Cheap land innit? Developers can drain it, put a rudimentary drainage system in place, build houses and hope that no-one looks at the small print. It’s been going on for years. All you can do about it is bring it to people’s attention and hope no-one falls for it.
What is it with building plots on known flood plains?
https://www.rightmove.co.uk/commercial-property-for-sale/property-102118607.html