New version of fes ppt


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New version of fes ppt

  1. 1. UNDERSTAND THE OCCURRENCE OFFLOODING IN THE NORTH NEWTERRITORIES Li Tsun Sang 52621940 Ng Tsz Wa 52622020 Chow Lai Yin 52621822 Tam Chun Man 52379840 Lam Kwok Tung 52610985
  2. 2. WHAT IS FLOODING ?• surface water > carrying capacity of the channel• exceed bankfull stage•inundation occurs at flat ground (flood-plain)alongside the river banks
  3. 3. MAGNITUDE OF FLOODING IN HKBlackspot Scales: Major - affecting area > 100 Medium - affecting hectares area > 10 hectares Small - affecting  serious  significant Minor - area >0.25 hectares  agricultural property socio- affecting area < damage , damage/ economic isolated serious 50x50m (0.25 property traffic disruption hectare)  damage/ traffic disruption minor public nuisance and disruption inconvenienc Source: e DSD
  6. 6. COMING UP NEXT … Rainfall Natural factors Catchment1. Causes of flooding features Human influence2. Measures taken by government to tackle flooding3. Evaluation of gov.’ s effort and suggestion
  7. 7. RAINFALL
  8. 8. BACKGROUND• Humid subtropical climate condition Located at northern hemisphere Close to equator• Many typhoons and rain band Heavy and more rainfall
  9. 9. SEASON OF RAINFALL• Summer is a rainy season• some regions in northern N.T. and low-lying area cause serious flooding the drainage system is overloaded.
  10. 10. OTHER FACTORS OF HEAVYRAINFALL•Global warming El nino La nina
  11. 11. OTHER FACTORS OF HEAVYRAINFALL .rainfall (mm) Year of El nino Year of La nina Normal Year Increase annual rainfall by El nino and La nina
  12. 12. OTHER FACTORS OF HEAVY RAINFALL Rainfalls intense More easily to cause flooding especially in northern N.T
  15. 15. CATCHMENT FACTOR OF NORTH DISTRICT• Hong Kong has no large rivers.• The larger rivers are mainly in the northwest, including: Shan Pui River, Shenzhen River, Kam Tin River, Sheung Yue River, and Ng Tung River.• Mountain• Low lying
  16. 16. THE REASON OF FLOODING INNORTH DISTRICT Private land developer and government continue change the use of land in north Land area use to dredge water greatly reduces due to the reconstruction of land. In order to continence the work of drain flooded, government connect the drains directly from Sheung Shui, Fanling Town Centre to Ng tung river
  17. 17. THE STRUCTURE OF RIVER IN HONGKONG Rivers in Hong Kong are generally short and small, without a distinctive middle course. Upper course - steep, many narrow, V-shaped valleys are formed by the prevailing downward erosion Lower course - flat terrain, it is easy cause flooding
  18. 18. SHAPE OF RIVER BASIN IN HONGKONG From the distribution of tributary(river), three kind of shape are list below : Dendritic Drainage Pattern Rectangular Drainage Pattern Radial Drainage Pattern
  19. 19.  Dendritic Drainage Pattern the most common drainage pattern in Hong Kong e.g. Lam Tsuen River Rectangular Drainage Pattern Appear at regions of the western New Territories e.g. the upper course of Tuen Mun River Radial Drainage Pattern found on roughly conical mountains e.g. Sunset Peak
  20. 20. THE OCCURRENCE OF SHENZHENRIVER Longest river in Hong Kong Dendritic Drainage Pattern Between New territories and Shenzhen Early 90s, lots rainfall lead to flooding Total four Regulation work of Shenzhen River Main source of flooding in Hong Kong
  22. 22. Humaninfluence
  23. 23. Construction Many constructions of rivers and channel operating in North New Territories Some constructions need many years to finish
  24. 24. Sha Po Tsai Village accident Serious accident causing death in 2010 The river constructions near found many industrial barriers and big stones after flooding maybe caused by the construction
  25. 25. Sha Po Tsai Village accident One of the branches in the village is blocked by the construction The rainstorm water cannot be drained out
  26. 26. Construction Kind of waste or barrier at riverbed Industrial waste Sand , stone and mud
  27. 27. Construction The roads are paved with sand and stones Dug from the riverbed Not be held tightly Wash away easily Clog up the river and channel Decrease the velocity of water flowing
