FEMA FIRM map fraud
I've often proposed that after any flood event that sets a new high-water record, the governments should send people out to permanently mark that level on buildings, trees, lamp posts, or whatever. You would no longer need analysts sitting in offices staring at incomplete and hypothetical data, and any fool could see what they were risking by buying a property. Why go through all this nonsense of calculated BFE measured off who-knows-what benchmark when you could find a high-water mark within a short distance of any property?
I think we should eliminate any government involvement in flood insurance or paying for flood damage. Let the people who choose to take the risk of flooding personally pay for that risk. I see no need to protect a fool who chooses to live below sea level.
As others have indicated, FEMA isn't in the floodplain modeling business, it's in the business of risk and political expectation management. (Floodplain modeling is one of the tools it uses, knowing that it's an imperfect tool.) It is an insurer of last resort, a role created and maintained for it by elected officials. Whether or not that's a good thing is a political discussion not suitable for this forum, but flood insurance and all the bureaucracy and engineering flaws and unintended inequities inherent in the process are facts we have to deal with.
Complaining about FEMA might feel good, but it's unlikely to change anything.
The benchmarks you talk about in error. What are they? What is the stability? We’re they on the same level runs originally? I personally have never found a problem with a benchmark unless the stability was an issue.
There are a number of issues in play here. You state that the data sheet doesn't indicate an accuracy. That is a huge red flat. I only use first order bench marks to control FIRM map BFE's.
Although, I suppose I'm lucky to have so many of them.
There were older (by that I mean pre-NGVD29) bench marks run. Some of those are still around but it's not at all surprising to find one of them to be feet "off". Doesn't mean they weren't legitimate at the time they were set. If the data sheet doesn't give an accuracy then I wouldn't use it for anything.
You mentioned a BFE for the log house. If the engineer used this bench mark to run cross sections then it should be used to figure out the BFE. Typically in a Zone A BFE determination there is a report filed by the engineer. I would get with the engineer, explain what you found and it may well be that the log house isn't really in the flood zone after all. I would not tell anyone anything until I figured out what's going on with the elevation control. Whenever you take on a Zone A or even a Zone AE flood zone job all the issues with map making, elevation control, BFE determination is placed on you. This isn't really about OPUS or NGS bench marks.