Last summer we bought a 24-year-old house that had no history of flooding. Last fall, we experienced 100-year storms twice in 6 weeks. Both times our walk-in basement flooded. By flooding I mean that ground water welled up at the seam between the poured concrete floor and the concrete footers and cinderblock foundation soaking the entire floor. All carpets and most drywall had to go. Part of the basement is finished and we planned to finish most of the rest. It comprises about 1/2 of our 3,000 square feet of living space. Is there is rule of thumb on estimating how much our house is devalued because the basement floods?