×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Duration of Inundation

Duration of Inundation

Duration of Inundation

(OP)
I am filling out an Army Corps of Engineers application that asks for the "duration of inundation". I know that this is defined as the amount of time it takes for the water surface elevation to return to it's starting elevation, however what order of accuracy should I be using?

EXAMPLE, 24 hour storm duration:
Starting water surface elevation: el.393.18 @0.0 hrs
Water elevation "sees" the storm: el.393.19 @9.6 hrs
Peak water surface elevation: el. 395.93 @19.8hrs
Tail end of hydrograph:
el. 393.78 (starting+6") @89.8hrs
el. 393.51 (starting+4") @114.8hrs
End of model: el. 393.38 @144.0hrs (note that el. 393.38 starts at 142.2hrs, is definitely trailing off at this point)

What would YOU use as the duration of inundation in this example?

Any rules of thumb as to how to define the tail end of the storm? Is it truly when the water surface returns to delta0.00?
 

RE: Duration of Inundation

You may get better answers if you tell us which Corps of Engineers form you are filling out.

If you are working on a project located in a regulatory flood plain that may be a different form than if you are working on a project located in or near a jurisdictional wetland or in a navigable waterway. These things matter to regulators.

How do you know the example you have provided is the appropriate example for your project ?

There is nothing magic, or sacred, about a 24 hour storm.
There is nothing magic about a so called 100 year storm ( 1% Annual Exceedence Probablity storm).

Finally, because regulatory flood elevations are considered accurate to only plus or minus 1 foot this suggest that your duration need only be accurate to a similar range.

good luck

RE: Duration of Inundation

KatiLynSki:  Are you sure it's the time required to return to the starting elevation, rather than the time that a certain flood elevation is exceeded?

Returning to the starting elevation can take a very long time, especially if the dropping WSE is asymptotically approaching the starting elevation.  This would present a real challenge in deciding "how close" you have to get.  On the other hand, the (higher) flood elevation is likely to be reached and crossed at a clearly defined time.
 

Peter Smart
HydroCAD Software
www.hydrocad.net
 

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources