New single family build in the Floodway on a studied stream - cost insights?

[Russell R Massey]

I am looking at a constructing a single family that would extend into the floodway (not Floodzone) of a studied stream. This is in Georgia. Not near a river or lake or ocean. 

I really just want to add 2 piers tat would be the size of medium size tree trunks and elevate that section over. 

Assuming that I left the whole area open like a beach house, the impact is VERY minimal, but has to be checked. 
Does anyone have any experience with the cost ballpark and requirement to do this with a single residential (not multifamily complex)? 

Time delay is not an issue. Is there any quicker easier path when the impact is less minimal than 3 large trees growing in the area? 

Thank you for the insight. I have read many posts, but many are old and may not be looking at a single building vs complex.