Flooding is the most common and expensive natural disaster in the U.S. It affects homeowners in every state, including properties that aren’t on coastlines or interior waterways. If you’re interested in buying a home or already own one, here are five facts to know regarding flooding.

1. The cost of flood damage can add up quickly.

According to the Federal Emergency Management Association (FEMA), just one inch of water can cause $25,000 of damage to your home.

Even if your home’s lowest levels are unfinished spaces, your furnace, water heater, washer and dryer, and other expensive appliances often located in a basement could be damaged.

Additionally, water inside your home ofter triggers mold issues, which is hazardous to your health and can cause structural damage to your home if left untreated.

2. FEMA flood maps only tell part of the story.

Since FEMA flood zone studies are expensive, labor-intensive, and time-consuming, they do not include two-thirds of U.S. stream miles, half of the coastline, or inland areas where heavy rainfall can cause flooding.

To view and download FEMA’s flood zone maps, visit MSC.FEMA.gov.

3. New mapping tools are filling in some of the gaps.

New flood simulations use high-resolution topographic maps and advanced modeling techniques to understand where water flows during heavy rainfall and spring thaws.

For example, realtor.com® now includes a risk visualization tool developed by the First Street Foundation called Flood Factor. It behaves similarly to the site's other mapping filters, like Schools, Noise, and Crime. The tool also displays FEMA’s flood zone risk score for individual properties.

Bear in mind that these models don’t always know the precise location and elevation of buildings on a property. But they can give you an indication of whether further research is warranted on a home’s flooding risk.

4. It’s up to you to do your due diligence.

If you’re concerned that a home has a flooding problem, do your homework and enlist the help of experts who can help you make an informed purchase decision. In most states, sellers must disclose any known flooding issues. But specific disclosure requirements vary, and buyers should do their own due diligence.

Your Accredited Buyer’s Representative (ABR®) can help you identify local flood experts and other helpful resources. While your buyer’s rep is an excellent source of other resources, they cannot offer flooding advice since this is beyond their area of professional expertise.

5. Consider flood insurance, even in low-risk areas.

If you buy a home in a FEMA-designated high-risk zone, your lender will probably require you to purchase flood insurance. The current owners may be able to transfer their policy to you, providing uninterrupted coverage from one owner to the next.

Even if flood insurance isn't required, you might want to buy a policy anyway since most homeowners insurance policies do not include coverage for flooding. Plus, flood insurance is relatively inexpensive in low-risk areas.

Flood insurance is offered through the National Flood Insurance Program and private insurers. FloodSmart.gov also provides additional details on understanding flood risk, flood insurance, and other useful resources.