Will food become scarce?
What you might find in that instance is rationing, if you look at Britain during WWII when we were under forced blockade and food and other basic goods became scarce the government brought in a ration book system. This system was enforced and helped control what little was available and made sure that everyone got the basics needed to get from day to day.. In Britain during this time some enterprising individuals prospered from what was known as the black market.. Of course it was outlawed by government, but that didn't prevent things being bought and sold under shop counters, in back ally ways and pubs etc... Essentially a free market of sorts due to the fact that no duty was paid on these goods

There will be a rise in crime as the things people need to get by become harder and harder to obtain.. How the government respond and what measures they take, through police actions, powers and martial law etc will prolly determine what levels of civil unrest there will be... That being said your government already has the detention camps and enabling act/acts in place to deal with any civil disobedience...
How will you know when this is likely to happen? ... When the government force changes to gun ownership and your asked to turn in fire arms at local police stations?