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So for people with the relevant engineering knowledge: how adaptable would a modern urbanized environment be in a post-apocalyptic setting? The type of apocalypse doesn't have to be particularly apocalyptic: simply that large plants designed for utilities no longer operate (water, electricity, etc).

We have seen many such settings in recent years (particularly in the zombie genre) but most stories have avoided discussing how easy or difficult it would be to locally adapt office-blocks or sub-urban buildings to live in. Can extant infrastructure be cannibalized (sewers, power-lines, mains water, category cables) or would the entire system have to be overhauled? Can modern urban warfare give any insight into this? Can partially inhabited cities survive without a government?

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  • $\begingroup$ I'm a bit confused about what you're asking. What size city are we talking about? What size population? If the 20 million+ people living in NY lost all utilities they would be dying in droves within days. Living there would certainly not be a possibility. So what exactly is the setup here? Are a handful of people trying to live in a post-apocalyptic city some decades after everyone else was killed? What sort of urban warfare are you envisioning? $\endgroup$ – AndreiROM May 20 '16 at 13:49
  • $\begingroup$ @AndreiROM assuming that what ever large-scale event has passed (thereby making it strictly post-apocalyptic). Any modern 1st world city. Not talking about such a long time span that the environment is itself a factor (in terms of weathering for instance). However the assumption is that major utility facilities are either unreachable or out-of-commission. The number of people we are talking about would be a small community: a couple of hundred, for the sake of argument; tiny by the scale of the environment, but typical size for genre. $\endgroup$ – Stumbler May 20 '16 at 14:05
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Sewers can continue to be sewers. The wastewater treatment will most likely be inoperable, but the sewers themselves are just tubing, i.e. empty space surrounded by a suitable material, set up ever so slightly sloped in order to make the wastewater flow in the desired direction (i.e. away). Nothing fancy.
More or less the same is true for water supply. You may need a water tower or similar, and means to get the fresh water into that tower, but after that, you have fresh water delivered to your faucets, by gravity and pressure alone.
Electrical installations are just bits of (conductive) metal, isolated against each other. They continue to be operable, but you may need a new power source. (This is not taking into account transformers, but they are simple enough, too) Once that is established (and balanced, and...) your wall sockets will be functional, provided you manage to feed them 110V or 230V, or you regulate / balance etc. on the consumer side.

So yes, existing infrastructure can be cannibalized, but it will take some tools, some basic understanding of what you are doing, and the work that was previously done by large machinery will need to be replaced somehow.

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  • $\begingroup$ Without a working power grid you will not have running water at any faucet. Water is pumped into those towers you spoke of. The only water source without electricity will be environmental. $\endgroup$ – user2448131 May 20 '16 at 15:44
  • $\begingroup$ Wouldn't sewage systems back up if the treatment plant becomes inoperable? $\endgroup$ – Stumbler May 20 '16 at 22:37
  • $\begingroup$ @Stumbler they would. But given that they will be used by a lot less people, who still would be able to clear out blockings manually, they should continue to be useable for decades, even centuries. $\endgroup$ – Burki May 23 '16 at 6:59
  • $\begingroup$ @XandarTheZenon you can still easily add a water tower to your freshwater supply system. Plus: Are you sure about your claim? $\endgroup$ – Burki May 23 '16 at 14:53
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    $\begingroup$ Not entirely, but I know that in a lot of cities if all electricity stopped running water would not be available. My dad did some research in case of emergencies, and the water to my house is gravity fed from a spring, but the nearby town's water would not work because of something electronic. I know very little, but it is worth researching. $\endgroup$ – Xandar The Zenon May 23 '16 at 15:00
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I would say you may be able to use portions of a cities infrastructure, but only on such a small scale that the 'cons' of trying to re-inhabit a large city would out way the 'pros'. And the larger the city, the more complex all the utility infrastructure would be.

