Green design retrofit as an alternative to conventional storm-water management


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Green design retrofit as an alternative to conventional storm-water management

  1. 1. Green Infrastructure Retrofitas an alternative toConventional Stormwater ManagementSubmitted by : Pranav Mishra , M.Tech. 1st semester, RCGSIDM, IIT Kharagpur Page 1
  2. 2. Introduction•Stormwater –Water that originates from precipitation events.•Surface runoff -Stormwater that does not soak into ground.•Stormwater pollution –Runoff picks up sediments and pollutants in it’s flow pathand carry these to recieving water boodies. Page 2
  3. 3. Why…? •Instant flooding •Increased turbidity •Habitat destruction •Downstream flooding •Steam bank erosion Page 3
  4. 4. How…? Conventionally stormwater management focussed on – •Collecting stormwater in piped networks. & •Transfering it off site, as quickly as possible. to •Directly a stream or river. •Stormwater basin. •Combined sewer wystem. By implementing techniques such as •Curbs •Gutters •Piping systems Page 4
  5. 5. Problems…? Conventionally stormwater management is efficient to prevent on site flooding, but has proven devastating to downstream waters by – •Increasing magnitude of flood. •Reduced ground soaking. •Increased frequency of floods. •Altering stream channel. Because it rely on – •Conveyance efficiency. •End of pipe treatment. Hence key to effective management is to reduce the stormwater generated at first place. Page 5
  6. 6. Green Infrastructure It is management approach and technology that utilise, enhance and mimic the natural processes for reducing impact of stormwater by •Reducing the quantity of stormwater generated. •Reducing the speed. •Reducing the polution. Page 6
  7. 7. Benefits of Green Infrastructure Not only environmental friendly and sustainable but cost effective as well. Environmental - improve air quality replenish ground water flood protection restore nature Economic - reduces hard infra construction cost reduces energy consumption increases life cycle cost saving increases land value Social - enhanced liveability additional recreational space urban heat island mitigation public role in sustainable stormwater management Page 7
  8. 8. Green measures •Green roofs •Rain garden •Vegetated swales •Porous pavements •Contained planters •Flow through planters •Infiltration planters •Rain water harvesting •Rain barrels and cistern •Disconnect/redirect downspout Page 8
  9. 9. Green roofs•It reduces impervious surfacewithin a developed zone.•Decreases and delays peakflow rate by retaining someportion of rainfall.•It is found that 8c.m. deepmedia reduces runoff by upto50% Page 9
  10. 10. Green roofsBenefits – •A practical alternative for new construction and retrofitting existing structures. •Suitable for urban areas where limited space is available to inplement conventional system. •Reduces pollutant content of rainfall. •Reduces heat island effect. •Reduces surrounding air temperature by evapotranspiration. Page 10
  11. 11. Rain garden (Infiltration basin)•These are landscaped depressionsthat are either excavated or createdwith slope on sides.•Located close to source of runoff •To slow down stormwater. •Reduce it’s erosive power. •Less oppertunity to gain momentum.•Designed to withstand extrememoistures and concentration ofnutrients. Page 11
  12. 12. Rain garden (Infiltration basin)•Surface of garden is designed toallow hydrologic action of healthyforst. •Water is not only absorbed but cleaned as well.•These are self-contained raingarden.•If bottom has <4’ clearance toseasonal mean high water level,•Or, if adjacent soil are highlycontaminated, •Infiltration is undesired.•These are calledunder-drained rain garden. Page 12
  13. 13. Vegetated swales•Gently sloping depressionsplanted with dense vegetation.•As the runoff flows along thelength of the swale, thevegetation slows and filters itand allows it to infiltrate into theground.•These also convey runoff to drywells or soaking trench.•Sometimes it also includescheck dams to slow down anddetain the flow. Page 13
  14. 14. Vegetated swales•Some benefits of swales are •Reduced volume of runoff •Reduced speed •Natural infiltration •Ground water replenishment. •Attractive •Cost effective. Page 14
  15. 15. Pervious pavers•Pervious pavers are usuallymade of pre-cast concrete, brick,stone or cobbles.•These are placed within a rigidframe on top of a sand bed andform inter-locking patterns.•Sand and gravels fills gapsbetween pavers, allowing waterto pass through.•It can support heavy trafficloads and weights.•Can be used as replacement forconventional asphalt or concretepaving in parking lots, roads andsidewalks. Page 15
  16. 16. Pervious pavers•Benefits •Reduces stormwater runoff flow rate and volume. •Help recharge ground water. •Reduces the need for under- ground drain system. •Durable, attractive.•Maintenance •They are easy to repair and replace. •Require occassional weeding or vaccum sweeping or sand and gravel replacement to maintain permeability. Page 16
  17. 17. Contained planters•These are containers withimpervious bottoms.•They do not infiltrate into theground.•It accepts precipitation only andno runoffs from other sources.•Sometimes weep holes areprovided at bottom to drain outexcess water.•They can be placed anywhere onimpervious surface.•Attractive landscape feature. Page 17
  18. 18. Infiltration planters•These are structures with openbottom to allow stormwater toinfiltrate into the ground.•These are made of stone,concrete, brick, plastic or wood.•Runoff temporarily pools of ontop of soil and then slowlyinfiltrates.•Not recommended for soils thatdon’t have good drainage.•Ideal for sites with limitedspace.•Attractive landscape feature. Page 18
  19. 19. Flow through planters•These are structures withimpervious bottoms.•They do not infiltrate into ground.•These are filled with gravel, soiland vegetation and are typicallywaterproofed.•These temporarily store runoff ontop of soil and filter pollutants as itinfiltrates down to bottom.•Excess water passes through aperforated pipe at bottom to aconveyance syatem.•Ideal for constrained sites withpoorly draining soils.•Attractive landscape feature. Page 19
  20. 20. Rain water harvesting•Rain water harvesting systemcollects water runoff fromimpervious surfaces and stores itfor a later use while allowing forexcess water to infiltrate into theground.•Provides inexpensive supply ofwater.•Reduces stormwater runoff andpollution.•Reduces load on seweragesystem.•Reduces erosion.•Reduces peak summer waterdemands. Page 20
  21. 21. Rain barrels & cisterns•These are the containers that collects & storesrainwater from downspouts and roof tops for futureuse of washing lawns and gardening. Page 21
  22. 22. Disconnect/redirect downspout•Most of downspouts sends rainwater off roof todriveways, sidewalks or underground drainage pipes.•Large paved areas around the building prohibitsinfiltration.•Increases load on conventional drainage system.•It is advisable to diconnect downspout from sewerconnections and redirect them to open lawn or grassareas. Page 22
  23. 23. Urban forestryOther measures Green highways Brownfield development Pocket wetlands Green parking Page 23
  24. 24. Barriers in implementation•Though these techniques are not new, these arestill considered innovative due to several potentialbarriers. •Cost concerns. •Lack of confidence. •Site constraints. •Maintenance concerns. •Conflicting local by-laws. Page 24
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  26. 26. References•••• garden.htm••• r.pdf Page 26