A study found that eight of the top ten U.S. cities experiencing increases in flooding that cause annoying disruptions such as road closures, overflowing drains and hampered infrastructure are situated along the East Coast.
This kind of flooding, aptly named "nuisance flooding", is caused by climate-related rising sea levels, excess extraction of groundwater and the steady loss of geographical, natural barriers.
The National Oceanic and Atmospheric Administration (NOAA) conducted the study in the hopes of finding information to aid coastal communities that have recently been plagued by flooding. In the concluding report--Sea Level Rise and Nuisance Flood Frequency Changes--the NOAA found that nuisance flooding on all U.S. coasts has increased 300-925 percent over the last 50 years.
Areas on the East Coast, particularly Annapolis and Baltimore, Maryland, experienced a 920 percent increase in nuisance flooding since 1960.
With the steady rise in sea levels, flooding is no longer triggered only by severe storms and hurricanes, says William Sweet, an oceanographer at NOAA's Center for Operational Oceanographic Products and Services. He explains that now, all it takes is high tide in some of the threatened locations to induce flooding. Such locations are beleaguered with surrounding sea level rise and overwhelming groundwater extraction.
The researchers look at many factors when determining the degree of nuisance flooding, including the topography of different locations as well as amount of land cover. NOAA's National Weather Service has set flooding thresholds depending on such variables; any daily water level rise above the threshold is regarded as nuisance flooding.
The ten cities with the greatest increases in nuisance flooding are Annapolis, Md.; Baltimore; Atlantic City, N.J.; Philadelphia; Sandy Hook, N.J.; Port Isabel, Texas; Charleston, S.C.; Washington, D.C.; San Francisco and Norfolk, VA.
The NOAA report aims to help these and other communities combat the dangers of flooding and assess the risk of future effects of sea level rise.
"The effects of rising sea levels along most of the continental U.S. coastline are only going to become more noticeable and much more severe in the coming decades, probably more so than any other climate-change related factor," says Sweet.