100 year flood

First off..... it's really difficult to decipher your all caps stream of consciousness. 

I gather that you are proposing to stake the flood line that you have downloaded from FEMA's GIS. Am I to suppose that you do boundary surveys by downloading and staking GIS lines also? I presume that you would consider doing so just as absurd as I do. No - you have to find the flood elevation on the ground and stake that.        

I am use to using caps because we draft our maps with CAPS. No we do not stake property lines from GIS lines. We use deeds and the recorded plats. We have always in the past used the flood elevation on the ground and staked that.  That was the purpose of this post to get other's professional opinion. I agree also with your presumption.  Thanks for your reply.

If I am understanding you correctly, it seems that at a recent state society meeting it was stated to mark on the ground the line that is downloaded with the FEMA digital flood information - holding those x,y positions over the published zone AE elevation when marking the line on the ground.

IMO:  I would not agree with marking the x,y of the downloaded data at all.  The line as drawn is not always accurate (which is why there is a map amendment process).  The base flood elevation as published (while I have disagreed with some of them) is the point that should be marked on the ground.

If the elevation marked is below the line from the downloaded data, a letter of map amendment might be useful depending on what the client is doing with the land.

Marking the Flood limits on the ground isn't something that's done here (much). If it's needed for some reason, it's not done from lines in CAD. 

Unfortunately, they don't follow the elevation close enough to use. The last one I did, the ground was 2.5 feet higher than the CAD lines. Which was great news for the client. 

Same with property lines, the deeds and plats are a starting point, but the focus is normally monuments and boundary evidence. 

I'll chime in with agreement on all the other posters so far. Stake the elevation of the predicted flood as it falls on the ground. The mapping done by F.E.M.A. has improved over the years with use of LiDAR data, but the flood line as mapped is still only approximate. Water doesn't care how the maps were drawn.

The official answer would be to determine your 100 year elevation (1% change of flooding annually)from the Flood Insurance Study(FIS) Profile. One fun fact on lakes the 100 year flood elevation is sometimes different then what shows on the maps. 

I am in agreement with all. We did not stake the map line. We used the base flood elevation as I have always done in the past. Our state uses the LIDAR data also. After we staked the elevation and compared it to the map line, they were close but not right on. Thanks for all the input.