Status and Trends of Inland Wetland and Aquatic Habitats in the Corpus Christi Area
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STATUS AND TRENDS OF INLAND WETLAND AND AQUATIC HABITATS IN THE CORPUS CHRISTI AREA by Thomas A. Tremblay, Jeffrey S. Vincent, and Thomas R. Calnan* *Coastal Assistance Division, Texas General Land Office Final Report prepared for the Coastal Bend Bays and Estuaries Program, Texas General Land Office, and National Oceanic and Atmospheric Administration under CBBEP Contract No. 0722 A report of the Coastal Coordination Council pursuant to National Oceanic and Atmospheric Administration Award No. NA04NOS4190058 This investigation was funded by a grant from the National Oceanic and Atmospheric Administration administered by the Texas General Land Office. The views expressed herein are those of the authors and do not necessarily reflect the views of NOAA or any of its subagencies. Bureau of Economic Geology Scott W. Tinker, Director John A. and Katherine G. Jackson School of Geosciences The University of Texas at Austin University Station Box X Austin, TX 78713-8924 March 2008 EXECUTIVE SUMMARY .................................................................................................. vi INTRODUCTION ..................................................................................................................1 Study Area ..................................................................................................................2 General Setting of the Corpus Christi–Aransas Bay System......................................2 Bay-Estuary-Lagoon Setting...........................................................................7 Relative Sea-Level Rise..................................................................................7 METHODS ............................................................................................................................8 Mapping and Analyzing Status and Trends................................................................8 Wetland Classification and Definition........................................................................9 Interpretation of Wetlands ..........................................................................................9 Historical Wetland Distribution.....................................................................9 Revision of Historical Wetland Maps..........................................................10 Current Wetland Distribution ......................................................................11 Field Investigations......................................................................................11 Variations in Classification..........................................................................12 Map-Registration Differences......................................................................13 CLASSIFICATION OF WETLAND AND DEEPWATER HABITATS IN THE STUDY AREA .......................................................................................................17 Marine System ..........................................................................................................19 Estuarine System.......................................................................................................19 Palustrine System .....................................................................................................24 Lacustrine System.....................................................................................................25 Riverine System........................................................................................................25 STATUS OF WETLANDS AND AQUATIC HABITATS IN 2004...................................27 Estuarine System.......................................................................................................34 Marshes (Estuarine Intertidal Emergent Wetlands)......................................34 Tidal Flats (Estuarine Intertidal Unconsolidated Shores and Aquatic Beds)34 Scrub/Shrub (Estuarine Intertidal Scrub/Shrub ............................................34 Seagrass Beds (Estuarine Subtidal Aquatic Beds)........................................35 Open Water (Estuarine Subtidal Unconsolidated Bottom)...........................35 Oyster Reefs (Estuarine Reefs).....................................................................35 Palustrine System......................................................................................................35 Marshes (Palustrine Emergent Wetlands).....................................................35 Shrubs and Trees (Palustrine Scrub-Shrub and Forested Wetlands) ............36 Open Water and Flats (Palustrine Unconsolidated Bottom and Unconsolidated Shore).................................................................................36 Lacustrine System.....................................................................................................36 Open Water and Flats (Lacustrine Unconsolidated Bottom, Unconsolidated Shore, and Aquatic Bed)....................................................36 HISTORICAL TRENDS IN WETLAND AND AQUATIC HABITATS...........................37 Methods Used to Analyze Trends.............................................................................37 Geographic Information System...................................................................37 Possible Photointerpretation Errors ..............................................................37 ii Wetland Codes..............................................................................................38 Wetland Trends and Probable Causes, 1950’s through 2004 ...................................38 Analysis of Wetland Trends by Geographic Area ....................................................41 Copano Mainland......................................................................................................41 Lamar Peninsula........................................................................................................44 Mission River Valley ................................................................................................49 Aransas River............................................................................................................52 Live Oak Peninsula...................................................................................................54 Coastal Prairie...........................................................................................................57 Port Bay ....................................................................................................................58 Redfish Bay...............................................................................................................62 Nueces River Delta ...................................................................................................64 Corpus Christi Bay and Estuary................................................................................66 Oso Bay and Encinal Peninsula ................................................................................70 SUMMARY AND CONCLUSIONS ..................................................................................75 ACKNOWLEDGMENTS ....................................................................................................83 REFERENCES .....................................................................................................................84 APPENDIX...........................................................................................................................86 Executive Summary Figures I. Index map of study area. .................................................................................................................... vii II. Areal extent of selected habitats in the study area in 2004................................................................viii III. Distribution of selected habitats by geographic area in 2004.............................................................. ix IV. Areal distribution of major habitats in the study area in the 1950’s, 1979, and 2004. ........................ xi Executive Summary Table I. Total area of major habitats in the 1950’s, 1979, 2004 in study area...................................................... xi FIGURES 1. Big Lake (oxbow) at Welder Wildlife Refuge................................................................................................. 2 2. Index map of wetland status and trends in study area ..................................................................................... 3 3. Map showing boundaries of the different geographic areas investigated........................................................ 4 4. Natural systems in the Corpus Christi–Aransas Bay area ............................................................................... 5 5. Photo looking south across Rincon Bayou ...................................................................................................... 6 6. Lidar digital elevation model of the Nueces River Delta ................................................................................ 6 7. Sea-level rise at the Rockport tide gauge located near the landward margin of Aransas Bay......................... 8 8. Map of field-survey sites used for ground-truthing aerial photo delineations and recording vegetation composition and water regimes ........................................................................................................................... 11 9. Field crew at Fennessey Ranch ......................................................................................................................