This video explains the need for having flex hose to both your water heater and furnace, tying down your water heater, and the need for also tying down your gas pipes ! (which most people are unaware of a need for).
The one youtube I did for it is entitled "Buckets, Lids, & Food Storage", so you can do a youtube search for that and find it. The you can go to the site that has my same youtube name and click on the link at the top entitled "3-Month Supply" and get all our info on it.