|
|
| (4 intermediate revisions by 3 users not shown) |
| Line 2: |
Line 2: |
| [[Category:Dam Breach Inundation Analysis]] | | [[Category:Dam Breach Inundation Analysis]] |
| ---- | | ---- |
| <!-- Delete any sections that are not necessary to your topic. Add pictures/sections as needed --> | | {{Picture |
| “Typically, several hydrologic and non-hydrologic (fair weather) events are evaluated as part of an event-based dam safety analysis. For hydrologic failure events, an extreme flood event ranging from the 50-year event for low-hazard dams up to the PMF for high-hazard dams is selected based on the potential for loss of life due to a dam failure or for significant economic and [[environmental]] losses. Typically the hazard potential classification of the dam is used to selected the extreme hydrologic failure event. The PMF is the flood that may be expected from the most severe combination of critical meteorological and hydrologic conditions that are reasonably possible in the drainage basin under study. The Probable Maximum [[Precipitation]] (PMP) is an estimate of the maximum possible precipitation depth over a given size catchment for a given length of time (Stedinger et al., 1996).
| | |image= |
| | <!-- Add image file name --> |
| | Kennick_Reservoir_Dartmoor.jpg |
|
| |
|
| “A fair weather (Sunny Day) breach is a dam failure that occurs during fair weather (i.e. non-hydrologic or non-precipitation) conditions. A fair weather breach is analyzed by establishing an initial reservoir water level and commencing a breach analysis without additional inflow from a storm event. A fair weather breach is typically used to model piping failures for hydrologic, geologic, [[structural]], [[seismic]], and human-influenced failure modes.
| | |link= |
|
| |
|
| “Base flow conditions for a fair weather failure are typically ignored because of the small discharge and volume compared to that of a dam breach. As a general guidance, base flow can be ignored if the dam breach flow is two times greater than the base flow. Where base flow is considered, the discharge is typically estimated based on reported base flows through the dam’s outlet works or from stream gage records. The three most common initial water level elevations for fair weather breach analyses are as follows:
| | |caption= |
| * “Normal Pool Elevation (invert of the highest elevation of the primary outlet): A breach at the normal pool elevation of the reservoir is used to estimate the volume and associated breach discharge that would result from a failure event during fair weather conditions. For an embankment dam, this type of event is modeled as piping/internal erosion failure, whereas for a concrete dam, this event is modeled as a monolith collapse resulting from sliding, foundation instabilities, or a seismic event.
| | <!-- Add picture caption --> |
| | Kennick Reservoir from a bridge. |
| | (Image Source: [https://commons.wikimedia.org/wiki/File:Kennick_Reservoir,_Dartmoor,_July_2020.jpg Wikipedia]) |
| | }} |
|
| |
|
| * “Invert of Auxiliary Spillway (lowest uncontrolled spillway): A breach of the dam with the reservoir water level set at the auxiliary spillway (also referred to as an emergency spillway) is common practice to simulate a breach during misoperation of the primary outlet works. Initiation of dam failure is typically the same as for the reservoir level at normal pool.
| | <!-- Delete any sections that are not necessary to your topic. Add pictures/sections as needed --> |
| | | In order to simulate failure of a dam and estimate the impacts of the resultant flood wave, stage-storage information for the full depth of the reservoir is required. This can often be obtained from historical design or [[construction]] records. If significant changes to storage are anticipated due to [[sedimentation]] or other causes, bathymetric [[survey]] can be used to develop updated stage-storage information for the reservoir. |
| * “Top of Dam / Maximum High Pool: The reservoir level set to the top of the dam to represent the maximum amount of volume that may be stored in the reservoir. This condition may be selected to evaluate the most conservative non-hydrologic event. In practice, dams without adequate [[spillways]] or pump storage facilities, where the water level during non-hydrologic events is maintained at the top of the dam, are unique situations subject to this conservative assumption. A breach event when the water level is at the top of the dam may be modeled as a piping/internal erosion failure or as an overtopping failure with the water level just above the top of dam invert.
| |
| | |
| “Various Federal agency publications provide guidance for establishing the initial water surface elevation of a reservoir during a fair weather failure event. Each of these specified elevations is used to characterize different failure modes as well as the potential volume of the reservoir at the time of failure” <ref name ="FEMA P-946">[[Federal Guidelines for Inundation Mapping of Flood Risks Associated with Dam Incidents and Failures (FEMA P-946) | FEMA P-946 Federal Guidelines for Inundation Mapping of Flood Risks Associated with Dam Incidents and Failures, FEMA, 2013]]</ref>.
| |
|
| |
|
| ==Best Practices Resources== | | ==Best Practices Resources== |
| {{Document Icon}} [[Federal Guidelines for Inundation Mapping of Flood Risks Associated with Dam Incidents and Failures (FEMA P-946)|Federal Guidelines for Inundation Mapping of Flood Risks Associated with Dam Incidents and Failures (FEMA P-946) (Federal Emergency Management Agency)]] | | {{Document Icon}} [[Federal Guidelines for Inundation Mapping of Flood Risks Associated with Dam Incidents and Failures (FEMA P-946) | Federal Guidelines for Inundation Mapping of Flood Risks Associated with Dam Incidents and Failures (FEMA P-946), FEMA]] |
|
| |
|
| <!-- For information on notation for in text citations visit https://www.mediawiki.org/wiki/Help:Cite Or simply enclose the citation as shown <ref> citation </ref> in the location of the in text mention. Citations will automatically populate below--> | | <!-- For information on notation for in text citations visit https://www.mediawiki.org/wiki/Help:Cite Or simply enclose the citation as shown <ref> citation </ref> in the location of the in text mention. Citations will automatically populate below--> |
