Surge, Wave, and Tide Hydrodynamics (SWaTH) Network

Science Center Objects

During large coastal storms, the storm surge and waves are the main cause of destruction and landscape change, transporting saline water, sediment, and debris inland. The USGS, in collaboration with stakeholders, has constructed the Surge, Wave, and Tide Hydrodynamics (SWaTH) Network along the Northeastern Atlantic Coast. SWaTH monitors and documents the height, extent, and timing of storm surge.

Image: SWaTH Nework Bracket Level

Tim Sargent, a hydrologic technician at the New England Water Science Center, is checking to make sure that the sensor bracket he installed is level. (Credit: Craig Brown)

Scientific information, if reliably obtained and wisely applied, can strengthen our efforts to build resilient coastal communities before storms strike, and guide our response and recovery strategies. Past storms, such as Hurricane Sandy, have shown that storm surge and waves are the primary drivers of coastal-community destruction and dramatic changes in the coastal and near-coastal environment. The energy of the surge and accompanying waves cause physical changes to the landscape. The landward extent of the surge (storm tide) transports saline water, sediment, and debris to constructed and ecologically sensitive environments that are, otherwise, rarely impacted by direct ocean waters. As we develop more effective coastal-management approaches, we have the opportunity to build on our experience and knowledge to prepare for and minimize risks from future storms. Documenting the height, extent, and timing of storm surge and understanding how overland storm tide and waves evolve and dissipate when they move across natural and man-made landscapes, is critical for improved storm-surge modeling. That in turn, will promote coastal resilience, facilitate better planning, and provide more effective early warning of storm-driven flooding.

For decades, the USGS has provided critical information on near-shore storm hydrodynamics for decisions regarding emergency response and resource allocation before, during, and immediately after landfall of hurricanes and nor’easters. Much of this information was provided via a few real-time tide gages focused on near-shore waters that supplemented and extended the National Oceanographic and Atmospheric Administration’s (NOAA) National Ocean Service (NOS) tide-gage network. In addition, data from temporary sensors and high-water marks occasionally obtained by the USGS in cooperation with the Federal Emergency Management Agency (FEMA), the U.S. Army Corps of Engineers (USACE), and various state agencies, provided post-storm documentation of coastal floods; however, neither strategy provided sufficient, timely information for emergency operations or to facilitate improvements in storm-tide and wave modeling and prediction.

A map showing the USGS SWaTH Network.

The Surge, Wave, and Tide Hydrodynamics (SWaTH) Network stretches along the Northeastern Atlantic Coast from North Carolina to Maine.

Following Hurricane Sandy, the USGS began construction of an overland Surge, Wave, and Tide Hydrodynamics (SWaTH) Network along the Northeastern Atlantic Coast from North Carolina to Maine (figure 1). This network, developed collaboratively with local, State, Tribal, and Federal agency partners, features the integration of long-term NOS and USGS real-time tide gages; mobile, rapidly deployable, but temporary, real-time gages (RDGs), and mobile storm-tide sensors (STSs). A central strategy enabling the effective use of SWaTH is that most locations for the mobile RDGs and STSs have been pre-surveyed to NGVD 1988 datums and equipped with receiving brackets that permit rapid installation of instrumentation in the hours and days prior to a storm.

Image: SWaTH Bracket Installation, Assateague Island Maryland

USGS scientist installs sensor bracket on Assateague Island in prepration for Hurricane Sandy. (Credit: Mark Nardi)

SWaTH consists of 71 existing and new flood-hardened, real-time telemetered tide gages, 61 RDGs, and up to 555 temporary STSs. The STSs will be deployed in three distinct but integrated network configurations consisting of (1) a distributed array of stations representing the range of landscape types and infrastructure subject to surge and wave forces, (2) along transects from the coastline through the inland resource of concern (e.g. a wetland or coastal community), and (3) at existing tide and river monitoring stations where new data can be integrated with long-term records.

The transects will provide data for the analysis of wave height, frequency, and devolution as functions of distance inland. Associated meteorological data, supplemental high water marks, coastal river flow gages, coastal current monitoring, and other hydrologic data will provide ancillary information for interpreting changes in coastal hydrology and vulnerability of coastal ecosystems and communities in response to storm damage.

Delivering these data rapidly and in an easily accessible manner is critical to emergency agencies and local emergency responders. SWaTH data deliverables will include times series information for water elevation, wave height and frequency, and selected meteorological data. The system is being developed to enhance the data availability from historical hurricanes on the Atlantic and Gulf coasts and agency preparedness for all future storm events. These data are stored in a nation-wide database and made available via a mapping application and direct web services. These services are structured to allow other agencies to directly use the data as it is collected and approved during, or shortly following, a flood event.