Alternative Floodplain Solutions Needed for Zone AE Property

[Brooklyn_22]

Hi everyone,

I'm facing a challenge with a new build in a 100-year floodplain (Zone AE). I need to provide compensating storage on a cup-for-cup basis but can't use swales or ponds due to lot and construction size, plus no storm inlets for outfall. Considering a French drain, but unsure if it's suitable. Any alternative suggestions or advice?

Thanks!

 

[swazimatt]

I assume you are building a platform and removing flood volume and looking to compensate for the lost volume. triton or vault system would provide better volume than a french drain (99% volume vs 35% volume between rocks in your french drain)and you could put it under your driveway, but you will probably need to demonstrate that your system is not going to be full of groundwater when the flood arrives

https://tritonsws.com/

 

[darthsoilsguy2]

Is there no room to just lower the yard area? you don't have to make a "pond" with structures or anything.... just have to show a depression with the offsetting volume that has been freed up..... Theoretically, if you are above the seasonal high groundwater table at the bottom of the excavation, a giant filter fabric wrapped stone deposit centered in a drywell would give you some offsetting volume. I don't know if it is supported by FEMA tech guidance, but if you just have to satisfy the zoning officer you might be able to convince them. In most situations, the zoning officer is the only checkpoint on floodplain issues. Compensatory storage isn't really flood science as much as land use control policy. If we didn't have compensatory storage policies, people would just dump fill on their properties until they were above BFE. I can come up with a lot of good reasons why floodplain policy should restrict any other forms of compensatory storage except for depressions/ponds.