There was recently another article covering the construction of homes in the flood reservoir area.
https://news.ycombinator.com/item?id=15472082
According to the article, it sounds pretty bad. The city and county knew where the flood reservoirs were. The developers knew, there were "small notices on the plats" for these properties (which developers fought). Homewoner's never saw these plats and had no idea they were in a flood zone.
"In the end, over significant opposition from developers, the county agreed to put a one-sentence disclosure of possible “controlled inundation” for plots of land in neighborhoods inside Barker. But the sentence was buried in the plat documents, which are not typically shown to homebuyers."