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Stormwater Management and Elements of

Low Impact Development

Protecting Our Water Resources – An Ecological

Approach to Land Care & Design

Chatham Community CenterNovember 16, 2013Rich Claytor

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Today’s Agenda

• The basics of stormwater and watershed management

• The evolution of stormwater management towards Low Impact Development(LID)

• Examples of LID Practices

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Stormwater basics

http://planetearth.nerc.ac.uk/features/story.aspx?id=668

Watershed Hydrology What is a watershed?A: a building for water storage

B: the land area that drains to a given water body

C: a shack from which fishing occurs

D: a moment in time when you cross into a new area

E: a new way of organizing environmental agencies

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Stormwater basicsUrbanization results in

increased surface runoff

BEFORE AFTER

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Components of Impervious Cover in the Urban Landscape

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Stormwater basics

At ~10% impervious we begin to see: •Water quality issues•Impacts to biological communities•Increased flooding•Stream erosion•Loss of recreational uses•Shellfish bed closures•Reduced baseflow and recharge

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Community Planning

LID Site Design

LID BMPs

Large Conventional BMPs

Receiving Waters

Low Impact Development (LID)

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LID Site Planning and Design Approach

Objective - to provide a process by which LID is considered at an early stage in the planning process to prevent stormwater impacts rather than mitigate them.

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AVOIAVOIDD

REDUCE

REDUCE MANAGEMANAGE

AVOID

AVOID

REDUCEREDUCE MANAGE

MANAGE

MANAGEMANAGE

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Low Impact Development (LID)

• Site fingerprinting– Preserve natural areas– Retain key pervious areas

• Residential– Narrow streets– Alternative turnarounds– Smart sidewalks – Shared driveways– Reduced setbacks– Open section roads– Downspout disconnection

• Non-residential– Pervious spillover parking– Maximum parking ratios– Shared parking– Reduced stall dimensions

Traditional Design LID• Mass clearing and

grading– Loss of trees– Compaction of native soils

• Residential– Wide streets and cul-de-sacs– Sidewalks to nowhere– Lots of turf– Curb and gutter– Ponds

• Non-residential– Big parking lots– Minimum parking ratios– Large stall dimensions

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Low Impact Development (LID)

Site Design

Traditional LID

BMPs

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Traditional controls

• Goal: Get the water out of here as fast as possible

• Collect and storage in big, “hole in ground” off-site

• Pipe discharge to a stream or wetland

• Limited water quality treatment and infiltration

• Stormwater is a waste product

LID controls• Goal: Reduce the amount of

surface runoff by reducing impervious cover and preserving natural areas

• Rely on small, distributed on-site practices

• Infiltrate or reuse as much as possible; filter before discharge

• Source controls to minimize pollution

• Stormwater is a resource

Low Impact Development (LID)

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Which of these is not LID?A

B

C D

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Which of these is not LID?

A

C D

B

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Which of these is not LID?

A B

C D

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Which is not considered LID?

A B

C D

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LID Practice Library: Bioretention

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• Bioretention Retrofit

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LID Practice Library: Bioretention

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LID Practice Library: Bioretention

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LID Practice Library: Rain gardens

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LID Practice Library: Planters

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LID Practice Library: Tree pits

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LID Practice Library: Porous Pavement

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LID Practice Library: Porous Pavement

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LID Practice Library: Infiltration

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LID Practice Library: Infiltration

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LID Practice Library: Green/blue roofs

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LID Practice Library: Green/blue roofs

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LID Practice Library: Swales

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LID/GI Practice Library: Gravel wetlands

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Resources

There are many…

• MA Smart Growth/Smart Energy Toolkit

• MAPC LID checklist

• Town of Franklin Best Development Practices Guidebook

• RI Community LID Site Planning and Design Guidance Document

• Better Site Design Handbook (CWP)

• NH Innovative Land Use Planning Techniques

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Questions?