West Galveston Bay Regional Sediment Management Plan (An Eco-geomorphologic Approach)

Transcription

1 West Galveston Bay Regional Sediment Management Plan (An Eco-geomorphologic Approach) Juan Moya, Matthew Mahoney and Mike Smith Restore America s Estuaries Conference Tampa, FL, October 23, 2012 Atkins Coastal Planning and Restoration

2 West Galveston Bay Regional Sediment Management Plan Goals 1. Develop a plan that uses the understanding of sediment dynamics including input, output, and circulation 2. Identify sediment sources needed for habitat and environmental protection, restoration, and conservation 3. Propose ideas to manage sediments using adaptive management approaches, taking advantage of the natural processes and sedimentary patterns 4. Support initiatives to reduce or mitigate coastal erosion, coastal storm damage, and costs of sediment management

3 Sediment Sources for Coastal Restoration Geological Deposits Geomorphogical Resources (Estuary) Accretion/Erosion Watershed Sediments Dredging on Navigation Channels Dredging on Borrow Sites for Restoration Can we restore our marshes using natural geomorphologic processes?

4 Morphologic Units in WGB Chocolate Bayou GIWW Bastrop Bay Oyster Lake WGB Carancahua Reef N. Deer Island Drum Bay Christmas Bay Follets Island San Luis Pass Galveston Island Gulf of Mexico

5 Source: Anderson, North South Pleistocene Clays Holocene Coastal Deposits

6 Holocene Geologic Evolution of West Galveston Bay & Galveston Island Source: Anderson, Shoreface

7 WGB Coring Strategy

8 Submerged Sediments in WGB (White et al. 1985) Cores Grab Samples Pleistocene-Holocene Boundary Sampled Sediments in WGB (2011) ΛTKINS

9 WGB Geomprphology, Marshes and Hydric Soils Pleistocene Clays: Tascosa Soil Series Holocene Sands: Karankawa Soil Series

10 Washover Fans and Marsh Creation on the Barrier Island

11 The Concept of the Shoreface Shoreface Anderson, 2007.

12 Maximum spring tide flood flow for the San Luis Pass, Bolivar Roads, and West Galveston Bay (ADCIRC model). ΛTKINS

13 Maximum spring tide ebb flow for the San Luis Pass, Bolivar Roads, and West Galveston Bay (ADCIRC model). ΛTKINS

14 Circulation and shoreline retreat is mainly dominated by wind Average Summer Winds Average Winter Winds

15 The Concept of the Bay Shoreface Pilkey et al., 1993.

16 Pilkey et al., Bay Bottom Shoreface Island Shoreline Bay Bottom Shoreface Island Shoreline Throwbridge. 1998

17 Circulation Cells/Sedimentary Basins in WGB Chocolate Bayou Submerged Shorelines of North WGB Jones Bay WGB West Basin WGB East Basin Bays and Lakes Barrier Island Shoreface San Luis Pass Submerged Shorelines of Galveston Island

18 USACE Projects: Dredging files by reaches

19 Sediment Bars on Galveston Island Core WB-31 on Galveston Island

20 Paleo-Brazos River Clays Core WB-6 West Shorelines

21 Galveston Island Submerged Sediment Bars (Ridges) Zone of Active Sediment Transport Zone of Active Sediment Transport

22 Limited Data Area Volumes in Cubic Meters Volumes in Cubic Yards 1. San Luis Pass Flood Delta 1,500,000 1,962, West of West Basin 4,800,000 6,278,000 5a. Galveston Island West Basin 5a 660, ,247 5b. Galveston Island West Basin 5b 960,000 1,255,632 5c. Galveston Island West Basin 5c 840,000 1,098,678 6a. Galveston Island East Basin 6a 720, ,724 6b. Galveston Island East Basin 6b 1,800,000 2,354,000 6c. Galveston Island East Basin 6c 792,000 1,036, Central Portion of WGB West Basin 5,500,000 7,000,000 Total 17,572,000 22,789,281

23 N N Embayment created in Marshes since ~100 ft N

24 Deposition along the shorelines of Galveston Island Wind Direction Wind Direction Wind Direction Wind Direction Sediment Sediment Transport Sedimentation Transport Modifier Delehite Cove Delehite Cove Delehite Cove Newly Naturally Created Habitat Area Delehite Cove

25 RSM Proposed Concept Zone of Marsh Establishment: A dynamic zone based on energy/lee side interaction Zone of Active Sediment Transport

26 Sediment Accretion and Eco-Geomorphology Sedimentation Modifier Zone of Active Sediment Circulation/Transport Zone of Marsh Establishment (No Dredging Zone)

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28 Recommendations : A. Reduce dependency on dredging: consider building with Nature B. Better understanding of the Bay shoreface processes C. Better understanding of intertidal hydrology: Include hydrologic improvements as part of restoration practices before marshes disappear D. Establish a zone of no-dredging: 1. On the top of the Bay shoreface; 2. On the lee side of energy 3. In coves between peninsulas E. Consider the concept of the zone of potential marsh establishment as restoration criteria F. Consider that hydric soil series in marsh creation: - Karancawa soils (sandy) on Galveston Island - Tascosa soils (clay) on Pleistocene

29 ΛTKINS Can we restore our marshes using natural geomorphologic processes? Juan Moya Atkins Global