Annapolis has already reached a "tipping point" with more than 30 nuisance flooding events per year, and Baltimore is expected to surpass that total by 2020, according to a NOAA study published Thursday.
By 2050, a majority of the U.S. coastline will face such frequent coastal flooding because of sea level rise, according to the article in the journal Earth's Future.
The timing varies because not all areas are as prone to flooding. Annapolis has one of the lowest nuisance flooding thresholds at 0.29 meters above a measure known as mean higher high water, the average height of an area's highest daily high tide.
Nuisance flooding occurs in Baltimore an average of 13 times per year, but that frequency is expected to grow quickly. The city is among seven points expected to experience such flooding at least 30 days a year within this decade, according to the study.