Bullneck Run at Spring Hill Rec Center Stream Restoration Project June 2014
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Bullneck Run at Spring Hill Rec Center Stream Restoration Project June 2014
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Bullneck Run at Spring Hill Rec Center Stream Restoration Project June 2014
- 1. Middle Potomac Watershed Plan Implementation Bull Neck Run at Spring Hill Recreation Center Stream Restoration Project Public Meeting June 18, 2014 Stormwater Planning Division Department of Public Works and Environmental Services
- 2. Meeting Outline • Fairfax County Stormwater Management • Countywide Watershed Plan Implementation • Project Introduction and Objectives • Existing Conditions • Proposed Improvements - Options • Example Projects • Questions?
- 3. Fairfax County Department of Public Works and Environmental Services (DPWES) Department of Public Works and Environmental Services Land Development Services Capital Facilities Solid Waste Stormwater Stormwater Planning Division Maintenance and Stormwater Management Division Wastewater
- 4. Stormwater Infrastructure • Conveyance System – 1,600 miles pipe and paved channel – 43,000 structures – 6,800 outfalls • Management Facilities – 1,540 County Maintained – 3,720 Privately Maintained • State Regulated Dams
- 5. Service Drivers In response to The Clean Water Act of 1972 National Pollutant Discharge Elimination System (NPDES) Virginia Stormwater Management Program (VSMP) Regulations Municipal Separate Storm Sewer Permit (MS4) Total Maximum Daily Loads (TMDLs) Chesapeake Bay Local Streams
- 6. Countywide Watershed Planning “Healthy Watersheds, Healthy Communities” • 30 Designated Watersheds • All 15 watershed plans have been adopted by Fairfax County http://www.fairfaxcounty.gov/dpwes/watersheds/
- 7. Middle Potomac Watershed Plan • Watershed Characterization – Water Quality Monitoring – Land Use Change – Pollutant Loading • Structural Project – 25 year plan • Non-Structural Practices – Policy and Regulations http://www.fairfaxcounty.gov/dpwes/watersheds/
- 8. Bull Neck Run Watershed Plan • Bull Neck Run has a drainage area of 2.5 mi2 • Projects identified in the watershed management plan • Pond retrofits • LID Stormwater Enhancements • Stream Restoration • Neighborhood Stormwater Improvements http://www.fairfaxcounty.gov/dpwes/stormwater /projects/project_list.htm
- 9. Goal is to provide water quality control and channel protection volume for the Spring Hill Recreation Center expansion project. Partnership:LIDStormwaterEnhancements SpringHill Rec-Center 26 Space Pavers and 1 Tree Box Filter
- 10. Partnership: LIDStormwaterEnhancements SpringHill Rec-Center Detention Pond Retrofit Before and After
- 11. Before Wakefield Run Stream Restoration After
- 12. Wakefield Run Stream Restoration Before After
- 13. Rabbit Branch Stream Restoration Before After
- 14. Bull Neck Run Stream Restoration
- 15. Next Steps • Conceptual Design • Land Acquisition/Coordination • Preliminary Design • Public Meeting • Final Design • Project Construction (Phase I and II) • Phase I Funding FY2016 or FY2017 • Phase II Funding to be allocated in future • Community Coordination: Pardon our Dust • Maintenance and Operation
- 16. Bull Neck Run Project Area
- 17. Natural Channel Design Background and Design Approach
- 20. Stream Design Approaches Natural Channel Design 3 design approaches 1)Analog 2)Empirical 3)Analytical
- 24. Phase 1 Bull Neck Run at Spring Hill
- 31. Phase 2 Bull Neck Run at Spring Hill
- 47. Looking upstream at boulder rock toe and constructed riffle Looking upstream at boulder rock toe – 2 and 3 courses
- 50. Cross Vane Cross Vane Cross Vane
- 51. Step Pool
- 52. Infill mix comprised of cobbles, gravels, sand, silt, topsoil Larger material, usually cobble Constructed Riffle (aka Reinforced Streambed)
- 53. Riffle
- 54. Access
- 56. Ratna Pottumuthu Ratna.Pottumuthu@FairfaxCounty.gov Matt Meyers Matthew.Meyers@fairfaxcounty.gov Stormwater Planning Division Department of Public Works and Environmental Services Fairfax County 12000 Government Center Parkway, Suite 449 Fairfax, Virginia 22035 www.fairfaxcounty.gov/dpwes/stormwater Questions ? • Contact Information A Fairfax County Publication, April 2014 ADA Statement: To request this information in an alternate format call 703-324-5500, TTY 711
Notas del editor
- VICINITY MAP OF SITE.
