The flood everybody's talking about in the stories was probably the September 2009 flood - worst since 1919 and hopefully will not recur anytime soon. We live near the river and I have never seen the water anywhere near as high as that before.
The US census indicates a 10% increase in population over the past decade and the city’s own websites says that 2009 assessed valuation of permitted construction of 18.4 million and the median house value is over 300K.
They have had lots of development all over, it doesn’t have to be next door to the lot, run off into creeks will come from many more points, but the overflow is going to happen in that flood zone at the confluence of those two creeks.
They could have just bought him out when he offered to sell it to the city. It’s in their development plan, so you tell me why they didn’t take him up on the offer.
Because somebody saw a chance to create a “nuisance” property, buy it up cheap and then resell it to the city.