I'll admit I've given more thought to this than many people. It's become a sort of hobby, I've made disaster preparedness fun through incorporating zombies into my standard "Shit has hit the fan" survival plan.
Firstly my real life reasoning: Western Canada sits uncomfortably close to a fault line that, while currently stable, may not be so indefinitely, large scale earthquakes can wreak havoc on unprepared infrastructure (See, San Fransisco). And Canada is laughably unprepared for an event of any large scale. Secondly, and closer to home, The area I live in is prone to flooding in hte early spring when ice flows clog the river. It hasn't overflowed it's banks to any major extent recently, but I have ben put on evacuation alert twice since I moved here.
Naturally, with those situations in mind, it's my responsibility as an intelligent human being who values his continued existance to be prepared for two scenarios, Firstly, I need to be prepared to vacate my house at a moment's notice, taking essential things I will need to survive several days at an aid shelter. and secondly, I need to be prepared for a near total collapse of local infrastructure for an unknown period of time, this figures things such as stocking food, water, and medical supplies. to ammo. While the last might seem extreme, I feel I need to be prepared to defend myself from people who may become desperate if aid does not arrive quickly.
How zombies fit into my plan is simple, I plan to bunker down in my home, with my trusty shotgun and enough supplies to last several weeks without power, running water, or heat. After that, well I might be in trouble, but here's hoping that it doesn't come to that.