Modelling Accuracy Uncertainties Impact Mapping - Revision history

Anne.Kolega: /* What are the reasons for models to vary widely in their accuracy? */ e.g.

2026-04-01T22:24:02Z

What are the reasons for models to vary widely in their accuracy?: e.g.

← Older revision		Revision as of 08:24, 2 April 2026
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	* The level of uncertainty/inaccuracy in the input data, especially uncertainties in hydrological inflows (which can be considerable) and topography.		* The level of uncertainty/inaccuracy in the input data, especially uncertainties in hydrological inflows (which can be considerable) and topography.
	* Whether the model is calibrated, and if calibrated, the range of calibration events and quantity/quality/type of calibration data. A model well calibrated to a range of flood events will be much more accurate than an uncalibrated model. More information on calibration can be found in <u>[https://www.tuflow.com/Download/Publications/October2016_FMA_Newsletter_HuxleyRyan.pdf Flood Modelling: How Accurate is Your Model?]</u> or an Australian Water School webinar <u>[https://www.tuflow.com/library/webinars/#maximise_accuracy Maximising Hydraulic Model Accuracy]</u>.		* Whether the model is calibrated, and if calibrated, the range of calibration events and quantity/quality/type of calibration data. A model well calibrated to a range of flood events will be much more accurate than an uncalibrated model. More information on calibration can be found in <u>[https://www.tuflow.com/Download/Publications/October2016_FMA_Newsletter_HuxleyRyan.pdf Flood Modelling: How Accurate is Your Model?]</u> or an Australian Water School webinar <u>[https://www.tuflow.com/library/webinars/#maximise_accuracy Maximising Hydraulic Model Accuracy]</u>.
	* Has the model’s sensitivity to changes in uncertain parameters (eg. Manning’s n values) been tested/quantified. Sensitivity testing can help firm up on error margins, especially if the model is uncalibrated.		* Has the model’s sensitivity to changes in uncertain parameters (e.g. Manning’s n values) been tested/quantified. Sensitivity testing can help firm up on error margins, especially if the model is uncalibrated.
	* The scale of the hydraulics. ±10mm would be a large error margin for a flume model flowing 10cm deep, but is negligible for a deep river system flowing 10m or more deep. It’s important to think about the error margin as a percentage (not an absolute amount) of the depth/flow in the main flow paths.		* The scale of the hydraulics. ±10mm would be a large error margin for a flume model flowing 10cm deep, but is negligible for a deep river system flowing 10m or more deep. It’s important to think about the error margin as a percentage (not an absolute amount) of the depth/flow in the main flow paths.
	* The suitability of the software being used for the application, whether a 1D or 2D solution, how the equations are solved, and whether any key terms in the equations are omitted. For example, for non-complex (i.e. slow moving) flows, terms such as the sub-grid turbulence (commonly known as eddy viscosity) can be omitted, however, this can be an essential term for faster, complex flow hydraulics.		* The suitability of the software being used for the application, whether a 1D or 2D solution, how the equations are solved, and whether any key terms in the equations are omitted. For example, for non-complex (i.e. slow moving) flows, terms such as the sub-grid turbulence (commonly known as eddy viscosity) can be omitted, however, this can be an essential term for faster, complex flow hydraulics.

Anne.Kolega: /* What are the reasons why models vary widely in their accuracy? */ for model to vary...

2024-08-28T01:26:10Z

What are the reasons why models vary widely in their accuracy?: for model to vary...

← Older revision		Revision as of 11:26, 28 August 2024
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	=What are the reasons ~~why~~ models vary widely in their accuracy?=		=What are the reasons for models to vary widely in their accuracy?=
	* The level of uncertainty/inaccuracy in the input data, especially uncertainties in hydrological inflows (which can be considerable) and topography.		* The level of uncertainty/inaccuracy in the input data, especially uncertainties in hydrological inflows (which can be considerable) and topography.
	* Whether the model is calibrated, and if calibrated, the range of calibration events and quantity/quality/type of calibration data. A model well calibrated to a range of flood events will be much more accurate than an uncalibrated model. More information on calibration can be found in <u>[https://www.tuflow.com/Download/Publications/October2016_FMA_Newsletter_HuxleyRyan.pdf Flood Modelling: How Accurate is Your Model?]</u> or an Australian Water School webinar <u>[https://www.tuflow.com/library/webinars/#maximise_accuracy Maximising Hydraulic Model Accuracy]</u>.		* Whether the model is calibrated, and if calibrated, the range of calibration events and quantity/quality/type of calibration data. A model well calibrated to a range of flood events will be much more accurate than an uncalibrated model. More information on calibration can be found in <u>[https://www.tuflow.com/Download/Publications/October2016_FMA_Newsletter_HuxleyRyan.pdf Flood Modelling: How Accurate is Your Model?]</u> or an Australian Water School webinar <u>[https://www.tuflow.com/library/webinars/#maximise_accuracy Maximising Hydraulic Model Accuracy]</u>.

