Green Infrastructure Retrofit as an alternative to Conventional Stormwater Management

7/30/2019 Green Infrastructure Retrofit as an alternative to Conventional Stormwater Management

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Green InfrastructureretrofitAs an alternative to conventional

stormwater management

Prevention is better than cure. Conventional stormwater management systems

attempts to cure the problem of runoffs after it is created. Whereas the targetshould be to prevent or minimize the generation of stormwater at first place.

Besides providing ample of environmental, social and economic benefits, Green

Infrastructure aims at just that, i.e. reducing volume and velocity of the runoff

generated.

2011

Pranav Mishra

1st sem., M.Tech.

11/28/2011


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Contents

S. No. Title

1 Introduction2 Conventional stormwater management3 Green Infrastructure

4 Green Infrastructure benefits5 Green Ifrastructure measures

6 Roof garden7 Rain garden

8 Vegetated swales

9 Porous pavers10 Contained planters

11 Flow-through planters12 Infiltration planters

13 Rain water harvesting14 Rain barrels and cisterns

15 Disconnecting/redirecting downspout.16 Others

17 conclusion


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List of figures

Figure 1 pervious and impervious surface

Figure 2 components of stormwater

Figure 4 layers of typical roof garden

Figure 3 roof garden

Figure 5 rain garden

Figure 6 Swales

Figure 7 cross section of a swale

Figure 8 pervious pavers

Figure 9 Roadside pervious pavers

Figure 10 Contained planter

Figure 11 Flow-through planter

Figure 12 Cross section of a flow-through planter

Figure 13 Infiltration Planter

Figure 14 Cross section of an infiltration planter

Figure 15 Elements of a typica RWH system

Figure 16 Rain barrels

Figure 17 Method of redirecting downspout

Figure 18 Green parking

Figure 19 Brownfield development

Figure 20 Pocket wetland

Figure 21 Trees and urban forestry

Figure 22 Green streets
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Introduction

Many communities, ranging from highly developed cities to newly developing

towns, are looking for ways to assure that the quality of their rivers,streams, lakes, and estuaries is protected from the impacts of development

and urbanization. Traditional development practices cover large areas of the

ground with impervious surfaces such as roads, driveways, and buildings.

Once such development occurs, rainwater cannot infiltrate into the ground,

but rather runs offsite at levels that are much higher than would naturally

occur. The collective force of such rainwater scours streams, erodes stream

banks, and thereby causes large quantities of sediment and other entrained

pollutants to enter the water body each time it rains.

Figure 1 pervious and impervious surface

In addition to the problems caused by stormwater and nonpoint source

runoff, many older cities, have combined sewage and stormwater pipes

which periodically and in some cases frequently overflow due to precipitation

events. In the late 20th

century, most cities that attempted to reduce sewer

overflows did so by separating combined sewers, expanding treatment

capacity or storage within the sewer system, or by replacing broken or

decaying pipes. However, these practices can be enormously expensive andtake decades to implement. Moreover, piped stormwater and combined

sewer overflows (CSOs) may also, in some cases, have the adverse effects

of upsetting the hydrological balance by moving water out of the watershed,

thus bypassing local streams and ground water. Many of these events also

have adverse impacts and costs on source water for municipal drinking

water utilities.


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Conventional Stormwater Management

Stormwater is rainwater and melted snow that runs off streets, lawns, andother sites. When stormwater is absorbed into the ground, it is filtered and

ultimately replenishes aquifers or flows into streams and rivers. Indeveloped areas, however, impervious surfaces such as pavement and roofs

prevent precipitation from naturally soaking into the ground. Instead, thewater runs rapidly into storm drains, sewer systems, and drainage ditches

and can cause:

Downstream flooding Stream bank erosion Increased turbidity (muddiness created by stirred up sediment) from

erosion

Habitat destruction Changes in the stream flow hydrograph (a graph that displays the flow

rate of a stream over a period of time)

Combined sewer overflows Infrastructure damage Contaminated streams, rivers, and coastal water

Figure 2 components of stormwater

Conventional stormwater management has focused on removing stormwaterfrom a site as quickly as possible to reduce on-site flooding. This has meant


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implementing management techniques, such as curb and gutter and piping

systems, that discharge runoff to the nearest receiving water, to reducepeak runoff discharge rates.