- Fluvial Geomorphology Principles Lanes Balance Equation Changes in one variable tip the balance and must be accounted for by a shift in a combination of the other variables. Streams adjust their width, depth, slope, and pattern through erosional and depositional processes to accommodate changes in discharge and sediment load. When discharge and sediment load are not significantly changing, stream adjustment processes shift toward stability. Streams that transport sediment loads and convey flows without significant erosion or deposition are in balance and have achieved dynamic equilibrium. Dynamic equilibrium represents a state of natural stability. Streams in dynamic equilibrium maintain a consistent dimension, pattern, and profile in the current environment, although some change may occur in the short term. Changes in watershed hydrology or sediment supplies (i.e. current environment), may result in changes in the dimension, pattern and/or profile, as the stream adjusts to a new state of equilibrium.
- Conduct Geomorphic and Watershed (HH assessment). CEM Incision (also know as downcutting or headcutting) can occur independently or simultaneously with meander migration. The bed is eroded and the base level of the stream is lowered. Downcutting increases bank height, which can eventually lead to bank failure and channel widening. Widening and downcutting continue until equilibrium is regained. Aggradation occurs when sediment supply exceeds transport capacity and the stream deposits sediment in the channel. Aggradation can be triggered by an increase in sediment supply due to upstream channel erosion or land development, or by a decrease in discharge, which reduces the transport capacity of the system. Deposition continues until a new state of dynamic equilibrium is achieved.
- Stream Design Approaches – Natural Channel Design – 3 design approaches 1)Analog 2)Empirical 3)Analytical. All 3 are part of the NCD process. Analog approaches use a stream in dynamic equilibrium as a template for design. This approach represents one of three approaches to NCD. Empirical design uses equations derived from regional data sets of various channel characteristics of dynamically stable streams. Analytical design makes use of hydraulic equations and sediment transport functions to derive equilibrium conditions. These three approaches must be given equal validity if the end product meets the above definition of stream design. 1- Analog / Reference Reach 2-Empirical: e.g. Regional Curves 3-Analytical:
- NCD process Dimension Plan Profile
- NCD process Hydrologic Analysis Hydraulic Analysis Bankfull Discharge
- Design strategies Priority 1 establish new channel at historic FP elev. Priority 2 Create New Floodplain and Stream Pattern Below the Historical Floodplain Elevation but Above Current Stream Elevation Priority 3 Widen FP at existing BF elev. Priority 4 Stabilize channel in place
- PHASE 1 – FCPA PROPERTY DOWN TO LOG CABIN.
- PHASE 1 START POINT
- PHASE 1 DOWNSTREAM IN R2 BANK EROSION
- PHASE 1 END AT CABIN
- TRIB 1 FROM PETTIT CT AT BOTTOM
- TRIB 1 FROM PETTIT CT AT BOTTOM
- PHASE 2 – LOG CABIN DOWN TO PED. BRIDGE
- PHASE 2 START POINT AT CABIN
- PHASE 2 REPRESENTATIVE PIX OF R4 – LOOKING U/S.
- PHASE 2 DOWNSTREAM AT STEP LEFT BANK BEFORE THE RIPRAP WAS PLACED BY OTHERS. MARCH 2013.
- PHASE 2 DOWNSTREAM AT STEP LEFT BANK AFTER THE RIPRAP WAS PLACED BY OTHERS.
- PHASE 2 BOTTOM OF PHASE (BOTTOM R4) LOOKING U/S FROM PED. BRIDGE
- PHASE 1 R1 R2 DISCUSS DESIGN, ACCESS, TREES, BENEFITS, CHALLENGES, TRAILS, LF= X PHASE 1
- R1 XS TRIB 3 XS HIGHLIGHT THE CHANGE
- PHASE 1 TRIB 1 LF=
- TRIB 1
- PHASE 1 END AT CABIN PHASE 2 START AT CABIN LF= X PHASE 2
- END OF PHASE 1 TRANSITION – TIE INTO EX BED
- PHASE 2 END AT PED. BRIDGE
- PHASE 2 TYP XS
- Goose Creek – small trib
- Selma Estates constructed riffle
- Taft Ave. Riffle and modified CV aka Jhook