You are correct that it is the landlord's responsibility to provide you with a clean and healthy rental and to pay the entire cost of the repairs resulting from the flood.  The landlord's failure to do so is a breach of the implied warranty of habitability.  This is a health and safety issue.You can sue the landlord for breach of the implied warranty of habitability.  It would also be advisable to contact your local housing code inspector to insure the landlord's compliance.