More than 160 USGS scientists, technicians, and specialists are responding to Hurricane Sandy’s aftermath, from Virginia to Massachusetts. Crews from USGS are working hard to retrieve data for emergency managers.

Hurricane Sandy’s impacts have been significant. Many USGS tidal sensors recorded peaks of record and several were completely overtopped. In addition, high-water marks flagged by USGS crews show sizeable storm surge, including 18.98 feet at Long Branch, NJ; 12.93 feet at the Verazzano Narrows Bridge between Brooklyn and Staten Island, NY; and 7.43 feet at Lindenhurst on Long Island, NY.

Storm-Surge Sensors

USGS crews are currently out retrieving the more than 150 storm-surge sensors that were deployed prior to Sandy’s landfall. These sensors extended from the mouth of the Chesapeake Bay in Virginia to the coast of Maine.

The data from these sensors will be used to create models of 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 is being used to assess storm damage, discern between wind and flood damage, and improve computer models used to forecast future coastal change.

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

High-Water Marks

In addition, at the request of FEMA, USGS scientists are marking high-water marks. Crews in New York currently have 150 sites they are checking, many established in the 1992 Noreaster that struck the Long Island area. New Jersey crews have an additional 100 sites they are checking along the Atlantic shoreline as conditions are safe to do so. USGS scientists from Maryland, Delaware, Connecticut, and Rhode Island are also be looking for high-water marks in their areas.

High-water marks serve a very important function in assessing damage. USGS crews look for sustained high-water marks, meaning indications of the highest level the water stayed for a time. Because water-levels change often due to wave action, sustained high-water marks allow USGS scientists to determine the levels the water stayed at long enough to cause significant impacts.

High-water marks are useful in determining the amount of damage sustained due to flooding and storm surge. Impact models use high-water marks to determine likely levels of damage to a building’s structural integrity, as well as potential scour damage. Scour damage is the abrasive erosion caused by dissolved solids in water rubbing against buildings or other structures that can wear away the surface, eventually leading to instability.

In addition, FEMA uses high-water marks to determine what damage comes from wind and what damage comes from water when formulating their own impact models.

Coastal Change

In addition, USGS crews have returned to coastal New Jersey and Long Island to do lidar surveys for before and after studies of coastal change, using the pre-storm lidar surveys taken October 26^th and 27^th.

Also, USGS crews will conduct aerial surveys from Cape Hatteras, North Carolina, to Montauk, New York. These surveys will include oblique aerial photography and lidar topography. The photographs will be compared to pre-storm photography for a qualitative look at coastal erosion, while the lidar data will be compared to pre-storm beach elevations to quantify actual changes in the beach, such as dune erosion and overwash.

Water Quality

USGS crews have also performed water quality sampling at various locations, including the Delaware River near Trenton, New Jersey; from the Potomac River and the Eastern Shore in Maryland; various sites in Washington, DC, and sites throughout Northern Virginia.

USGS crews sampled for contaminants like pesticides, E. coli, nutrients, and sediment to document water quality in areas affected by the hurricane. These samples will now be analyzed, and their results shared with emergency responders.

***Updated: coastal change section edited from original, based on an updated assessment from October 29, 2012***

As millions of northeast residents bought water, batteries and food this weekend in preparation for Hurricane Sandy, USGS scientists, engineers, and technicians worked up and down the Atlantic Coast, deploying storm-surge sensors and maintaining real-time streamgages in preparation for Hurricane Sandy’s arrival.

Storm-Surge and Real-Time Sensors

Much of the work involved installing 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 strapped 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 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 91 percent of the coast along the Delmarva Peninsula is very likely to experience beach and dune erosion from the storm, while overwash is expected to affected more than  half of the shoreline, and 22 percent of the beaches are expected to experience inundation by waves and storm surge   In these areas, waves and storm surge transport large amounts of sand across coastal environments, depositing sand both inland and offshore, causing significant changes to the landscape.

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.

The models show that along the New Jersey shore, 98 percent of the coast is very likely to experience beach and dune erosion, while 54 percent is very likely to experience overwash, and 9 percent to experience inundation.

It also indicates that on the south shore of Long Island, N.Y., including Fire Island National Seashore, 93 percent of the coast is very likely to experience beach and dune erosion, 12 percent to experience overwash, and 4 percent to experience inundation; the lower percentages of overwash and inundation in these areas is because of the relatively high dune elevations.

The impact of previous storms on sandy beaches along the mid-Atlantic Coast has made them increasingly vulnerable to significant impacts such as erosion.

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.

