A simple tarp can be useful in an urban setting. Quick shade and portable shelter from rain can be handy. A tarp spread over a damaged roof can keep the inside of a house dry.

Following a hurricane standing water means you get clouds of mosquitoes. A tent or screened shelter can help a lot. That said bringing your own shelter is less of an issue in an urban setting.

It is pretty hard to think of a situation that would make the buildings completely unusable for shelter. Even flattened, look at pictures of houses felled by tornadoes, there are still wall sections and plenty of lumber to assemble a decent shelter out of.