USGS Scientists Document Hurricane Dorian’s Impacts

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Editor’s Note: This story was revised Sept. 10, 2019 to include the later phases of USGS’ response to Hurricane Dorian.

To learn more about USGS’ role providing science to decision makers before, during and after Hurricane Dorian, visit the USGS Hurricane Dorian page at www.usgs.gov/dorian.

After a rapid response to Hurricane Dorian that involved scientists from multiple science centers in five states, the USGS is beginning to gather and analyze the evidence of storm tides and coastal erosion left behind by the hurricane. Field crews are recovering the more than 350 scientific instruments that documented storm-tides triggered by the hurricane, and are processing the instruments’ recorded data. Research oceanographers are examining photographic evidence of storm-caused coastal erosion.

The scientific assessments already beginning can help decision makers, emergency responders and communities recover from the effects of Hurricane Dorian and prepare for future storms. During Dorian’s nearly two-week passage from the Caribbean to Canada, the USGS provided the public and emergency managers with comprehensive scientific capabilities and information. This included the ability to forecast coastal change; track storm tides, river and stream levels and flow; measure coastal and inland flooding across entire regions; capture high-resolution ground elevation and topographic data; and create detailed maps used by disaster teams responding in the aftermath of storms.

This is how the USGS’ continuing response to Hurricane Dorian has progressed:

Planning and Preparation

Before a coastal storm is predicted to make landfall, the USGS begins collecting data that can improve forecasting, guide relief work, and speed up recovery from the powerful storms’ effects.

The Coastal Storm Response Team, a multidisciplinary group of specialists from throughout the USGS, works closely with the National Hurricane Center and other federal agencies and confers daily when forecasters indicate a hurricane or tropical storm is likely to make landfall in the U.S. The Storm Team closely follows the storm’s forecast intensity and track. Once a hurricane or tropical storm is considered likely to strike somewhere in the U.S., the team leaders decide whether it is necessary and safe to deploy USGS field crews to the storm’s projected path along the coast. 

Since Dorian, as a tropical storm, was expected to hit Puerto Rico Aug. 28, the Storm Team began meeting on Aug. 26. But the storm gave Puerto Rico a near miss, stalled over the Bahamas and then slowly moved up the Florida coast. So USGS preparations for the hurricane adapted and expanded in response to changing forecasts from the National Hurricane Center.

Sensing the Storm

A USGS hydrologic technician, installs a storm tide sensor Sept. 3 on a tidal creek in Onslow County, North Carolina.

Ryan Rasmussen, USGS hydrologic technician, installs a storm tide sensor Sept. 3 on a tidal creek in Onslow County, North Carolina. Photo by David Stillwell, USGS. (Public domain.)

Teams of U.S. Geological Survey hydrologists and hydrologic technicians deployed more than 350 storm-tide sensors, beginning Aug. 29 and 30 in Florida, then rolling along the coasts of Georgia, South Carolina and North Carolina over the long Labor Day holiday weekend. By Sept. 5, technicians had deployed about a half-dozen sensors in coastal Virginia as the storm’s high water approached that state’s Tidewater region. 

The sensors gathered information used by the National Oceanic and Atmospheric Administration and by emergency managers to monitor the timing, extent and magnitude of storm tides.

Storm-tide sensors record water-level and wave data. The sensors, housed in vented steel pipes a few inches wide and about a foot long, are designed to be rapidly installed on bridges, piers, and other structures that have a good chance of surviving a hurricane, and are part of the USGS Storm Tide Monitoring Network. They remain in place throughout the storm, until it is safe for USGS crews to collect them.

The sensors collect water pressure readings that help define the depth, duration and timing of a storm tide. Some of them are arranged in long transects perpendicular to the coast, to help measure how local topography, natural features and land use can reduce or increase wave heights and the resulting flood damage.

That information helps public officials assess storm damage, tell the difference between wind and flood damage, and improve storm-tide and coastal change forecasts for future events.

USGS technician on a bridge with instruments and laptop

Hydrographer Keith Lambert installing a rapid deployment gage at New Mill Creek at Chesapeake, VA Sept. 5, in advance of Hurricane Dorian. Photo: Blake Dudding, USGS 

USGS crews also installed rapid deployment gauges at locations that are not monitored year-round, but were at risk of flooding due to an approaching storm. These RDGs provided real-time information to emergency managers tracking floodwaters, such as water level, precipitation, wind speed, humidity and barometric pressure. Both sets of instruments helped augment the USGS’ nationwide real-time network of about 8,500 streamgages that transmit both streamflow and water levels, and another 1,700 streamgages that transmit only water levels. The National Weather Service uses data from streamgages that provide both water level and streamflow to develop flood forecasts, and the U.S. Army Corps of Engineers uses the data to make flood-control decisions. The streamgages and RDGs that provide only water levels are used by local agencies to track flood locations and plan emergency response and allow the public to monitor local rivers and stream levels in real time.

As soon as Dorian’s wind and rain eased, field crews began collecting the storm-tide sensors and other instruments deployed in advance of the storm. That process is already done in Florida, Georgia, and Virginia, and is expected to be finished in the Carolinas by Sept. 10. The wave-height and barometric pressure information recorded on the devices is downloaded and analyzed to help improve future flood and coastal change forecasts.

