A screenshot of the USGS Coastal Change Hazards Portal showing erosion, overwash and inundation potentials along the east coast from Hurricane Maria. (Public domain.)
Reston, Va. — About two-thirds of beaches from North Carolina to Maryland have a high probability of eroding as Hurricane Maria moves up the coast, according to the latest U.S. Geological Survey (USGS) coastal change forecast. Approximately 15 percent of that same shoreline has a high probability of experiencing overwash, where surge and waves overtop dunes.
While the hurricane that devastated Puerto Rico is not currently forecast to make landfall on the East Coast, high winds and large waves generated by the storm have the potential to affect the coast.
As of Tuesday morning, the USGS coastal change forecast showed:
- Approximately 60 percent of North Carolina dunes are expected to be impacted by dune erosion, with 5 percent of that stretch of coastline expected to experience overwash.
- Two thirds of Virginia beaches north of the mouth of the Chesapeake Bay are likely to erode while one-third are likely to be overwashed.
- Elevated water levels are also likely to reach and erode sand dunes along two thirds of the Maryland coastline with less than 5 percent of the coastal dunes being overwashed.
Many factors are taken into account when trying to forecast what a storm like Maria might do to the coast, such as differences in the waves that reach the coast and the elevation of the sand dunes in the areas affected.
“Although Hurricane Maria’s strength has diminished, its strong winds will still generate large waves that will travel to a stretch of the coastline from North Carolina to Maryland’s eastern shore,” said Joseph Long, USGS research oceanographer and one of the lead developers of a series of coastal change forecasting tools. “As the storm moves north, those large waves are expected to erode and in some cases overwash sandy beaches and dunes that serve as protection for coastal communities.”
This USGS Coastal Change Forecast model uses the National Hurricane Center’s storm surge predictions and National Oceanic and Atmospheric Administration wave forecast models as input. The USGS model adds information about the beach slope and dune height to predict how high waves and surge will move up the beach and whether the protective dunes will be eroded of overtopped. Results of the modeling indicate Hurricane Maria could have a significant impact on the beaches and dunes along portions of the U.S. East Coast.
As waves and surge reach the base of sand dunes that line many coastal areas, they begin to erode and narrow the dune. In some locations water levels may reach higher than the top of the dune and a process known as overwash occurs, often transporting large amounts of sand across coastal environments, depositing sand inland and causing significant changes to the landscape.
Inundation, the most severe type of coastal impact, occurs when beaches and dunes are completely and continuously submerged by surge. The models currently show that very few beaches are expected to be inundated by Hurricane Maria.
The most up-to-date forecasts for potential coastal change predictions are available on the Coastal Change Hazards Portal page (https://marine.usgs.gov/coastalchangehazardsportal), which is easily accessible to the public. The coastal change forecast can be used by emergency managers to help identify locations where coastal impacts might be the most severe, such as where roads will be overwashed by sand or where it’s possible that roads might go underwater because of storm surge and large waves.