Here's another negative event idea. (If anyone else is interested in coming up with these, please do. Also, how many will be needed before they can be included?)
Dust Bowl
A massive drought has struck the lands surrounding <city name>! What should be done? (For the duration of any of the choices, possibly 5 turns, rivers and other sources of fresh water provide no benefit to the afflicted city)
Organize aid from across our nation! Each other city looses a total of 1 Food per two citizens in the afflicted city, totaled across the nation, for 5? turns (Not sure how long this should last). (That is, if the afflicted city had a pop of 14, and there are 8 cities total, including the afflicted city, then the other cities would each loose 1 Food for the duration) This option requires the existence of at least one other city in the civ.
Purchase aid from afar! Costs some amount of Gold, dependent on the pop of the afflicted city. (Requires better than neutral opinion of at least one major civ, or friendship or better with a mercantile CS.)
Tell them to work harder! All Food boosting improvements around the city are razed. The city generates 1 extra unhappiness per two pop for 5? turns. (Requires the existence of at least one food boosting tile improvement within the city's working radius.)
Tell them nothing can be done. The city's Food production is reduced to 1/4 for 5? turns. The city's population is reduced by 1/2. The total number of citizens lost is randomly distributed around the rest of the cities in the civ. (This is an attempt to simulate migrations that occur due to times of famine generally, and Hoovervilles specifically.)
Please let me know what needs to be changed for this. My apologies for going over the usual three options. I hope having four choices isn't a problem. If it is, I think the first option would probably be the one to drop.