Although this is an efficient way to remove water quickly and prevent on-site

flooding, it has proven to be devastating to downstream waters byincreasing the frequency and magnitude of floods, altering stream channel

morphology (alignment, cross-section geometry, streambed composition)and reducing groundwater recharge, all of which make less water available

for drinking water withdrawal and stream base flows.


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Green Infrastructure

A set of techniques, technologies, approaches and practicescollectively

referred to as green infrastructurecan be used to eliminate or reduce theamount of water and pollutants that run off a site and ultimately are

discharged into adjacent water bodies. As cities move towards sustainable

infrastructure, green infrastructure can be a valuable approach.

Green infrastructure approaches currently in use include green roofs, trees

and tree boxes, rain gardens, vegetated swales, pocket wetlands, infiltration

planters, porous and permeable pavements, vegetated median strips,

reforestation/revegetation, and protection and enhancement of riparian

buffers and floodplains. It can be used almost anywhere soil and vegetation

can be worked into the urban or suburban landscape. This also includesdecentralized harvesting approaches, such as the use of rain barrels and

cisterns to capture and re-use rainfall for watering plants or flushing toilets.

These approaches can be used to keep rainwater out of the sewer system so

that it does not contribute to a sewer overflow and also to reduce the

amount of untreated runoff discharging to surface waters. Green

infrastructure also allows stormwater to be absorbed and cleansed by soil

and vegetation and either re-used or allowed to flow back into groundwater

or surface water resources.

Green infrastructure applications and approaches can reduce, capture, and

treat stormwater runoff at its source before it can reach the sewer system.

Site-specific practices, such as green roofs, downspout disconnections, rain

harvesting/gardens, planter boxes, and permeable pavement are designed

to mimic natural hydrologic functions and decrease the amount of

impervious area and stormwater runoff from individual sites. The

applications and design approaches can also be applied in neighborhood

settings (i.e., green streets) or at larger regional scale (i.e. urban forestry)

to manage stormwater. These applications and approaches can keep

stormwater out of the sewer system to reduce overflows and to reduce the

amount of untreated stormwater discharging to surface waters.

In managing wet weather, green infrastructure practices, like all types of

practices, need to be implemented at multiple scales: site, neighborhood,

and regional or watershed. The most beautifully designed site, even if


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multiple green infrastructure practices are used, may actually result in an

overall increase in impervious surfaces and thus stormwater discharges, if

new or expanded roads, parking lots and commercial development are

needed to serve it. For that reason, we include approaches such as infill,

redevelopment and preserving natural areas in our suite of greeninfrastructure approaches.


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Green Infrastructure Benefits

Green infrastructure has a number of environmental and economic and

social benefits in addition to reducing the volume of sewer overflows and

runoff.

Cleaner Water Vegetation, green space and water reuse reduce the

volumes of stormwater runoff and, in combined systems, the volume of

combined sewer overflows, as well as reduce concentrations of pollutants in

those discharges.

Enhanced Water Supplies Most green infiltration approaches involve

allowing stormwater to percolate through the soil where it recharges the

groundwater and the base flow for streams, thus ensuring adequate water

supplies for humans and more stable aquatic ecosystems. In addition,

capturing and using stormwater conserves water supplies.

Cleaner Air Trees and vegetation improve air quality by filtering many

airborne pollutants and can help reduce the amount of respiratory illness.

Transportation and community planning and design efforts that facilitate

shorter commute distances and the

ability to walk to destinations will also reduce vehicle emissions.

Reduced Urban Temperatures Summer city temperatures can average

10F higher than nearby suburban temperatures. High temperatures are also

linked to higher ground level ozone concentrations. Vegetation creates

shade, reduces the amount of heat absorbing materials and emits water

vapor all of which cool hot air. Limiting impervious surface and using light

colored impervious surfaces (e.g., porous concrete) also mitigate urban

temperatures.

Moderate the Impacts of Climate Change Climate change impacts and

effects vary regionally, but green infrastructure techniques provide

adaptation benefits for a wide array of circumstances, by conserving and

reusing water, promoting groundwater recharge, reducing surface water

discharges that could contribute to flooding. In addition, there are mitigation


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benefits such as reduced energy demands and carbon sequestration by

vegetation.

