The U.S. Geological Survey (USGS) deployed a temporary monitoring network of water-level sensors at 212 locations along the Atlantic coast from South Carolina to Maine during August 2011 to record the timing, areal extent, and magnitude of inland hurricane storm tide and coastal flooding generated by Hurricane Irene. Water-level sensor locations were selected to augment existing tide-gage networks to ensure adequate monitoring in areas forecasted to have substantial storm tide. As defined by the National Oceanic and Atmospheric Administration (NOAA; 2011a,b), storm tide is the water-level rise generated by a coastal storm as a result of the combination of storm surge and astronomical tide.

Open the Internet mapping site to view map showing sensor site locations and view data and charts.

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Hurricane Irene initially made landfall on the coast of North Carolina near Beaufort on August 27, 2011, as a category 1 hurricane on the Saffir-Simpson hurricane scale (National Hurricane Center, 2010), and after traversing the coast and Outer Banks of North Carolina, the storm went back out to sea and made a second landfall as a category 1 hurricane near Atlantic City, New Jersey, on August 28. Of the 212 locations monitored, 202 sensors recorded a storm tide. Three water-level sensors were lost or malfunctioned during the storm, and five sensors did not record storm tide because of either a lack of water-level rise above astronomical tide or a storm tide lower than the elevation of the sensor.

A typical storm tide sensor installation is shown in figure 2. At the 202 locations, these sensors were programmed to record water pressure at a 30-second interval, which was converted to water level in feet above the North American Vertical Datum of 1988 (NAVD 88). In addition, 75 of the 202 sites included a sensor to record barometric pressure at a 30-second interval, expressed in pounds per square inch. Water-level elevation and barometric pressure were recorded over time by the sensors during the storm, as shown by the example graph for a single location in figure 3. A high-water mark (HWM) was flagged and surveyed near each sensor in order to verify the peak value recorded by the sensor. Eight additional locations were instrumented with rapid deployment gages, which were real-time water-level sensors that recorded water-level elevations every 15 minutes and updated hourly to USGS Web pages (table 1; fig. 4). Lastly, wave height was measured every 2 seconds at two locations near the mouth of Chesapeake Bay near Norfolk, Virginia. The total number of sensors deployed in each State are shown in table 1.

Data were collected and processed following protocols established by McGee and others (2005), which includes correcting water pressure for changes in barometric pressure and salinity. Quality-control checks were made by (1) co-locating water-level sensors at a subset of sites and comparing data from those sensors to water levels computed from recorded pressure data at the sites, and (2) comparing water levels computed from recorded pressure data to water levels recorded at nearby USGS streamgages in addition to nearby high-water marks, to the extent possible. In the aftermath of the storm, an additional 137 independent high-water mark locations were surveyed in relation to NAVD 88; 104 locations in North Carolina, 14 locations in New York and 19 locations in Virginia. Elevation surveys using survey-grade global positioning systems (fig. 5) and differential levels were conducted to relate all water-level data, HWM data, reference marks, new benchmarks, and sensor measuring points to NAVD 88.

Table 1. U.S. Geological Survey data-collection sites equipped to monitor Hurricane Irene storm tide in 2011, by State.

State	Storm tide	Wave height	Real-time rapid deployment gages	Barometric pressure
South Carolina	4	0	0	0
North Carolina	42	0	1	19
Virginia	11	2	1	9
Maryland	25	0	0	9
Delaware	27	0	2	6
New Jersey	6	0	0	3
New York	25	0	2	10
Connecticut	21	0	0	6
Rhode Island	16	0	0	4
Massachusetts	14	0	0	5
New Hampshire	4	0	2	1
Maine	7	0	0	3
Total	202	2	8	75

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The data from the Hurricane Irene storm-tide network constitute an extensive collection of continuous water-level records that document a single land-falling hurricane. The data can be used to evaluate the performance of storm-tide models for (1) maximum and incremental water level, (2) flood extent, and (3) site-specific effects of storm tide on natural and anthropogenic elements of the environment. The data from the temporarily deployed sensors are considered approved, while the streamgage or tidal gage data are being made available on a provisional basis becauase they are subject to the USGS annual data report approval process. All data are presented in tab-delineated, ASCII format for each sensor location by using a USGS interactive storm-tide mapper Web application available at http://wim.usgs.gov/stormtidemapper/stormtidemapper.html#.

Digital photographs of select locations also are available from the interactive mapper. Data for each sensor include location, date, time, water level, and barometric pressure and the data-processing date is provided in the file header. Data files for HWMs include location, type and quality of the mark, and elevation. The interactive mapper also includes wave-height data collected in collaboration with the North Carolina Sea Grant and The University of North Carolina, Institute of Marine Sciences.

A list of the 212 temporarily deployed storm-tide sensor locations and the peak storm-tide elevation recorded by each sensor are provided in table 2. Data-collection sites were categorized as surge, riverine, or wave height with respect to the interval of data collected and the site proximity to the coast. Riverine sites can be influenced by upstream runoff from inland flooding. Permanent monitoring network data at 80 locations that are operated by the USGS and were augmented by the temporary sensors are provided in table 3 and 46 locations that are operated by NOAA are provided in table 4. Additional NOAA water-level and meteorological data for Hurricane Irene that include affected areas outside the USGS deployment region were released recently by Fanelli and Fanelli (2011). A listing of the additional HWM data collected and surveyed following the passage of Hurricane Irene are presented in table 5.

Acknowledgments

This report was prepared in cooperation with the Federal Emergency Management Agency and U.S. Army Corps of Engineers. The data in this report are the result of tireless hours by numerous staff in USGS Water Science Centers in South Carolina, North Carolina, Virginia, Maryland, Delaware, New Jersey, New York, Connecticut, Rhode Island, Massachusetts, New Hampshire, Maine, and Georgia. The authors would like to particularly highlight the leadership and dedication of USGS employees in North Carolina, Virginia, and Maryland in delivering valuable data to numerous stakeholders in a very timely and accurate manner.

References Cited

Fanelli, C., and, Fanelli, P., 2011, NOAA water level and meteorological data report—Hurricane Irene: U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Ocean Service Center for Operational Oceanographic Products and Services, available at http://tidesandcurrents.noaa.gov/publications/Hurricane_Irene_Water_Level_and_Meteorological_Data_Report.pdf.

McGee, B.D., Goree, B.B., Tollett, R.W., Woodward, B.K., and Kress, W.H., 2005, Hurricane Rita surge data, southwestern Louisiana and southeastern Texas, September to November 2005: U.S. Geological Survey Data Series 220, available at http://pubs.usgs.gov/ds/2006/220/.

National Hurricane Center, 2010, The Saffir-Simpson hurricane wind scale: National Oceanic and Atmospheric Administration, National Weather Service Web site, http://www.nhc.noaa.gov/aboutsshs.shtml.

National Oceanic and Atmospheric Administration, 2011a, Storm surge overview: Accessed November 11, 2011, at http://www.nhc.noaa.gov/ssurge/ssurge_overview.shtml.

National Oceanic and Atmospheric Administration, 2011b, Hurricane Irene track: Accessed October 24, 2011, at http://www.noaawatch.gov/2011/irene.php.

First posted March 2, 2012