Science Center Objects

Preventing flood hazards, such as hurricane-induced tidal surge, from becoming human disasters requires an understanding of the relative risks floods pose to specific communities and knowledge of the processes by which flood waters rise, converge, and abate. Historically, hurricane-induced tidal surge has been documented through measurement of high-water marks left on structures or vegetation. These remnant signals are not always reliable or accurate, however, and do not provide quantitative information about the timing of flooding, the sequencing of multiple paths by which storm-surge waters arrive, or the magnitude of waves.

To gain better knowledge about the effects of hurricanes, the U.S. Geological Survey Caribbean-Florida Water Science Center (USGS-CFWSC), in cooperation with municipal, State, and Federal agencies, uses two monitoring approaches to measure the timing, magnitude, and duration of hurricane tidal surge. The first approach uses the existing fixed network of gages that provide "real-time" data on water levels, and the second uses tidal-surge sensors that are temporarily-deployed in advance of hurricanes.

Real-Time Monitoring Network

Barometric Storm Surge Sensor struck by sailboat

Barometric Storm Surge Sensor struck by sailboat.

The USGS maintains a network of real-time gaging stations along the Florida and Puerto Rico coasts. These stations record data at 15-minute intervals that are available on the web at water.usgs.gov, and include measurements of water level, velocity, specific conductance, salinity, temperature, nitrogen, turbidity, pH, chlorophyll, blue green algae, and dissolved oxygen. The real-time network monitors a large range of hydrologic conditions, from droughts to floods, and provides the data on the web for a broad base of stakeholders. In the event of a hurricane, the real-time network allows individuals to monitor the storm-surge data in near real time (maximum 1-hour delay). Depending on the elevation of the gage-house structure, real-time gages may be at risk of being inundated by flood waters during extreme storm surges.

Temporary Deployment of Hurricane Storm Surge Sensors

To augment the real-time gaging network, a temporary network of hurricane storm-surge sensors can be deployed prior to a hurricane that record data at 30-second intervals. As part of this monitoring approach, water-level and barometric-pressure sensors are deployed to areas of projected hurricane landfall. The addition of these sensors creates a concentrated network of storm-surge monitors that provide more spatially-dense information on hurricane tidal surge. For example, temporary deployment of sensors in the projected hurricane path can be placed to monitor the escalation and attenuation of the hurricane storm surge along coastal rivers and across barrier islands, low-lying areas, and wetlands. After the passing of a storm the locations of the temporarily-deployed sensors must be surveyed to a known elevation. The USGS has successfully deployed temporary tidal surge-networks for Hurricanes Rita (2005), Wilma (2005), Gustav (2008), Ike (2008), Irene (2011), Hermine (2016), Matthew (2016), Irma, 2017, Maria (2017), and Michael (2018) Tropical Storm Ernesto (2006), and Isaac (2018).

 

USGS hydrologic technician, installs a storm surge sensor.

USGS hydrologic technician, installs a storm surge sensor in Aguirre, Puerto Rico. 

USGS Response to Hurricanes

CFWSC had been responding to the rains and flooding being forecast by ensuring that USGS real-time gages are operational and providing critical information on river stage and rainfall to the public, National Weather Service, and emergency management officials. In addition, USGS will deploy staff to make streamflow measurements at streamgages across the state to verify and update the river stage and streamflow discharge ratings. These ratings are critical for determining the volume of water that passes a streamgaging station at any given river stage and are used in issuing flood warnings, mapping floodplains, monitoring water-quality and environmental conditions, and managing water resources.

 

Summary

The use of existing fixed network stations along with temporarily-deployed water-level and barometric pressure sensors provides a cost-effective hurricane storm-surge monitoring network for Florida and Puerto Rico. The combined networks effectively leverage resources of many cooperative funding agencies in Florida and Puerto Rico to monitor hurricane storm surge. The data are a valuable resource for emergency preparedness agencies to better protect public safety, for engineers to improve structural design of coastal infrastructures, and for oceanographers to evaluate and improve hurricane storm-surge computer models.