Pavlina Monhartova: /* What are the main flood modelling uncertainties? */

2024-08-28T01:14:57Z

What are the main flood modelling uncertainties?

← Older revision		Revision as of 11:14, 28 August 2024
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	*Approach used for solving the underlying mathematical equations describing free surface fluid flow.		*Approach used for solving the underlying mathematical equations describing free surface fluid flow.
	*Degree and quality of model calibration / verification.		*Degree and quality of model calibration / verification.
	*Understanding the degree of uncertainty is important for setting absolute metrics such as design levels and freeboard. While less important for impact mapping because the uncertainties are present in both sides of the comparison. The hydraulic modelling carried out should be based on recommended industry and software guidelines, and follow sound modelling practices.<br> An overview on uncertainties in flood modelling can be viewed in Australian Water School webinar <u>[https://www.tuflow.com/library/webinars/#jul2019_how_wrong How Wrong is Your Flood Model?]</u> <br> <br>		Understanding the degree of uncertainty is important for setting absolute metrics such as design levels and freeboard. While less important for impact mapping because the uncertainties are present in both sides of the comparison. The hydraulic modelling carried out should be based on recommended industry and software guidelines, and follow sound modelling practices.<br> An overview on uncertainties in flood modelling can be viewed in Australian Water School webinar <u>[https://www.tuflow.com/library/webinars/#jul2019_how_wrong How Wrong is Your Flood Model?]</u> <br> <br>

	=What is numerical noise?=		=What is numerical noise?=
	The nonlinear nature of the shallow water (long wave) equations used for modelling floods, can cause localised differences in the results that occur in locations well removed from where the model has changed. These differences should be treated as artefacts of the solution, often referred to as numerical noise.<br>		The nonlinear nature of the shallow water (long wave) equations used for modelling floods, can cause localised differences in the results that occur in locations well removed from where the model has changed. These differences should be treated as artefacts of the solution, often referred to as numerical noise.<br>

Anne.Kolega: /* What are the main flood modelling uncertainties? */

2024-08-27T01:30:34Z

What are the main flood modelling uncertainties?

← Older revision		Revision as of 11:30, 27 August 2024
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	*Approach used for solving the underlying mathematical equations describing free surface fluid flow.		*Approach used for solving the underlying mathematical equations describing free surface fluid flow.
	*Degree and quality of model calibration / verification.		*Degree and quality of model calibration / verification.
	*Understanding of the degree of uncertainty is important for setting absolute metrics such as design levels and freeboard. While less important for impact mapping because the uncertainties are present in both sides of the comparison. The hydraulic modelling carried out should be based on recommended industry and software guidelines, and follow sound modelling practices.<br> An overview on uncertainties in flood modelling can be viewed in Australian Water School webinar <u>[https://www.tuflow.com/library/webinars/#jul2019_how_wrong How Wrong is Your Flood Model?]</u> <br> <br>		*Understanding the degree of uncertainty is important for setting absolute metrics such as design levels and freeboard. While less important for impact mapping because the uncertainties are present in both sides of the comparison. The hydraulic modelling carried out should be based on recommended industry and software guidelines, and follow sound modelling practices.<br> An overview on uncertainties in flood modelling can be viewed in Australian Water School webinar <u>[https://www.tuflow.com/library/webinars/#jul2019_how_wrong How Wrong is Your Flood Model?]</u> <br> <br>
	=What is numerical noise?=		=What is numerical noise?=
	The nonlinear nature of the shallow water (long wave) equations used for modelling floods, can cause localised differences in the results that occur in locations well removed from where the model has changed. These differences should be treated as artefacts of the solution, often referred to as numerical noise.<br>		The nonlinear nature of the shallow water (long wave) equations used for modelling floods, can cause localised differences in the results that occur in locations well removed from where the model has changed. These differences should be treated as artefacts of the solution, often referred to as numerical noise.<br>

Anne.Kolega: /* What are the approaches for setting flood impact tolerances? */

2024-08-26T23:57:52Z

What are the approaches for setting flood impact tolerances?

