Every couple of years, the National Flood Insurance Program (NFIP) gets set to expire. This is a result of the way Congress funds the program as the typically only renew the program for a few years at a time. That is, if they renew the program on time.
Often times, the program is operating at a loss and Congress has a difficult time passing a long-term approval of the program. When this happens, the program is typically reapproved on a short-term basis, but there are cases where the program expires.