By Hailey Murphy, S.C. Sea Grant Consortium.
A water level sensor installed over Jeremy Creek in McClellanville, S.C. Photo credit: Hailey Murphy/S.C. Sea Grant Consortium.
The National Oceanic and Atmospheric Administration (NOAA) and its predecessor organizations have been measuring and predicting tidal phenomena on our coasts and the Great Lakes, including changes in water levels, since the early 1800s. They have implemented several technologies over the centuries to do this, beginning with human observation, then using submerged analog-to-digital recorders within “stilling” devices that reduced water movement, followed by submerged air acoustic measurement devices that incorporated microprocessors, allowing for more frequent measurements. With each new iteration of sensors, NOAA implemented an overlap period of a year or more to ensure that the new technology resulted in accurate measurements, resolving recurring errors and uncertainty in water level data.
In South Carolina, water level sensors served as crucial data points for emergency preparedness and response efforts during the catastrophic flooding events of Hurricane Joaquin (2015), Hurricane Matthew (2016), Hurricane Irma (2017), and Hurricane Florence (2018). Prior to Hurricane Matthew, South Carolina had 164 gauges in the state and requested an additional nine rapid-deployment gauges, on loan from neighboring Georgia, to fill in the gaps. The number of water level sensors and gauges in South Carolina has since increased, but the density of working sensors is still lacking compared to our neighboring states.
In 2016, the cost of high-tech water level gauges capable of sending information to satellites was between $15,000 to $18,000 each, plus an additional $15,000 per gauge in annual operating costs. Now the market for water level sensors has grown to include numerous options, including submerged pressure or hydrostatic sensors, or non-submerged sensors relying on ultrasonic waves or microwave/radar pulses. Rather than being weighted or anchored while submerged in a body of water, these non-submerged sensors are installed in a fixed location above the surface of the water, such as a pier or bridge, making the sensors easier and cheaper to install, maintain, and replace. The variety of sensors on the market also display different levels of longevity and accuracy, allowing for more targeted use in the field for research (likely high-accuracy, more expensive models) or for community preparedness (likely lower accuracy, more affordable models). Prices for these new non-submerged models of sensors (not including maintenance) range from $120 to $2,600 each, making the goal of an expanded network of sensors more attainable.
Sailboat beached in salt marsh following 2024 flooding on the Edisto River, S.C. Photo credit: Hailey Murphy/S.C. Sea Grant Consortium.
Enter the Southeast Coastal Ocean Observing Regional Association (SECOORA). Recognizing the need for further water level observation and improved interconnectivity between local, state, and federal resources related to flood preparedness and response, SECOORA issued funding for four state-led teams to lead a five-year project from 2020 to 2024 to install affordable water level sensors across the region to create the Southeast Water Level Network.
The South Carolina Sea Grant Consortium has joined the Southeast Water Level Network by partnering with SECOORA to develop the South Carolina Water Level Monitoring Initiative. The goal of this initiative is to deploy ultrasonic sensors across the state, focused on observational gaps where flood risk is high, and to assist communities in better understanding local water levels and flooding hazards.
In the first five years of the project (2020–2024), expanding water level observation in the Pee Dee River watershed was a priority, resulting in the deployment of four new water level sensors in this region. In the next five years of the project (2025–2029), the Consortium is focused on expanding the deployment of water level sensors in counties that contain at least part of a coastal watershed (i.e., counties with estuarine or marine waters or wetlands that are tidally influenced or have predicted category 4 hurricane storm surge inundation). The Consortium is also coordinating a regional team of Southeast Sea Grant programs that are expanding water level sensor networks in Georgia, Florida, and North Carolina, through funding from SECOORA. The Consortium’s Water Level Monitoring Specialist Ke’Ziyah Williamson works with SECOORA to develop and lead recurring meetings with this regional team every other month, allowing each Sea Grant program to share updates, lessons learned, engagement and funding opportunities, and best practices, contributing to a stronger network of water level monitoring.
Screenshot from the SECOORA water monitoring network portal indicating the locations of water level monitoring sensors across the coastal Southeast. Map courtesy of SECOORA.
The project, funded by SECOORA, covers the cost of installing, maintaining, and providing cell service (approximately $20/month) for the sensor until the end of the grant period unless additional grant funds are obtained. For sensors installed from 2020 to 2024, the community may assume the associated costs at the end of 2025. For sensors installed in the next grant period, between 2025 and 2029, the community may begin covering the costs after the grant period closes in 2029. These water level sensors will allow the public to observe real-time, publicly accessible data on the elevation of a waterbody’s surface in or near their community.
So, how do these non-submerged ultrasonic sensors work? Williamson explains: “The water level sensors used by the Consortium, in collaboration with SECOORA, conduct continuous water level measuring using ultrasonic sensors. The sensor emits ultrasonic waves, the water reflects the waves back to the sensor, and the time from emission to reception of the signal is proportional to the water level.”
Arrows indicating the locations of the sensor, solar panel, and battery housing at the installation in McClellanville, S.C. Image credit: Hailey Murphy/S.C. Sea Grant Consortium.