  28. 28. Deforestation or removal vegetation Removal of trees near the river Solid is washed away easily River bank collapses water comes up
  29. 29. City planning and developing Many natural rivers in New Territories Need to develop and construct channel Channel need to be changed or designed into narrow or bend Avoid the buildings or facilities Lower the strength of draining out water
  30. 30. City planning and developing Surface is made with concrete Increase water flowing on the surface Water cannot be held or stored in the farm, pond, underground or others
  31. 31. City planning and developing A map of Yuen Long and the shape of the channel
  32. 32. Ownership of the place Rural village Some private places cannot be built with channel No right to clean up and repair Clog up the water to flow out
  33. 33. Ownership of the place
  35. 35. THE IDEA OF FLOOD PREVENTION Drainage Channels Pumping station Flooding Storage
  36. 36. THE MAJOR DRAINAGE CHANNELS IN NNT Shenzhen River Ng Tung River Sheung Yue River Ma Wat River
  37. 37. Before the improvement Flooding was always appearing in NNT when a rainstorm came Flooding was risked who living in low-lying area
  38. 38. After the improvement The repaired Shenzhen River section required a drainage capacity that can resist a 50-year return flooding The flooding problems in Sha Tin, Fanling, Sheung Shui and Ta Kwu Ling area can be resolved.
  39. 39. THE FUNCTION OF THE FLOOD PUMPINGSTATION AND FLOODWATER STORAGEPOND• Collect rainwater within the village• Pump out the water collected in the pond• Convey the water to a floodwater from storagepond
  41. 41. EVALUATION
  42. 42. LACK OF PLANNING “In 2008, drainage improvement works along Ma Wat River in NNTwas substantially completed. The level of protection against floodingat Kau Lung Hang has been raised.” adapted from DSD 07-08annual report Then, in 2011…
  43. 43. “Recognising the aspirations of the public for greening to enhance quality of life and to help protect the environment, the DSD places great emphasis on the greening of drainage channel…” “One of these examples is the Drainage Improvement for Ma Wat River at Kau Lung Hang where large-scale greening work has started.” DSD Newsletter (09/04/2011)Criticism:  channel project carried out without comprehensive planning (e.g. lack of beautification work)  extra cost incurred in redundant greening work
  44. 44. EVALUATION Rivers are destroyed and cut down Drainage system cannot handle the rainfall effectively Poor maintenance of channels
  45. 45. EVALUATION Amount of silt bring the problem of flooding again Flooding constructions are processing slowly Not enough regulation with rural villages incomplete drainage system
  46. 46. IMPROVEMENT Flooding situation in the NNT has been alleviated because of the 4 main channel were rehabilitated and the flood pumping has been completed Around 30,000 people who live in low-lying are being protected
  47. 47. BEFORE THE CONSTRUCTION OFSHENZHEN RIVER Bend, meandering taking place Poor drainage of water
  48. 48. AFTER THE CONSTRUCTION OFSHENZHEN RIVER Depth of water increase from 3m to 7m Straight lower course flow has upgrade Thread of flooding Eliminate
  49. 49. SUGGESTION
  50. 50. SUGGESTION Set up more pumping stations Install additional drainage pipes Install additional grilles that can reduce the possibility of blockage
  51. 51. SUGGESTION Speed up the flooding prevention constructions Manage the industrial waste carefully More co-operation with the rural villages so as to build a complete drainage system
  52. 52. SUGGESTION Government should consider all aspects before implementation of the project(e.g. Greening) Consultation on experts from different fields (e.g. engineers, environmentalists) Consultation on public (esp. local residents)
  53. 53. CONCLUSION Serious flooding in northern N.T. caused by1. heavy rainfall2. special river pattern3. Low lying area4. Problems of construction The government have done improvements of flooding in northern N.T. Still need to reduce the occurrence of flooding