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Forecasters are calling for an above average hurricane season this year.  In comparison to the 2020 hurricane season – the busiest on record with 30 named storms of which 12 made landfall in the U.S, experts do not believe the 2021 season will be as active. This year, there is a 60% chance of an above average season and a 30% chance of a near-normal season according to the National Oceanic and Atmospheric Administration Climate Prediction Center’s  2021 hurricane season forecast. An average hurricane season produces 14 named storms with winds of 39 miles per hour or higher, and includes seven hurricanes, three of which are major hurricanes with winds of 111 miles per hour or higher. This year the NOAA forecast calls for 13 to 20 named storms, of which six to 10 could become hurricanes, with three to five of those being major hurricanes. 

Tropical storms, hurricanes and other large coastal storms can impact seaside and inland communities and ecosystems with high winds, storm surge, erosion and flooding. These forces can destroy buildings, roads and bridges and reshape the nation’s coastline.  

When a major storm threatens to make landfall in the U.S. or its territories, the USGS provides comprehensive scientific capabilities and information that decision-makers, emergency responders and communities can use to help them prepare, cope with and recover from a storm. This includes the USGS’s ability to forecast coastal change; track storm surge, river and stream levels and flow; capture high-resolution ground elevation and topographic data; create detailed maps that can be used by disaster teams responding in the aftermath of storms; measure coastal and inland flooding across entire regions; and determine the extent floodwaters may have spread non-native species. 

Forecasting Coastal Change as a Hurricane Approaches 

Before a storm’s expected landfall, USGS coastal change experts forecast how a storm may reshape the coastline using a sophisticated system they developed called the Total Water Level and Coastal Change Forecast model. The model provides detailed forecasts of a strong storm’s likely effects on sandy beaches along the Atlantic and Gulf coasts. 

Working with the National Weather Service, the USGS coastal hazards storm team updates forecasts–which are publicly available on the Total Water Level and Coastal Change Forecast Viewer–several times a day using real-time water levels from the National Weather Service’s Nearshore Wave Prediction System along with the USGS’s detailed data on the shape and elevation of the beach. The coverage area of the viewer was recently expanded and now displays forecasts from the coast from Texas to Maine, almost 3,000 miles.  

Additional forecasts are made when named storms approach stretches of sandy coastline with the Coastal Change Hazard Forecast model. This model estimates the timing and height of water levels at the shoreline as well as where protective coastal sand dunes are likely to be eroded at their bases or overtopped by storm waves and where coastal areas behind the dunes could be inundated by seawater. NOAA will use the predictions to help inform forecasters at the National Hurricane Center. 

These forecasts can help emergency managers make critical decisions before a major storm strikes, including which areas to evacuate, which roads to use and where to position storm cleanup equipment. The forecasts typically begin 72 hours before a storm is expected to make landfall, are updated based on the latest forecasts from the National Hurricane Center and are available at the  USGS Coastal Change Hazards Portal.  

For this year’s hurricane season, the coastal storm team is also testing new instruments as part of a pilot program that will monitor and measure wave heights and storm tides for any coastal storms that approach the Tampa Bay area. 

“The pilot test site will include a series of scientific instruments under water, floating on the water, on shore and all tied into our beach camera system we currently use to assess the accuracy of our Total Water Level and Coastal Change Forecast,” said oceanographer Kara Doran, USGS Coastal Change Hazards Storm Team leader. 

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Measuring and Monitoring the Storm 

Once it is determined a hurricane or tropical storm will likely strike somewhere in the U.S., and if it’s deemed safe and necessary, USGS field crews will deploy to the storm’s projected path along the coast to install special water-level measuring instruments called storm tide sensors. These sensors record data that track storm tides and coastal flooding. This information helps USGS and NOAA scientists improve forecast models. It also helps relief efforts by the Federal Emergency Management Agency and other federal, state and local agencies by pinpointing the areas hardest hit by storm tide flooding. 

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Storm tide sensor information can also help engineers design structures to better withstand floods and assess how well engineered dunes and wetlands reduce storm damage. It can help inform land-use practices and building codes which can lead to more resilient coastal communities. 

“This year, the USGS will be pilot testing a variety of new technologies that will expand our real-time data collection capabilities for storm tide level monitoring, wave statistics, water quality and more,” said Athena Clark, USGS Coastal Storm Team Leader. “This work is part of the USGS’s ongoing efforts to find innovate ways to record data from coastal storms that we can share with our cooperators, storm forecasters, emergency managers and the public.” 

USGS crews may also install rapid deployment gauges at locations that are not monitored year-round with permanent USGS streamgages but are at risk of flooding due to an approaching storm. These RDGs provide real-time information on water levels, precipitation, wind speed, humidity and barometric pressure to emergency managers tracking floodwaters. 

