Flood Loads

[strguy11]

I have a building located in flood zone AE with flood elevation of 8. (near the coast). The existing ground level is about 5.

If the site is raised with fill to an elevation of 8 or 9, do the structural loads for floods apply? It seems that I would be outside of the flood levels so any hydrostatic loads would not apply, and the only thing I would need to worry about is scour at the foundations.

It seems to me that the forces shown in the code would apply if the site were not raised, meaning in this case I would need to design for 3' of hydrostatic pressures + wave action.

Any thoughts?

 

[RESENG2]

You will have to design the columns to withstand the flood loads. Take a look at the FEMA Coastal Construction Manual. It's free!

 

[CarlB]

No you would not have to account for flood loads on the foundation. The reason the site would be raised is to keep the building above the 100-year flood level. Normally the site is raised so that lowest grade at building perimeter is 1 foot minimum above the flood level, so the building is no longer in the floodplain. The building and site elevation has to be certified by a surveyor, post construction, with an "elevation certificate".

 

[strguy11]

RESENG2 => I would only need to apply the load to the portion of the column below the DFE correct?

CARLB => If the foundation is below grade, I would need to design the foundation walls to account for the hydrostatic pressure of the flood, correct? I was anticipating a conrete bearing wall foundation with fill on both sides, say 3' deep.

 

[RESENG2]

actually I think CarlB is correct, if they fill to an elevation over the DFE then the foundation would never need to withstand the flood load. The structure would be on an "island". I was originally thinking the foundation would be exposed.