Inflow Design Flood - Revision history

Grichards@gfnet.com at 21:25, 28 March 2024

2024-03-28T21:25:09Z

← Older revision		Revision as of 21:25, 28 March 2024
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	According to the Association of State Dam Safety Officials (ASDSO), the most common dam failure incident mechanism between 2010 and 2019 was dam overtopping.<ref name="ASDSO">[https://damsafety.org/dam-failures Dam Failures and Incidents, ASDSO, 2022]</ref> The dam spillway, and its Inflow Design Flood (IDF), must have sufficient capacity and freeboard to prevent overtopping from occurring.		According to the Association of State Dam Safety Officials (ASDSO), the most common dam failure incident mechanism between 2010 and 2019 was dam overtopping.<ref name="ASDSO">[https://damsafety.org/dam-failures Dam Failures and Incidents, ASDSO, 2022]</ref> The dam spillway, and its Inflow Design Flood (IDF), must have sufficient capacity and freeboard to prevent overtopping from occurring.

	“Selection of an IDF can involve tradeoffs in trying to satisfy multiple objectives including: (1) providing acceptable safety to the public; (2) effectively applying the resources of the dam [[owner]]; (3) maintaining the credibility of the [[regulator]] in representing the interest of the public; (4) assessing the desire of the public for the [[benefits]] of a dam in exchange for the inherent risks that come from living downstream of a dam. No single approach to the selection of an IDF is adequate for the unique situations of thousands of existing or planned dams”.<ref name="FEMA-P94">[[Selecting and Accommodating Inflow Design Floods for Dams (FEMA P-94)\|FEMA-P94 Selecting and Accommodating Inflow Design Floods for Dams, FEMA, 2013]]</ref>		“Selection of an IDF can involve tradeoffs in trying to satisfy multiple objectives including: (1) providing acceptable safety to the public; (2) effectively applying the resources of the dam [[owner]]; (3) maintaining the credibility of the [[regulator]] in representing the interest of the public; (4) assessing the desire of the public for the benefits of a dam in exchange for the inherent risks that come from living downstream of a dam. No single approach to the selection of an IDF is adequate for the unique situations of thousands of existing or planned dams”.<ref name="FEMA-P94">[[Selecting and Accommodating Inflow Design Floods for Dams (FEMA P-94)\|FEMA-P94 Selecting and Accommodating Inflow Design Floods for Dams, FEMA, 2013]]</ref>

	FEMA P-94 provides federal guidelines for selecting the Inflow Design Flood (IDF) of a given dam using one of four recommended approaches: a prescriptive standard, a site-specific Probable Maximum [[Precipitation]] (PMP) study, an incremental [[Consequence Analysis\|consequence analysis]], or a Risk-Informed Decision Making (RIDM) analysis.		FEMA P-94 provides federal guidelines for selecting the Inflow Design Flood (IDF) of a given dam using one of four recommended approaches: a prescriptive standard, a site-specific Probable Maximum [[Precipitation]] (PMP) study, an incremental [[Consequence Analysis\|consequence analysis]], or a Risk-Informed Decision Making (RIDM) analysis.
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	==Incremental Consequence Analysis Approach==		==Incremental Consequence Analysis Approach==
	The incremental consequence analysis approach considers the overall effect that a failure of the dam due to hydrologic deficiencies would have in the consequences downstream with that of the same dam that would not fail due to sufficient spillway capacity. Should the difference in the consequences of the two scenarios become negligible, it is determined that increasing the IDF of the spillway would not significantly increase the benefit to the public when compared to the necessary costs.		The incremental [[Consequence Analysis\|consequence analysis]] approach considers the overall effect that a failure of the dam due to hydrologic deficiencies would have in the consequences downstream with that of the same dam that would not fail due to sufficient spillway capacity. Should the difference in the consequences of the two scenarios become negligible, it is determined that increasing the IDF of the spillway would not significantly increase the benefit to the public when compared to the necessary costs.
	<br />		<br />

