Hardwood floor is warped Tenant's responsibility?

[Luke H.]

After recently flooding, tenant called me to let me know that there was wet spots in the ceilings of the house. While I was there checking the ceiling issues they mentioned that there was a damaged section of the hardwood floor in one room.  It is in a bedroom a 2 feet by 1 foot section of hard wood floor

. They said that they think it was because the foundation is not leveled or due to the recent foods.  

If it was due to flooding or foundation, then how come other parts of the house aren't damaged? There is a room in the very back that is about 6 inches lower than that room so if it was flooding that back room would have been destroyed. In my opinion it was probably water they spilled as they do have a water dispenser in the dining room.

What is the best way to handle this? Should I charge them now or take it out of the security deposit? Should I not lease to them another year if the don't want to pay for this? Do I need to have an expert put in writing that it was human error and is that even possible?

Thanks