USGS… Preparations For Super Storm, Coastal Changes Imminent (Imagery)

[SatNews] USGS scientists, engineers, and technicians worked up and down the Atlantic Coast, deploying storm-surge sensors and maintaining real-time streamgages as Hurricane Sandy bears down on the East Coast of the U.S.

Storm-Surge and Real-Time Sensors

Much of the work involved the installation of more than 150 storm-surge sensors along the Atlantic coast, from the mouth of the Chesapeake Bay to Massachusetts. These sensors, which measure water elevation every 30 seconds, augment an already robust network of coastal and inland streamgages in place to monitor water levels throughout the storm. In addition, eight of the recently deployed sensors are Rapid Deployment Gages, which provide real-time information to help forecast floods and coordinate flood-response activities in affected areas. These real-time gages will complement the many near real-time streamgages already installed along rivers and streams.

All data collected by these sensors and the existing USGS streamgage network are available on the USGS Storm-Tide Mapper.

Working with various partner agencies such as NOAA, FEMA, and the U.S. Army Corps of Engineers, the USGS is strapping the storm-surge sensors—typically about 1-½ inches wide and a foot long—to piers, docks or other structures in the water expected to withstand the storm. They will record the precise time the storm-tide arrived, how ocean and inland water levels changed during the storm, the depth of the storm-tide throughout the event, and how long it took for the water to recede. This information gathered will be used to assess storm damage, discern between wind and flood damage, and improve computer models used to forecast future coastal change.

Anticipated Coastal Change

Elevated water levels and waves during tropical storms can lead to dramatic coastal change of beaches and dunes. The USGS has completed an assessment of likely coastal-change impacts from Hurricane Sandy.

Nearly three quarters of the coast along the Delmarva Peninsula is very likely to experience beach and dune erosion as the storm makes landfall, while overwash is expected along nearly half of the shoreline. Overwash, the landward movement of large volumes of sand from overtopped dunes, is forecasted for portions of the east coast with the projected landfall of the storm. The severity of overwash depends on the strength of the storm, the height of the dunes, and how direct a hit the coast takes. Fifteen percent of the Delmarva coastline is very likely to be inundated by waves and storm surge. In these areas, waves and storm surge would transport large amounts of sand across coastal environments, depositing sand both inland and offshore and causing significant changes to the landscape. The impact of previous storms on sandy beaches along the mid-Atlantic Coast has made them increasingly vulnerable to significant impacts such as erosion.

The models show that along the New Jersey shore, 81 percent of the coast is very likely to experience beach and dune erosion, while 7 percent is very likely to experience overwash. It also indicates that on the south shore of Long Island, N.Y., including Fire Island National Seashore, 43 percent of the coast is very likely to experience beach and dune erosion. Overwash and inundation are not expected in these areas because of the relative high dune elevations.

Beaches and dunes often serve as the first line of defense for coastal communities against flooding and other hazards associated with extreme storms. Any compromise to these features means that storm-related hazards are more likely to threaten coastal property, infrastructure, and public safety during a future extreme storm event.