A report from data provider CoreLogic says 52% of the properties in Houston that are at a high or moderate risk of flooding from Hurricane Harvey and its resulting rains are not in federally-designated flood zones. That means the homes and businesses in those areas may not have flood insurance, as it’s not a requirement for buildings outside of “special flood hazard area” zones. And that could be especially disastrous for Houstonians, who learn the hard way that their homeowners policy doesn’t cover some losses from the storm.

Flood damage isn’t typically covered under homeowners policies. But a little water can result in tremendous damage. Just one inch of water in a home can run up costs of $20,000, according to the National Flood Insurance Program.

If the aftermath of Hurricane Katrina is any indication, many of those home and business owners may find themselves in a battle with their insurance companies for a mutually agreeable settlement, entirely outside of the issue of flood insurance, before this is all over.