It is near future, Portland, Oregon, and the residents and neighboring farmers are sick of everyone moving there now that climate change has made it a (even more) fabulous place to live. In an extreme gesture, the entire city decides to build a wall around the city and neighboring farms, and (hand-waving) the governments involved are agreeable to it.

Their intention is to be self-reliant. What would they have to do to get to that point?

Note: this is specifically about logistics; I'm handling the government and people's attitudes. This is for a young adult short-story, so high-level is preferred. Assume no trade is occurring.

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    $\begingroup$ Thank you for the stub explaining the context of your question. That helps quite a lot! $\endgroup$
    – Cort Ammon
    Oct 23 '15 at 20:07
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    $\begingroup$ A freebie to anyone investigating this, while oregon is nearly 3/4 powered by sustainable energy, there's not that many hydro dams near the city of Portland, itself (eia.gov/state/?sid=OR). Power will be an interesting question $\endgroup$
    – Cort Ammon
    Oct 23 '15 at 20:10
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    $\begingroup$ @CortAmmon Yeah Bonneville is closest. It's also conveniently in the gorge, which is essentially a prebuilt wall along the river. Also quite beautiful. We'd keep that. $\endgroup$
    – Samuel
    Oct 23 '15 at 20:14
  • $\begingroup$ Have fun living in your own garbage and waste, Portland. $\endgroup$
    – Oldcat
    Oct 23 '15 at 20:49
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    $\begingroup$ If the nearest city to me built a frickin wall to keep me out, I'm not going to take their garbage and haul it off for free. $\endgroup$
    – Oldcat
    Oct 23 '15 at 21:22

This all depends on what standard of living your inhabitants want.

I mean are they going to watch TV? Turn on their lights? Eat canned food? Read Stack Exchange?

You have about 2 and a half million people living in Portland and the surrounding area. That's a huge amount of food, energy, and waste to deal with.

Do you have energy generation for that many people?

Waste disposal and sewerage is probably fine as that's already distributed although it does depend on where your treatment plants are.

Water supplies? That depends on whether the reservoirs are in your area. The taps may run dry.

Food you may be able to grow enough to live on if you have enough farm area. The diet is going to be much reduced in variety though as you lose all imported foods.

The problem you have is that the modern would is so inter-connected and everything depends on everything else. Your factories are going to shut down as they can't get components they need, and they can't sell their products to enough people. With all the people out of work there no longer spending money the rest of the economy also collapses.

Equipment is going to break down as you can't get spare parts. Do you make any cars in Portland? If not everyone is going to be walking soon.

Do you have oil wells or other sources of fossil fuels and the refinery to process them? If not people are going to be walking even sooner.

The good news is that with 90% of your population unemployed and no power for heating or food to eat that 90% are all going to die. The remaining 10% can then settle down to a simple agrarian subsistence farming existence that will let them survive for a while.

  • $\begingroup$ This seems more like a high level discussion of the issues that a general city might face when it is cut off from the world. The OP is asking what preparations need to be made to make it work, not why it would fail if suddenly dropped into place. (On a side note, 6% of daily commuters in Portland go by bike. One of the highest percentages for a large city) $\endgroup$
    – Samuel
    Oct 23 '15 at 23:45
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    $\begingroup$ Those are the problems that would need to be solved, so the preparation required is to fix them... $\endgroup$
    – Tim B
    Oct 24 '15 at 9:44

It is sometimes said that a city is only 3 days away from starvation or revolution. Cities are complex environments which require massive connections to the hinterlands to supply food, water, and energy, as well as places to dispose of the wast products. Cutting off the inflow or outflow would be similar to plugging either end of your digestive tract.

The other issue is that most of what happens economically in cities depends of being able to access markets outside of the city. While large cities have internal economies and can do import substitution to a certain extent (as per Jane Jacobs), this is still only a fraction of the external markets that cities serve. Without access to external markets, the city will have no source of income for their food, energy or waste disposal.

The end result of attempting autarky will be to diminish everyone's standard of living inside the city, and most of the people surrounding the city will also suffer a loss.

Edit to add:

Several cities are embarking on this experiment now, without walls. Adopting laws which require business to raise minimum wages to $15/hr, adopting hostile regulatory regimes against small business, trying to drive out new services like Uber and AirBnB, forcing parents to use public schools by preventing charter or other alternative schools to open or operate and very strict zoning that eliminates new suburbs and drives up the price of remaining housing stocks are some of the policies which "Progressive" cities like Seattle or NYC are adopting. Entry level jobs and small business are being shed rapidly there, and people are moving away if they have the means, or avoiding settling there in the first place. If you want to see the end result, there is always Detroit...


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