This document summarizes a public meeting to discuss plans for a stream restoration project on Turkey Run at Langley High School. The meeting outlined Fairfax County's stormwater management efforts, presented the objectives and existing conditions of the project site, and provided examples of previous stream restoration projects. Attendees were invited to ask questions about the conceptual design, next steps, and natural channel design approach for the Turkey Run project.
Turkey Run at Langley High School Stream Restoration Public Meeting
1. Middle Potomac Watershed Plan Implementation
Turkey Run at Langley High School
Stream Restoration Project
Public Meeting
September 16, 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 EnvironmDeenpatratmle Snt oef r Pvuibclice Wso r(ksD aPnd WES)
Environmental Services
Land
Development
Services
Capital
Facilities
Solid Waste Stormwater
Stormwater
Planning Division
Wastewater
Maintenance and
Stormwater
Management
Division
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. Turkey Run Watershed Plan
• Turkey Run has a drainage
area of 1.95 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
13. Next Steps
• Conceptual Design
• Land Acquisition/Coordination
• Preliminary Design
• Public Meeting
• Final Design
• Project Construction
• Funding FY2016 or FY2017
• Community Coordination: Pardon our Dust
• Maintenance and Operation
45. Questions ?
• Contact Information
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
A Fairfax County Publication, April 2014
ADA Statement: To request this information in an alternate format call 703-324-5500, TTY 711
Editor's Notes
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
VICINITY MAP OF SITE.
EX COND START POINT – JUST THE SITE
EX COND – ADD STREAM AND WETLAND AND REACH DESIGNATION AND TREES.
EX COND – STREAM ASSMNT BEHI TO INFOR THE DSGN – VERY HIGH
EX COND – STREAM ASSMNT BEHI TO INFOR THE DSGN – HIGH
EX COND – STREAM ASSMNT BEHI TO INFOR THE DSGN – MODERATE TO VERY LOW