Increased Energy Efficiency Green space helps lower ambient

temperatures and, when incorporated on and around buildings, helps shade

and insulate buildings from wide temperature swings, decreasing the energy

needed for heating and cooling. Further, diverting stormwater from

wastewater collection, conveyance and treatment systems reduces the

amount of energy needed to pump and treat the water. Energy efficiency not

only reduces costs, but also reduces generation of greenhouse gases.

Source Water Protection Green infrastructure practices provide pollutant

removal benefits, thereby providing some protection for both ground water

and surface water sources of drinking water. In addition, green

infrastructure provides groundwater recharge benefits.

Community Benefits Trees and plants improve urban aesthetics and

community livability by providing recreational and wildlife areas. Studies

show that property values are higher when trees and other vegetation are

present.

Cost Savings Green infrastructure may save capital costs associated with

paving, creating curbs and gutters, building large collection and conveyance

systems, and digging big tunnels and centralized stormwater ponds;

operations and maintenance expenses for treatment plants, pumpingstations, pipes, and other hard infrastructure; energy costs for pumping

water around; cost of treatment during wet weather; and costs of repairing

the damage caused by stormwater, such as streambank restoration.


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Green infrastructure measures

Roofs gardens. Rain gardens Vegetated swales Porous pavers. Contained planters Flow-through planters. Infiltration planters Rain water harvesting. Rain barrels and cisterns. Disconnecting/redirecting downspout.


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Roof garden

Greening of rooftops, by

incorporating plants into thedesign of roofing systems, has

been suggested as a method to

reduce the impacts of stormwater

runoff by reducing the impervious

surface within a developed zone.

The benefits of green roofs

(sometimes called Eco roofs) for

stormwater control include direct

retention of a portion of the

rainfall, and delaying and

decreasing the peak rate of runoff

from the site.

green roofs consist of four distinct layers:

an impermeable roof cover or roofing membrane; a drainage net, lightweight growth media, 3 in.(8 cm), adapted vegetation.

Figure 4 layers of typical roof garden

Figure 3 roof garden


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The drainage layer is an open, highly permeable material that quickly

channels gravitational water off the roof.

Growth media, in addition to providing a suitable rooting zone for

vegetation, is typically a low-density aggregate with high-water holding

capability while also providing good drainage. A lightweight media from 3 -6

in. (8 -15 cm) deep allows for retrofit installation on existing buildings, and

reduces the need for extra structural support in new buildings. Media depth

and porosity play an important role in stormwater retention and plant

growth.

Plants provide shade to the surface below foliage, intercept rainfall, and slow

direct runoff from sloped roofs. Plant size and selection depend on the depth

of the roof overburden (growing media) and local climate, but almost always

consists of winter-hardy, drought-tolerant, perennial plants.

Annual reductions of runoff of 38 -54% and 38 -45% have been reported for

3 in. (8 cm) deep media. A media depth of 2.5 in. (6.5 cm) can retain 40%

of the rain for an individual 2-in. (50-mm) storm.

Benefits

Green roofs offer a practical alternative for new construction and for

retrofitting existing structures.

It is suitable for urban areas where limited space is available to implement

traditional stormwater benefits.

It act as biofilter in reducing pollution content of rainfall.

Reduces urban heat island effect.

Reduces surrounding air temperature by evapotranspiration.


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Rain Gardens

Rain gardens are landscaped depressions thatare either excavated or created with sideslopes. An inlet pipe from or sheet flow over

impervious surfaces conveys stormwaterrunoff into the basin, where it is temporarily

stored until it infiltrates into the ground.

Basins often provide complete onsiteinfiltration for small storm events. Check

dams or weirs can be used to detain the flow.

They can be sized to infiltrate large storms inareas where soils drain well, or they mayrequire a safety overflow or disposal method.

On the surface, a rain garden looks like anattractive garden. It may support habitat for

birds and butterflies, it may be a formallandscape amenity or it may be incorporated

into a larger garden as a border or as anentry feature. What makes it a rain garden is

in how it gets its water and what happens tothat water once it arrives in the garden.

