Comprehensive Barrier Island Restoration Plan

Transcription

1 Mississippi Coastal Improvements Program (MsCIP) Comprehensive Barrier Island Restoration Plan 202 National Conference on Beach Preservation Technology February 0, 202 Justin McDonald, P.E. Lead Project Engineer, MsCIP US Army Corps of Engineers BUILDING STRONG

2 Presentation Outline MOBILE DISTRICT History of the Mississippi Coastal Improvements Program (MsCIP) Comprehensive Barrier Island Restoration Plan Restoration of the Barrier Island Sediment Budget Selection of Sand Placement Locations Identification of Borrow Sources Construction Alternatives/Methods Considered Recommended Plan Development of a revised Dredge Material Disposal Plan for Pascagoula Navigation Channel Restoration of the Northern Shoreline of West Ship Island Restoration of the Eastern Shoreline of Cat Island Conclusions 2

3 3 MOBILE DISTRICT Mississippi Coastal Improvements Program P.L , 30 December 2005 Comprehensive Planning to Address Hurricane and Storm Damage Reduction Salt Water Intrusion Shoreline Erosion Fish and Wildlife Preservation Other Water Related Resource Projects Cost Effective Projects in lieu of NED benefits Report requirements Interim Report within 6 months Comprehensive Plan within 2 years Compatible with State Coastal Restoration Plan

4 4 Hurricane / Storm Salt Water Intrusion Shoreline Erosion Fish & Wildlife MOBILE DISTRICT Comprehensive Plan Elements Interim Projects Phase I Projects Ecosystem Restoration Studies Other Studies Hancock County Harrison County Jackson County 6 2 Bay St. Louis Waveland Gulfport 5 Gulfport 2 7 Biloxi Gautier Moss Point 3 2 Pascagoula High Hazard Risk Area Cat Ship Horn Petit Bois % Chance Flood Risk Katrina Inundation Limits Littoral Zone Placement of Sand O&M Beneficial Use Placement

5 Comprehensive Barrier Island Restoration Plan Sediment budget of barrier island chain Revised dredge material disposal plan for Pascagoula navigation channel Northern shoreline of West Ship Island Eastern shoreline of Cat Island 5

6 Original Placements for Restoration of Sediment Budget Mississippi Barrier Islands Original Borrow 45 miles 6

7 Recommended Placements for Restoration of Sediment Budget Mississippi Barrier Islands 7

8 Criteria for Selection of a Borrow Source Sand compatibility Particle shape (roundness) Gradation (D 50 of sand on Ship Island = 0.30 mm) Color Out of active littoral transport system Minimal wave focusing Cost 8

9 Borrow Sites Being Considered 9

10 Ship Island Borrow Site MOBILE DISTRICT 0

11 DA-0 Borrow Site MOBILE DISTRICT

12 Petit Bois Borrow Site MOBILE DISTRICT 2

13 Other Borrow Sites Being Considered 3

14 4 MOBILE DISTRICT Available Borrow Quantities Borrow Site D50 (mm) Computed Volume (mcy) Dredge Efficiency % Available for Use (mcy) Petit Bois DA Ship Island Lower Tombigbee

15 Construction Alternatives/Methods Considered Alternative Camille Cut: (6.0 m.c.y, D 50 = 0.28 mm) Dredge coarser sand from Petit Bois using hopper dredge (8.0 m.c.y.) Dispose coarser sand on top of finer sand in Ship Island Borrow (8.0 m.c.y.) Use cutterhead to make single cut and place mixed material in Camille Cut East Ship Island: (Same for all alternatives) Pros: Dredge DA-0 using cutterhead and load into scows Pump-off directly to East Ship Island (5.4 m.c.y., D50 = 0.33 mm) Mixing will be achieved with the use of one dredge during final placement Cons: Sand from Petit Bois will have to be pumped off due to the depth of water in Ship Island Borrow Material will have to be double-handled ($$$$) Wave focusing due to excavation of Ship Island Borrow 5

16 Construction Alternatives/Methods Considered Alternative 2 Camille Cut: (6.0 m.c.y, D 50 =0.28) Dredge coarser sand from Petit Bois using hopper dredge Dispose coarser sand south of finer sand in Ship Island Borrow in deeper water Use two cutterhead dredges with merged discharge lines to place mixed material in Camille Cut East Ship Island: (Same for all alternatives) Pros: Dredge DA-0 using cutterhead and load into scows Pump-off directly to East Ship Island (5.4 m.c.y., D50 = 0.33 mm) Hopper dredges carrying Petit Bois sand can directly dispose in deep water south of Ship Island Borrow Cons: Material will have to be double-handled ($$$$) Wave focusing due to excavation of Ship Island Borrow 6

17 Construction Alternatives/Methods Considered Alternative 3 Recommended Camille Cut: (4.3 m.c.y., D 50 = 0.32 mm) Dredge coarser sand from Petit Bois using hopper dredge and dispose directly into Camille Cut via pump-off (3.3 m.c.y.) Dredge finer sand from Ship Island Borrow using a cutterhead dredge and pump directly to Camille Cut (.0 m.c.y.) Ship Island sand will serve as a cap on the fill section to facilitate the growth of beach vegetation East Ship Island: (Same for all alternatives) Pros: Dredge DA-0 using cutterhead and load into scows Pump-off directly to East Ship Island (5.4 m.c.y., D50 = 0.33 mm) Coarse material which results in a more stable fill section No double-handling of material Minimal wave focusing due to the small quantity from Ship Island Borrow Most cost effective alternative 7

18 Proposed Modification to Dredge Material Disposal Plan 8

19 West Ship Island North Shore Restoration 560,000 c.y. of Sand Placement,300 c.y. of Rock/Rubble Removal 5,200 ft of Turbidity Barrier 9

20 West Ship Island North Shore Planting 2, 800 ft of Sand Fence 430,000 Beach Plantings (Herbs, Grasses, & Shrubs) 20

21 Cat Island Eastern Shoreline Restoration CAT ISLAND FILL PLACEMENT 2.0 M C.Y. CAT ISLAND BORROW AREA 2

22 Conclusions MsCIP Comprehensive Barrier Island Restoration Plan was developed in response to Hurricane Katrina 4 Components Restore Sediment Budget Placement Locations Camille Cut/East Ship Island Borrow Sources Ship Island, DA-0, Petit Bois, and Lower Tombigbee River Recommended Plan 4.3 M c.y. in Camille Cut & 5.4 M c.y. at East Ship Island Revise Dredge Material Disposal Plan for Pascagoula Nav. Channel Dispose of dredge material further to the south and west of the existing site Restore Northern Shoreline of West Ship Island (90% Complete) Placement of approx. 560,000 c.y. of sand Removal of approx.,300 c.y. of rock/rubble Installation of 5,200 ft of turbidity barrier to protect SAV Install 2,800 ft of sand fence & plant approx. 430,000 plants Restore Eastern Shoreline of Cat Island Placement of approx. 2.0 M c.y. of sand 22

23 23 MOBILE DISTRICT