METHODOLOGY FOR DEFINING AND ASSESSING RIPARIAN AREAS TABLE OF CONTENTS EXECUTIVE SUMMARY ............................................................................................................ 9 INTRODUCTION ........................................................................................................................ 12 Riparian Areas......................................................................................................................................... 12 Policy in Managed Flooding Disturbances ............................................................................................. 13 The Difficulty in Defining ...................................................................................................................... 14 RIPARIAN AREA DEFINITIONS .............................................................................................. 17 Choosing a Definition ............................................................................................................................. 17 Applicable Definition .............................................................................................................................. 19 RIPARIAN AREAS OF THE SOUTHEAST AND SOUTHWEST U.S. ................................... 19 FUNCTIONS AND VALUES OF RIPARIAN AREAS.............................................................. 23 Delineation by Function .......................................................................................................................... 23 Important Riparian Area Functions ......................................................................................................... 24 RIPARIAN SOILS OF THE EAST TEXAS RIVER BASINS.................................................... 26 THE VEGETATION OF RIPARIAN AREAS WITH SPECIAL ATTENTION TO TEXAS.... 30 Sabine River Basin Vegetation ............................................................................................................... 32 Neches River Basin Vegetation .............................................................................................................. 33 Trinity River Basin Vegetation ............................................................................................................... 34 Sulphur River Basin Vegetation.............................................................................................................. 34 Nueces River Basin Vegetation .............................................................................................................. 35 Leona River Riparian Vegetation ........................................................................................................... 36 Sabinal River Riparian Vegetation.......................................................................................................... 36 Guadalupe River Riparian Vegetation .................................................................................................... 37 1 | P a g e San Antonio River Riparian Vegetation ................................................................................................. 38 Middle Rio Grande River Riparian Area ................................................................................................ 38 THE HYDROLOGY OF RIPARIAN AREAS ............................................................................ 39 Hydrologic Regime ................................................................................................................................. 39 Seed Dispersal in Riparian Areas ............................................................................................................ 41 REVIEW OF RIPARIAN AREA SURVEY METHODS ............................................................ 62 Classification Techniques ....................................................................................................................... 62 Classification Schemes ........................................................................................................................... 63 Ecological Based Guidebooks ................................................................................................................ 67 The Energy Theory ................................................................................................................................. 70 Functional Assessments .......................................................................................................................... 72 RIPARIAN BOUNDARY DELINEATION ................................................................................ 79 STUDY SITE ................................................................................................................................ 82 Sabine River: Toledo Bend Reservoir ..................................................................................................... 82 Technique 1 ............................................................................................................................................. 84 Methods................................................................................................................................. 84 Data Acquisition ............................................................................................................... 84 GIS Riparian Soils ............................................................................................................ 84 Classification..................................................................................................................... 90 Remote Sensing Model Development .............................................................................. 97 Soils ......................................................................................................................................................... 98 Hydrology ............................................................................................................................................... 98 Vegetation ............................................................................................................................................... 98 Determining Number of Control Points ............................................................................ 99 Ground Truthing ............................................................................................................. 101 2 | P a g e Statistical Analysis .......................................................................................................... 101 Results of Technique 1 .......................................................................................................................... 102 Discussion ........................................................................................................................... 109 Technique 2 ................................................................................................................................. 111 Background ........................................................................................................................................... 111 FLOW REQUIREMENTS ......................................................................................................... 111 Ecology and Geomorphology ............................................................................................. 111 Forest Hydrology ......................................................................................................................... 112 Riparian Vegetation Ecophysiological Response ................................................................. 112 Methods....................................................................................................................................... 114 Flood Recurrence Interval ..................................................................................................................... 114 Results of Technique 2................................................................................................................ 125 Discussion ............................................................................................................................................. 132 Technique 3 ................................................................................................................................. 133 Methods ................................................................................................................................................. 133 Results ................................................................................................................................................... 134 Discussion ............................................................................................................................................. 141 Analysis of Combining First and Third Techniques ................................................................... 142 Method .................................................................................................................................................. 142 Discussion ............................................................................................................................................. 144 Conclusion ............................................................................................................................................ 145 Riparian Ecological Effects Downstream of Dams 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