The U.S. Geological Survey deployed a record number of sensors prior to Hurricane Matthew’s move up the southeast coast. More than 70 USGS staff were out from Florida to Virginia installing 393 sensors at 290 locations. These sensors were a combination of 190 storm-tide sensors, 92 barometric pressure sensors, 79 Wave Sensors and 32 Rapid Deployment Gauges, which were put in place to collect information about the hurricane’s effects on the Atlantic Coast. Retrieval of the sensors began Saturday in Florida and is expected to begin Sunday in the other states.

Here are some frequently asked questions about these important sensors:

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1. What does a storm-tide sensor look like? They are 1-1/2” aluminum or steel pipes strapped or bolted to a piling or other stable structure. The top will have a metal or PVC cap and the bottom will be open for the water to enter. The sensor housing protects a water-level sensor inside. A unique USGS visual ID sticker will be on the outside. They may be yellow or aluminum in color. If you find one and have questions about it, please call the phone number on the sticker.

2. What type of data do the sensors collect? Water-level and barometric pressure are recorded every 30 seconds for most sites. Sensors located on beaches record wave height every 2 seconds. The recording period lasts for 1 to 3 days depending on the magnitude of the storm and post-storm access to the sensor sites.

3. What is a storm-tide sensor deployment? The USGS has developed a mobile network of rapidly, deployable instruments with which to observe and document hurricane-induced storm-surge as they make landfall and interact with coastal features.

4. Why are you undertaking this work? The work will enable us to compile data so that we can quantify storm-tide dynamics (wave heights, forces, speeds, and extent) for various storm conditions, topographies, ecologies, built environments, and land uses. This information will lead to better storm-tide models, more accurate flood forecasts, more effective flood-protection infrastructure, and wiser land use policies.

5. What is the nature of the work? Hundreds of storm-tide sensors (non-vented pressure transducers) are strapped to bridge piers, power and light poles, and other structures along and inland of the coast about 50 miles left and 100 miles right of the projected path of hurricane landfall. The effort involves dozens of 2-person teams that deploy the instruments 24 to 48 hours prior to landfall.

6. What are you going to do with the data? Data are uploaded to the web as stage and pressure time series. We generate various graphics to create 3-D water-surface images, and depth and duration maps. Together they enable us to study surge flooding, including wave height, and moment by moment, visualize its interaction with the coastal features such as beaches, islands, estuaries, and streams. By tying these data together and with local topography, we can determine the rates at which flood waters transverse various water bodies and landforms, the major paths of penetration, their duration, and the height and frequency of waves that strike dunes and built infrastructure.

Data of this nature is quite rare and very valuable for determination of flood insurance maps, building codes, and for calibration of the hurricane inundation models. Accurate model forecasts are critical for community preparation of storm response and evacuation plans.

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7. Are the surge data reported in real-time? The surge data are not reported in real time but are logged on-site and are not available until they are processed and calibrated for barometric pressure, water density, and elevation data. Real-time information is available from rapid deployed gauges that are installed at sites where we do not currently have permanent gauges, but may be impacted by storm surge or floodwaters along critical roadways. These rapid deployed gauges will augment a network of existing U.S. Geological Survey gauging stations already in place before the storm arrives.

8. What other kinds of data are needed? There are several kinds of data that would complement this work and for which we seek collaborators. These include offshore water-level and wave-height data, wind speed and direction, inland water salinity, post-storm ecological assessments, and geological evaluations of beach and landform behavior, and engineering evaluations.

9. Who uses this information? Our data is used by the Federal Emergency Management Agency, National Ocean and Atmospheric Administration, National Weather Service, and National Hurricane Center and the U.S. Army Engineer Research and Development Center, as well as state responders and emergency management officials.

10. Where can learn more? Recent efforts by the USGS to deploy these storm-tide sensors in response to Hurricane Matthew can be read here. Reports on previous USGS storm surge documentation efforts as well as additional information about storm-tide sensors is available here.