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As powerful Hurricane Irma nears Puerto Rico and poses a threat to Florida, U.S. Geological Survey scientists are mobilizing to help measure storm surge, forecast coastal change expected from the storm, and provide key information on water and stream levels critical to forecasting floods.
As Hurricane Irma approaches Puerto Rico and poses a potential threat to the U.S. mainland, the U.S. Geological Survey’s experts on storm-related hazards are taking action, along with other federal agencies, to help minimize potential risks to lives and property.
The USGS is closely monitoring the approaching hurricane in consultation with the National Hurricane Center and other agencies. Since Monday, when USGS field crews in Puerto Rico rushed pre-storm work to completion, the USGS has been preparing to deploy field scientists in Florida, with teams as far north as the Carolinas on standby.
Storm surge, 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 on these hazards, computer models for forecasting them, and sophisticated equipment for monitoring actual flood and tide conditions.
On Puerto Rico’s northeast coast, USGS hydrologic technician Francisco Almanzar surveys reference elevation points to ensure the accuracy of water level data for a storm-tide sensor newly installed on a concrete support. USGS employees in Puerto Rico installed nine storm-tide sensors on Labor Day, Sept. 4, 2017 as Hurricane Irma approached. Photo: USGS
In Puerto Rico the field crews positioned nine storm-tide sensors – specialized scientific instruments for measuring the height and intensity of the hurricane’s surge – before Irma’s high winds and waters arrived. Crews are preparing now to place storm surge sensors in the Florida Keys on Wednesday, and may also place them at sites further north on Florida’s Atlantic and Gulf coasts Thursday and Friday, as Irma’s forecasted track becomes clearer.
Other instruments called streamgages will continuously monitor water levels of inland rivers and streams. This work provides critical information needed for accurate flood forecasting.
USGS researchers are also preparing to forecast the amount of coastal change projected to result from the storm surge, based on USGS models and the National Hurricane Center’s predictions of Hurricane Irma’s likely path. Once it becomes clearer whether Irma is likely to impact the Atlantic or Gulf coast, the researchers will use modeling to assess the likelihood of beach erosion, overwash or inundation at the local level and along the entire coastal zone in the hurricane’s path.
Prepared to Capture Storm Surges
Storm surges are increases in ocean water levels generated at sea by extreme storms. They can have devastating coastal impacts. Scientists at the USGS and elsewhere want to better understand storm surges so that forecasters can more accurately model and predict surge-related flooding, engineers can design better storm-resistant structures, and emergency responders can work more safely and effectively. Anticipating a storm’s path and intensity, and taking into account whether any permanent sensors are installed in the area, the USGS scientists often deploy extra storm-tide sensors at coastal locations just hours or days before an expected landfall. The sensors are housed in steel pipes a few inches wide and about a foot long. Working quickly, and often in severe weather, field crews install them on bridges, piers and other structures that have a good chance of surviving a hurricane’s storm surge.
In preparation for Hurricane Irma, the USGS is ready to install as many as 100 additional sensors in Florida. Storm tide sensors have been deployed along the Atlantic and Gulf coasts in preparation for Hurricane Irene in 2011, Hurricane Sandy in 2012 Hurricane Matthew in 2016, and Hurricane Harvey in August 2017, among others. The data they collected were instrumental in understanding the effects of hurricanes and tropical storms on the coasts and their communities.
Streamgaging Network at the Ready
The USGS Streamgaging Network operates sensors that record water levels and other key pieces of information on inland rivers and streams throughout the nation. With the support of local, state, and federal agencies, the USGS uses this nationwide network to provide real-time data to the National Weather Service, Federal Emergency Management Agency (FEMA), the U.S. Army Corps of Engineers, and others.
The streamgages’ information is routinely used for a variety of non-emergency purposes, such as tracking and managing water supplies, monitoring floods and droughts, designing roads and bridges, and planning recreational activities on rivers and streams. In extreme weather, these data help inform decision makers as they issue flood and evacuation warnings, coordinate emergency responses to communities, and operate flood-control reservoirs. During a storm’s landfall, the network helps capture the depth and duration of storm-surge, the time of its arrival, and its retreat.
One major hurricane hazard is inland flooding caused by heavy rainfall. USGS hydrologists in Puerto Rico have completed their preparations to track this threat, while their counterparts from Florida to North Carolina are gearing up to do the same work if it is needed.
Immediately after the worst of the storm has passed, the hydrologists will check inland streamgages to verify high river and stream flows and peak water levels, and measure high-water marks left by floodwaters on buildings, bridges and trees. In the days after the storm, this information helps emergency managers and insurers steer resources to the hardest hit areas. The crews will also calibrate and repair streamgages damaged by the storm to ensure they continue providing valuable information in the aftermath of the storm.
Scientists Will Track Coastal Changes
When a major hurricane strikes the U.S. coast, scientists at the USGS’ St. Petersburg Coastal and Marine Science Center collect thousands of aerial photographs to document coastal changes. A technology called “structure from motion” allows the team to convert information from the images into dune elevations, documenting where and how dunes change during the storm.
Research scientists at the center have developed the USGS Coastal Change Forecast Model, a sophisticated computer program that provides detailed predictions of a hurricane’s likely effects on sandy shorelines. The model uses the National Hurricane Center’s storm surge predictions and the National Oceanic and Atmospheric Administration’s wave forecast models as its starting point, and incorporates detailed geological information about beach slopes and dune heights along the entire coast wherever there are sandy beaches. The model can predict, at one-kilometer intervals, where protective sand dunes are likely to be eroded at their bases or overtopped by storm waves, and which coastal areas could be inundated by seawater. The information 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 coastal change forecasts will begin 48 hours before the storm’s expected landfall on the U.S. mainland, and are updated based on the latest forecasts from the National Hurricane Center. The forecasts will be available to the public at the USGS Coastal Change Hazards Portal.
More Resources to Help Everyone Prepare
As USGS continues to take all appropriate preparedness and response actions as Hurricane Irene develops over the coming days, those potentially in the storm’s path can visit www.ready.gov or www.listo.gov for tips on creating emergency plans and putting together an emergency supply kit.
Hurricane Irma Resources:
