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Considerations for Management of the Mouth State of California's Bar-Built

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Considerations for Management of the Mouth State of California’s Bar-built Estuaries Final Report to the Pacific States Marine Fisheries Commission and NOAA (NA14NMF437012) January, 2019 John Largiera, Kevin O’Connorb, & Ross Clarkb a) Coastal Oceanography Group @ Bodega Marine Laboratory (UC Davis) b) Central Coast Wetlands Group @ Moss Landing Marine Labs Arroyo Grande Creek 1 Table of Contents Table of Contents 1 List of Figures 3 List of Tables 5 Appendices 5 Terminology 6 Acronyms 9 Executive Summary 9 1. Introduction 11 2. Approach 14 3. Effect of Mouth State on Estuary Functions and Conditions 17 Overview 18 Water Elevation 18 Stratification 19 Water Quality 20 Marsh Plain Condition 20 Biotic Condition of the Channel 21 4. Effects of Managed Breaching 22 Overview 22 Study Sites 24 Extant Data and Environmental Observations 29 Expected Responses to Breaching 29 Statement 1. When the sand barrier is breached, the water level drops – then reverts to tidal fluctuations. 30 Statement 2. When the sand barrier is breached, high velocities occur as water flows out rapidly. 32 Statement 3. When the sand barrier is breached, a deep channel is cut by the scouring action of outflow. 32 Statement 4. When the sand barrier is breached, estuary salinity drops and later increases with new tidal inflows. 33 Statement 5. When the sand barrier is breached, estuary temperature changes. 34 Statement 6. When the sand barrier is breached, stratification is broken down – and subsequently restored with new seawater intrusion. 35 Statement 7. When the sand barrier is breached, oxygen is restored to the hypoxic lower layer. 36 Statement 8. When the sand barrier is breached prematurely and repeatedly, sand accumulates in the flood-tide shoal. 36 Statement 9: When the sand barrier is breached, water drains off the marsh plain and the marsh dries out. 37 Statement 10: When the sand barrier is breached repeatedly, marsh condition and plant 39 diversity are altered. 39 Statement 11. When the sand barrier is breached, small fish and invertebrates are flushed from the estuary. 42 2 Statement 12. When the sand barrier is breached, spawning fish may return to estuary and river habitats. 43 Statement 13. When the sand barrier is breached, phytoplankton and macro-algae are flushed from the estuary. 43 Statement 14. When the sand barrier is breached, poor water quality can occur nearshore. 44 5. Management Decisions on Estuary Breaching 45 6. Recommendations for Improved Management 47 Immediate Actions 47 Scientific Contributions Needed to Improve Management 47 Learning through Monitoring 48 Processed-Based Approach to Management 50 7. Conclusion 51 References 53 Gaviota Creek 3 List of Figures FIGURE 1. CONCEPTUAL MODEL OF THE EFFECT OF MOUTH STATE ON ESTUARY CONDITIONS. DIRECTION OF ARROW INDICATES INFLUENCE. .......... 15 FIGURE 2. WATER ELEVATION (RED LINE) IN THE MAIN CHANNEL OF THE GUALALA RIVER ESTUARY – A BBE IN NORTHERN CA. THIS PLOT SHOWS TIDAL (OPEN) AND NON-TIDAL (CLOSED AND DRAINING OR FILLING) STATES. BLUE LINES REPRESENT THE ELEVATIONS OF DIFFERENT FEATURES ON THE MARSH PLAIN, WHILE THE GREEN BAND REPRESENTS THE OVERALL MARSH PLAIN ELEVATION. DATA PROVIDED BY CCWG. ............. 19 FIGURE 3. SITES IN NORTHERN CALIFORNIA WITH RECENTLY PLANNED OR IMPLEMENTED MANAGED BREACHES THROUGH STATE AND FEDERAL PERMITS.......................................................................................................................................... 26 FIGURE 4. SITES IN CENTRAL CALIFORNIA WITH RECENTLY PLANNED OR IMPLEMENTED MANAGED BREACHES THROUGH STATE AND FEDERAL PERMITS. .......................................................................................................................................................................................... 27 FIGURE 5. SITES IN SOUTHERN CALIFORNIA WITH RECENTLY PLANNED OR IMPLEMENTED MANAGED BREACHES THROUGH STATE AND FEDERAL PERMITS. .......................................................................................................................................................................................... 29 FIGURE 6. NATURAL BREACH (GREY BAR) IN RUSSIAN RIVER ESTUARY, OCTOBER 2012 (ROBART & LARGIER, 2013). TOP PANEL: WATER LEVEL AT JENNER VISITORS CENTER (~1KM FROM MOUTH). MIDDLE PANEL: SALINITY NEAR-SURFACE AND NEAR-BOTTOM AT PATTY’S ROCK (~2.5 KM FROM MOUTH). BOTTOM PANEL: TEMPERATURE AT MULTIPLE DEPTHS AT PATTY’S ROCK (~2.5 KM FROM MOUTH). ............................... 31 FIGURE 7. MANAGED BREACH EVENT (GREY BAR) IN LOS PEÑASQUITOS LAGOON, APRIL 2014 (LOS PEÑASQUITOS LAGOON FOUNDATION (2016). TOP PANEL: WATER LEVEL. SECOND PANEL: SALINITY NEAR-BOTTOM. THIRD PANEL: TEMPERATURE NEAR-BOTTOM. BOTTOM PANEL: DISSOLVED OXYGEN NEAR-BOTTOM. .......................................................................................................................................... 