Middle Potomac Watershed Plan Dead Run Stream Restoration
1. Middle Potomac Watershed Plan Implementation
Dead Run Stream Restoration Project
Public Meeting
McLean Community Center
April 23, 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 of pipe and
paved channel
– 43,000 structures
– 6,800 outfalls
• Management Facilities
– 1,540 county maintained
– 3,720 privately maintained
• State Regulated Dams
A typical outfall
A dam in Fairfax County
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 Regulationshttp://www.fairfaxcounty.gov/dpwes/watersheds/
8. Dead Run Watershed Plan
• Dead Run has a drainage
area just over 3 square miles
• 24 priority 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. Approximately one third of the roof is covered with vegetation.
The benefits of a “living roof” include:
• Reduces the amount of stormwater runoff
• Absorbs air pollution and carbon dioxide
• Reduces the energy needed to cool the building in summer
Partnership:LIDStormwaterEnhancements
Dolley MadisonLibrary
Vegetated Roof- Delosperma and Allium plants in bloom
11. Dead Run – Before and After
Drainage Area
(acres)
Phosphorous Removal
(lbs/yr)
Nitrogen Removal
(lbs/yr)
Sediment Removal
(tons/yr)
415 15 283 3
Stream Restoration
13. Stream Monitoring Program
Study Objectives
1. Generate long-term monitoring data.
2. Evaluate relations between
observed conditions/trends and BMP
implementation.
3. Transfer the understanding gained
to other less-intensively monitored
watersheds.
http://va.water.usgs.gov/projects/ffx_co_monitoring.htm
15. Dead Run Stream Restoration
Segment 1 – Dominican Retreat
• 2,000 Linear Feet
• Extends to Old Dominion
Drive
• Residential lots along
Merrimac Drive and Van
Ness Court
16. Dead Run Stream Restoration
Segment 2 – McLean Central Park
• 800 Linear Feet
• Completely in Park
• Starts below
previously restored
section near library
17. Dead Run Stream Restoration
Segment 3 – McLean Central Park
• 1,500 Linear Feet
• Extends to Churchill Road
• Residential lots along
Elizabeth Drive and Carol
Rayes Street
18. Next Steps
• Conceptual Design
• Land Acquisition/Coordination
• Preliminary Design
• Public Meeting
• Final Design
• Project Construction
• Funding FY2016 and FY2017
• Community Coordination: Pardon Our Dust
• Maintenance and Operation
61. John Palmer
John.Palmer@fairfaxcounty.gov
Dipmani Kumar
Dipmani.Kumar@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
Questions ?
Contact Information
A Fairfax County Publication, April 2014
To request this information in an alternate
format call 703-324-5500, TTY 711
www.fairfaxcounty.gov/dpwes/
stormwater
Thank You!
Hinweis der Redaktion
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