There are two basic types of rain gardens

under-drained and self-contained. Both typesof rain gardens are used to improve stormwater quality, reduce runoff

volumes and generally facilitate infiltration of cleaned water. Which type ofgarden is selected to be built is a balance of volumes of water to be treated,

existing soil conditions, available space, and budget for the project.In some cases where infiltration is not desired, the underdrain system can

move excess water into a conventional storm sewer pipe system. Caseswhere infiltration would not be desirable would be if the bottom of thegarden has less than 4 of clearance to the seasonal mean high water table

or if the adjacent soils are contaminated and the cleaned water from thegarden would become recontaminated by coming in contact with theadjacent native solids.

BenefitsBasins or rain gardens eliminate or dramatically reduce stormwater flow

rates and volumes. They improve water quality by settling and filtering out

Figure 5 rain garden


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pollutants, they recharge groundwater, and they can provide stormwater

storage capacity in a large drainage area. Trees planted in infiltration basinscan shade buildings and parking lots or other paved areas, reducing runoff

temperatures. The vegetation also helps prevent soil erosion, provideswildlife habitat, and is visually attractive. Vegetated infiltration basins can

have an informal or formal design and are easily integrated into the overalllandscape or site design.

VegetationVegetated infiltration basins can be plantedwith a variety of trees, shrubs,grasses, and ground covers. Trees are highly recommended for their shading

and temperature reduction benefits. Avoid permanent irrigation wherepossible. Basins are likely to need watering and weed pulling during the first

one to three years.

Maintenance

Inspect the vegetation and structure periodically and after major stormevents. Vegetation maintenance is similar to that used for other types of

managed landscapes. Maintenance needs include removing sediment anddebris; cleaning and repairing inlets, embankments, berms, dams, and

outlets as needed; controlling erosion; and ensuring proper drainage. Someplant replacement may be necessary. With proper construction and

maintenance, a vegetated infiltration basin can last indefinitely.


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Vegetated Swales

Swales are gently sloping depressions planted with dense vegetation or

grass that treat stormwater runoff from rooftops, streets, and parking lots.

As the runoff flows along the length of the swale, the vegetation slows and

filters it and allows it to infiltrate into the ground. Where soils do not drain

well, swales are typically lined and convey runoff to a drywell or soakage

trench. Swales can include check dams to help slow and detain the flow. A

swale can look like a typical landscaped area.

Figure 6 Swales

Benefits

The plants in a swale filter and slow stormwater runoff while sediments and

other pollutants settle out. Swales are costeffective, attractive and can

provide wildlife habitat and visual enhancements. Single or multiple swale

systems can treat and dispose of stormwater runoff from an entire site.

Swales can reduce the number and cost of storm drains and piping required

when developing a site.

Vegetation

Swales can be planted with a variety of trees, shrubs, grasses, and ground

covers. Plants that can tolerate both wet and dry soil conditions are best.


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Plant grassy swales with native broadleaf, dense-rooted grass varieties.

Avoid trees in areas that require enhanced structural stability, such as

bermed side slopes. Summer irrigation and weed pulling may be required in

the first one to three years.

Maintenance

Inspect swales periodically, especially after major storm events. Remove

sediment and trash, clean and repair inlets, curb cuts, check dams, and

outlets as needed. Maintain side slopes to prevent erosion and ensure proper

drainage. With proper construction and maintenance, swales can last

indefinitely.

Safety and Siting Requirements

Swales should not be located closer than 10 feet from building foundations.

Locate swales at least 5 feet from any property line.

Grade the site so that water drains to the swale, or provide some form of

conveyance such as a trench to direct the runoff into the swale if site

grading is impractical.

Many parking lot planting islands can be excavated and retrofitted into

swale systems with curb cuts.

Figure 7 cross section of a swale


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Pervious pavers

Pervious pavers are typically made of pre-cast concrete, brick, stone, or cobbles.

Pavers usually form interlocking patterns,and are placed within a rigid frame on top

of a sand bed or an under drain system.Sand or gravel fills the gaps between

pavers, allowing water to pass to theunderlying subgrade then infiltrate into the

ground. Some pavers also have small voidsin the pavement surface to increase

permeability. Pervious pavers are available

in many colors, shapes, sizes, and textures,

and can support heavy traffic loads andweights. They can replace conventionalasphalt or concrete paving in parking lots,

roads, and sidewalks.

