Are banks required to buy flood insurance on branches if they are located in flood zones? What's the cite for this? Thank you.

If you mean under the NFIP the answer is generally no as this ownership wouldn't be a "specially designated loan".

But the reality is, why wouldn't you. Not only is it a poor example, but property in a 100 year flood plain have a 26% greater chance of flooding than burning. You do have fire coverage, don't you!