HEC RAS Warning and Notes

[ateshome]

The Steady Flow analysis on the HEC RAS model I am working on run successfully. However, numerous warning messages were generated. the following are among the messages. What should I look at to address these warning?

1. Conveyance ratio is either less than 0.7 or greater than 1.4, this may indicate a need for additional XS
2. The Velocity Head has changed by more than 0.5ft. this may indicate a need for additional XS
3.The Energy loss was greater that 1.0 ft between current and previous XS, this may indicate a need for additional XS
...

P.S. I have added new XS at the RS where the warnings are fired off, but that didn't address the warning
thanks

[jarvus lunt]

Are you getting these messages at a bridge/culvert? Many bridges get these messages and it isn't usually a problem. (Or, it isn't a problem unless you are required to eliminate all warnings--it would have been better if RAS showed them as notes).

If it is just regular cross sections, intepolating enough cross sections will usually fix the problem (unless there is something more serious going on).

[ateshome]

Originally Posted by ateshome

The Steady Flow analysis on the HEC RAS model I am working on run successfully. However, numerous warning messages were generated. the following are among the messages. What should I look at to address these warning?

1. Conveyance ratio is either less than 0.7 or greater than 1.4, this may indicate a need for additional XS
2. The Velocity Head has changed by more than 0.5ft. this may indicate a need for additional XS
3.The Energy loss was greater that 1.0 ft between current and previous XS, this may indicate a need for additional XS
...

P.S. I have added new XS at the RS where the warnings are fired off, but that didn't address the warning
thanks

Thanks, the warnings show uo at all bridges, but also show up at other regular XS. I will try interpolating more XS in between.

thanks

[psill]

I'm getting the same errors on mine and have added additional XS's so that some of them are only 25 feet apart. Mine is a small watershed of 110 acres and ends at a road with a culvert. I've included several XS's downstream of the culvert. I'm fairly new to the program so I'm wondering if I'm just missing something. Are some of these common errors that can generally be ignored at some point?
Thanks!

[MattZ]

Most of the common errors can be disregarded at some point. If you really want to do some research, I refer you to Engineer Manual 1110-2-1416 page D-6 and D-7.

EM 1110-2-1416 (15 October 1993)

The error messages you see can be referenced back to those pages. You can also see when to disregard some of the messages because of other factors.

I am considering putting together an one hour webinar for ASCE on HEC-RAS warning messages and notes. Do you think yourself and others would find that type of webinar useful (i.e. would you pay for it?)?

[psill]

Hey Matt,
Thanks for the link. I'll go through that and see what I can find. And, yes, I would be interested in your webinar, of course, depending on cost. Keep us updated.
Thanks!