RDGs can quickly be installed at critical locations to help augment the USGS’s nationwide real-time network of streamgages, about 8,500 of which transmit both streamflow and water level, while another 1,700 streamgages transmit only water levels. The National Weather Service uses data from the streamgages that provide both water level and streamflow to develop flood forecasts. The U.S. Army Corps of Engineers uses these data to make flood-control decisions. The streamgages that provide only water levels are used by local agencies to track flooding and plan emergency response; they also allow the public to monitor local rivers and stream levels in real time. 

You can track storm tide sensor and RDG deployments and view past storms on the  USGS Flood Event Viewer  and see USGS streamgage readings in real time on both the viewer and the  USGS National Water Dashboard. The dashboard is a new online tool that provides real-time information on water levels, weather and flood forecasts all in one place on a computer, smartphone or other mobile device. It provides critical information to decision-makers, emergency managers and the public during flood events. 

The National Water Dashboard presents real-time stream, lake and reservoir, precipitation and groundwater data from more than 13,500 USGS observation stations across the country. This information is shown along with NOAA weather data such as radar, watches and warnings, past precipitation totals, precipitation forecasts and drought conditions from other open water-data sources. The dashboard also links to the USGS WaterAlert system, which the public can customize to send out instant, updates about water conditions in their local area. 

Determining the Extent of Flooding 

Once it is safe to do so after the storm has passed, USGS field crews usually travel to affected areas to take streamflow measurements, verify the accuracy of streamgage readings and quickly repair or replace damaged or lost gauges. This work is vital to flood forecasting and informs decisions on how best to protect communities. 

USGS crews often fan out across affected areas to document high water. They look for telltale lines of seeds, leaves, grass blades and other debris left behind on tree trunks, buildings, bridges and other structures as floodwaters recede. Once they find these high-water marks, they photograph them, take notes, and survey them to determine the depth and range of the flooding. This field work is time-sensitive because high-water marks can be destroyed by weather and property owners’ cleanup efforts. FEMA uses high-water mark data and related information to steer relief to areas of greatest need in the days after a storm, and later, to update flood insurance maps. 

USGS specialists can develop indirect measurements of water flow using high-water marks in places where flooding is not measured by an instrument. A computer model uses information about the stream’s shape, depth and vegetation to determine how much water flow it would take to create a flood that produced the high-water marks. 

To analyze field data gathered after a storm, USGS scientists need accurate, detailed information about land elevation, which is provided by the USGS 3D Elevation Program. That program collects data using lidar – a technique that uses light pulses to produce high resolution elevation imagery – over the U.S. and its territories. These data are used for mapping storms’ flood inundation, modeling storm surge, evaluating topographic changes, such as beach and dune erosion, and pinpointing damage to buildings and other infrastructure. Up-to-date elevation data are also essential for supporting infrastructure repair and redevelopment after a storm. 

The USGS 3D Elevation Program acquires the information nationwide and makes it available on The National Map. 

Creating Maps and Apps for Hurricane Response 

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During hurricanes, first responders often rely on the  USGS National Geospatial Program,  which collects, archives and shares digital records of the nation’s topography, natural landscape and human-made environment. The program coordinates, communicates, disseminates and facilitates the use of geospatial information to aid situational awareness and resource management during disaster events.

“For the 2021 hurricane season, the USGS will continue working with partners, including NOAA, the U.S. Army Corps of Engineers, and FEMA, to enhance the Multi-Agency High Water Mark Dashboard, which was created to improve the coordination of post-storm planning and high water mark field collections,” said USGS physical scientist Lance Clampitt, who leads the Geospatial Information Response Team. “The application allows response teams to view each agency’s high water mark collection plans and see the marks collected to date by each agency within a single map interface, which improves collaboration efforts between agencies.” 

Tracking Where Invasive Species Spread During Flooding  

Coastal and inland flooding has the potential to spread non-native freshwater plants and animals into new water bodies. Some of these plants and animals can become invasive, disrupting living communities or changing the landscape.  

To help land managers find and manage these flood-borne newcomers, USGS scientists create maps that show where non-native aquatic plant and animal species may have been spread by floodwaters. To create the maps, scientists with the Nonindigenous Aquatic Species Database use USGS data on water levels and flow, and storm surge heights to identify places where lakes, rivers, streams and other waterways may have merged during flooding. Once this is determined they combine that information with established plant and animal populations in the area to identify what aquatic species may have spread.

The first flood and storm tracker map was produced in 2017 after Hurricane Harvey made landfall on the Texas Gulf Coast. The map proved to be a useful tool for land managers as they worked to mitigate the potential spread of non-native species. Since then, the USGS has created 12 additional maps for major flooding events.

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