34 FIGURE 8. NATURAL BREACH EVENT (GREY BAR) IN SCOTT CREEK ESTUARY, DECEMBER 2009 (NYLEN 2015). TOP PANEL: DAILY AVERAGE SALINITY NEAR-SURFACE (DASHED LINE) AND NEAR-BOTTOM (SOLID LINE). MIDDLE PANEL: DAILY AVERAGE TEMPERATURE NEAR-SURFACE (DASHED LINE) AND NEAR-BOTTOM (SOLID LINE). BOTTOM PANEL: DAILY AVERAGE DISSOLVED OXYGEN NEAR-SURFACE (DASHED LINE) AND NEAR- BOTTOM (SOLID LINE). ............................................................................................................................................................ 35 FIGURE 9. SHOALING AT THE MOUTH OF LOS PEÑASQUITOS LAGOON, JUST EAST OF PACIFIC COAST HIGHWAY. (© 2002-2015 KENNETH & GABRIELLE ADELMAN, CALIFORNIA COASTAL RECORDS PROJECT, WWW.CALIFORNIACOASTLINE.ORG). .................................................. 37 FIGURE 10. LEFT PANEL: PERCENT OF TIME THAT POINTS ON THE MARSH PLAIN AND SIDE CHANNEL LOCATIONS ARE INUNDATED IN SCOTT CREEK ESTUARY FROM 2013 TO 2016, OVER A PERIOD OF 1164 DAYS. RIGHT PANEL: PERCENT OF TIME SAME POINTS ON THE MARSH PLAIN WOULD BE INUNDATED IF A HYPOTHETICAL MANAGED BREACHING REGIME LIMITED WATER LEVEL TO 1.45 MSL. ............................................... 38 FIGURE 11. PERCENT OF THE MARSH PLAIN FLOODED UNDER NATURAL CONDITIONS (GREEN BARS) AND UNDER A HYPOTHETICAL 1.45 M MAXIMUM WATER ELEVATION BREACHING STRATEGY (BLUE BARS) .................................................................................................................. 39 FIGURE 12. PLANT SPECIES COMMONLY FOUND IN BAR-BUILT ESTUARIES ORGANIZED BY THE AMOUNT OF TIME THEY WERE INUNDATED AT 30 ESTUARIES ALONG THE CALIFORNIA COASTLINE. THE BOX REPRESENTS THE QUARTILES OF THE DATA. THE MID-LINE OF EACH BOX IS THE MEDIAN, LOWER END OF THE BOX IS THE MID-VALUE BETWEEN THE LOWEST VALUE AND THE MEDIAN. THE HIGHER END OF THE BOX IS THE MID- VALUE BETWEEN THE HIGHEST VALUE AND THE MEDIAN. THE WHISKERS SHOW THE EXTREMES (MAX & MIN) VALUES, WHILE THE DOTS ARE OUTLIERS. (DATA PROVIDED BY CCWG). .................................................................................................................................... 40 FIGURE 13. CRAM METRIC SCORES AT BBES WITH REFERENCE HYDROLOGY CONDITIONS (ORANGE LINE) AND AT BBES WITH BREACHING AND IMPEDIMENTS TO NATURAL MOUTH MIGRATION THAT LEAD TO REDUCED MARSH INUNDATION (GREY LINE). POINTS FURTHER FROM THE CENTER DENOTE HIGHER QUALITY HABITAT CONDITIONS (UNPUBLISHED DATA BY CCWG AVAILABLE FROM ECOATLAS.ORG) ...................... 41 FIGURE 14. AVERAGE BIOLOGICAL VOLUME OF PHYTOPLANKTON (+/- STANDARD ERROR OF THE MEAN) AT SCOTT CREEK ESTUARY WHEN THE MOUTH IS OPEN AND CLOSED FROM 2003-2005 (DATA FROM BECK ET AL. 2006). SEE APPENDIX 2 FOR MORE INFORMATION. ................ 43 Malibu Creek 4 List of Tables TABLE 1.KEY PARAMETERS CHARACTERIZING THE ABIOTIC STATE OF BBES .................................................................................................. 16 TABLE 2. KEY PARAMETERS CHARACTERIZING THE BIOTIC STATE OF BBES. .................................................................................................. 16 TABLE 3. KEY INFORMATION ON THE THREE FOCAL SITES. ........................................................................................................................ 24 TABLE 4. AVERAGE COUNT OF INDIVIDUALS OF BENTHIC INVERTEBRATE GROUPS DURING OPEN AND CLOSED MOUTH CONDITIONS FROM 2003-2005, SHOWING LARGE DIFFERENCES IN COUNTS FOR EACH CATEGORY AND IN OVERALL ABUNDANCE (DATA FROM BECK ET AL. 2006). SEE APPENDIX 2 FOR MORE INFORMATION. .................................................................................................................................................... 42 TABLE 5. AVERAGE PERCENT COVER OF BENTHIC MACRO-ALGAE, TWO SPECIES OF SUBMERGED AQUATIC VEGETATION, AND ULVA AT SCOTT CREEK ESTUARY FROM 2003-2005 (DATA FROM BECK ET AL. 2006). SEE APPENDIX 2 FOR MORE INFORMATION. ........................................... 44 Mattole River 5 Appendices Appendix 1: Focal Site #1: Russian River Estuary – Summary of Existing Data and Information Appendix 2: Focal Site #2: Scott Creek Estuary – Summary of Existing Data and Information Appendix 3: Focal Site #3: Los Peñasquitos Lagoon – Summary of Existing Data and Information Appendix 4: Summary of California Rapid Assessment Method (CRAM) Appendix 5: Permits needed to conduct Managed breaching of bar-built estuaries in California Appendix 6: List of special conditions placed on breaching permits for BBEs throughout California El Refugio Creek 6 Terminology Sand barrier – a ridge of sand built across the mouth of an estuary or lagoon by waves; the crest of the ridge is typically above high-tide
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