As I understand the process…

As I understand the process for determining the flood hazard includes assumptions regarding storm water management facilties (ponds) and their failure during a storm event. I believe it is included on the table under: Peak or Volume Reduction.
Based upon the approval process for a pond, which includes both municipal reviews and approvals through either subdivision or site plan (sometimes both), provincial review and approvals, including ECA's, each of which commonly includes monitoring and maintenance provisions any provision for failure of a pond when determining the flood risk seems to be overly conservative.

The City of Ottawa has now used some form of programming to map a 1:350 year event, with no policy in any document - Official Plan or Infrastructure Master Plan - that provides guidance for this information. We have had cases where development officers have been requiring information on specific development as it relates to this event. Please provide clear guidance as to what storms are to be used to establish flood risk mapping and why others may be included and the reason for including them.