Forecasting Coastal Change

Hurricanes generate dangerous waves and high water levels that can move large amounts of sand, destroy buildings and infrastructure, and take lives. Through processes like dune erosionoverwash and inundation, storms reshape the nation's coastline. USGS coastal change experts forecast how Dorian might affect the coastline using a sophisticated system they developed called the Coastal Change Hazard Forecast model.

The model provided detailed, frequently updated forecasts of Dorian’s likely effects on sandy shorelines along the Atlantic coast. It predicted where protective sand dunes were likely to erode at their bases or be overtopped by storm waves, and where seawater could inundate coastal areas behind the dunes. These forecasts can help emergency managers decide which areas to evacuate, which roads to use, and where to position heavy equipment for post-storm clean-up.

The model works by combining NOAA-modeled waves and surge with the USGS’ detailed coastal elevation data to estimate total water levels at the shoreline and the probability of coastal erosion. Forecasts in the portal are updated as NOAA projections of storm path and strength change. 

Now that Dorian is gone, the USGS research oceanographers who developed the forecasts are closely examining, by eye, aerial imagery of the coast to document hurricane-caused changes to sandy beaches. The team’s analysis will show what percentage of coastal dunes were eroded, overwashed or inundated by Dorian’s storm-tides.

Informing First Responders and the Public

During Hurricane Dorian and all other major hurricanes, the USGS strives to ensure that the disaster response community has quick access to timely, accurate, and relevant geospatial imagery, products, and services. 

First responders often rely on the USGS National Geospatial Program, which collects, archives and shares digital records on the nation’s topography, natural landscape and human-made environment. The program’s Geospatial Information Response Team, also known as the GIRT, works within the USGS and with partner agencies to provide key information to federal, state and local agencies, emergency managers and first responders. Information such as the storm’s track, the USGS facilities that lie in its path, lidar elevation data, and the locations of hospitals, airports, government buildings and other important sites, is shown on multi-layered websites or on custom-printed maps. 

As Florida was preparing for Hurricane Dorian's arrival, USGS worked with the Defense Logistics Agency to prepare more than 2,600 detailed topographic maps of 10 Florida counties likely to be affected by the storm, so that first responders could have detailed information in hand. 

To make a broad range of information easily accessible to the public, first responders, emergency managers and government decision makers, the GIRT also quickly collects and posts information for each major hurricane in an event support map. On the publicly accessible Event Support Map website for Dorian, anyone interested in detailed information can find many sources on a single web page. 

A screenshot of the USGS Hurricane Dorian Flood Event Viewer

A screenshot of the USGS Hurricane Dorian Flood Event Viewer from Sept. 5, 2019. Public domain.

A custom-made composite Storm Event Map brings together a variety of information, including the storm track, hurricane watches and warnings, landscape features, major roads, streamgages, rapid deployment gauges and more. (Click anywhere on the map to view details.) Also on the website is the most recent Coastal Change Hazard Forecast ; a Flood Event Viewer with readings from permanent streamgages, and from storm-tide sensors and rapid deployment gauges up until they are removed from the shoreline; satellite imagery and photos; and elevation information. In partnership with the Heritage Emergency National Task Force, which includes FEMA and the Smithsonian Institution, the GIRT also included arts, historical and cultural institutions in the storm’s path on the Hurricane Dorian event support map.

Also included on the USGS’ public event support map is information from other government agencies, such as forecasts from the National Hurricane Center, NOAA imagery, and crowdsourced hurricane photos collected by FEMA.

Rebuilding after a big storm, getting ready for the future

Hurricanes reshape the landscape, sometimes subtly, sometimes dramatically. Hurricane Maria in 2017 damaged or destroyed 83 streamgages in Puerto Rico. Hydrologic technicians from the Caribbean-Florida Water Science Center, working under difficult conditions, repaired or replaced all 83, and deployed 33 new rain gauges that were paid for with special disaster recovery funds. The streamgages transmitted information throughout then-Tropical Storm Dorian’s close brush with Puerto Rico, and the island’s emergency managers used the new rain gauges to track the storm’s rainfall.  In Florida, 99 streamgages that were damaged during 2017’s Hurricane Irma are back online and ready to monitor any flooding.

The supplemental storm funding the USGS received also allowed the acquisition of high-resolution lidar data for large areas of Florida. Lidar uses pulses of light beamed from an airplane to develop very detailed elevation information, which can be used to create precise maps of the land’s surface. USGS now has lidar data for Florida’s east coast watersheds from the Florida/Georgia line to the southern boundary of Broward County. That lidar data will give researchers an important baseline for measuring coastal change and assessing potential damages caused by Hurricane Dorian.

For more information please visit these websites:

USGS Coastal Change Hazards: Hurricanes and Extreme Storms – Information on coastal change

USGS Flood Information—Information about current and past flooding

USGS WaterAlert – Sends email or text messages from the USGS streamgage of your choice

USGS WaterWatch— Provides current USGS water data for the nation

NOAA’s National Hurricane Center