Washington, D.C. and Annapolis, Md. are already past a "tipping point" for frequent flooding caused by sea level rise, a new study finds.

Using tide-gauge data and sea level rise projections, researchers from the National Oceanic and Atmospheric Administration (NOAA) found Washington, D.C., Annapolis and Wilmington, N.C. have already reached a point where the cities will receive over 30 days of flooding per year with water rising up to two feet above high tide levels.

By 2050, the study asserts, the majority of U.S. coastal areas will most likely be affected by similar flooding trends.

"Unfortunately, once impacts are noticed, they will become commonplace rather quickly," said William Sweet, an oceanographer with NOAA's National Ocean Service. "We find that in 30 to 40 years, even modest projections of global sea level rise -- 1½ feet by the year 2100 -- will increase instances of daily high tide flooding to a point requiring an active, and potentially costly response."

The authors claim roads and heavily utilized infrastructure will be seriously affected by the flooding, especially since there will be little time for repairs between floods in many places.