BenefitsBy infiltrating precipitation, pervious paversreduce stormwater runoff flow rate,volume, and temperature, and filter

pollutants. They help recharge groundwaterand maintain stream base flows. Pervious

pavers may reduce or eliminate the need for an underground storm drainsystem or a curb and gutter system. They are durable and attractive, and

allow great flexibility of design. Pervious paver areas can serve as an

overflow for other stormwater management techniques.

MaintenanceIt is important to control site erosion and sedimentation to prevent clogging.

Annual vacuum sweeping helps maintain permeability. The gaps betweenpavers may require occasional weeding or scorching and sand or gravel

replenishment. Because pervious pavers are easily lifted and reset, they are

easy to repair or replace.

Safety and Siting Requirements

Use over soils that drain well such as gravelly or loamy sand. Do not use pervious pavers in areas with high sediment loads that can clog

pores in the pavement.

Figure 8 pervious pavers


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Pervious pavers are not allowed in areas where hazardous material is

stored or transported.

Figure 9 Roadside pervious pavers


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Contained planters

A contained planter is filled with soil and plants thataccept precipitation only, not stormwater runoff

from another source. It is placed above ground onan impervious surface. Rainwater is temporarily

stored above the soil, and then filters down throughthe planter. In some cases, weep holes provide

drainage through the bottom of the planter onto theimpervious surface. Contained planter boxes can be

prefabricated pots or constructed in place. They

come in all shapes and sizes, are made of stone,

concrete, brick, plastic lumber or wood, and canhold a variety of plants.

BenefitsA contained planter reduces impervious area and

stormwater runoff. Contained planters are simple,cost-effective, and visually appealing. They can beplaced on many types of flat impervious surfaces,

such as sidewalks, plazas, and rooftops.

VegetationPlanters can contain small trees, shrubs, flowers, bulbs, and groundcovers.

Trees are especially recommended because they provide canopy cover forimpervious surfaces not covered by the planter. Self-sustaining plants that

do not require additional fertilizers or pesticides are recommended.

MaintenanceContained planters require minimal maintenance. Check them periodically to

maintain adequate drainage. They are likely to need summer watering andweeding. Potted plants require more water than the same plants growing in

the ground.

Figure 10 Contained planter


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Flow through planters

Flow-through planters are structures

or containers with imperviousbottoms or placed on impervious

surfaces. They do not infiltrate intothe ground. They can be placed in or

above the ground level. Flow-throughplanters are filled with gravel, soil,

and vegetation and are typicallywaterproofed. They temporarily store

stormwater runoff on top of the soil

and filter sediment and pollutants as

water slowly infiltrates down throughthe planter. Excess water collects in aperforated pipe at the bottom of the

planter and drains to a destinationpoint or conveyance system. Flow-

through planters come in many sizesand shapes, and are made of stone,concrete, brick, plastic lumber or wood.

BenefitsBecause flow-through planters can be built immediately next to buildings,

they are idealfor constrained sites with setback limitations, poorly draining soils, steep

slopes, or contaminated areas. Flow-through planters reduce stormwater

flow rates, volume, and temperature, and improve water quality. They canalso provide shading and energy benefits when sited against building walls.

They can be an attractive landscape feature and provide wildlife habitat.

VegetationFlow-through planters can contain a variety of shrubs, small trees, and other

plants appropriate for seasonally moist and dry soil conditions. Summer

irrigation and weed pulling may be required. Minimize the need forpermanent irrigation as much as possible by using native and well-adaptedplants.

Maintenance

Inspect plants and structural components periodically. Maintenance is similarfor all container

Figure 11 Flow-through planter


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plantings. Other maintenance needs may include removing sediment,

cleaning and repairing pipes, and maintaining proper drainage. Downspouts,curb cuts, and other features where debris may obstruct flow must be

inspected and cleaned periodically.

Safety and Siting Requirements Flow-through planters are recommended for compact sites because theirsize can vary.

An approved overflow to a proper destination disposal point is required. Flow-through planters can be located next to building foundations or in

other situations where infiltration is a concern. They are ideal for sites with soil that does not drain well, and are suitable

to all soil types.

