Difference between revisions of "748.6 High Water Surface Elevation"

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m (Per Bridge, re-titled article and added definitions)
m (Per Bridge, updated links & verbiage (Design High Water changed to Design Flood Elevation or Normal High Water and High Water changed to Base Flood Elevation). Figure updated w/ new verbiage)
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==748.6.1 Design High Water==
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==748.6.1 Design Flood Elevation==
  
The design high water surface elevation is the normal water surface elevation at the centerline of the proposed roadway for the [[748.2 Roadway Design Criteria|roadway design criteria]] discharge.  The normal water surface elevation is the elevation of the water surface across the floodplain without MoDOT bridges, culverts, or roadway fills in place.
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The design flood elevation is the high water surface elevation at the location of the [[748.4 Headwater and Backwater|backwater]] with MoDOT bridges, culverts and roadway fills in place. The frequency (for example, 25-year, 50-year) and discharge of the design flood is based on the [[748.2 Roadway Design Criteria| roadway design criteria]].
  
[[image:748.6 Figure Design High Water.gif|center]]
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[[image:748.6.1.jpg|center|900px]]
 
   
 
   
==748.6.2 Backwater/Base Flood High Water==
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==748.6.2 Base Flood Elevation==
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The base flood elevation is defined the same as the design flood elevation except that the discharge is based on Base (100-year) Flood frequency.
  
The high water elevation for the Backwater/Base Flood is the same as the design high water surface elevation except that the design discharge is based on Base (100-year) Flood discharge.
 
  
 
==748.6.3 Freeboard High Water==
 
==748.6.3 Freeboard High Water==
  
The high water surface elevation for freeboard is the design water surface elevation for the [[748.3 Freeboard#748.3.5 Bridges and Culverts|freeboard]] design frequency discharge at the lower limit of the bridge superstructure (with structure in place). Consideration should be given to using the approach high water surface elevation, which is the water surface elevation just upstream of the bridge, as the freeboard high water elevation when the minimum freeboard is at the upstream edge/girder of the bridge. The freeboard high water surface elevation should not be lower than the normal high water surface elevation.  
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The high water surface elevation for freeboard is the design water surface elevation for the [[748.3 Freeboard#748.3.5 Bridges and Culverts|freeboard]] design frequency discharge at the lower limit of the bridge superstructure (with structure in place). Consideration should be given to using the approach high water surface elevation, which is the water surface elevation just upstream of the bridge, as the freeboard high water elevation when the minimum freeboard is at the upstream edge/girder of the bridge. The freeboard high water surface elevation should not be lower than the [http://epg.modot.org/index.php?title=750.3_Bridges#750.3.2.4.1_Normal_Water_Surface_Elevation normal water surface elevation].
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The location of the freeboard high water surface elevation should be noted in the hydraulics report.
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==748.6.4 Accuracy==
  
The location of the freeboard high water surface elevation should be noted in the hydraulics report.
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See [http://epg.modot.org/index.php?title=751.5_Structural_Detailing_Guidelines#Hydraulic_Data EPG 751.5.2.1, Hydraulic Data].
  
  
 
[[Category:748 Hydraulics and Drainage|748.06]]
 
[[Category:748 Hydraulics and Drainage|748.06]]

Revision as of 10:28, 5 December 2014

748.6.1 Design Flood Elevation

The design flood elevation is the high water surface elevation at the location of the backwater with MoDOT bridges, culverts and roadway fills in place. The frequency (for example, 25-year, 50-year) and discharge of the design flood is based on the roadway design criteria.

748.6.1.jpg

748.6.2 Base Flood Elevation

The base flood elevation is defined the same as the design flood elevation except that the discharge is based on Base (100-year) Flood frequency.


748.6.3 Freeboard High Water

The high water surface elevation for freeboard is the design water surface elevation for the freeboard design frequency discharge at the lower limit of the bridge superstructure (with structure in place). Consideration should be given to using the approach high water surface elevation, which is the water surface elevation just upstream of the bridge, as the freeboard high water elevation when the minimum freeboard is at the upstream edge/girder of the bridge. The freeboard high water surface elevation should not be lower than the normal water surface elevation.

The location of the freeboard high water surface elevation should be noted in the hydraulics report.

748.6.4 Accuracy

See EPG 751.5.2.1, Hydraulic Data.