DAMBRK bridge overtopping

Thanks for the info on the bridge discharge coefficient you sent me last week.

In the same category of bridges, how does DAMBRK calculate the flow which overtops the bridge? In the bridge description screen, I see the mention of emergency spillway weir, but nothing about a bridge overtopping coefficient. The scenario would be that the bridge does not breach, but it's submerged to the point where there is an orifice-type flow occurring at the bridge opening (bridge discharge coef.) while water is overtopping the bridge much like it is a broad crested weir. Does the spillway option take care of this (elev = road crest and length=roadway length) and if so, where is the overtopping C specified?

Also, is there an updated version of the DAMBRK manual on your website or ftp site anywhere? We have a manual that is (C) 1988-1991 but I wanted to make sure there wasn't a more recent edition out there that wasn't sent to us when we upgraded our 2 dambrk licenses a month or so ago.

Thanks.
David M. Leone
GZA GeoEnvironmental, Inc.

Dear David :

DAMBRK assumes a weir coefficient of 3.0, and so does not allow you to specify a weir discharge coefficient at a bridge structure. The program uses the defined width and the default weir coefficient of 3.0 to determine the roadway and emergency spillway overflow using the weir equation.

Note that we are just finishing up the new DAMBRK User Manual, and it will be posted on our DAMBRK download area as a PDF file. I expect it to be available in about a week. This new manual has been completely updated to reflect the current release of the software.

If you have any additional questions or need any further information, please contact me again.

Sincerely,

Chris E. Maeder, M.S.
Senior Technical Engineer
chris.maeder@bossintl.com