Mpollei@gfnet.com at 20:09, 18 July 2023

2023-07-18T20:09:05Z

← Older revision		Revision as of 20:09, 18 July 2023
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	\|caption=		\|caption=
	<!-- Add picture caption -->		<!-- Add picture caption -->
	A diagram discussing inflow design flood analysis. ([[Technical Release 210-60: Earth Dams and Reservoirs \| TR-210-60 Earth Dams and Reservoirs, NRCS, 2019]])		A diagram discussing inflow design flood analysis.
			(Image Source: [[Technical Release 210-60: Earth Dams and Reservoirs \| TR-210-60 Earth Dams and Reservoirs, NRCS, 2019]])
	}}		}}

	According to the Association of State Dam Safety Officials (ASDSO), the most common dam failure incident mechanism between 2010 and 2019 was dam overtopping.<ref name="ASDSO">[https://damsafety.org/dam-failures Dam Failures and Incidents, ASDSO, 2022]</ref> The dam spillway, and its Inflow Design Flood (IDF), must have sufficient capacity and freeboard to prevent overtopping from occurring.		According to the Association of State Dam Safety Officials (ASDSO), the most common dam failure incident mechanism between 2010 and 2019 was dam overtopping.<ref name="ASDSO">[https://damsafety.org/dam-failures Dam Failures and Incidents, ASDSO, 2022]</ref> The dam spillway, and its Inflow Design Flood (IDF), must have sufficient capacity and freeboard to prevent overtopping from occurring.

	“Selection of an IDF can involve tradeoffs in trying to satisfy multiple objectives including: (1) providing acceptable safety to the public; (2) effectively applying the resources of the dam owner; (3) maintaining the credibility of the regulator in representing the interest of the public; (4) assessing the desire of the public for the benefits of a dam in exchange for the inherent risks that come from living downstream of a dam. No single approach to the selection of an IDF is adequate for the unique situations of thousands of existing or planned dams”.<ref name="FEMA-P94">[[Selecting and Accommodating Inflow Design Floods for Dams (FEMA P-94)\|FEMA-P94 Selecting and Accommodating Inflow Design Floods for Dams, FEMA, 2013]]</ref>		“Selection of an IDF can involve tradeoffs in trying to satisfy multiple objectives including: (1) providing acceptable safety to the public; (2) effectively applying the resources of the dam [[owner]]; (3) maintaining the credibility of the [[regulator]] in representing the interest of the public; (4) assessing the desire of the public for the [[benefits]] of a dam in exchange for the inherent risks that come from living downstream of a dam. No single approach to the selection of an IDF is adequate for the unique situations of thousands of existing or planned dams”.<ref name="FEMA-P94">[[Selecting and Accommodating Inflow Design Floods for Dams (FEMA P-94)\|FEMA-P94 Selecting and Accommodating Inflow Design Floods for Dams, FEMA, 2013]]</ref>

	FEMA P-94 provides federal guidelines for selecting the Inflow Design Flood (IDF) of a given dam using one of four recommended approaches: a prescriptive standard, a site-specific Probable Maximum Precipitation (PMP) study, an incremental consequence analysis, or a Risk-Informed Decision Making (RIDM) analysis.		FEMA P-94 provides federal guidelines for selecting the Inflow Design Flood (IDF) of a given dam using one of four recommended approaches: a prescriptive standard, a site-specific Probable Maximum [[Precipitation]] (PMP) study, an incremental [[Consequence Analysis\|consequence analysis]], or a Risk-Informed Decision Making (RIDM) analysis.

	==Prescriptive Standard Approach==		==Prescriptive Standard Approach==
	The prescriptive standard approach, being the simplest, is based on a particular dam’s potential for causing loss of life and significant economic and environmental damage in the event of its failure. This potential for causing loss of life and other damages was defined by FEMA previously in the document ''Federal Guidelines for Dam Safety: Hazard Potential Classification System for Dams''.<ref name="FEMA 2004">[[Federal Guidelines for Dam Safety: Hazard Potential Classification System for Dams (FEMA P-333)\|Federal Guidelines for Dam Safety: Hazard Potential Classification System for Dams, FEMA, 2004]]</ref> Dams can fall under one of three Hazard Potential Classifications: Low Hazard Potential, Significant Hazard Potential, and High Hazard Potential. Depending on the classification assigned to a particular dam, different requirements for the IDF are applied by FEMA P-94 as listed in Table 2 of the document.		The prescriptive standard approach, being the simplest, is based on a particular dam’s potential for causing loss of life and significant economic and [[environmental]] damage in the event of its failure. This potential for causing loss of life and other damages was defined by FEMA previously in the document ''Federal Guidelines for Dam Safety: [[Hazard Potential Classification]] System for Dams''.<ref name="FEMA 2004">[[Federal Guidelines for Dam Safety: Hazard Potential Classification System for Dams (FEMA P-333)\|Federal Guidelines for Dam Safety: Hazard Potential Classification System for Dams, FEMA, 2004]]</ref> Dams can fall under one of three Hazard Potential Classifications: Low Hazard Potential, Significant Hazard Potential, and High Hazard Potential. Depending on the classification assigned to a particular dam, different requirements for the IDF are applied by FEMA P-94 as listed in Table 2 of the document.
	<br />		<br />