Figure 12 Cross section of a flow-through planter


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Infiltration Planters

Infiltration planters are structures or

containers with open bottoms to allowstormwater to slowly infiltrate into the

ground. They contain a layer of gravel, soil,and vegetation. Stormwater runoff

temporarily pools on top of the soil, and thenslowly infiltrates through the planter into the

ground. Infiltration planters come in manysizes and shapes, and are made of stone,

concrete, brick, plastic lumber, or wood.

Infiltration planters are not recommended for

soils that dont drain well. Use flow-throughplanters instead.

BenefitsInfiltration planters are ideal for space-

limited sites with good drainage. They reducestormwater runoff flow rate, volume,temperature and pollutants, and rechargegroundwater. Infiltration planters can be

attractive, and are easily integrated into theoverall landscape design. They can also

provide energy benefits when sited near building walls.

Vegetation

Infiltration planters can contain a variety of shrubs, small trees, and otherplants appropriate for seasonally moist and dry soil conditions. Avoid

permanent irrigation if possible. Planters are likely to need watering andweeding in the first one to three years.

Maintenance

Inspect plants and structural components periodically. Remove sediment and

clear debris from inlet pipes and curb cuts to maintain proper drainage.

Figure 13 Infiltration Planter


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Safety and siting requirements

Locate planters at least five feet from any property line. Infiltration planters are only suitable for soil types that drain well.

Place them flush to the ground or above it. An approved overflow to a proper destination point is required.

Figure 14 Cross section of an infiltration planter


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Rain water harvesting

Rainwater harvesting, collecting rainwater from impervious surfaces and

storing it for later use, is a technique that has been used for millennia. It hasnot been widely employed in industrialized societies that rely primarily on

centralized water distribution systems, but with limited water resources andstormwater pollution recognized as serious problems and the emergence of

green building, the role that rainwater harvesting can play for water supplyis being reassessed.

Rainwater reuse offers a number of benefits.

Provides inexpensive supply of water; Augments drinking water supplies; Reduces stormwater runoff and pollution; Reduces erosion in urban environments; Provides water that needs little treatment for irrigation or non-potable

indoor uses; Helps reduce peak summer demands; and Helps introduce demand management for drinking water systems.

Rainwater harvesting has significant potential to provide environmental andeconomic benefits by reducing stormwater runoff and conserving potable

Figure 15 Elements of a typica RWH system


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water, though several barriers exist that limit its application. Rainwater

harvesting systems typically divert and store runoff from residential andcommercial roofs. Often referred to as clean runoff, roof runoff does contain

pollutants (metals or hydrocarbons from roofing materials, nutrients fromatmospheric deposition, bacteria from bird droppings), but they are

generally in lower concentrations and absent many of the toxics present inrunoff from other impervious surfaces. Installing a rainwater collection

system requires diverting roof downspouts to cisterns or rain barrels tocapture and store the runoff. Collection containers are constructed of darkmaterials or buried to prevent light penetration and the growth of algae.From the storage container, a dual plumbing system is needed for indoor

uses and/or a connection to the outdoor irrigation system.


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Rain barrels and cistern

A rainwater barrel is a water tank

used to collect and store rain waterrunoff, typically from rooftops via

rain gutters. Rainwater tanks are

devices for collecting and

maintaining harvested rain.

Rainwater tanks are installed to

make use of rain water for later use,

reduce water use from mains for

economic or environmental reasons,

and aid self-sufficiency. Storedwater may be used for watering

gardens, agriculture, flushing toilets,

in washing machines, washing cars,

and also for drinking, especially

when other water supplies are

unavailable, expensive, or of poor

quality.

Rainwater tanks can also be used for retention of stormwater for release at alater time. In arid climates, rain barrels are often used to store water during

the rainy season for use during dryer periods.

Rainwater tanks may have a high initial cost. However, many homes use

small scale rain barrels to harvest minute quantities of water for

landscaping/gardening applications rather than as a potable water surrogate.

These small rain barrels are often inexpensive. There are also many low cost

designs that use locally available materials and village level technologies for

applications in developing countries where there are limited alternatives for

potable drinking water. While most are properly engineered to screen out

mosquitoes, the lack of proper filtering or closed loop systems may create

breeding grounds for larvae. With tanks used for drinking water, the user

runs a health risk if maintenance is not carried out.

