Map Reading 201 Where Does the Water Go?? - …clear.uconn.edu/lua/publications/hottopics1/Map 201...
Transcript of Map Reading 201 Where Does the Water Go?? - …clear.uconn.edu/lua/publications/hottopics1/Map 201...
Map Reading 201: Where Does the Water Go??
A Key Skill for Land Use Commissioners
Today’s Presenters:
John Rozum, NEMO ProgramPaula Stahl, Green Valley Institute
As the map is rolled out at the P&Z meeting ...
Wonder what those lines
mean?
Where is this ?
I’m hungry.
Oh, geeze I’ll never get home in time for the
game
Map Reading 101 …..
Topics requested:Stormwater SystemsGrading and DrainageCut and FillRoad DesignDesign Guidelinesand more …
201
Stormwater BasicsPlan Reading for Stormwater
Conventional SystemsAlternatives
Today’s Topics:
Map Reading 201 Interconnected Systems
Interconnected Systems Interconnected Systems
Interrupted Systems
Stormwater: Water from rain or melted snow that cannotbe absorbed into the ground where it falls
onto impervious surface …..streets and roadsparking lotsroof-tops
GOAL:
Minimize impacts from non-point pollution, Control down stream erosion and flooding, and Preserve the natural hydrologic cycle
Stormwater Management Plans
Stormwater Systems: The Options
Conventional
Low Impact
Stormwater Systems: Conventional
Streets and Roads
Parking Lots
Rooftops
Collect
Convey
Centralized
Cs
Stormwater Systems: ConventionalCollect
ConveyCentralized
Stormwater Systems: Conventional
Most municipal systems
Collect
Convey
to a Centralized
Stream
Plan Reading - Tips
Water flows downhill...
Plan Reading - Tips
Water flows downhill...
so …the direction of flow is always perpendicular to the contour lines, since this is the steepest slope.
Roads Roads
Roads
42
4141
Existing TopoExisting Topo42
Roads
42
4141
42
Crowned
Cross sloped
Two basic designs
Roads
20 18 16 14 12
20 18 16 14 12
Roads
0+00 6+00 11+55500496492488484480476472468
Distance is 1155’ Change in Elevation is 26’ (494-468) Slope =2.25%
vertical scale increased to show detail
20’
Roads
0+00 6+00 11+55500496492488484480476472468
Distance is 1155’ Change in Elevation is 26’ (494-468) Slope =2.25%
Parking Lots
Stormwater Collection & Conveyance Stormwater Collection & Conveyance
Plan Review Stormwater System
Water flows downhill...
Plan Review Stormwater System
But sumps aren’t
perfect...
Plan Review Stormwater System
INV or Invert where storm water enters catch basin
OUT or Outlet where storm water leaves catch basin
Bottom of Invert pipe usually is even with top of Outlet pipe
TF Top of Flange, oraka Rim or CBR
Plan Review Stormwater System
TF 609.10
EO 600.50
BP 559
Question: Any concerns?
System Schematic
Rooftops Rooftops
Collect
Convey
Centralized
Rooftops Rooftops
As the map is rolled out at the P&Z meeting ...
Oh, that LUA workshop is
going to come in handy!
Plan Reading Tip … take ownership!
I bet there’s a better way.
Interconnected System
Why Stormwater Matters
More Runoff
Arriving Faster
Stormwater Systems: ConventionalCollect
ConveyCentralized
C’s
Stormwater Systems: Low Impact
Distributed
Disconnected
De-centralized
3Ds
Stormwater Systems: a better approach
Low Impact Development (LID):A site design strategy intended to maintain or replicate a site’s natural hydrology systems through the use of small-scale controls integrated throughout the site to manage runoff as close to its source as possible
LID…Connecticut-style
TraditionalTraditional
LID ClusterLID Cluster
Glen Brook Green (Jordan Cove)Research/Demo Project
Glen Brook Green (Jordan Cove)Research/Demo Project
12 Lots on 4 acres with 6.3 acres open space
Using many LID strategies
Low-mow areas
Bio-retentioncul-de-sac
Shared Driveways& Porous Pavers
Grass swales
Bio-retentiongardens
Street 24’ wide, loop 16’ wide
Subdivision – Jordan Cove
But Does It Work?
Traditional LID
More Runoff
Arriving Faster
Adapted from J. Clausen, UConn
Jordan Cove Monitoring ResultsBefore vs. after construction
LIDLID Traditional
Flow
Nitrogen
Phosphorus
Metals
TSS nc
The big picture: LID significantly reduced flow and pollutant export!!
