shaping a world in ruins ...

If you have read the Walking Dead comic or seen episodes of the show, you are familiar with the state of the world, as it exists. Entire cities abandoned by the living, surrendered to the risen dead - all of whom were once living beings. Vehicles often abandoned or wrecked, left to lie in the roads and streets - serving as little more than obstacles for those who remain ... however the timeframe is short enough that the world has not begun to crumble around the living - a topic that tends to be a favorite of dystopian/post-apocalyptic writers. Buildings have been abandoned, however they have not begun to crumble in most places - mother nature may have wreaked her havoc in some ways, but not to the point of worldwide destruction. However, nature will still proceed on its normal cycle, as if nothing has happened to mankind. So, how does one craft a world that doesn't exist, in a location familiar to the PC's?
That is the task that I face with my "world" inside the game. In my previous runs as a D&D GM, one can take liberties on descriptions of the land - it is all fantasy, craft and manipulate as the GM requires. A game set in the 'real world', however, does not offer that same option. I cannot make a building not exist because it does not serve my purpose - especially if that building is one that is familiar to the players. My game is set in Des Moines, a city that all of my PC's are very familiar with.
So, instead of crafting the world, I get to do the next best thing - manipulating what has happened between our prologues and the start of 'chapter one'. What has happened to our city now that it is overrun by the walking dead? What actions did civic leaders take prior to their downfall? Were structures damaged or destroyed in an attempt to hinder the dead? What remains of the city's "normalcy" from before? What "toys" will be at the disposal of the PC's as they decide how to approach the city and her new challenges?
Key to the future, to me, are the two rivers that form two of the downtown borders - the Des Moines and Raccoon Rivers. A number of bridges cross these rivers prior to their merger on the SE side of downtown ... what happens when some of these thoroughfares are missing?
The group has already shown, in the prologues themselves, the ability and willingness to be daring, to think outside the box ... something I look to push even further as their world opens up. Since I am running the game "sandbox style" (giving the PC's relatively free run of the city), it will be a challenge for us all. How do they get from here to there and how many challenges can I put in their way? ;)