WGB - Restore America's Estuaries


WGB - Restore America's Estuaries

West Galveston BayRegional Sediment Management Plan(An Eco-geomorphologic Approach)Juan Moya, Matthew Mahoney and Mike SmithRestore America’s Estuaries ConferenceTampa, FL, October 23, 2012Atkins Coastal Planning and Restoration

West Galveston Bay Regional Sediment ManagementPlan Goals1. Develop a plan that uses the understanding of sedimentdynamics including input, output, and circulation2. Identify sediment sources needed for habitat andenvironmental protection, restoration, and conservation3. Propose ideas to manage sediments using adaptivemanagement approaches, taking advantage of the naturalprocesses and sedimentary patterns4. Support initiatives to reduce or mitigate coastal erosion,coastal storm damage, and costs of sediment management

Sediment Sources for Coastal RestorationGeologicalDepositsGeomorphogicalResources (Estuary)Accretion/ErosionWatershedSedimentsDredging on NavigationChannelsDredging on BorrowSites for RestorationCan we restore our marshesusing natural geomorphologic processes?

Morphologic Units in WGBChocolateBayouGIWWBastropBayOysterLakeWGBCarancahuaReefN. Deer IslandDrumBayChristmasBayFollets IslandSanLuisPassGalveston IslandGulf ofMexico

Source: Anderson, 2007.NorthSouthPleistocene ClaysHolocene CoastalDeposits

Holocene Geologic Evolution of West Galveston Bay & Galveston IslandSource:Anderson, 2007.Shoreface

WGB Coring Strategy

WGB Geomprphology, Marshes and Hydric SoilsPleistocene Clays:Tascosa Soil SeriesHolocene Sands:KarankawaSoil Series

Washover Fans and Marsh Creation on the Barrier Islandhttp://www.cr.nps.gov/history/online_books/pais/1980-17/sec3d.htm

The Concept of the ShorefaceShorefaceAnderson, 2007.

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

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

Circulation and shoreline retreat is mainlydominated by windAverage Summer WindsAverage WinterWinds

The Concept of the Bay ShorefacePilkey et al., 1993.

Pilkey et al., 1993.Bay BottomShorefaceIsland ShorelineBay BottomShorefaceIsland ShorelineThrowbridge. 1998

Circulation Cells/Sedimentary Basins in WGBChocolateBayouSubmergedShorelines ofNorth WGBJonesBayWGB West BasinWGB East BasinBays andLakesBarrierIsland ShorefaceSanLuisPassSubmerged Shorelines ofGalveston Island

USACE Projects:Dredging files by reaches

Sediment Bars on Galveston IslandCore WB-31 on Galveston Island

Paleo-Brazos River ClaysCore WB-6 West Shorelines

Galveston IslandSubmergedSedimentBars (Ridges)Zone of Active Sediment TransportZone of Active Sediment Transport

LimitedDataAreaVolumes in CubicMetersVolumes in CubicYards1. San Luis Pass FloodDelta1,500,000 1,962,0004. West of West Basin 4,800,000 6,278,0005a. Galveston IslandWest Basin 5a660,000 863,2475b. Galveston IslandWest Basin 5b960,000 1,255,6325c. Galveston IslandWest Basin 5c840,000 1,098,6786a. Galveston IslandEast Basin 6a720,000 941,7246b. Galveston IslandEast Basin 6b1,800,000 2,354,0006c. Galveston IslandEast Basin 6c792,000 1,036,0007. Central Portion ofWGB West Basin5,500,000 7,000,000Total 17,572,000 22,789,281

NNEmbayment created in 1995. Marshes since 20050~100 ftN

Deposition along the shorelines of Galveston IslandWind Direction Wind Direction Wind Direction Wind Direction SedimentSedimentTransportSedimentation TransportModifierDelehiteCoveDelehiteCoveDelehiteCoveNewly NaturallyCreated HabitatAreaDelehiteCove1-19952-20041-200911-201124

RSM Proposed ConceptZone of Marsh Establishment: A dynamic zone based onenergy/lee side interactionZone of Active Sediment Transport

Sediment Accretion and Eco-GeomorphologySedimentationModifierZone of Active Sediment Circulation/TransportZone of MarshEstablishment(No Dredging Zone)

Recommendations :A. Reduce dependency on dredging: consider building with NatureB. Better understanding of the Bay shoreface processesC. Better understanding of intertidal hydrology: Include hydrologicimprovements as part of restoration practices before marshesdisappearD. Establish a zone of no-dredging:1. On the top of the Bay shoreface;2. On the lee side of energy3. In coves between peninsulasE. Consider the concept of the “zone of potential marsh establishment”as restoration criteriaF. Consider that hydric soil series in marsh creation:- Karancawa soils (sandy) on Galveston Island- Tascosa soils (clay) on Pleistocene

ΛTKINSCan we restore our marshes using naturalgeomorphologic processes?Juan MoyaAtkins GlobalJuan.moya@atkinsglobal.com512-432-3234

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