Delineation of Tidal Scour through Marine Geophysical Techniques at Sloop Channel and Goose Creek Bridges, Jones Beach State Park, Long Island, New York U.S. GEOLOGICAL SURVEY Water-Resources Investigations Report 00-4033 Prepared in cooperation with the NEW YORK STATE DEPARTMENT OF TRANSPORTATION Delineation of Tidal Scour through Marine Geophysical Techniques at Sloop Channel and Goose Creek Bridges, Jones Beach State Park, Long Island, New York By Frederick Stumm, Anthony Chu, and Richard J. Reynolds ____________________________________________________________ U.S. GEOLOGICAL SURVEY Water-Resources Investigations Report 00-4033 Prepared in cooperation with the NEW YORK STATE DEPARTMENT OF TRANSPORTATION Coram, New York 2001 Contents i U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. Geological Survey Charles G. Groat, Director The use of firm, trade, and brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey. ______________________________________________________________________ For additional information Copies of this report may be write to: purchased from: U.S. Geological Survey U.S. Geological Survey 2045 Route 112, Bldg. 4 Branch of Information Services Coram, NY 11727 Box 25286, Bldg. 810 Denver, CO 80225-0286 ii Contents CONTENTS Abstract ............................................................................................................................................................................ 1 Introduction ...................................................................................................................................................................... 2 Purpose and scope ..................................................................................................................................................... 3 Location of study area ............................................................................................................................................... 3 Acknowledgments ..................................................................................................................................................... 3 Methods of study .............................................................................................................................................................. 3 Narrow-beam fathometer surveys.............................................................................................................................. 4 Continuous seismic-reflection surveys ...................................................................................................................... 5 Acoustic Doppler current profiler.............................................................................................................................. 5 Delineation of tidal scour at Sloop Channel and Goose Creek Bridges........................................................................... 6 Sloop Channel Bridge ............................................................................................................................................... 6 Fathometer survey .............................................................................................................................................. 6 Seismic-reflection profiles.................................................................................................................................. 6 Piers 1 and 2......................................................................................................................................... 6 Piers 4 and 5......................................................................................................................................... 9 Piers 6 and 7......................................................................................................................................... 9 Piers 9 and 10....................................................................................................................................... 9 Discharge measurement ..................................................................................................................................... 11 Goose Creek Bridge .................................................................................................................................................. 13 Fathometer survey .............................................................................................................................................. 13 Seismic-reflection profiles.................................................................................................................................. 13 Centerspan ........................................................................................................................................... 13 Piers 5 and 6......................................................................................................................................... 14 Piers 2 and 3......................................................................................................................................... 16 Piers 1 and 2......................................................................................................................................... 16 Summary and conclusions................................................................................................................................................ 17 References cited................................................................................................................................................................ 18 FIGURES 1. Maps showing location of Sloop Channel Bridge and Goose Creek Bridge study area, and of tide-stage gage, Nassau County, N.Y. A. General location. B. Study area ................................................................................... 2 2. Generalized sketches showing pier-numbering systems for piers during July 1998 seismic-reflection survey, Nassau County, N.Y. A.Goose Creek Bridge. B. Sloop Channel Bridge ........................................................... 4 3. Map showing sea-floor elevation at Sloop Channel Bridge, Nassau County, N.Y., July 1998............................. 7 4. Narrow-beam fathometer profiles between piers 2 and 3 at Sloop Channel Bridge, Nassau County, N.Y., July 1998............................................................................................................................................................... 8 5-8. Interpreted high-frequency seismic-reflection profiles at Sloop Channel Bridge, Nassau County, N.Y., July 1998: 5. Between piers 1 and 2....................................................................................................................................... 8 6. Between piers 4 and 5....................................................................................................................................... 10 7. Between piers 6 and 7....................................................................................................................................... 10 8. Between piers 9 and 10..................................................................................................................................... 11 9. Acoustic Doppler current profiler (ADCP) velocity profiles between piers 9 and 10 during flood tide at Sloop Channel Bridge, Nassau County, N.Y. A. East-west velocity. B. Vertical velocity ............................................ 12 10. Bathymetric contour map of the sea floor at Goose Creek Bridge, Nassau County, N.Y., July 1998.................. 14 11-14. Interpreted high-frequency seismic-reflection profiles at Goose Creek Bridge, Nassau County, N.Y., July 1998: 11. Between centerspans....................................................................................................................................... 15 12. Between piers 5 and 6..................................................................................................................................... 15 13. Between piers 2 and 3..................................................................................................................................... 16 14. Between piers 1 and 2..................................................................................................................................... 17 Contents iii CONVERSION FACTORS, VERTICAL DATUM, AND ABBREVIATIONS Multiply By To Obtain Length foot (ft) 0.3048 meter mile (mi) 1.609 kilometer Flow cubic foot per second (ft3/s) 0.02832 cubic meter per second Velocity feet per second (ft/s) 0.3048 meter per second Other abbreviations used in this report hertz (hz) kilohertz (kHz) minute (min) second (s) Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)--a geodetic datum derived from a general adjustment of the first-order level nets of the United States and Canada, formerly called Sea Level Datum of 1929. iv Contents Delineation of Tidal Scour through Marine Geophysical Techniques at Sloop Channel and Goose Creek Bridges, Jones Beach State Park, Long Island, New York By Frederick Stumm, Anthony Chu, and Richard J. Reynolds Abstract The thickness of sediment that has settled within scour holes could not be interpreted from Inspection of the Goose Creek Bridge in fathometer data alone because fathometer southeastern Nassau County in April 1998 by the frequencies cannot penetrate