Electricity. Accepting post-apocalyptic conditions of no grid, then a building in a city has no advantage over a building anywhere else. You will have to supply power one building, perhaps even one circuit at a time. Many commercial buildings, and utility systems such as pumps, in a city will require different voltages and phases then a survivor group can generate. Best bet here might be some locations with their own generators, but again that's a finite resource. No more fuel, no more spare parts.

Water. Most cities get their water from two sources:Intake and treatment from rivers, and pumped from underground wells. Both of these require electricity, and on a scale generally not available to 'survivors'. So the CITIES infrastructure again provides nothing above that of an individual building anywhere else. The best water source is a flowing river, in or out of a city, but in the city how contaminated is it?

Sewers. Once again, the larger the city, the higher the probability that it requires electricity running on a large scale. Pumping stations are required in most city locations. It would be amazing to be able to run sewer lines through an entire city 'on grade'. Secondly, your toilet wont flush without the water system connected to it, or you dump a bucket of water into it after use.

Sewers are one location where rural situations would have an advantage, as they usually are self contained, and do 'just flow downhill'.Even those, however, eventually fill up.

Food. Without knowledge of the nature of the apocalypse, its hard to say what availability of food resources might be. In most events such as approaching hurricanes or such, you notice many stores with empty shelves, so stores and restaurants are a finite resource at best, or more likely have been emptied completely during the initial 'event'.

Farming.If you have to grow your own food, it takes acres of open land to raise enough food to support any sizable population. The city has acres of buildings. Those with parks, many rely on sprinklers to keep them green, so...

Manufactured Resources. This is the one aspect that the city may have an advantage over a more rural setting would be the vast amount (if not destroyed by whatever event) of manufactured materials. Mining the city for aluminum, glass, containers, ect, would possibly be of value in the long run. The vast variety of things to be found would be overwhelming. But directly affecting survival that you can't find elsewhere?

Problems. Whether war or plague, the cities will be the largest targets. Depending on 'the event', the cities will suffer fires, looting, and death on a scale most have not seen. No one will be there to clean this up, so if all but a handful have died, then there are thousands or millions of dead in the streets and homes, lots of disease, lots of decay infecting everything around. The other issue being other groups of survivors will be attracted to the city, and they might not be friendly to your group...

All said, it seems any infrastructure being used will have to be provided at the individual building level, so the city would have no advantage over any other location. A smaller location then a large city provides the same shelter, wiring and pipes, but at a scale which might be overcome to restore some semblance of Society again.

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Very, but it depends on the nature of the apocalypse. In a sense, your physical infrastructure is there. You have materials available with very little need to refine. You have shelter. If you have fewer survivors, you have lesser needs - fire for warmth, water can be filtered or boiled to a lesser extent than modern municipal water. Rather than large scale, you'd work on a smaller scale - engines running as generators off scounged power or water gas for example.

Useful skills would vary. A smart engineer would be as valuable as your average paranoid survivalist or your ren faire enthusiast. Copper cable is useful for power or 'low tech' tools. Cars could be useful modified as horse carts, running off water gas or simply water resistant storage.

If I was in an apocalypse, I'd consider cities to be an easier place to survive, both in terms of resources and defensibility for a city slicker than the countryside, or the wilderness.

One could salvage household piping, and other materials, reuse existing shelters with repairs and so on much more easily than remaking it. Lots of steel around, and if you can find fuel, it can be reforged in many cases into more useful 'primitive' tools. With more battery powered devices these days, a DIY power generator might turn out handy, and buildable with fairly basic electronics skills out of salvaged parts.

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Well, yes, people can move into a city, and survive there somehow. Have you seen the movie "I Am Legend"? Will Smith's character was surviving in a post-apocalyptic NY. He would scavenge for supplies in different neighborhoods, he would plant crops in Central Park, etc.

Even in shows such as The Walking Dead you see people surviving in new abandoned towns or neighborhoods.

There is no conceivable reason why they wouldn't be able to as long as they have access to water and can grow food, raise livestock, and/or hunt nearby.

The biggest factor in these situations is the threat you're trying to keep at bay. In a zombie apocalypse the cities are the last places you want to go. In other situations maybe that's not a problem.

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