	==Site-Specific PMP Study Approach==		==Site-Specific PMP Study Approach==
	The site-specific PMP study approach relies on a more detailed, rigorous, and current hydrologic analysis that is more tailored to the conditions at the location of the particular dam rather than more generalized and commonly available PMP studies such as the Hydrometeorological Reports (HMR) published by the National Weather Service (NWS) for the region in which the dam is located. The extra effort required to conduct a more site- and project-specific study can reduce the uncertainty in the calculation of the resulting PMP estimate for the dam, potentially lowering the resulting magnitude of the IDF resulting in a smaller spillway and savings in construction costs.		The site-specific PMP study approach relies on a more detailed, rigorous, and current hydrologic analysis that is more tailored to the conditions at the location of the particular dam rather than more generalized and commonly available PMP studies such as the Hydrometeorological Reports (HMR) published by the [[National Weather Service]] (NWS) for the region in which the dam is located. The extra effort required to conduct a more site- and project-specific study can reduce the uncertainty in the calculation of the resulting PMP estimate for the dam, potentially lowering the resulting magnitude of the IDF resulting in a smaller spillway and savings in [[construction]] costs.
	<br />		<br />

Cort at 19:26, 13 September 2022

2022-09-13T19:26:44Z

← Older revision		Revision as of 19:26, 13 September 2022
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	inflowdesignflood.png		inflowdesignflood.png
	\|link=		\|link=
	<!--~~https~~:~~//www.semanticscholar.org/paper/APP-LICATION-OF-THE-INFLOW-DESIGN-FLOOD-ANALYSIS-TO-Hoeft-Locke/190ccc03c792c3b7f14fdee49ca17c22dfef0eb3~~-->		<!--Technical Release 210-60: Earth Dams and Reservoirs-->

	\|caption=		\|caption=
	<!-- Add picture caption -->		<!-- Add picture caption -->
	A diagram discussing inflow design flood analysis. (TR-210-60 Earth Dams and Reservoirs, NRCS, 2019)		A diagram discussing inflow design flood analysis. ([[Technical Release 210-60: Earth Dams and Reservoirs \| TR-210-60 Earth Dams and Reservoirs, NRCS, 2019]])
	}}		}}

Rmanwaring at 19:03, 13 September 2022

2022-09-13T19:03:35Z

← Older revision		Revision as of 19:03, 13 September 2022
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	==Risk-Informed Decision Making Approach==		==Risk-Informed Decision Making Approach==
	The RIDM analysis approach allows for dam owners to assess and compare all potential failure modes, as well as their estimated consequences, for the dam and assigning probabilities to each. This allows dam owners to compare the risks associated with every potential failure mode and informs their decisions on how to most efficiently allocate limited resources to most effectively reduce the risk of a failure of the dam.		The RIDM analysis approach allows for dam owners to assess and compare all potential failure modes, as well as their estimated consequences, for the dam and assigning probabilities to each. This allows dam owners to compare the risks associated with every potential failure mode and informs their decisions on how to most efficiently allocate limited resources to most effectively reduce the risk of a failure of the dam.

