Cities are hard places to live if order breaks down.
I wish you luck.
It's almost impossible without your tribe (next door folks,friends co-occupants).
Fixed sites always can be breached by determined aggressors.
Of course you don't have to make it easy, but a community approach is typically more effective as it shares the workload and provides more diversity skills wise.
No matter how tactically prepared a person is, few can stand by and watch other suffer and ignore their plight like a Kafka novel.

The main lesson from Katrina is supplies for two weeks to 30 days if the Government doesn't intervene and years if they do.
BTW we still have friends now living in Baton Rouge recovering from all the "Help" in New Orleans.