Ten years have passed since Hurricane Sandy ravaged the eastern seaboard, damaging 200,000 homes, cutting power to 8 million residents and causing more than 100 fatalities.
A Decade of Evolution
Hurricane Sandy’s Historic Impacts Propel USGS Science
In the past decade, U.S. Geological Survey scientists have made significant advancements in collecting and analyzing storm data and modeling storm impacts to ensure local, state and federal partners have the necessary data to make informed decisions that can protect lives and property. This includes temporarily expanding the locations of gauges and sensors that document flooding when needed, developing new software for viewing and analyzing data and improving coastal change forecast models.
“Hurricane Sandy transformed how the USGS collects storm data, which yielded a vast increase in information needed by scientists to understand storm processes and predict their impacts, ultimately helping forecasters, engineers and local officials protect communities from powerful storms in the future,” said Robert Mason, the USGS Water Resources Mission Area Extreme Hydrologic Events Coordinator. “After Sandy, the USGS built upon existing knowledge and technology and enhanced our ability to provide more data much more quickly to partners and the public.”
Expanding the Network of Instruments to Monitor Flooding
USGS scientists collected a broad range of hurricane and tropical storm data before Hurricane Sandy. USGS flood monitoring traditionally included documenting high-water marks, collecting insight from a national network of permanent streamgages and installing temporary real-time gauges and water-level sensors in locations within the coastal and inland storm track as needed.
Over the past ten years, one research focus was to better understand the timing, height and extent of flooding and waves. To enhance storm data collection efforts, the USGS developed the Surge, Wave, and Tide Hydrodynamics Network, which originally spanned from North Carolina to Maine. Currently, the network has grown to include U.S. coasts along the southern Atlantic, Gulf of Mexico and Pacific, as well as Hawaii and Puerto Rico. The SWATH Network includes permanent real-time monitoring gauges, rapid deployment gauges that can be quickly installed anywhere and temporary portable water-level sensors on and near the coasts that document hurricane-induced flooding, or storm tide. Storm tide is the elevation of water caused by wind induced storm surge combined with astronomical tidal cycles.
“The SWATH network provides emergency managers with vital real-time information about flooding and forecasters with post-event data to advance storm surge and wave models,” said USGS Coastal Storm Team Leader Athena Clark. “The expanded SWATH network is an effective way for the USGS to record data from coastal storms more efficiently so we can share additional storm information with our cooperators and the public sooner.”
In recent years, the USGS has considerably increased the number of sensors available to deploy ahead of a storm and established a network of pre-positioned sites where the sensors can be quickly installed. These sites are dispersed within a variety of coastal landscapes and placed in areas, or on infrastructure, that have historically been subjected to strong surge and wave forces.
Before Hurricane Sandy, locations were chosen in real time as the storm approached, and time-consuming elevation surveying was required after the storm when the sensors were retrieved, delaying data accessibility. Now, the field crews know where to deploy the instruments in advance and the installation process is much quicker. When these sensors are recovered after a storm, surveys are not needed, and the data are processed and made available in days instead of weeks.
“What the network did for the USGS at a national level was position us to pursue a new strategy to more efficiently collect storm-event data,” Mason said. “Strategically, it was a game-changer – it allowed us to collect and share a lot of data representing a vast area, much faster and more completely than we could before.”
Software Development Improve Forecasts
The storm-tide sensors used before Hurricane Sandy recorded data every 30 seconds. However, accurate wave analyses require measurements at much faster intervals so the USGS acquired some wave sensors that can record as much as 16 observations per second. To fully utilize these higher data-recording rates, USGS experts developed a software program called WaveLab that calculates storm-tide and wave statistics.
This innovative program calculates precise static water levels by averaging out the peaks and valleys of the waves. The wave information can then be separated from static water levels, providing a new piece of information that older sensors did not provide. These calculations are used to validate the National Hurricane Center’s storm surge models and are available on the USGS Flood Event Viewer, a map that displays all data associated with large flood events.
The additional depth and duration information these sensors provide has greatly improved flood and wave model accuracy, which is critical for storm preparation and public safety. Additionally, precise post-storm surge and wave data help identify places where storm damage was caused by water, which informs recovery funding, flood insurance map updates, evacuation strategies and infrastructure upgrades.
Enhancing Coastal Change Science
The USGS’s capability to forecast coastal change has evolved dramatically over the past decade.
“In terms of the coastal forecasts, we now have information we can share in real-time that we couldn’t 10 years ago,” said Meg Palmsten, a USGS research oceanographer.
In 2012, the USGS released a coastal change forecast for Hurricane Sandy based on data provided by the National Oceanic and Atmospheric Administration. However, it wasn’t provided to the public in a way that met their needs.
“It was a single realization, a single timestamp of what that storm might do,” said Hilary Stockdon, the USGS Acting Program Coordinator for the Coastal and Marine Hazards and Resources Program.
Following Sandy, the USGS and NOAA recognized the need to improve coastal forecasts and how they are delivered. Since that time, the USGS developed two products to forecast coastal change.
“These new forecasts are interactive and provide more useful information for local officials who need to make quick decisions related to reducing risk and protecting coastal communities,” said Stockdon.
The USGS created the Coastal Change Hazards Portal, which includes several features such as an interactive, high-resolution map that allows users to view a named storm’s forecasted coastal impact. Knowing the chances of severe flooding and coastal erosion before a storm is invaluable for emergency managers planning evacuations and for homeowners who reside in those areas. The map displays the probabilities of storm surge causing erosion, water flowing over the top of the dunes, and of complete coastal inundation, which is when water flows inland behind dunes. This map is updated as the storm makes landfall or as storm conditions change.
Similarly, the Total Water Level and Coastal Change Forecast Viewer, developed in cooperation with NOAA, displays predicted storm surge and wave-induced water levels and dune changes continuously – not just ahead of a named storm. Currently, hourly forecasts are produced for almost 3,000 miles of sandy coastline along the Atlantic Ocean and Gulf of Mexico. USGS forecasts are publicly available and used by NOAA forecasters in their coastal forecasts. The USGS continues to add more coastline to the viewer and is creating coastal impact models for cliff- and coral reef-lined beaches, including efforts in Puerto Rico and Guam.
After a storm, the USGS evaluates model accuracy by comparing the data recorded by the SWATH network, offshore wave buoys and coastal cameras to the forecast. This analysis can take years after a large storm, and USGS and NOAA meet regularly to share information to fine-tune forecasting.
Looking to the Future
USGS hurricane science has evolved in many ways over the past decade since historic Sandy struck the U.S.
“It’s not just the science that has progressed, but the USGS’s ability as a whole to respond to hurricanes and the information that we provide to people before, during and after hurricanes has changed so much,” Stockdon said.
Scientists with varied expertise from across the USGS continue to find new ways to forecast coastal change, measure flooding, create detailed maps of at-risk areas, work with partners to measure waves and storm tide, monitor water levels and flow in rivers and streams and provide an array of other resources and tools. This valued hurricane science can inform decision-makers and benefit communities and the public during future storms for years to come.
Learn more about USGS hurricane science.