Apartments, office buildings and retail structures are at risk of $13.5B in flood damage next year, a total that is expected to grow to $16.9B each year by the mid-21st century, according to a new report by First Street Foundation and engineering firm Arup.

The report, called the 4th National Risk Assessment: Climbing Commercial Closures, assesses the risk of flood damage to 3.6 million multifamily, office and retail properties across the United States, along with related economic impacts. Driving the growth in damage is the climate change anticipated over the next 30 years.

Besides outright damage to structures, floods could result in 3.1 million days of lost business operation in 2022, growing to 4 million days by 2051, the report says.

Damage to commercial buildings also has consequences for metro and state economies, the report notes. The annualized financial impact to local economies is expected to grow from $49.9B in 2022 to $63.1B in 2052.

"American businesses and local economies face much more uncertainty and unpredictability when it comes to the potential impact of flooding on their bottom line than they may realize," First Street Foundation Executive Director Matthew Eby said in a statement. "Flooding that leads to lost days of operation and lengthy repair times for local businesses could have significant broader national and even global economic consequences.”

The report methodology determines vulnerability to flood risk through the development of 30 building archetypes representing multifamily, office, retail structures of various heights, construction materials and basement configurations. Each archetype has a specific model to estimate structural damage and downtime associated with flooding.

Last year was a record year for expensive disasters, according to the National Oceanic and Atmospheric Administration's National Centers for Environmental Information. The NCEI counts total damage for its report, not just damage to buildings.

There were 22 weather and climate disasters nationwide in 2020 that did more than $1B each in damage, the agency reported, well over the previous record of 16 in 2017 and in 2011. Almost all of those involved flooding as at least part of the disaster, since 20 were either hurricanes or severe storms. The other two were a severe drought and a massive wildfire.

Adding the 2020 events to the record, which the agency began keeping in 1980, the U.S. has sustained 285 weather and climate disasters costing $1B or more, with all cost estimates adjusted to the consumer price index as of December 2020. The total cost for these 285 events is more than $1.875 trillion in 2020 dollars.

The study's release comes as a large swath of the country is dealing with the aftermath of its own severe weather. Kentucky Gov. Andy Beshear said 64 people are confirmed dead across the commonwealth as a result of tornadoes that tore through Kentucky and other states over the weekend. More than 100 people in Kentucky were still unaccounted for as of Monday morning.