The U.S. Geological Survey is keeping careful watch as Hurricane Sandy continues to track northeast along the east coast of Florida and the Atlantic coast.  Along with federal partners, the agency is taking actions to help minimize potential risks to lives and property.

Before, during and after any hurricane or tropical storm affecting the United States, the USGS is involved in measuring the height and intensity of the storm surge, and monitoring water levels of inland rivers and streams, providing critical information used to forecast floods.  Using state-of-the-art modeling, the USGS is also involved in forecasting coastal change caused by storm surge, assessing the likelihood of beach erosion, overwash or inundation.

USGS Streamgaging Network at the Ready

The USGS, in cooperation with local, state and federal agencies, operates long-term sensor networks on inland rivers and streams throughout the nation. These networks provide real-time data important to the National Weather Service, FEMA, the U.S. Army Corps of Engineers, and other USGS partners involved in issuing flood and evacuation warnings, coordinating emergency responses to communities, and operating flood-control reservoirs.

The USGS streamgaging network is primed and ready to go for Hurricane Sandy, no matter where the storm finally makes landfall.

Data from the USGS Streamgaging Network are routinely used for water supply and management, monitoring floods and droughts, bridge and road design, determination of flood risk, and for many recreational activities. However, during a storm’s landfall, this network helps capture the depth and duration of storm-surge, as well as the forecasted time of its arrival and retreat.  Understanding storm surge allows for more accurate modeling and prediction capabilities and for improved structure designs and response for public safety. Inland streamgages also are used to track the rainfall and flooding caused by the remnants of the storm.

USGS crews are on alert.  Immediately after the worst of the storm has passed, USGS hydrologists will deploy to measure high-water marks at rivers and streams and to verify high river flows and peak stages. The crews will also calibrate and repair streamgages damaged by the storm to ensure they continued to transmit information in real time to users working to protect lives and property.

USGS Deploys Additional Storm Surge Sensors on the Atlantic Coast

Storm surges are increases in ocean water levels generated at sea by extreme storms and can have devastating coastal impacts.  Prior to extreme weather events, the USGS may also deploy storm surge sensors at key coastal locations just a few days – or sometimes hours — before a Hurricane or Tropical Storm’s anticipated landfall. These storm surge sensors, housed in vented steel pipes a few inches wide and about a foot long, are installed on bridges, piers and other structures that have a good chance of surviving a storm surge during a hurricane. The number of sensors installed and their locations depend on the strength of the storm as well as what gages may already be in place.

In preparation for Hurricane Sandy, the USGS is ready to install additional sensors along the Atlantic coast, from Virginia to Massachusetts.  These sensors can record water level and barometric pressure every 30 seconds to document storm-surge crests – or waves of water – as they make landfall.

Storm tide sensors were previously deployed along the Atlantic coast in preparation for Hurricane Irene, in 2011. The data they collected were instrumental in understanding the effects of hurricanes and tropical storms on the East Coast.

Together, the USGS Streamgaging Network and the mobile USGS storm surge sensors provide critical data to the National Weather Service, FEMA and other USGS partners involved in issuing flood and evacuation warnings and in coordinating emergency responses to communities. In the event of a large tropical storm event, storm surge information will also help public officials assess storm damage, discern between wind and flood damage, and improve computer models used to forecast future floods.

Monitoring Coastal Change

Overwash, which occurs when waves and storm surge overtop dunes and transport sand landward, is a likely impact of hurricanes and tropical storms. The severity of erosion and overwash depends on the strength of the storm, beach elevation, and how direct a hit the coast takes.

While it’s difficult to tell where exactly the storm is headed or what its impacts may be, USGS scientists are using state-of-the art models to give emergency managers and local residents an accurate picture of what coastal changes are likely to occur if Hurricane Sandy makes landfall along the Atlantic coast.

Using the same system that modeled coastal impacts from Hurricane Isaac earlier this year, USGS scientists will post interactive maps using data on coastal features and models of hurricane waves and surge to predict the likely impact of Hurricane Sandy to the coast.

Tracking River Levels in Real Time

All information from USGS Nationwide Streamgaging network can be accessed at the USGS WaterWatch website. In a storm, this information can be particularly useful to local residents who want to know how increased rainfall from tropical storm Isaac will impact the rivers and stream in their areas. This site displays maps, graphs and tables that describe current and past streamflow conditions for the United States. The real-time streamflow data are generally updated on an hourly basis.

WaterAlert also allows users to receive updates about groundwater levels, water temperatures, rainfall and water quality at sites where USGS collects real-time water information.

For information on the latest storm track, listen to NOAA radio.  For information on preparing for the storm, go to Ready.gov or Listo.gov.