How to sell land in floodway

[NA Morris]

We purchased 11 lots across the street from our homestead Approx 20 years ago in order to prevent building and overcrowding. We are now disabled and maintaining the land (in city limits) is becoming too much, AND property tax values are TOO high, due to a few lots that keep selling and owners later finding out new fema guidelines have made lots unbuildable.
We had an engineer come out, and according to his opinion, the lots are not buildable. We were told just a year ago that we could scrape part of land and build up a certain amt of feet above BFE. BUT NOW, city adopted FEMA's new requirements for "NO RISE CERTIFICATES" and "FLOOD ELEVATION CERTIFICATES". We sold one lot only to be told that it is not buildable, AND that non of our lots are buildable. We refunded money to buyer out of courtesy, since we had NO CLUE of these new FEMA NO RISE building requirements implemented in 2023.
We now own 11 platted lots that are supposedly unbuildable, being highly taxed, and require being maintained and mowed continuously.
Have any of you found a way around these FEMA building restrictions in FLOODWAY? We really don't know what to do. We were hoping to sell all lots together to an engineer who knows how to build in floodway inside city limits of SEGUIN, Tx.
Any advice is greatly appreciated.