← Older revision		Revision as of 09:57, 27 August 2024
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	<br>		<br>

	=What are ~~the approaches~~ for setting flood impact tolerances?=		=What approaches are there for setting flood impact tolerances?=
	Establishing guidelines for mapping tolerances for flood impact assessments typically follow one of the approaches below, with the approach taken dependent on the objectives and the type of hydraulic modelling output field being mapped:		Establishing guidelines for mapping tolerances for flood impact assessments typically follow one of the approaches below, with the approach taken dependent on the objectives and the type of hydraulic modelling output field being mapped:
	*A percentage, for example, a maximum increase in velocity of 10%. A threshold or cutoff is sometimes used below which the impact is assumed to be inconsequential or to discard slight changes to near zero values.		*A percentage, for example, a maximum increase in velocity of 10%. A threshold or cutoff is sometimes used below which the impact is assumed to be inconsequential or to discard slight changes to near zero values.

Anne.Kolega: /* What are the main flood modelling uncertainties? */

2024-08-26T23:36:50Z

What are the main flood modelling uncertainties?

← Older revision		Revision as of 09:36, 27 August 2024
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	*Accuracy of the input data (e.g. terrain, landuse, hydrologic inflows).		*Accuracy of the input data (e.g. terrain, landuse, hydrologic inflows).
	*Approach used for solving the underlying mathematical equations describing free surface fluid flow.		*Approach used for solving the underlying mathematical equations describing free surface fluid flow.
			*Degree and quality of model calibration / verification.
	*~~Degree and quality of model calibration / verification.~~ Understanding of the degree of uncertainty is important for setting absolute metrics such as design levels and freeboard. While less important for impact mapping because the uncertainties are present in both sides of the comparison. The hydraulic modelling carried out should be based on recommended industry and software guidelines, and follow sound modelling practices.<br> An overview on uncertainties in flood modelling can be viewed in Australian Water School webinar <u>[https://www.tuflow.com/library/webinars/#jul2019_how_wrong How Wrong is Your Flood Model?]</u> <br> <br>		*Understanding of the degree of uncertainty is important for setting absolute metrics such as design levels and freeboard. While less important for impact mapping because the uncertainties are present in both sides of the comparison. The hydraulic modelling carried out should be based on recommended industry and software guidelines, and follow sound modelling practices.<br> An overview on uncertainties in flood modelling can be viewed in Australian Water School webinar <u>[https://www.tuflow.com/library/webinars/#jul2019_how_wrong How Wrong is Your Flood Model?]</u> <br> <br>
	=What is numerical noise?=		=What is numerical noise?=
	The nonlinear nature of the shallow water (long wave) equations used for modelling floods, can cause localised differences in the results that occur in locations well removed from where the model has changed. These differences should be treated as artefacts of the solution, often referred to as numerical noise.<br>		The nonlinear nature of the shallow water (long wave) equations used for modelling floods, can cause localised differences in the results that occur in locations well removed from where the model has changed. These differences should be treated as artefacts of the solution, often referred to as numerical noise.<br>

Anne.Kolega: /* What are the main flood modelling uncertainties? */

2024-08-26T23:31:40Z

What are the main flood modelling uncertainties?

← Older revision		Revision as of 09:31, 27 August 2024
Line 18:		Line 18:
	*Accuracy of the input data (e.g. terrain, landuse, hydrologic inflows).		*Accuracy of the input data (e.g. terrain, landuse, hydrologic inflows).
	*Approach used for solving the underlying mathematical equations describing free surface fluid flow.		*Approach used for solving the underlying mathematical equations describing free surface fluid flow.
		⚫	*Degree and quality of model calibration / verification. Understanding of the degree of uncertainty is important for setting absolute metrics such as design levels and freeboard. While less important for impact mapping because the uncertainties are present in both sides of the comparison. The hydraulic modelling carried out should be based on recommended industry and software guidelines, and follow sound modelling practices.<br> An overview on uncertainties in flood modelling can be viewed in Australian Water School webinar <u>[https://www.tuflow.com/library/webinars/#jul2019_how_wrong How Wrong is Your Flood Model?]</u> <br> <br>
	*The degree and quality of model calibration / verification.
⚫	*Understanding the degree of uncertainty is important for setting absolute metrics such as design levels and freeboard. While less important for impact mapping because the uncertainties are present in both sides of the comparison. The hydraulic modelling carried out should be based on recommended industry and software guidelines, and follow sound modelling practices.<br> An overview on uncertainties in flood modelling can be viewed in Australian Water School webinar <u>[https://www.tuflow.com/library/webinars/#jul2019_how_wrong How Wrong is Your Flood Model?]</u> <br> <br>
	=What is numerical noise?=		=What is numerical noise?=
	The nonlinear nature of the shallow water (long wave) equations used for modelling floods, can cause localised differences in the results that occur in locations well removed from where the model has changed. These differences should be treated as artefacts of the solution, often referred to as numerical noise.<br>		The nonlinear nature of the shallow water (long wave) equations used for modelling floods, can cause localised differences in the results that occur in locations well removed from where the model has changed. These differences should be treated as artefacts of the solution, often referred to as numerical noise.<br>

Anne.Kolega: /* What are the main flood modelling uncertainties? */

2024-08-26T23:28:02Z

What are the main flood modelling uncertainties?