A “NEW” Way to Deal with Stormwater
The “Runoff Reduction” MethodStrategy includes:
1. Minimizing disturbance through Environmental Site Design
2. Runoff Reduction Practices
3. Pollutant Removal Practices
Runoff Reduction Methods
Minimizing disturbance through EnvironmentalSite Design
1. Site Design that Minimizes Impervious Cover &Soil Disturbance
2. Conservation of Forested Areas
3. Reforestation of Cleared Areas
Runoff Reduction Practices
Pollutant Removal Practices
Environmental Site Design
• Cluster design
• Zoning regulations to limit site clearing
Environmental Site Design
• Buffer streams and wetlands
Protects water bodies from development impacts
Research shows that buffers can mitigate the effect of impervious surfaces, up to about 15% IC*
In addition, there are many benefits beyond water quality
*Schueler, et al. 2008. Chesapeake Stormwater Network
Minimize disturbance
Reduce impervious cover
Use porous pavement on walks and overflow parking areas
Environmental Site Design
Decrease pavement requirements
Runoff Reduction Methods
Minimizing disturbance through EnvironmentalSite Design
Runoff Reduction Practices1. LID Practices2. Rooftop Disconnect3. Sheet flow to Conserved Open Space
Pollutant Removal Practices
Low Impact Development
Pervious parkingGrass swales
Green roofs Bioretention (rain gardens)
Rain Barrels/Cisterns
Interrupt sheet flow
Reduce Runoff Practices
Runoff Reduction Methods
Minimizing disturbance through EnvironmentalSite Design
Runoff Reduction Practices
Pollutant Removal Practices1. Filtering Practices2. Constructed Wetlands3. Wet Ponds4. Wet Swales5. Many LID Practices
Low Impact Development Practices
• Bioretention/Rain Gardens
• Vegetated Swales, Buffers, and Filter Strips
• Permeable Pavements
• Dry Wells/Leaching Trenches
• Rainwater Harvesting
• Vegetated Roof Covers
LID Practices
• Bioretention/Rain Gardens
Ponding area
Overflow pathSoil, mulch and plants
Flow entrance
Vegetated areas designed to infiltrate and process stormwater
Key Bioretention Concepts Rules of Thumb:
• No closer than 10’ to building foundation• Basin depth should handle first 1” of runoff• Inflow and outflow need to be detailed• Soil “perc” should be tested and verified before
construction• Planting plan should specify appropriate plants
From 2004 CT Stormwater Quality Manual
Runoff Reduction: 40-80%
Pollution Reduction: 25-50%
Runoff Reduction: 40-80%
Pollution Reduction: 25-50%
Important factors with bioretention
• Infiltration capacity of native soils• Underdrain
– Recommended in Bioretention Manual & CT SWQM
– May not always be necessary– Depends on local soil conditions
Design variation: high sediments
• Heavy sediment loading may clog infiltrating surface of bioretention
• A grass filter strip or sediment forebay can be installed to reduce this impact
Design variation: “hot spots”• “Hot spots” are areas with high loadings
of certain pollutants• Impervious liner can be installed and pipe
access can be provided (MD Bioretention Manual)
Design variation: low permeability soils
• Extra storage can be gained by installing crushed stone below the underdrain (MD Bioretention Manual)
Important factors with Bioretention• Seasonal high water table• Soil compaction before, during construction
Important factors with bioretention
• “Over-Engineering”
Low Impact Development Practices
• Bioretention/Rain Gardens
• Vegetated Swales, Buffers, and Filter Strips
• Permeable Pavements
• Dry Wells/Leaching Trenches
• Rainwater Harvesting
• Vegetated Roof Covers
Water Quality Swales
Road is crowned to direct water to edges Stormwater infiltrates into the swale
Benefits:• Promote infiltration• Most effective sediment removal• Installation cost comparable to piped system• Easier to maintain and troubleshoot
LID RoadsRunoff Reduction: 40-60%
Pollution Reduction: 20-40%
Runoff Reduction: 40-60%
Pollution Reduction: 20-40%
LID Road
ROW
Portland Oregon
LID Roads Key LID Subdivision Concepts
Types of SwalesGrass ChannelDry Water Quality Wet Water Quality
Rules of ThumbNeed grades of 5% or lessWide ‘bottom’ and gentle side slopes
In summary…• We have drastically altered the hydrologic
cycle
• “Traditional” treatment practices really don’t help much
• Proper S.W. Management starts with Site Design
• LID practices work, they enhance aesthetics, increase property values, and can cost less!!
Resources to help you…
Connecticut Stormwater Quality Manual
Planning
Design
Sizing
Specifications
Model Regulations
Resources to help you…
Jordan CoveResearch and Demonstration
Project
http://jordancove.uconn.edu
Resources to help you…
http://nemo.uconn.edu/tools
I know there’s a better way
Now I really want to
know where this is
Swales are swell !
To heck with the game, I’m rooting
for LIDs
The next time a map is rolled out …..