LONG ISLAND TIDAL WETLANDS TRENDS ANALYSIS Prepared for the NEW ENGLAND INTERSTATE WATER POLLUTION CONTROL COMMISSION Prepared by July 2015 Long Island Tidal Wetlands Trends Analysis July 2015 Table of Contents TABLE OF CONTENTS EXECUTIVE SUMMARY ........................................................................................................................................... 1 INTRODUCTION ..................................................................................................................................................... 5 PURPOSE ...................................................................................................................................................................... 5 ENVIRONMENTAL AND ECOLOGICAL CONTEXT ..................................................................................................................... 6 FUNDING SOURCE AND PARTNERS ..................................................................................................................................... 6 TRENDS ANALYSIS .................................................................................................................................................. 7 METHODOLOGY AND DATA ................................................................................................................................... 9 OUTLINE OF TECHNICAL APPROACH ................................................................................................................................... 9 TECHNICAL OBJECTIVES ................................................................................................................................................... 9 Identification of discrete wetland complexes ..................................................................................................... 10 Scanning, orthorectification, and normalization of color-infrared imagery ...................................................... 11 Field reconnaissance to identify and groundtruth wetland and other plant species ......................................... 13 Classification of color-infrared imagery via application of a spectral library ..................................................... 15 Digitize tidal wetland boundaries using “heads-up” digitizing techniques ........................................................ 22 Trends Analysis ................................................................................................................................................... 26 RESULTS AND DISCUSSION................................................................................................................................... 27 LONG ISLAND TIDAL WETLANDS TRENDS .......................................................................................................................... 27 Conversion of High Marsh to Intertidal Marsh and Panne/Pond Formation ..................................................... 29 Widening of Tidal Creeks and Man-made Ditches ............................................................................................. 36 Erosion and Retreat of Seaward Edge ................................................................................................................ 36 Phragmites australis Expansion ......................................................................................................................... 41 SOUTH SHORE ESTUARY TRENDS ..................................................................................................................................... 49 East Rockaway Inlet to Fire Island Inlet .............................................................................................................. 54 Fire Island Inlet to Smith Point County Park ....................................................................................................... 59 Moriches and Shinnecock Bays .......................................................................................................................... 70 At-Risk Marsh Complexes ................................................................................................................................... 77 LONG ISLAND SOUND ESTUARY....................................................................................................................................... 82 PECONIC ESTUARY ..................................................................................................................................................... 101 SOUTH FORK PONDS: MECOX BAY, SAGAPONACK POND, AND GEORGICA POND.................................................................... 120 ERROR ANALYSIS ............................................................................................................................................... 122 RELATIVE ERROR ........................................................................................................................................................ 124 CLASSIFICATION ERROR ............................................................................................................................................... 122 FUTURE APPROACHES FOR MAPPING TIDAL WETLANDS ................................................................................... 125 HYPERSPECTRAL DATA ................................................................................................................................................ 127 SECONDARY LANDSCAPE ATTRIBUTES............................................................................................................................. 127 OTHER METHODS ...................................................................................................................................................... 128 SUMMARY ................................................................................................................................................................ 128 LITERATURE CITED ............................................................................................................................................. 129 LIST OF FIGURES FIGURE 1: PROJECT STUDY AREA ........................................................................................................................................... 5 FIGURE 2: TIDAL WETLANDS BY ESTUARY ................................................................................................................................. 8 LL Long Island Tidal Wetlands Trends Analysis July 2015 Table of Contents FIGURE 3: MARSH COMPLEXES OF THE STUDY AREA ............................................................................................................... 11 FIGURE 4: LLOYD POINT WETLANDS ..................................................................................................................................... 16 FIGURE 5: LLOYD POINT WETLANDS (DETAIL VIEW) ................................................................................................................ 17 FIGURE 6: FLAX POND (COMPLEX #103)TIDAL WETLANDS IN 1974 .......................................................................................... 25 FIGURE 7: FLAX POND WITH ORIGINAL DELINEATION (YELLOW) AND ENHANCED DELINEATION ......................................................... 25 FIGURE 8: CEDAR & NEZERAS ISLANDS (COMPLEX ID #401) .................................................................................................... 30 FIGURE 9: TIMBER POINT (COMPLEX ID #431) ...................................................................................................................... 31 FIGURE 10: CRAB MEADOW (COMPLEX ID #222) - EXPANSION & WIDENING OF TIDAL CREEKS & MAN-MADE DITCHES ................... 37 FIGURE 11: PINE MARSH (COMPLEX ID #356) – EXPANSION AND WIDENING OF TIDAL CREEKS & MAN-MADE DITCHES .................... 38 FIGURE 12: TOBAY SANCTUARY (COMPLEX ID # 385) / MARSH ISLANDS NORTH & SOUTH OF STATE BOAT CHANNEL (COMPLEX ID # 386) – MARSH EDGE RETREAT .................................................................................................................................. 39 FIGURE 13: INNER HEMPSTEAD HARBOR WEST SHORELINE (COMPLEX ID # 267) – MARSH EDGE RETREAT...................................... 39 FIGURE 14: CUBA, MIDDLE, AND EAST ISLANDS (COMPLEX ID # 367) – MARSH EDGE RETREAT ..................................................... 40 FIGURE 15: MECOX BAY (COMPLEX ID #540) – PHRAGMITES AUSTRALIS EXPANSION ................................................................... 44 FIGURE 16: ACCABONAC HARBOR (COMPLEX ID #156) – PHRAGMITES AUSTRALIS EXPANSION ...................................................... 45 FIGURE 17: BAITING HOLLOW MARSH (COMPLEX ID #85) – PHRAGMITES EXPANSION ................................................................. 46 FIGURE 18: PEARSALIS HASSOCK (COMPLEX ID #333) – CONVERSION OF FORMER PHRAGMITES AUSTRALIS STANDS .......................... 47 FIGURE 19: BLACKBANK HASSOCK (COMPLEX ID #336) – CONVERSION OF FORMER PHRAGMITES AUSTRALIS STANDS TO NATIVE MARSH ........................................................................................................................................................................... 48 FIGURE 20: RELATIVE CHANGE IN INTERTIDAL MARSH AREA COMPARED TO LONGITUDE IN THE SOUTH SHORE ESTUARY FOR COMPLEXES GREATER THAN 50 ACRES IN 1974 AREA ...................................................................................................................... 51 FIGURE