Map Reading 201 Where Does the Water Go?? - …clear.uconn.edu/lua/publications/hottopics1/Map 201 Nov1 Final.pdf · Map Reading 201: Where Does the Water Go?? A Key Skill for Land

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


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



But sumps aren’t

perfect...


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


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


• 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


Decrease pavement requirements



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 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


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%



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


• 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%




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


Jordan CoveResearch and Demonstration

Project

http://jordancove.uconn.edu


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 …..

Map Reading 201 Where Does the Water Go?? - …clear.uconn.edu/lua/publications/hottopics1/Map 201 Nov1 Final.pdf · Map Reading 201: Where Does the Water Go?? A Key Skill for Land

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