10 User Manual	Backward Compatibility Command
New Intel Fortran Compiler version produces slightly different results (usually fractions of a mm).	Section 9.5	No workaround.
w32 and w64 versions will give slightly different results for the same simulation.	Section 9.5	No workaround. Use the same platform (w32 or w64) for all simulations. Use Model Platform to force which platform should be used.
New default settings.	Section 9.5	Set Defaults == PRE 2010-10 if similar results are required to the 2008-08 or 2009 07 releases.
Generation of TINs for polygons in Read GIS Shape layers is more robust and uses an improved approach. In rare cases, the TIN would fail and TUFLOW would abort the start-up.	Section 9.5	No workaround.

18.12 2009-07 Release

No default changes were made in the 2009-07 release. For feature changes, see the 2009-07 Release Notes.

18.13 2008-08 Release

Table 18.12 outlines the changes made to the default settings for the 2008-08 release and lists commands to revert the setting to those used by the prior major release group (2007-07). All default settings can be reverted to the prior release by using the command, “Defaults == Pre 2008-08”. For more information on these changes, see the 2008-08 Release Notes.

Table 18.12: **Default Changes in the 2008-08 Release and Backward Compatibility to 2007-07**
Command Change	Description of Change
Uses a new set of defaults for a number of commands.	The new defaults produce slightly different results, and very slight differences also occur between the three versions offered. For established models run using the 2007-07-XX builds, use Defaults == PRE 2008-08 to use the default settings used by the 2007-07-XX builds. Testing of a range of models has shown zero change in results if Defaults == PRE 2008-08 switch is set, and the Compaq Fortran compiled version (cSP) is used. Each of the new default settings and their effects are discussed in the rows below.
The method for interpolating n values where the 2D Manning’s n varies with depth has been enhanced from a linear interpolation of the M (1/n) value to a spline interpolation of the n value. See Bed Resistance Depth Interpolation == .	Generally has little effect other than when the flow is predominantly in the depth range that the n value is varying. The new approach offers a smoother transition in n values from one depth to the other.
The default viscosity coefficient is now a combination of a 0.2 Smagorinsky and 0.1 constant coefficient, and there are some enhancements to the application of the viscosity term. See Viscosity Coefficient.	This has slight effect for the majority of models. For fine grid models (<2m cell size) with low bed resistance and significant variations in velocity vectors the effect is more pronounced but is still slight.
Inertia and viscosity terms are now not transferred across dry cell sides when constructing the coefficients for the solution arrays. This was having the effect of generating a circulation on the other side of the wall (albeit a very weak one), which of course shouldn’t happen!	Generally little effect, but can have some minor influence for urban models where buildings and fences are modelled as solid thin Z lines.
1D weir flow has been improved as the water level difference across the weir approaches zero. The new method is more stable. See Weir Flow.	Very little difference other than improved stability.
Incorporates minor improvements for transitioning between Regimes A and B, and between inlet and outlet controlled regimes, for circular culverts.	Very little difference other than improved stability.
The new automatic selection of cells for 2D SX connections using the 1d_nwk Conn_1D_2D attribute may choose more than one 2D cell.	Very little difference other than improved stability at the pit 2D connections.
The default setting for Shallow Depth Stability Factor has changed in the 2008-08-AC release.	Set Shallow Depth Stability Factor == 3 for models without direct rainfall to achieve the same results as Builds 2008-08-AA and 2008-08-AB. See Shallow Depth Stability Factor for more information.

18.14 2007-07 Release

Table 18.13 outlines the changes made to the default settings for the 2007-07 release and lists commands to revert the setting to those used by the prior major release group (2006-06). All default settings can be reverted to the prior release by using the command, “Defaults == Pre 2007-07-AA”. For more information on these changes, see the 2007-07 Release Notes