			==Examples==
			{{Website Icon}} [https://damsafety.org/dam-failures Dam Failures and Incidents]

	==Best Practices Resources==		==Best Practices Resources==
	~~{{Document Icon}} [https://damsafety.org/dam-failures Dam Failures and Incidents]~~
	{{Document Icon}} [[Federal Guidelines for Dam Safety: Hazard Potential Classification System for Dams (FEMA P-333)]]		{{Document Icon}} [[Federal Guidelines for Dam Safety: Hazard Potential Classification System for Dams (FEMA P-333)]]
	{{Document Icon}} [[Selecting and Accommodating Inflow Design Floods for Dams (FEMA P-94)]]		{{Document Icon}} [[Selecting and Accommodating Inflow Design Floods for Dams (FEMA P-94)]]

	==Trainings==		==Trainings==
	{{~~Website~~ Icon}}		{{Video Icon}}

	</br>		</br>

Cort at 17:25, 13 September 2022

2022-09-13T17:25:16Z

← Older revision		Revision as of 17:25, 13 September 2022
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	}}		}}

	According to the Association of State Dam Safety Officials (ASDSO), the most common dam failure incident mechanism between 2010 and 2019 was dam overtopping.<ref name="ASDSO">[https://damsafety.org/dam-failures ASDSO, 2022]</ref> The dam spillway, and its Inflow Design Flood (IDF), must have sufficient capacity and freeboard to prevent overtopping from occurring.		According to the Association of State Dam Safety Officials (ASDSO), the most common dam failure incident mechanism between 2010 and 2019 was dam overtopping.<ref name="ASDSO">[https://damsafety.org/dam-failures Dam Failures and Incidents, ASDSO, 2022]</ref> The dam spillway, and its Inflow Design Flood (IDF), must have sufficient capacity and freeboard to prevent overtopping from occurring.

	“Selection of an IDF can involve tradeoffs in trying to satisfy multiple objectives including: (1) providing acceptable safety to the public; (2) effectively applying the resources of the dam owner; (3) maintaining the credibility of the regulator in representing the interest of the public; (4) assessing the desire of the public for the benefits of a dam in exchange for the inherent risks that come from living downstream of a dam. No single approach to the selection of an IDF is adequate for the unique situations of thousands of existing or planned dams”.<ref name="FEMA-P94">[[Selecting and Accommodating Inflow Design Floods for Dams (FEMA P-94)\|FEMA-P94 Selecting and Accommodating Inflow Design Floods for Dams, FEMA, 2013]]</ref>		“Selection of an IDF can involve tradeoffs in trying to satisfy multiple objectives including: (1) providing acceptable safety to the public; (2) effectively applying the resources of the dam owner; (3) maintaining the credibility of the regulator in representing the interest of the public; (4) assessing the desire of the public for the benefits of a dam in exchange for the inherent risks that come from living downstream of a dam. No single approach to the selection of an IDF is adequate for the unique situations of thousands of existing or planned dams”.<ref name="FEMA-P94">[[Selecting and Accommodating Inflow Design Floods for Dams (FEMA P-94)\|FEMA-P94 Selecting and Accommodating Inflow Design Floods for Dams, FEMA, 2013]]</ref>
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	==Best Practices Resources==		==Best Practices Resources==
	{{Document Icon}}		{{Document Icon}} [https://damsafety.org/dam-failures Dam Failures and Incidents]
			{{Document Icon}} [[Federal Guidelines for Dam Safety: Hazard Potential Classification System for Dams (FEMA P-333)]]
			{{Document Icon}} [[Selecting and Accommodating Inflow Design Floods for Dams (FEMA P-94)]]

	==Trainings==		==Trainings==

Cort at 17:13, 9 September 2022

2022-09-09T17:13:40Z

← Older revision		Revision as of 17:13, 9 September 2022
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	\|caption=		\|caption=
	<!-- Add picture caption -->		<!-- Add picture caption -->
	A ~~team of geotechnical engineers operating a borehole drilling rig~~. (TR-210-60 Earth Dams and Reservoirs, NRCS, 2019)		A diagram discussing inflow design flood analysis. (TR-210-60 Earth Dams and Reservoirs, NRCS, 2019)
	}}		}}