← Older revision		Revision as of 09:28, 27 August 2024
Line 19:		Line 19:
	*Approach used for solving the underlying mathematical equations describing free surface fluid flow.		*Approach used for solving the underlying mathematical equations describing free surface fluid flow.
	*The degree and quality of model calibration / verification.		*The degree and quality of model calibration / verification.
	Understanding the degree of uncertainty is important for setting absolute metrics such as design levels and freeboard. While less important for impact mapping because the uncertainties are present in both sides of the comparison. The hydraulic modelling carried out should be based on recommended industry and software guidelines, and follow sound modelling practices.<br>		*Understanding the degree of uncertainty is important for setting absolute metrics such as design levels and freeboard. While less important for impact mapping because the uncertainties are present in both sides of the comparison. The hydraulic modelling carried out should be based on recommended industry and software guidelines, and follow sound modelling practices.<br> An overview on uncertainties in flood modelling can be viewed in Australian Water School webinar <u>[https://www.tuflow.com/library/webinars/#jul2019_how_wrong How Wrong is Your Flood Model?]</u> <br> <br>
	An overview on uncertainties in flood modelling can be viewed in Australian Water School webinar <u>[https://www.tuflow.com/library/webinars/#jul2019_how_wrong How Wrong is Your Flood Model?]</u> <br>
	<br>

	=What is numerical noise?=		=What is numerical noise?=
	The nonlinear nature of the shallow water (long wave) equations used for modelling floods, can cause localised differences in the results that occur in locations well removed from where the model has changed. These differences should be treated as artefacts of the solution, often referred to as numerical noise.<br>		The nonlinear nature of the shallow water (long wave) equations used for modelling floods, can cause localised differences in the results that occur in locations well removed from where the model has changed. These differences should be treated as artefacts of the solution, often referred to as numerical noise.<br>

Anne.Kolega: /* What are the main flood modelling uncertainties? */ added a space for readability

2024-08-26T23:27:00Z

What are the main flood modelling uncertainties?: added a space for readability

← Older revision		Revision as of 09:27, 27 August 2024
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	*Accuracy of the input data (e.g. terrain, landuse, hydrologic inflows).		*Accuracy of the input data (e.g. terrain, landuse, hydrologic inflows).
	*Approach used for solving the underlying mathematical equations describing free surface fluid flow.		*Approach used for solving the underlying mathematical equations describing free surface fluid flow.
	*The degree and quality of model calibration/verification.		*The degree and quality of model calibration / verification.
	Understanding the degree of uncertainty is important for setting absolute metrics such as design levels and freeboard. While less important for impact mapping because the uncertainties are present in both sides of the comparison. The hydraulic modelling carried out should be based on recommended industry and software guidelines, and follow sound modelling practices.<br>		Understanding the degree of uncertainty is important for setting absolute metrics such as design levels and freeboard. While less important for impact mapping because the uncertainties are present in both sides of the comparison. The hydraulic modelling carried out should be based on recommended industry and software guidelines, and follow sound modelling practices.<br>
	An overview on uncertainties in flood modelling can be viewed in Australian Water School webinar <u>[https://www.tuflow.com/library/webinars/#jul2019_how_wrong How Wrong is Your Flood Model?]</u> <br>		An overview on uncertainties in flood modelling can be viewed in Australian Water School webinar <u>[https://www.tuflow.com/library/webinars/#jul2019_how_wrong How Wrong is Your Flood Model?]</u> <br>

Pavlina Monhartova: /* I am running existing and developed case and see differences away from the model changes. Why? */

2022-11-01T03:47:07Z

I am running existing and developed case and see differences away from the model changes. Why?

← Older revision		Revision as of 13:47, 1 November 2022
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	* Use depth varying manning's n (lower manning's n for shallow water depths), specifically for direct rainfall models.		* Use depth varying manning's n (lower manning's n for shallow water depths), specifically for direct rainfall models.
	* Set appropriate <font color="blue"><tt>Map Cutoff Depth </tt></font> for the modelling task. e.g. direct rainfall models might have higher values to avoid undesirable noise on the wet/dry interface.<br>		* Set appropriate <font color="blue"><tt>Map Cutoff Depth </tt></font> for the modelling task. e.g. direct rainfall models might have higher values to avoid undesirable noise on the wet/dry interface.<br>
			* Use smaller 1D timestep for models with 1D features.
			* Try double precision, specifically for models with higher elevation, 1D features and or very small flow/rainfall depth increments.
			* When running HPC and or Quadtree, test control number factor smaller than 1.
	<br>		<br>