How bad do you want to plan for. In your area, earthquakes or the next Mt Saint Helens or maybe wild fires? Are you worrying about only your own or are you wanting to go in to help others? A lot of questions that only you can answer.
How many people do you have to support and do you want minimum essential for survival or do you want sustainment? For how long?
A lot to think about and it's significantly different for different disasters/areas/weather.
Suggest thinking about it similar to the way the military breaks down their supply system:
Class I: food and water (are you going to carry water or have purification capability)
Class II: general supply items such as tents and tools
Class III: petroleum products, oil, lubricants
Class IV: engineering material to include barrier and construction
Class V: ammo
Class VI: personal demand items to include shaving kit supplies, tampons for the ladies, alcohol
Class VII: major equipment such as trucks, trailers, weapons,
Class VIII: medical supplies and equipment
Class IX: repair parts
Class X: anything not covered in other areas but a biggie for thought is plant seeds for agriculture
Start off with a 3 days supply and build from there. If you have think you need a years supply, let me know where you get your tin foil hat at. Katrina showed a 30 day supply would not be out of the norm. You will need to look at bug out supplies and hunkering down supplies and potentially caches at secure locations away from your area. Carrying 90 days of supply for a family of 4 will take a deuce and most likely a 105 trailer or better yet a water buffalo or 1061 trailer with fuel pod. Then you'll need to be able to guard your fuel 24/7. So that may mean having to bring trusted neighbors which means more food and water. Before you know it, you need 3 deuces one with a water trailer, one with a fuel trailer, and one with a generator. Then you have shelter on one, food on another, and all the kids in the third with the weapons/ammo/repair parts(actually you'd cross level the vehicles as best as possible). OK break out the tin foil hat (LOL).
Seriously though, for natural disasters everyone should plan and FEMA urges everyone to do so for the probably scenarios for your area and if you are staying put or beating feet.