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When a major storm is on the horizon, the USGS uses its water monitoring, coastal change, mapping, and modeling expertise to help prepare for, respond to, and recover from hurricanes and tropical storms.
The 2017 hurricane season is more than halfway over and has already seen nine major storms, on par with the prediction by the National Weather Service of as many as 11 to 17 named storms and two to four major hurricanes. But this year, as in the past, whenever a major hurricane is forecast to hit the nation’s Atlantic or Gulf Coast, U.S. Geological Survey scientists are ready to go well before the red-and-black hurricane warning flags unfurl. Starting about three days before a major storm’s predicted landfall, the USGS begins collecting data that can improve forecasting, guide relief work, and speed up recovery from the powerful storms’ effects.
Storm tides, coastal erosion, and inland flooding are among the most dangerous natural hazards unleashed by hurricanes, with the capacity to destroy homes and businesses, wipe out roads, bridges, water and sewer systems, and profoundly alter landscapes. The USGS has experts in these hazards, ready and willing to provide their expertise and to support the relief and recovery effort.
Throughout the hurricane season, the USGS Coastal Storm Response Team, made up of managers and scientists, works closely with the National Hurricane Center and other federal agencies and confers daily when forecasters indicate that a hurricane is likely to make landfall in the U.S.
Before: Preparation
A USGS hydrologic technician deploying instrumentation before a storm. (Public domain.)
Installing Sensors and Gauges That Ride Out the Storm
The USGS Coastal Storm Response Team decides the timing and extent of the USGS’ storm response based on the storm’s forecast intensity and track. If the storm is a Category 3 (with sustained winds of 111 miles per hour) or greater, or if especially vulnerable communities or ecosystems lie in its forecast path, USGS crews will be deployed in advance. Among the early decisions the team makes are when and where to position the special storm-tide sensors that can measure the height, extent, and timing of the storm tide that happens when the hurricane makes landfall.
These storm-tide sensors, housed in vented steel pipes a few inches wide and about a foot long, are part of the USGS Storm Tide Monitoring Network. The storm tide sensors are designed to be rapidly installed on bridges, piers, and other structures that have a good chance of surviving a hurricane.
The sensors collect water pressure readings that help define the depth and duration of a storm tide, the time of its arrival, and its retreat. That information helps public officials assess storm damage, tell the difference between wind and flood damage, and improve computer models.
Another important decision: whether specially designed rapid deployment gauges will be needed in areas where flooding is likely but that are not covered by the USGS’ network of more than 8,200 permanent streamgages. Data from the streamgage network is used by the National Weather Service to develop flood forecasts, by the U.S. Army Corps of Engineers to make flood control decisions, and by local agencies in emergency response.
Forecasting Coastal Change
Research scientists at the USGS’ St. Petersburg Coastal and Marine Science Center have developed a coastal change hazard forecast model, a sophisticated computer program that provides detailed predictions of a hurricane’s likely effects on sand dunes and other coastal features. The forecasts cover the Atlantic and Gulf coast regions where storm effects are expected, at one-kilometer intervals. They predict where protective sand dunes are likely to be eroded at their bases or overtopped by storm waves, and where coastal areas could be inundated by seawater.
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 forecasts begin 48 hours before a storm is expected to make landfall and are updated based on the latest forecasts from the National Hurricane Center. The forecasts are available to the public at the USGS Coastal Change Hazards Portal.
This season the team is also testing and refining new forecasts of coastal water levels, using a model developed with the National Weather Service. These experimental forecasts will predict how far up the beach waves will push seawater, showing hour-by-hour estimates of wave runup, updated several times a day. This work uses stationary video cameras installed in Tampa Bay and on North Carolina’s Outer Banks.
During: Response
Tracking Flood Effects
Post-Hurricane Irma flooding on Atlantic Avenue in Garden City, SC on September 11, 2017. (Credit: John Erbland, USGS. Public domain.)
