Southeastern New York Tide-Telemetry and Coastal-Flood-Warning System Active

The coastal areas of southeastern New York (fig. 1) are highly vulnerable to tidal flooding (fig. 2). Timely evacuation of people from flood-threatened areas in advance of approaching hurricanes and nor'easters (northeast coastal storms) requires adequate flood-warning time. To begin addressing this need for immediate information on coastal flooding, the U.S. Geological Survey (USGS), in cooperation with the Town of Hempstead Department of Conservation & Waterways, Village of Freeport, and New York State Department of Environmental Conservation, has operated a network of real-time tidal water-elevation and meteorological stations since 1997 in the coastal areas of Long Island and New York City.

Each tidal water-elevation station is equipped with a pressure sensor connected to a data-collection platform, which, together with all other electrical components, is mounted several feet above the 100-year coastal-flood elevation inside a reinforced shelter. Data from this monitoring network are recorded at 6-minute intervals, stored onsite, and then transmitted to USGS offices using satellite and telephone telemetry every hour when water levels are below the National Weather Service (NWS) minor coastal-flood elevation. When a station detects water levels above this threshold, it issues a synthesized-speech message via telephone to warn municipal and county emergency-management officials and NWS forecasters, and increases the frequency of satellite transmissions to 6-minute intervals. On arrival at USGS offices, data are automatically archived, processed, and screened in the USGS National Water Information System, and are available at USGS websites within a few minutes of their transmission. Real-time tidal water-elevation data at New York sites are available at http://waterdata.usgs.gov/ny/nwis/current?type=tidal.

Examples of hydrographs available in real time from https://www.usgs.gov/centers/ny-water for USGS tidal water-elevation stations in southeastern New York are shown in figure 3. Figure 3A shows the observed water elevation in feet above NGVD 1929 (National Geodetic Vertical Datum of 1929) from USGS station 01310521 on Hudson Bay at Freeport, N.Y. (dark blue line in fig. 3A), for a 7-day period in August 2011. Also shown in figure 3A are reference lines for the NWS minor, moderate, and major coastal flood elevations (blue, brown,and orange lines, respectively, in fig. 3A) and Federal Emergency Management Agency 10- and 100-year stillwater and 100-year base flood elevations (orange, green, and red lines, respectively, in fig. 3A). Figure 3B displays the same water elevation record from USGS station 01310521 (orange crosses in fig. 3B) for the last 3 days of this period; it also displays the astronomical-tide elevation in feet above NGVD 1929 for nearby National Ocean Service tidal prediction station 1271 at Hempstead Bay, Freeport, Baldwin Bay (blue line in fig. 3B). The residual water level (green squares in fig. 3B) is calculated from the difference between the observed water elevation and predicted (astronomical) tide elevation. Its increase to nearly 5 feet on August 28, 2011, shown in figure 3B is due to significant storm surge associated with the passage of Tropical Storm Irene across western Long Island.

Related Publications

Schubert, C.E., 2003, USGS Coastal Flood-Monitoring Stations in Southeastern New York: Long Island Ground-Water Symposium Proceedings, June 6, 2003, Brookhaven National Laboratory, Upton, N.Y., sponsored by the U.S. Geological Survey, Stony Brook University's Long Island Groundwater Research Institute, and Brookhaven National Laboratory.

Schubert, C.E., and Busciolano, Ronald, 1994, Peak storm-tide elevations produced by the December 1992 storm along the coast of Long Island, New York, with historical peak storm-tide elevations [abs.], in Association of Long Island Geologists, First Conference on Geology of Long Island and Metropolitan New York, Programs with Abstracts, State University of New York at Stony Brook, NY, April 23, 1994, p. 130-136.

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