Restoring Natural Drainage System of Delhi


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Restoring Natural Drainage System of Delhi

  1. 1. Restoring Natural Drainage Systems of Delhi
  2. 2. Advantages of having natural drainage systems 1. Support of riparian and wetland vegetation. 2. Creation of habitat for wildlife and aquatic species. 3. Slowing down and attenuating floodwater by spreading out flows over vegetated overbanks. 4. Promotion of infiltration and groundwater recharge. 5. Enhancement of water quality. 6. Provision of corridors for trails and open space. 7. Enhancement of property values and quality of life.
  3. 3. FUNCTIONS AND BENEFITS OF HEALTHY STREAMS Source: Douglas County Storm Drainage Design and Technical Criteria Manual
  4. 4. IMPACTS OF STREAM DEGREDATION Source: Douglas County Storm Drainage Design and Technical Criteria Manual
  5. 5. Adverse affects of Destroying natural drainage systems 1. Environmentally bad decision as the problem gets out of sight-out of mind-not solving the problem! 2. The concrete slab effectively stops groundwater recharge. 3. The slab cover over the nala shall aggravate the ‘heat island’ effect. 4. The siltation in the drain shall become difficult and more expensive to manage and would require specialised super-suction machines. 5. The sewage being carried by the drain shall be deprived of sunlight and oxygen, creating septic conditions and effectively increase the pollution load on the river.
  6. 6. Alternatively… 1. The drains could use on-line decentralised biological wastewater treatment to treat the waste water and reuse the same for irrigation and create a landscaped parkway like ‘OSHO PARK’ in Pune. 2. The sanitised drain then could be used for creating picnic hubs, jogger’s park, a NMT connection to achieve interconnectivity between various residential neighbourhoods, etc. Before Case example: Osho Park, Pune After
  7. 7. Delhi….
  8. 8. Delhi….
  9. 9. Barapullah Nallah corridor - Before
  10. 10. Barapullah Nallah corridor - After
  11. 11. Undo the mistakes.… Restoration/Daylighting of Natural Drainage systems Daylighting refers to projects that uncover and restore streams and rivers previously buried in underground pipes and culverts, covered by decks, or otherwise removed from view. Source:
  12. 12. Case example: San Antonio, Texas
  13. 13. Case example: Seoul, South Korea Reclamation of Cheong Gye Cheon river “Seoul peels back concrete to let a river run freely once again”
  14. 14. Cheong Gye Cheon river stream- Before
  15. 15. Cheong Gye Cheon river stream- After
  16. 16. Timeline of Cheong Gye Cheon river stream Named Cheong gye cheon meaning clear water stream Construction of road/ highway/freeway over polluted streams 1970 1300 2011 1945 Shanty towns along polluted & open sewage channels for city Stream restored to its ecological function
  17. 17. Timeline of Delhi water channels Settlement along water channel Construction of road/ highway over polluted streams 2010 1200 1945 Slums along natural drainage channels & open sewage channels for city ------- ?
  18. 18. Policy principles required… Source: Urban Drainage and Flood Control District (Colorado), 2001 A natural drain policy must highlight followed principles; 1. Drainage is a regional phenomenon that does not respect the boundaries between government jurisdictions or between properties. 2. A storm drainage system is a subsystem of the total urban water resource system. 3. Every urban area has an initial and a major drainage system, whether or not they are actually planned and designed. 4. Runoff routing is primarily a space allocation problem. 5. Planning and design of storm water drainage systems generally should not be based on the premise that problems can be transferred from one location to another. 6. An urban storm drainage strategy should be a multi-objective and multi-means effort. 7. Design of the storm water drainage system should consider the features and functions of the existing drainage system. 8. In new developments, attempts should be made to reduce storm water runoff rates and pollutant load increases after development to the maximum extent practicable. 9. The storm water management system should be designed, beginning with the outlet or point of outflow from the project, giving full consideration to downstream effects and the effects of off-site flows entering the system. 10. The storm water management system should receive regular maintenance. 11. Floodplains need to be preserved whenever feasible and practicable. 12. Reserve sufficient right-of-way to permit lateral channel movement whenever the floodplain is contained within a narrow natural channel. Urban Drainage and Flood Control District (Colorado), 2001
  19. 19. Strategy for protecting and restoring storm water channels Create City level Watershed Management Plan (WMP) and Urban Drainage Master Plan Typical Watershed Map of a City, with multiple watersheds Watershed map using Digital Elevation Model (DSSDI)