A flood claim goes to your NFIP or private flood carrier, not to your homeowners insurer — they are separate policies and a homeowners claim will be denied for flood water. Report it the day you find it. NFIP requires a signed Proof of Loss, normally within 60 days of the loss, and the documentation you gather in the first hours is what it is built from: video of every affected room before anything is moved, photographs of the high-water line, a list of damaged contents with what you paid, and receipts for emergency mitigation.
Hendersonville homeowners on Old Hickory Lake should obtain private flood insurance as NFIP policies cap structural coverage at $250,000 and exclude many finishing materials common in lakefront homes. Mitigation is not optional — every policy requires you to stop further damage, so drying starts before the adjuster arrives, and you keep the invoices.