Rmanwaring at 17:01, 9 September 2022

2022-09-09T17:01:18Z

← Older revision		Revision as of 17:01, 9 September 2022
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	\|caption=		\|caption=
	<!-- Add picture caption -->		<!-- Add picture caption -->
	A team of geotechnical engineers operating a borehole drilling rig. (~~USDA/NRCS~~ TR-60)		A team of geotechnical engineers operating a borehole drilling rig. (TR-210-60 Earth Dams and Reservoirs, NRCS, 2019)
	}}		}}

Cort at 15:33, 9 September 2022

2022-09-09T15:33:20Z

@@ Line 1: / Line 1: @@
 __NOTOC__
 ----
 According to the Association of State Dam Safety Officials (ASDSO), the most common dam failure incident mechanism between 2010 and 2019 was dam overtopping.<ref name="ASDSO">[https://damsafety.org/dam-failures ASDSO, 2022]</ref> The dam spillway, and its Inflow Design Flood (IDF), must have sufficient capacity and freeboard to prevent overtopping from occurring.

Rmanwaring at 19:51, 6 September 2022

2022-09-06T19:51:05Z

← Older revision		Revision as of 19:51, 6 September 2022
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	__NOTOC__		__NOTOC__
	----		----
	According to the Association of State Dam Safety Officials (ASDSO), the most common dam failure incident mechanism between 2010 and 2019 was dam overtopping.<ref name="ASDSO">~~ASDSO, 2022,~~ https://damsafety.org/dam-failures</ref> The dam spillway, and its Inflow Design Flood (IDF), must have sufficient capacity and freeboard to prevent overtopping from occurring.		According to the Association of State Dam Safety Officials (ASDSO), the most common dam failure incident mechanism between 2010 and 2019 was dam overtopping.<ref name="ASDSO">[https://damsafety.org/dam-failures ASDSO, 2022]</ref> The dam spillway, and its Inflow Design Flood (IDF), must have sufficient capacity and freeboard to prevent overtopping from occurring.

	“Selection of an IDF can involve tradeoffs in trying to satisfy multiple objectives including: (1) providing acceptable safety to the public; (2) effectively applying the resources of the dam owner; (3) maintaining the credibility of the regulator in representing the interest of the public; (4) assessing the desire of the public for the benefits of a dam in exchange for the inherent risks that come from living downstream of a dam. No single approach to the selection of an IDF is adequate for the unique situations of thousands of existing or planned dams”.<ref name="FEMA-P94">FEMA-P94 Selecting and Accommodating Inflow Design Floods for Dams, FEMA, 2013</ref>		“Selection of an IDF can involve tradeoffs in trying to satisfy multiple objectives including: (1) providing acceptable safety to the public; (2) effectively applying the resources of the dam owner; (3) maintaining the credibility of the regulator in representing the interest of the public; (4) assessing the desire of the public for the benefits of a dam in exchange for the inherent risks that come from living downstream of a dam. No single approach to the selection of an IDF is adequate for the unique situations of thousands of existing or planned dams”.<ref name="FEMA-P94">[[Selecting and Accommodating Inflow Design Floods for Dams (FEMA P-94)\|FEMA-P94 Selecting and Accommodating Inflow Design Floods for Dams, FEMA, 2013]]</ref>

	FEMA P-94 provides federal guidelines for selecting the Inflow Design Flood (IDF) of a given dam using one of four recommended approaches: a prescriptive standard, a site-specific Probable Maximum Precipitation (PMP) study, an incremental consequence analysis, or a Risk-Informed Decision Making (RIDM) analysis.		FEMA P-94 provides federal guidelines for selecting the Inflow Design Flood (IDF) of a given dam using one of four recommended approaches: a prescriptive standard, a site-specific Probable Maximum Precipitation (PMP) study, an incremental consequence analysis, or a Risk-Informed Decision Making (RIDM) analysis.

