Overbank Flooding

• Can damage downstream property and drainage structures

• Development can dramatically increase these peak discharges

• Overbank flooding can be beneficial

• Most storm drains and open channels designed to convey at least the 10 year storm

• Typical practice is to maintain 2 and 10 year storm peak discharges to pre-developed or existing condition levels

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Overbank flooding occurs when flow events exceed the bankfull capacity of the channel and therefore must spill over into the floodplain. This can cause downstream property damage where structures have encroached the flood plain, but it can also be a beneficial event to the flora and fauna ecosystems in the �near bank� zone.