Stormwater Management in Floodplains

[ropotto]

What are the pros and cons of placing a stormwater runoff control facility within a floodplain? ie, such as an infiltration bed.

 

[LCruiser]

It depends on a lot of things. Is it the 5 yr or 100 yr floodplain? Is there now a dam upstream? What type of facility? What kind of riparian habitat is there? What type of soil?

 

[LCruiser]

Also is it to a river or dry wash, or what?

 

[tsgrue]

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What is the mean depth to high water?

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tsgrue: site engineering, stormwater
management, landscape design, ecosystem
rehabilitation, mathematical simulation

http://hhwq.blogspot.com

 

[LCruiser]

And the depth to groundwater (seasonable range if possible)?

 

[ropotto]

I talking about larger storm, such as 50 & 100 yr. The flooding source is a river. The flood depth at the structure would two (2) feet more or less.

 

[Highway27]

I'd think the major con to something like an infiltration bed placed in a floodplain, as LCruiser gets at, is that the infiltration of such a facility may be minimal at best, as groundwater in a low area like a floodplain is likely to be very close to the surface, leaving you no depth to actually infiltrate water.

Additionally, putting any sort of embankment in that floodplain area will have an effect on the flood depths, and could change the flood elevations. There's also a question of whether the relevant permitting authority would allow such a facility within the floodplain.

 

[LCruiser]

Plus, you might reroute flows - and even if not significant, it could appear you are increasing neighbor's risk.

 

[cvg]

the facility will require significant maintenance, reconstruction after any significant flood event. Generally it is better to place these types of facilities closer to the source - ie: higher up in the watershed