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This was a presentation regarding how multi-use greenways can be designed and constructed with no adverse impact to the 100-yr floodplain. I co-presented this at the 2005 conference of the Association of State Floodplain Managers.
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Colorado Examples
John Pflaum, P.E.
ASCG Incorporated
Cindy Thrush, P.E.
Urban Drainage & Flood Control District
with no Adverse Impact
Denver Metropolitan Greenways
Born from a Flood
Evolution Of Denver’s Greenways
1965 Major Flood with Millions in Damages
1969 Urban Drainage & Flood Control
District Forms
1973 Significant Flood
1974 Platte River Development formed
1976 Initial Confluence Project Completed
1976 to 1996 South Platte River Greenway
Extended North & South
1980’s to Present – Greenways Developed
along Tributary Drainageways
1996 to Present – Second Wave of South
Platte River Greenway Improvements
(Downtown Riverfront and Suburban
Greenways)
The Urban Drainage and Flood Control District and
Public Agency Partnering
Who is the Metro Denver Urban Drainage
and Flood Control District?
Quasi-governmental agency established by the
Colorado State Legislature in 1969 to assist local
governments in 6 counties, 34 cities with multi-
jurisdictional drainage and flood control projects.
Who is UDFCD? Continued
Governed by 20 member Board Of Directors
18 – Elected Officials
2 – Professional Engineers
Budget is about 15 million each year, funded by
property taxes. 20 full time staff, all engineering
design, project construction and maintenance
work contracted out to private industry.
MAJOR AREAS OF ACTIVITY
Drainageway Maintenance
Capital Improvement Projects
Master Planning
Floodplain Management
Flood Warning
NPDES Permitting - Storm
Water Quality
Criteria Development - Manuals
Floodplain Preservation
New Development Plan Review
6 Counties
1,608 square miles
1,600 miles of
major drainage ways
Map of UDFCD
Boundaries
Denver Drainageway
Characteristics
Semi-arid climate, 15 inches of rain per year
Most erosion and flooding due to thunderstorms
Only 6-8 creeks have more than 5 cfs base flow
About 95% are natural open channels (only a small portion contained by levies)
Elevation: 5,280 ft – “Mile High City”
Population 2.2 Million
Partnering on Trail Projects
for Over 35 Years
Work with Cities, Counties, Park Districts
Maintenance access trails proposed in Drainageway Master Plans since the 70’s
Drainageways platted in separate tracts of land dedicated to Park Districts or HOAs
Denver area’s network of trails is linked together through the drainage ways
Many projects have combined stream restoration and trail construction/maintenance together
UDFCD Trail Participation Policy
Trail must serve a maintenance access need for a
drainage way
Right-of way, design, construction and restoration
maintenance eligible for funding
Participation limited to 50% of the design and
construction cost for a “soft” surface trail, or 25%
of a concrete trail
Design must be reviewed by UDFCD, either party
can manage the project
Planning and Designing Greenways
Planning:
Identify watershed, jurisdictions, land ownership
Involve public
Continuity, connectivity, accessibility
Resource preservation and protection
Floodplain and geomorphology
Buffering, vistas, views
Education and stewardship
Signage and way-finding
Multiple use benefits
Safe and maintainable
Planning
and Designing Greenways
Design:
Multi-Disciplinary Team
Public officials/representatives
Engineers
Surveyors
Landscape Architects
Ecologists
Biologists
Right-of-way agents
Trail & Greenway Routing Considerations No Adverse Impacts To Floodplain
Minimize Impacts to Stream Riparian Areas
Trail Grading to Avoid or Minimize Floodplain Impacts
South Platte Greenway at Commons Park
Sand Creek Greenway
Stream Crossings
Bridges
Low Flow Crossings
Informal Boulder Step Crossings
Must be designed to withstand flow velocities during storm events
Low Flow Crossings
Prefab. or Reinforced Concrete Construction
Fixed or Collapsible Handrails
Erosion Protection at Corners
Often Combined with Channel Stabilization Measures
Goldsmith Gulch at Bible Park Grange Hall Creek
Appropriate for Wide Floodplain Conditions
Designed for Overtopping
Big Dry Creek Greenway
Cherry Creek
Bridges
Span 100-yr. Floodplain
Durability/Low Maintenance
Safety and Rub Rails
Concrete Deck Preferred
Cherry Creek
Centennial Bridge over
Cherry Creek
at Confluence Park
16th Street Bridge over South
Platte River Downtown Denver
South Platte River Greenway at
Cuernavaca Park
Big Dry Creek
Trail Connection
Underpasses
Safe Grade Separation from Vehicles
Often Inundated Several Times per Year
Ramp to Street Grade Desirable
• Safe Route During Flooding
• Access Point for Public & Maintenance
Separate Underpass Structures
• More Costly, but:
• Separated from Streamside Environment
• Can Provide Supplemental Flood
Capacity
Big Dry Creek Tail Underpasses
Sand Creek Greenway
Willow Creek at
Dry Creek Road
Summary Sensitive Routing – Avoid Fills
Be Creative to
Overcome
Problems
Encourage Citizen Participation
Celebrate your Success!
Happy Trails!