Extreme Flood Criteria
Goal: Maintain boundaries of existing flood plain, & prevent flood damage from extreme storms.
Best tool:
- Prevent future development from the ultimate 100 year flood plain (Often fits within stream buffer)
Worst tool:
- Detention of 100 year storm to pre-development peak discharge rate
- Consumes about 3% of watershed area
- Most expensive form of stormwater storage
No control is needed if development is excluded from 100 year floodplain and downstream conveyance is adequate.
Notes:
The intent of the extreme flood criteria is to prevent flood damage from large storm events, to maintain the boundaries of the ultimate 100 year floodplain, and to protect the physical integrity of stormwater management control structures.
Detention of the 100 year storm to pre-development peak discharge rate is a very expensive and land-consuming way to prevent flood damage from extreme storms. Preventing future development is a much more efficient way to meet extreme flood criteria.
Normally, no control is needed if development is excluded from the 100 year floodplain and the downstream conveyance is adequate.