Not "reality" shows, but the couple that have some urban scenarios I've seen (or at least seen advertised are) Surviving Disaster on Spike and Worst Case Scenario with Bear Grylls on the Discovery Channel. Spike has full episodes of Surviving Disaster online.

I haven't seen the Bear Grylls one yet, and I've only seen bits and pieces of the Spike one. From what I've seen they are focussed more on short-term survival (e.g., getting out of a burning hi-rise) as opposed to the more mid to long-term focus of The Colony.

As far as improvisation and building things go, I always liked Junkyard Wars but I haven't seen anything like it on TV lately.