If the infrastructure fails (mega-farms, manufacturing, transportation, warehousing, etc.), what will small communities do to support their members?
It is my assumption that large communities (cities over, say, 10000 people) will be de-populated very rapidly. Everything will be "small" community groups.
So this article discusses some options that a "small" community may face. It is a good read and short.
https://projectchesapeake.wordpress.com/2015/05/05/small-towns-and-local-currency/