	==Prescriptive Standard Approach==		==Prescriptive Standard Approach==
	The prescriptive standard approach, being the simplest, is based on a particular dam’s potential for causing loss of life and significant economic and environmental damage in the event of its failure. This potential for causing loss of life and other damages was defined by FEMA previously in the document ''Federal Guidelines for Dam Safety: Hazard Potential Classification System for Dams''.<ref name="FEMA 2004">Federal Guidelines for Dam Safety: Hazard Potential Classification System for Dams, FEMA, 2004</ref> Dams can fall under one of three Hazard Potential Classifications: Low Hazard Potential, Significant Hazard Potential, and High Hazard Potential. Depending on the classification assigned to a particular dam, different requirements for the IDF are applied by FEMA P-94 as listed in Table 2 of the document.		The prescriptive standard approach, being the simplest, is based on a particular dam’s potential for causing loss of life and significant economic and environmental damage in the event of its failure. This potential for causing loss of life and other damages was defined by FEMA previously in the document ''Federal Guidelines for Dam Safety: Hazard Potential Classification System for Dams''.<ref name="FEMA 2004">[[Federal Guidelines for Dam Safety: Hazard Potential Classification System for Dams (FEMA P-333)\|Federal Guidelines for Dam Safety: Hazard Potential Classification System for Dams, FEMA, 2004]]</ref> Dams can fall under one of three Hazard Potential Classifications: Low Hazard Potential, Significant Hazard Potential, and High Hazard Potential. Depending on the classification assigned to a particular dam, different requirements for the IDF are applied by FEMA P-94 as listed in Table 2 of the document.
	<br />		<br />
	==~~Probable Maximum Precipitation (~~PMP) Study==
			==Site-Specific PMP Study Approach==
	The site-specific PMP study approach relies on a more detailed, rigorous, and current hydrologic analysis that is more tailored to the conditions at the location of the particular dam rather than more generalized and commonly available PMP studies such as the Hydrometeorological Reports (HMR) published by the National Weather Service (NWS) for the region in which the dam is located. The extra effort required to conduct a more site- and project-specific study can reduce the uncertainty in the calculation of the resulting PMP estimate for the dam, potentially lowering the resulting magnitude of the IDF resulting in a smaller spillway and savings in construction costs.		The site-specific PMP study approach relies on a more detailed, rigorous, and current hydrologic analysis that is more tailored to the conditions at the location of the particular dam rather than more generalized and commonly available PMP studies such as the Hydrometeorological Reports (HMR) published by the National Weather Service (NWS) for the region in which the dam is located. The extra effort required to conduct a more site- and project-specific study can reduce the uncertainty in the calculation of the resulting PMP estimate for the dam, potentially lowering the resulting magnitude of the IDF resulting in a smaller spillway and savings in construction costs.
	<br />		<br />
	==Incremental Consequence Analysis==
			==Incremental Consequence Analysis Approach==
	The incremental consequence analysis approach considers the overall effect that a failure of the dam due to hydrologic deficiencies would have in the consequences downstream with that of the same dam that would not fail due to sufficient spillway capacity. Should the difference in the consequences of the two scenarios become negligible, it is determined that increasing the IDF of the spillway would not significantly increase the benefit to the public when compared to the necessary costs.		The incremental consequence analysis approach considers the overall effect that a failure of the dam due to hydrologic deficiencies would have in the consequences downstream with that of the same dam that would not fail due to sufficient spillway capacity. Should the difference in the consequences of the two scenarios become negligible, it is determined that increasing the IDF of the spillway would not significantly increase the benefit to the public when compared to the necessary costs.
	<br />		<br />
	==Risk-Informed Decision Making ~~(RIDM) Analysis~~==
			==Risk-Informed Decision Making Approach==
	The RIDM analysis approach allows for dam owners to assess and compare all potential failure modes, as well as their estimated consequences, for the dam and assigning probabilities to each. This allows dam owners to compare the risks associated with every potential failure mode and informs their decisions on how to most efficiently allocate limited resources to most effectively reduce the risk of a failure of the dam.		The RIDM analysis approach allows for dam owners to assess and compare all potential failure modes, as well as their estimated consequences, for the dam and assigning probabilities to each. This allows dam owners to compare the risks associated with every potential failure mode and informs their decisions on how to most efficiently allocate limited resources to most effectively reduce the risk of a failure of the dam.

Cort: Created page with "NOTOC ---- According to the Association of State Dam Safety Officials (ASDSO), the most common dam failure incident mechanism between 2010 and 2019 was dam overtopping.ASDSO, 2022, https://damsafety.org/dam-failures The dam spillway, and its Inflow Design Flood (IDF), must have sufficient capacity and freeboard to prevent overtopping from occurring. “Selection of an IDF can involve tradeoffs in trying to satisfy multiple objectives includ..."

