You seem to imply that this story shows how obvious it is for people to know when they're in a food plain.
I think it shows the opposite. This person bought a house, was a victim of a flood, and still didn't realize they were in a flood plain.
I think it shows the opposite. This person bought a house, was a victim of a flood, and still didn't realize they were in a flood plain.
Private Mortgages may require flood insurance depending on factors, depends on the bank and their rules. Govt Backed mortgages (i.e. FHA) will require for 'high risk' areas. However you can still have a flood within 100 years in your area but not be required to have insurance (I live in such an area.) Typically this is for cases where flooding is going to be very minor; i.e. in this area it can happen but it's a small enough flood both in size and depth it doesn't meet the criteria. As a result, savvy folks just make sure not to keep anything expensive out of their basements. Less savy folks take extra trash out after a bad rain.
To the savvy real estate buyer, I recommend https://floodfactor.com to accurately quantify the flood risk of a potential property. They have stepped in where FEMA has dropped the ball.
I used to do permitting for construction of aerial and buried fiber networks.
Typically if you're doing some sort of thing where floodplain data is needed, you'll start by finding the dataset from USGS/FEMA/USGIS/etc. Import that in, you'll get a whole bunch of data that depending on package (i.e. if you are doing stuff in AutoCAD instead of working with real GIS software) you might have to shape to get more proper information; floodplain data looks like a bunch of contoured lines (often semiparallel to each other.) based on the survey, and have different embedded metadata accordingly.
So you'll do your drawing based on that, and ideally at some point, a Surveyor goes out and will Verify the map. They'll do this by probably re-pulling the original survey data, going out to the site, and basically making sure you didn't lie in your map.
This last part BTW is an important check&boundary, and IMO the more important one than municipal approval. A good professional surveyor knows that if he does the wrong (i.e. potentially harmful) thing, he could lose his license and livelyhood forever. Professional Seals are something that I have a lot of respect for.
FWIW, this is often the easier part of getting a permit as long as you are building sanely. The city is where politics, money, and process gets broken.
realistically they're measuring "big floods" and "bigger floods" in a way that is consistent, however the stated time frequency with which they supposedly occur is so extremely inaccurate that it does not rise to the level of 'science.'