Figure 16 Rain barrels


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Downspout disconnection

If managed properly, the water that flows off rooftops can help keep lawns

and gardens green while lowering utility bills during spring and summermonths. However, most downspouts send rainwater down driveways,

sidewalks, and underground pipes that lead to storm drains or sanitarysewer lines.

This "stormwater runoff" picks up pollutants from motor oil, lawn chemicals,

and pet waste along the way, before entering lakes and streams untreated. The large amount of untreated water entering the storm sewer

system and eventually our streams and lakes has lasting health, safety,

environmental and economic impacts on communities. Fortunately, there are

many things can be done to put rainwater to good use while reducing theamount of stormwater runoff that ends up in local waterways.

The problem with pavementDuring the construction of homes, roads and office buildings vegetation is

often removed and replaced by large paved areas. These surfaces keep rainfrom infiltrating the soil and recharging groundwater supplies. The infiltrationprocess helps clean water and feed the underground springs that supplydrinking water.

Paved surfaces also increase the speed and amount of water that rushes intostreams, causing stream bank erosion and harming wildlife habitats. Direct

the flow of water from downspouts away from paved surfaces wheneverpossible.

Combined sewer overflowsCombined sewers are older systems that carry both stormwater and

wastewater to treatment plants. When rainstorms fill combined sewersbeyond capacity, the result is a Combined Sewer Overflow a discharge of

untreated wastewater and stormwater into local waterways. Combinedsewers are costly to replace and still used in older areas of the region.

Residents are encouraged to disconect downspouts from sewer pipes or

redirect downspouts to grassy areas or gardens to reduce the rain thatenters sewers.

Disconnecting downspoutDownspouts that connect directly to sewer pipes increase the risk of sewer

overflow and flooding. Disconnecting your downspout from a sewer intake


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pipe (standpipe), then redirecting the flow of water to a grassy area or

garden is a simple process that makes a big difference to the environment.

Figure 17 Method of redirecting downspout


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Other measures

Figure 19 Brownfield development

Figure 18 Green parking

Figure 22 Green streets

Figure 21 Trees and urban forestry

Figure 20 Pocket wetland


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Conclusion

Stormwater sewer systems are necessary in urban and suburban

environments where substantial amounts of impervious surfaces (e.g.,buildings, pavement) have replaced natural pervious surfaces (e.g., soil,

wetlands) that once absorbed storm precipitation. It is estimated that atypical city block generates over five times the amount of surface runoff as a

wooded area of the same Size.Using green infrastructure not only reducespressure on existing stormwater system, but simultaneously helps in

maintaining healthy environment. We all are aware of the grave situationour environment is in today and hence it is not advisable to go for

conventional stormwater management system alone for new development,

which tries to alter the natural process of ground infiltration by carrying

water through piping systems. Besides it also fails to carry the runoff loadduring peak hours, leading to water logging. The situation becomes worse atplaces where combined sewer system is in practice. As overflow there means

soiled and contaminated, untreated water on street posing serious healthrisks to peoples. Hence, using stormwater management system in sync with

green infrastructure practices allows to manage stormwater by nauralprocess while still enjoying the benefits of conventional stormwatermanagement.


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References

http://teknologimalaysia.academia.edu/NoradilaRusli/Papers/580758/LOW_IMPACT_DEVELOPMENT_AN_APPROACH_TO_RETROFIT_A_CONVENTIONAL_STORMWATER_MANAGEMENT_SYSTEM

http://des.nh.gov/organization/divisions/water/stormwater/documents/wd-08-20a_ch3.pdf

http://www.lowimpactdevelopment.org/raingarden_design/whatisaraingarden.htm

http://www.marc.org/Environment/Water/downspout.htm http://www.marc.org/Environment/Water/rainbarrels.htm http://www.crwa.org/projects/bmpfactsheets/crwa_stormwater_plante

r.pdf

http://www.cnt.org/repository/GreenInfrastructureReportCivicFederation%2010-07.pdf

Documents

Green Infrastructure Retrofit as an alternative to Conventional Stormwater Management