Table 18.13: **Default Changes in the 2007-07 Release and Backward Compatibility to 2006-06**
Command Change	Description of Change
Uses a new set of defaults for a number of commands.	The new defaults may produce slightly different results. For established models run using the 2006-06-XX builds, use Defaults == PRE 2007-07-AA to use the default settings used by the 2006-06-XX builds. Each of the new default settings and their affects are discussed in the rows below.
Change Zero Material Values to One == OFF (previously ON)	Will not cause different results if a Set Mat == 1 is specified before other material settings in the .tgc file, or if every cell has been assigned a material value.
Inside Region == Method B (previously Method A)	Testing thus far has not shown any difference between the two methods (other than the substantial gains in processing time of polygons).
Line Cell Selection == Method D (previously Method C)	May change results slightly, but improved stability and a smoother water levels along HX lines result.
VG Z Adjustment == MAX ZC (previously ZC)	May change results slightly, but stability should be significantly enhanced in some situations.
Bed Resistance Cell Sides == INTERROGATE (previously AVERAGE M)	Will influence results, usually slightly, but more pronounced where there are sudden changes in Manning’s n values such as in the urban environment.
Culvert Flow == Method D (previously Method C) Culvert Critical H/D == OFF (previously 1.5)	The most significant influences are the selection of upstream or downstream controlled regimes depending on the H/D ratio, and the bug fix relating to Regime E if Structure Losses == ADJUST. Offers improved stability, better convergence for Regime C and smoother transitioning between some regimes.
Changed the setting of the default width (if eN1 < 0.001) of automatic weirs over R and C channels (i.e. RW and CW) to be the diameter/width multiplied by the number of culverts (previously, the width was not multiplied by the number of culverts).	For backward compatibility, original weir width can be set by manually setting the eN1 attribute to the Diameter_or_Width attribute value of the culvert.
Bug fix that when using a restart file TUFLOW occasionally set the 2D FC bridge deck additional loss value incorrectly.	No backward compatible workaround provided.
Bug fix that incorrectly set the water levels on dried VG cells (only applies to simulations with source inflows, e.g. SA or RF, somewhere within in the model).	May cause slight changes in results. Backward compatibility provided if Defaults == PRE 2007-07-AA is set (noting that setting this command reinstates the bug). This bug also causes the mass error calculations to falsely give a mass error that is not occurring.
Fixed bug that did not correctly apply the reduction in conveyance for a FC BD (bridge deck) of FD (floating deck) cell using the 2d_fc Mannings_n attribute.	Backward compatibility applied if Defaults == PRE 2007-07-AA is set, however, note that this reinstates the bug and the resistance to flow at FC BD and FD cells may need to be reviewed. Indications are that only minor changes in results occur. The flow area under 2D FC BD and FD cells is correctly calculated.

18.15 2006-06 Release

Table 18.14 outlines the changes made to the default settings for the 2006-06 release and lists commands to revert the setting to those used by the prior release. All default settings can be reverted to the prior release by using the command, “Defaults == Pre 2006-06-AA”.

Table 18.14: **Default Changes in the 2006-06 Release and Backward Compatibility to 2005-05**
Command Change	Description of Change
Uses a new set of defaults for a number of commands.	The new defaults will produce different results. For established models run using the 2005-05-XX builds, use Defaults == PRE 2006-06-AA to use the previous default settings. Each of the new default settings and their affects are discussed in the rows below.
Cell Wet/Dry Depth == 0.002 (previously 0.05) and Cell Side Wet/Dry Depth == 0.001 (previously 0.03)	The most pronounced effect of the shallower wet/dry depths is likely to occur in areas that are still filling at the flood peak, such as behind a levee that is only just overtopped. The shallower wet/dry depths provides a greater flow depth for a longer period over the levee.
Adjust Head at ESTRY Interface == OFF (previously ON)	Usually does not have a major influence on results except where very high velocities occur.
Boundary Cell Selection == Method C (previously Method A) and Line Cell Selection == Method C (previously Method A)	May select slightly different cells along boundary/link lines. This may cause a difference where the line is along the top of levee, possibly creating a “hole” in embankment.
Viscosity Formulation == Smagorinsky (previously Constant) and Viscosity Coefficient == 0.2 (previously 1.0)	Can have a significant effect where the viscosity term is influential. This occurs where the friction term is less dominant (i.e. low Manning’s n and/or deeper water such as the lower, tidal, reaches of rivers).
Structure Losses == ADJUST (previously FIX)	Can have a significant affect in the vicinity of structures within a 1D network and for culvert networks. Does not affect 1D structures linked to a 2D domain or at the structure ends not connected to another 1D channel.
Storage Above Structure Obvert (%) == 5 (previously CHANNEL WIDTH)	Usually negligible effect unless the model storage is predominantly within 1D closed sections (i.e. B, C and R channels). The 1D domain is likely to be more sensitive to instabilities due to the much smaller storage above the top of the closed sections, therefore, a smaller 1D timestep may be required and/or the Storage Above Structure Obvert (%) increased.
Depth Limit Factor == 10 (previously 1)	No effect as previously the model would have become “unstable” as the trigger for an instability was the top of the channel/node.
Culvert Flow == Method C (previously Method B)	Usually only minor effects plus improved stability.
Culvert Add Dynamic Head == ON (previously OFF)	Minor influence.
Bridge Flow == Method B (previously Method A)	Negligible influence plus improved stability. However, note the different treatment of energy losses once the bridge deck obvert/soffit is submerged if a BG or LC table is specified.
WLL Approach == Method B (previously Method A)	Only affects the presentation of results. Note, that Method A is no longer recommended or supported.
Apply All Inverts == ON (previously OFF)	Does not affect hydraulic calculations, however, if a Blank, B or W channel is now lowered/raised because the inverts are now used, this will affect results/stability - see note at end of Apply All Inverts).

18.16 Pre 2006-06 Release

For backward compatibility of builds prior to the 2006-06 release, contact support@tuflow.com.