That’s why the government is the only insurer of flood insurance in a flood zone (I lived in New Orleans for many years, which is a well-recognized flood zone).
My house is alongside a regularly flooding major stream. I was just outside the C zone and had to verify that. The government was the provider had I been inside the zone.
You know the same thing from being in New Orleans.
I don’t think there’s a mandate to buy their insurance if you already own your property, but the mortgage company will require it of you if you are still on their dime.
The government is underwriting what would otherwise be viewed as a bad decision on where one builds.