2022-09-02T18:52:19Z

Created page with "__NOTOC__ ---- According to the Association of State Dam Safety Officials (ASDSO), the most common dam failure incident mechanism between 2010 and 2019 was dam overtopping.<ref name="ASDSO">ASDSO, 2022, https://damsafety.org/dam-failures</ref> The dam spillway, and its Inflow Design Flood (IDF), must have sufficient capacity and freeboard to prevent overtopping from occurring. “Selection of an IDF can involve tradeoffs in trying to satisfy multiple objectives includ..."

New page

__NOTOC__
----
According to the Association of State Dam Safety Officials (ASDSO), the most common dam failure incident mechanism between 2010 and 2019 was dam overtopping.<ref name="ASDSO">ASDSO, 2022, https://damsafety.org/dam-failures</ref> The dam spillway, and its Inflow Design Flood (IDF), must have sufficient capacity and freeboard to prevent overtopping from occurring.

“Selection of an IDF can involve tradeoffs in trying to satisfy multiple objectives including: (1) providing acceptable safety to the public; (2) effectively applying the resources of the dam owner; (3) maintaining the credibility of the regulator in representing the interest of the public; (4) assessing the desire of the public for the benefits of a dam in exchange for the inherent risks that come from living downstream of a dam. No single approach to the selection of an IDF is adequate for the unique situations of thousands of existing or planned dams”.<ref name="FEMA-P94">FEMA-P94 Selecting and Accommodating Inflow Design Floods for Dams, FEMA, 2013</ref>

FEMA P-94 provides federal guidelines for selecting the Inflow Design Flood (IDF) of a given dam using one of four recommended approaches: a prescriptive standard, a site-specific Probable Maximum Precipitation (PMP) study, an incremental consequence analysis, or a Risk-Informed Decision Making (RIDM) analysis.

==Prescriptive Standard Approach==
The prescriptive standard approach, being the simplest, is based on a particular dam’s potential for causing loss of life and significant economic and environmental damage in the event of its failure. This potential for causing loss of life and other damages was defined by FEMA previously in the document ''Federal Guidelines for Dam Safety: Hazard Potential Classification System for Dams''.<ref name="FEMA 2004">Federal Guidelines for Dam Safety: Hazard Potential Classification System for Dams, FEMA, 2004</ref> Dams can fall under one of three Hazard Potential Classifications: Low Hazard Potential, Significant Hazard Potential, and High Hazard Potential. Depending on the classification assigned to a particular dam, different requirements for the IDF are applied by FEMA P-94 as listed in Table 2 of the document.
<br />
==Probable Maximum Precipitation (PMP) Study==
The site-specific PMP study approach relies on a more detailed, rigorous, and current hydrologic analysis that is more tailored to the conditions at the location of the particular dam rather than more generalized and commonly available PMP studies such as the Hydrometeorological Reports (HMR) published by the National Weather Service (NWS) for the region in which the dam is located. The extra effort required to conduct a more site- and project-specific study can reduce the uncertainty in the calculation of the resulting PMP estimate for the dam, potentially lowering the resulting magnitude of the IDF resulting in a smaller spillway and savings in construction costs.
<br />
==Incremental Consequence Analysis==
The incremental consequence analysis approach considers the overall effect that a failure of the dam due to hydrologic deficiencies would have in the consequences downstream with that of the same dam that would not fail due to sufficient spillway capacity. Should the difference in the consequences of the two scenarios become negligible, it is determined that increasing the IDF of the spillway would not significantly increase the benefit to the public when compared to the necessary costs.
<br />
==Risk-Informed Decision Making (RIDM) Analysis==
The RIDM analysis approach allows for dam owners to assess and compare all potential failure modes, as well as their estimated consequences, for the dam and assigning probabilities to each. This allows dam owners to compare the risks associated with every potential failure mode and informs their decisions on how to most efficiently allocate limited resources to most effectively reduce the risk of a failure of the dam.

==Best Practices Resources==
{{Document Icon}}

==Trainings==
{{Website Icon}}

</br>
Citations:
<references />


{{revhistinf}}