Effects of Segmented Offshore Breakwater Structures on Shallow

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

Location

Location HPO 3 State Park HPO 1 Wildlife Refuge

HPO 3 Pre-Construction Condition

HPO 1 Pre-Construction Condition

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 HP 03 • Construction complete in 2002

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

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

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

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

Results • HP 03 – Structures remained stable – Riprap stabilized shoreline

Results • HP 01 – Structures remained stable – Shoreline finding stable angle of repose

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

Results

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

Results

Results Control Data Breakwater Data

Results

Results • SAV – 6 species • Hydrilla verticillata • Myriophyllum spicatum • Najas minor • Vallisneria americana – Bed density • 2003 – 5% HP 03 – 50% HP 01 • 2007 – ~90% both sites

Results

Results HP 03 in 2007

Results HP 03 in 2008

Results HP 01 in 2007

Results HP 01 in 2008

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

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