When users such as emergency managers access the resulting water level data, it may help them to identify a flooding threshold, a specific water level indicating the beginning of a flood event that varies by location. Establishing this flooding threshold allows emergency managers to move quickly in response to flood hazards: clearing storm drains, closing roads or bridges, or issuing evacuation procedures should that threshold be reached.
With 2024’s double feature of Tropical Storm Debby and Hurricane Helene leading to flooding events across the state of South Carolina, the urgency of expanded water level observation couldn’t be higher. Williamson reports:
“The entire South Carolina coast is facing more frequent and intense flooding. These sensors are being deployed to allow for better flood modeling to understand the extent and timing of flooding. Placing sensors in locations that are significant to communities, such as bridges and riverfront parks, will allow communities to have access to their localized data and help them prepare and respond to flooding conditions that could affect their infrastructure and roads. Sensors that are installed upstream can allow downstream communities to be better prepared for incoming flooding conditions, almost like an early warning system. Beyond flood monitoring, there are recreational benefits to more localized water level monitoring, including boating and fishing activities. Ultimately, residents and emergency managers can get a better understanding of their local flood hazards.”
S.C. coastal watershed regions included in the Water Level Monitoring Initiative’s scope of work for 2025-2029. Coastal watersheds include estuarine or marine waters or wetlands that are tidally influenced or can experience predicted category 4 storm surge inundation. Map courtesy of U.S. Geological Survey Watershed Boundary Dataset; U.S. Census Bureau Dataset; and S.C. Department of Health and Environmental Control.
River basins of the 14 counties in South Carolina with a coastal watershed; riverine flooding may compound other coastal hazards. Map courtesy of U.S. Geological Survey Watershed Boundary Dataset; U.S. Census Bureau Dataset; and S.C. Department of Health and Environmental Control.
Factors considered when determining where to deploy a water level sensor include whether the location is within a coastal watershed county of South Carolina; the existence of a bridge, pier, dock, or similar structure over a waterbody; whether other measurements are being collected nearby that may correlate to the data, such as water quality or weather conditions; frequency of flooding in the area; and access to a Verizon cell signal and direct sunlight to allow for proper function of the transmitter and solar panel.
As of March 2025, four water level sensor locations have been identified and coordinated by the Consortium as a part of this effort, and sensors have been installed by SECOORA partners in the following locations in S.C.: Crooked Creek in Bennettsville; Jeremy Creek in McClellanville; Little Pee Dee River in Marion; and the Black River in Kingstree.
Summer on the Black River—so named for its dark, tannin-rich water—at Gilland Memorial Park, Kingstree, S.C. Photo credit: Hailey Murphy/S.C. Sea Grant Consortium.
The Consortium aims to raise community awareness and understanding of their localized flooding levels to better prepare for flooding events. This preparation might look like preventing vehicular fatalities by blocking off low-lying roads, assigning reliable evacuation or detour routes, informing emergency responders of flood risk areas in advance, establishing emergency shelters, and planning for school or business closures. Recognizing how water levels rise during a variety of weather events, seasonal changes, and development or construction within a community could go a long way in informing local policymakers on topics of coastal resilience, urban planning, and property insurance.
How can you get involved in the Water Level Monitoring Initiative? Access the water level data in your area at the Consortium’s South Carolina Water Monitoring Initiative webpage. Stay informed on flood risks and emergency procedures using the resource list below. To learn more, including how to install a water level sensor in your community, contact Water Level Monitoring Specialist Ke’Ziyah Williamson or Coastal Resilience Program Manager Landon Knapp.
Flood Safety and Preparedness Resources:
- NOAA National Weather Service Flood Safety
- U.S. Dept. of Homeland Security Flood Preparation
- U.S. Geological Survey Flood Information
- South Carolina Emergency Management Division
- NOAA Sea Level Rise Viewer
Southeast Coastal Ocean Observing Regional Association Resources:
Reference List:
“Coastal Resilience Collective.” 2025. S.C. Sea Grant Consortium. March 13, 2025. https://www.scseagrant.org/coastal-resilience-collective/.
“Communities Under Water: Lessons Learned from Extreme Floods.” 2016. S.C. Sea Grant Consortium. October 5, 2016. https://www.scseagrant.org/communities-under-water-lessons-learned-from-extreme-floods/.
Samadi V., Lunt S. Historical Floods of South Carolina. Clemson (S.C.): Clemson Cooperative Extension, Land-Grant Press by Clemson Extension; May 2023. LGP 1164. https://lgpress.clemson.edu/publication/historical-floods-of-south-carolina/.
U.S. Department of Commerce, NOAA. n.d. “Flooding in South Carolina.” Weather.gov. https://www.weather.gov/safety/flood-states-sc.
U.S. Department of Commerce, NOAA. “NOAA 200th Foundations: Tides and Currents.” NOAA.gov. 2024. https://celebrating200years.noaa.gov/foundations/tides/welcome.html?itid=lk_inline_enhanced-template#intro.