MIAMI—It's almost mind-boggling. US losses from flood damage to commercial real estate properties are likely to average over $1 billion a year by 2050—and multifamily owners in low-lying coastal areas could together face average annual losses over $190 million.

That's according to a new report from CBRE. Making matters worse, market disruption after extreme flooding is likely to cause commercial real estate owners hundreds of millions of dollars more every year.

"American cities are among the most vulnerable in the world to flood loss because, as a wealthy nation, the US has a high overall value of assets in low-lying coastal areas, but we have minimal protective measures in place relative to other wealthy nations in Europe and Asia," says Quinn Eddins, director of research and analysis a CBRE. "One of the things this study makes evident is that as costly as it may be to build up our flood defense infrastructure, inaction will be far more costly. We also need to rethink land-use policies and building practices that encourage development in high-risk coastal areas."