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Effects of Segmented Offshore Breakwater Structures on Shallow Water Habitat at Mason Neck Virginia. Location. Location. HPO3 State Park. HPO1 Wildlife Refuge. HPO3 . Pre-Construction Condition. HPO1 . Pre-Construction Condition. Design / Construction. Off-shore segmented breakwater

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  1. Effects of Segmented Offshore Breakwater Structures on Shallow Water Habitat at Mason Neck Virginia

  2. Location

  3. Location HPO3 State Park HPO1 Wildlife Refuge

  4. HPO3 Pre-Construction Condition

  5. HPO1 Pre-Construction Condition

  6. Design / Construction • Off-shore segmented breakwater • 4 riprap segments • Segments 175 feet long • Gaps 60 feet wide • Placed 1.5 feet below MLLW • Riprap revetment at HP03 • Construction complete in 2002

  7. Monitoring • Required by project permits • Annually for 5 years following construction • Success criteria • Stable structure • Stabilize shoreline / control erosion • Create shallow water fish habitat

  8. Monitoring • Fish utilization of riprap structures • Electrofishing each breakwater segment • Once each fall (typically September) • Catch tallied by species, and released

  9. Monitoring • Fish utilization of protected waters (shoreward of the structures) • Beach seine (60 foot long with 6X6 offset bag) • Behind each breakwater segment • Control seines of unprotected shoreline areas • Once each fall (typically September) • Catch tallied by species, and released

  10. Monitoring • Shallow water habitat enhancements • SAV • Bed sketches • Total percent cover • Species composition • Bathymetric survey • 2003 and 2007

  11. Results • HP03 • Structures remained stable • Riprap stabilized shoreline

  12. Results • HP01 • Structures remained stable • Shoreline finding stable angle of repose

  13. Results • Riprap structure utilization • 21 species • 11 species per breakwater • 55 individuals per breakwater • 60 percent bluegill and pumpkinseed sunfish

  14. Results

  15. Results

  16. Results

  17. Results • Protected waters utilization • 30 species • 7 species per seine • 153 individuals per seine • Beach seine not effective in dense SAV

  18. Results

  19. Results

  20. Results Control Data Breakwater Data

  21. Results

  22. Results • SAV • 6 species • Hydrilla verticillata • Myriophyllum spicatum • Najas minor • Vallisneria americana • Bed density • 2003 • 5% HP03 • 50% HP01 • 2007 • ~90% both sites

  23. Results

  24. Results HP03 in 2007

  25. Results HP03 in 2008

  26. Results HP01 in 2007

  27. Results HP01 in 2008

  28. Conclusions • Stable structures • Effective shoreline stabilization • Enhanced shallow water habitat • Promoted SAV growth • Provided structure/refuge for fish • Rigorous sampling methods needed to measure effect on fish utilization • Long term effect of structures will likely be conversion of shallow waters to beach habitat

  29. Thank You Justin Reel Rummel, Klepper & Kahl, LLP 410-728-2900 jreel@rkk.com

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