OYSTER REEF RESTORATION; RESTORING ECOLOGICAL FUNCTION

Transcription

1 OYSTER REEF RESTORATION; RESTORING ECOLOGICAL FUNCTION Paul Jensen, David Buzan, and Ka-Leung Lee; Atkins Mark Dumesnil and Julie Sullivan; The Nature Conservancy

2 Presentation Overview The Nature Conservancy restoration programs The selection of Halfmoon Reef Events influencing the Reef Changes in freshwater inflow Navigation channel and salinity Commercial oyster dredging Major storms Design Construction and Status

3 Oyster Reef Restoration Online Newsletter

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5 Halfmoon Reef in acres Halfmoon Reef Mad Island Reef Shell Reef Dog Island Reef 1905 Moore Survey

6 Major Changes in Reef From 1905 Moore Survey the reef was exposed at low water Before Civil War, the Port of Matagorda was reported to be the second largest port in Texas, after Galveston Halfmoon Reef was a major factor in navigation as well as oysters

7 Changes in Colorado River Inflow Locations The Colorado River mouth has moved extensively In Texas first century ( ) it discharged to Matagorda Bay For the next 50 years it went directly to the Gulf It has now been moved back to the Bay

8 Changes in River Flows Major impoundments on Colorado River built between Lavaca River impounded by 1980 Increasing agricultural, municipal and industrial water use

9 Harvesting Until 1920s tonging and dredging under sail were primary methods Internal combustion engines increased harvesting power Greater distribution range increased demand In some cases oyster shell dredging was done, but not certain for Halfmoon

10 Other Physical Changes Matagorda Ship Channel in early 1960s increased tidal exchange and salinities increased by about 5 ppt River diversion back into Matagorda Bay, River diversion project included rebuilding oyster reefs, 1994

11 Halfmoon Reef Restoration Shell Reef Halfmoon Reef Sammy s Reef Mad Island Reef Matagorda Bay Gulf of Mexico

12 1935 bathymetry (Source: NOAA Nautical Chart 11317, edition date July 1975

13 1992 bathymetry (Source: NOAA Nautical Chart On-Line Viewer, accessed 4/26/11, Chart 11317, edition date March 2009

14 Halfmoon Reef Restoration Shell Hash Hard Sand Mud 2009/2011 Surveys Shell Hash

15 Long-Term Ideal Restore Halfmoon Reef as close to 1905 condition as practical

16 Project Design Objectives TNC Minimums 12.7 ac w/ 20% coverage, 2 ft high after 2 years Habitat objectives maximize edge length and vertical relief, and spatial variability in size of openings and distance between rows Minimize sedimentation potential Basics stability, construction simplicity, cost minimization

17 Design Aspects Considered Materials Reef Height Row Spacing Angular Orientation Tidal Currents Material Size Distribution for Habitat and Wave Forces Construction Methods Field Experience

18 Design Decisions Limestone or recycled Concrete acceptable Size Range: 6 to 30, median 12 Rows 3 high, 18 wide and 650 long Spaced 30, 60 and 90 -as many as funds allow Two funds: CIAP and Federal PPA, requiring separate Plans and Specs

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20 CIAP and Corps Reef Rows

21 CIAP Project Luhr Bros. Tower Rock won CIAP Project 26 Rows Notice to Proceed Sept. 16, 2013 Construction Oct. 18 to Dec. 3, 2013 Final As-Built Survey received Feb. 10, 2014

22 Tower Rock Material Production

23 Reef Rock Loading - Barge 4

24 Barge 4

25 Luhr Bros Construction

26 Rock Placement

27 Corps Project RLB Construction had winning bid 6 Rows constructed using recycled concrete Feb. 25, 2014 RLB begins construction April 12, 2014 complete construction

28 Recycled Concrete w/ no Rebar

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31 INITIAL FINDINGS Timing matters CIAP rows: barnacles and bryzoans with some spat Corps rows: good spat set Shell between rows also has good spat set Fish are attracted to all rows and area popular with fishing guides

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36 Shell Between CIAP Rows

37 Follow-on Work TNC has contracted for longer term monitoring and studies to include: Colonization by mollusks, fishes and other reef species Sedimentation and substrate settlement Community health relative to surrounding areas

38 Questions