Hurricane rains can cause flooding far from the coast. To track inland flooding, the USGS gathers data from its network of streamgages, as well as from rapid deployment gauges. When flooding occurs, USGS field crews make real-time streamflow measurements to verify the streamgages’ readings. The crews also quickly replace storm-damaged or lost gauges. During and right after hurricane flooding, these records help the Federal Emergency Management Agency target emergency relief to the hardest-hit areas. You can track storm-surge sensor deployment and see streamgage readings in real time at the USGS Flood Viewer.
Monitoring Protective Dunes
This year, for the first time, scientists at the USGS’ St. Petersburg Coastal and Marine Science Center are using unmanned aerial systems – commonly known as drones – to study hurricane impacts. It is part of an extensive effort to forecast and document the impact of hurricanes and other weather events on Gulf and Atlantic shorelines.
When a major hurricane strikes the U.S. coast, the team collects thousands of aerial photographs to document coastal changes. This year the scientists plan to deploy the new drones – quadcopters that resemble oversized video game controllers – before and after storm strikes. The drones collect high-resolution images before and after the storm. Scientists will use a technology called “structure from motion” to convert information from the images into dune elevations. The image processing algorithms will allow the team to document how sand dunes changed during the storm and improve the models’ future coastal erosion forecasts.
Maps and Apps That Show the Big Picture
The USGS strives to ensure that the disaster response community has rapid access to timely, accurate, and relevant geospatial imagery, products, and services before, during, and after a hurricane or other disasters. The USGS Earth Resources Observation and Science Center provides access to remotely sensed imagery and geospatial datasets in response to requests from agencies engaged in disaster response. These products enable agencies to plan the response to conditions on the ground. The hosting of imagery through a common delivery portal such as the USGS Hazards Data Distribution System (HDDS) facilitates the sharing of imagery and other geospatial datasets.
With information pouring in, often while USGS staffers are still coping with the storm’s consequences, managers need a way to quickly shape the data into a clear picture of the situation on the ground. The USGS’ Geospatial Information Response Team (GIRT), a group of scientists with expertise in many different facets of mapping, handles that vital task during hurricanes and other natural disasters.
Using a web app designed to help storm team members, scientists, and others working on storm response, the GIRT collects and makes available key pieces of information, such as the storm’s track, the USGS facilities that lie in its path, Lidar elevation data, detailed local maps and more. The app is designed to provide managers with a basic overview of the information they need to understand the situation and respond to it effectively.
The GIRT also works with the USGS Earth Resource Observation and Science Center to coordinate the archiving of place-based storm data, from high water marks to photographs, and make it accessible. Finally, the GIRT provides the geographical information that USGS staffers and first responders need, including the USGS’ legendary topographical maps.
After: Recovery
Collecting and Assessing Flood Data
Measurements collected during the storm, including high-water marks — the telltale lines of seeds, leaves, silt and other debris left behind on buildings, bridges, and trees after floodwaters recede — and storm tide sensor and streamgage data, are integral to storm recovery. So are peaks of record, measurements of how much water flowed through a river or stream during a storm.
These data help insurers and property owners document damage, help affected areas rebuild, inform the forecasting, response, and recovery efforts of agencies like the National Weather Service, the Federal Emergency Management Agency, and the U.S. Army Corps of Engineers, and provide real-world information to update the USGS’ flood inundation maps and validate and improve forecasts that inform future disaster response.
Understanding and Documenting Coastal Change
After a storm, aerial photographs taken post-event are compared to pictures taken before in order to document changes to the coast. This process helps chronicle changes to the protective dunes and other coastal characteristics as well as improve modeling of coastal change for the future.
Information for the Future
From beginning to end, USGS science informs and assists the response to major storms. Whether it be through modeling and forecasting, mobilizing teams around the country to help where they’re needed, responding to emergencies or assisting other agencies, the USGS has and will continue to weather whatever storm may come.
