Bohemia Spillway in Southeastern Louisiana
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Bohemia Spillway in Southeastern Louisiana: History, General Description, and 2011 Hydrologic Surveys John Lopez, Ph.D., Theryn Henkel Ph.D., Ezra Boyd Ph.D., Paul Conner B.S., Megan Milliken B.S., Andrew Baker M.S., Kristian Gustavson M.S. and Luis Martinez M.S. Lake Pontchartrain Basin Foundation 2013 Acknowledgements The Lake Pontchartrain Basin Foundation would like to thank the following: The McKnight Foundation, Surdna Foundation, Environmental Defense Fund, National Audubon Society and Walton Family Foundation for funding to conduct the research described herein and the writing of this report. Tammy Fucich and Albertine Kimble for providing us with valuable information and history about the Bohemia Spillway. The Cox Bay Facility and Sundown Facility for allowing us to use their facilities for docking and access to parts of the Bohemia Spillway. Beshel's boat launch for providing access to the Bohemia Spillway. Emily Volk for editing this document thoroughly, elevating its quality. Amanda Moore, Alisha Renfro, Jared Serigne, Andreas Moshogianis and Eva Hillmann for help in the field. The Southeast Louisiana Flood Protection Authority - East Bank for access and letters of support. Picture on Front Cover: Taken at Ezra's Gully on May 11, 2011 during the 2011 Mississippi River flood showing flood waters rushing over land and through the gully, creating white-water conditions. 2 Table of Contents List of Figures ................................................................................................................................................ 5 List of Tables ................................................................................................................................................. 8 Executive Summary ...................................................................................................................................... 9 Introduction ................................................................................................................................................ 13 Location ...................................................................................................................................................... 13 History......................................................................................................................................................... 16 Timeline ...................................................................................................................................................... 21 LPBF Research Program Purpose ............................................................................................................... 35 Bohemia Spillway Geomorphology ........................................................................................................... 37 General Description .................................................................................................................................................................. 37 Bohemia Road ........................................................................................................................................................................... 38 Natural Geomorphic Features .................................................................................................................................................. 41 Manmade Geomorphic Features .............................................................................................................................................. 44 Hydrology ................................................................................................................................................... 61 Historic Hydrology .................................................................................................................................................................... 61 Hydrology of the 2011 Flood .................................................................................................................................................... 66 2011 Flood Overbank Hydrologic Survey ............................................................................................................................ 67 2011 Flood River ADCP Survey (UNO Contract Survey) ...................................................................................................... 77 2011 Flood Marsh ADCP Survey (UNO Contract Survey) .................................................................................................... 78 Modeling .............................................................................................................................................................................. 79 Hydro-geomorphic Classification ........................................................................................................................................ 80 Bohemia Spillway Land Change: 1932-2010 .............................................................................................. 83 Introduction .............................................................................................................................................................................. 83 Geology ..................................................................................................................................................................................... 83 Methods .................................................................................................................................................................................... 83 Results ....................................................................................................................................................................................... 85 2010 Bohemia Spillway Vegetation Survey ............................................................................................... 93 Methods .................................................................................................................................................................................... 93 Results ....................................................................................................................................................................................... 95 Forest Cover ......................................................................................................................................................................... 95 Herbaceous Cover ................................................................................................................................................................ 98 Species Richness ................................................................................................................................................................ 102 Aerial Study........................................................................................................................................................................ 104 Discussion ................................................................................................................................................................................ 108 Summary ................................................................................................................................................... 109 References ................................................................................................................................................ 111 Appendix A:Vibracore Report .................................................................................................................. 116 3 Appendix B:Equations for Daily Discharge Calculations ......................................................................... 119 Appendix C:Reach by Reach Discharge Calculations ............................................................................... 121 Appendix D:Species Found in Vegetation Study and Corresponding Codes .......................................... 176 4 List of Figures Figure 1: Location of the Bohemia Spillway within the Lake Pontchartrain Basin. .................................... 14 Figure 2: Close-up of the Bohemia Spillway ............................................................................................... 15 Figure 3: Segment of the pre-1926 levee still present in the Bohemia Spillway. ....................................... 16 Figure 4: Letter from Gloria Delta Subat, a young girl who lived in the Bohemia Spillway. ....................... 17 Figure 5: USGS quadrangle map of the Bohemia Spillway Area. ................................................................ 18 Figure 6: Graph published in 1927 just after the 1927 river flood, illustrating the purported effect on river stage due to the Bohemia Spillway and the subsequent artificial crevasse at Caernarvon. .......... 19 Figure 7: Land Change map comparing the Bohemia Spillway on the east bank to the west bank patterns of wetlands loss ....................................................................................................................................... 35 Figure 8: Composite wetland loss (change) map from USGS and USACE data sources ............................. 36 Figure 9: Idealized diagram of Bohemia landscape, a wedge shaped triangle located between the Mississippi River and Breton Sound. ......................................................................................................