[an error occurred while processing this directive] USGS Fire Island Wilderness breach, Bathymetry and Discharge Measurements, Post-Hurricane Sandy, New York - November 6, 2012 Untitled Document

Evaluation of a barrier-island breach created by Hurricane Sandy at Fire Island National Seashore, N.Y.—Continued.

Measurement of water velocities and depths on November 6, 2012 — methods and results


On November 6 and November 20, 2012, and June 26 and November 13, 2013, U.S. Geological Survey (USGS) New York Water Science Center (NYWSC) personnel collected data to evaluate channel geometry, water velocity, and discharge of an open breach in the Federal Wilderness area of Fire Island National Seashore, N.Y. The breach resulted from major coastal flooding and overwash created by Hurricane Sandy on October 29, 2012.  Data were collected using a Sontek1 M9 Acoustic Doppler Current Profiler (ADCP) with Real-Time Kinematic (RTK) Global Positioning System (GPS).  Data were processed into Geographic Information System (GIS) for interpolation and display. The following information generally summarizes the measurement of water velocities and depths within the Wilderness breach on November 6, 2012.


An initial series of transects was collected starting about 3 hours before ocean high tide on November 6, 2012.  Data were collected perpendicular to flow through the breach beginning at 0830 Eastern Standard Time (EST) and ending at 0928 EST.  The first set of transects was taken near the seaward side of the breach, with subsequent sets collected progressively closer to the bayward side of the breach.  Discharge ranged from 1,330 ft3/s (cubic feet per second) during the beginning set of transects to 1,660 ft3/s during the final set of transects.

A second series of transects was collected starting about 3 hours before ocean low tide on November 6, 2012.  Data collection began at 1410 EST and ended at 1500 EST.  The first set of transects was taken perpendicular to the flood tidal channels bayward of the former Great South Bay (GSB) shoreline; subsequent sets were collected progressively closer to the seaward side of the breach.  Discharge ranged from 1,060 ft3/s during the beginning set of transects to 1,380 ft3/s during the final set of transects.

Additional data were collected along the approximate centerline and adjacent to the shores of the channel to map the inundated area of the breach.  The overall mapped area includes data collected during discharge measurements of both incoming and outgoing tide conditions.  The Digital Elevation Model (DEM) was created by plotting the depths of all data points collected relative to North American Vertical Datum of 1988 (NAVD 88) and interpolating the elevation of the bathymetric surface between these points.

The average water surface elevation for all data collected was 1.38 ft NAVD 88. The volume of material lost during the breach beneath the average water surface elevation represented by a Triangular Irregular Network (TIN) was 47,700 yd3 (cubic yards).

Collection of water levels within GSB adjacent to the breach is being be done with a modified USGS storm-tide sensor. This sensor, which normally collects 7 days of 30-second-interval data, has been reprogrammed to collect about 2 months of routine (6-minute-interval) tide-gage observations. Two Onset1 HOBO sensors were installed on November 6, 2012, to help ensure that at least one would remain fully operational through the planned, 2-month deployment. (Fortunately, both of these instruments ultimately collected just under 3 months of continuous record each.) Note that the East-sensor record was obtained from a position on the Old Inlet dock near the former barrier island shoreline, whereas the West-sensor record was obtained from the end of the dock nearest to Pelican Island. Sensor data can be viewed here (sensor deployment notes, East-sensor record [plot, data], West-sensor record [plot, data]) or downloaded in a zip-file.

1Use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Available products:

<<  2 of 7  >>

Aerial Photographs of Wilderness breach—Before & After Hurricane Sandy

Oblique aerial photographs of Pelican Island and Fire Island, New York. The
view is looking northwest across Fire Island towards Great South Bay. This
location is within Fire Island National Seashore near Old Inlet—a very narrow
portion of the island that has experienced breaching in previous large storms.
The island breached during Hurricane Sandy, creating a new inlet. Despite the
breach, the fishing shack (yellow arrow) remained standing. Click on image to

oblique aerial photos of the Wilderness breach


Location Map:
Location map

Related Links:

Hurricane Sandy Information

Bathymetry and Tidal Discharge of Wilderness Breach—November 6, 2012 Download .zip file of gis data

Other Resources

Location 1