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- 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. WHAT IS FLOODING ? surface water > carrying capacity of the channel exceed bankfull stageinundation occurs at flat ground (flood-plain)alongside the river banks 3. MAGNITUDE OF FLOODING IN HKBlackspot Scales:Major - affecting area > 100Medium - affecting hectares area > 10 hectaresSmall - affecting serious significantarea >0.25 hectares agriculturalpropertysocio-Minor -affecting area damage ,damage/economic< 50x50m isolatedserious(0.25 hectare) property traffic disruption minor damage/publictrafficdisruptionnuisance anddisruptioninconvenience Source:DSD 4. FLOODING BLACKSPOTS IN H.K.Source :DSD 5. WHY IN NORTHERN NEW TERRITORIES? 6. COMING UP NEXT Rainfall Natural factors Catchment1. Causes of floodingfeatures Human influence2. Measures taken by government to tackle flooding3. Evaluation of gov. s effort and suggestion 7. RAINFALL 8. BACKGROUND Humid subtropical climate condition Located at northern hemisphere Close to equator Many typhoons and rain band Heavy rainfall 9. SEASON OF RAINFALL Summer is a rainy season some regions in northern N.T. andlow-lying area cause serious flooding the drainage system is overloaded. 10. OTHER FACTORS OF HEAVYRAINFALLGlobal warming El Nino La Nina 11. OTHER FACTORS OF HEAVYRAINFALL .(mm)rainfall Year of El Nino Year of La Nina Normal YearIncrease annual rainfall by El nino and La nina 12. OTHER FACTORS OF HEAVY RAINFALL Intense rainfall More easily to cause flooding especially innorthern N.T. 13. CATCHMENT FEATURES 14. CATCHMENT FACTOR OFNORTH DISTRICT Hong Kong has no large rivers. The larger rivers are mainly in thenorthwest, including: Shan Pui River,Shenzhen River, Kam Tin River, SheungYue River,and Ng Tung River. Mountain Low lying 15. THE REASON OF FLOODING INNORTHERN DISTRICT Private land developer and government continue tochange the use of land Land area use to dredge water greatly reduces dueto the reconstruction of land. In order to continence the work of drain flooded,government connect the drains directly fromSheung Shui, Fanling Town Centre to Ng tung river 16. 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-shapedvalleys are formed by the prevailing downwarderosion Lower course - flat terrain, it is easy to causeflooding 17. SHAPE OF RIVER BASIN IN HONGKONG From the distribution of tributary(river), three kind ofshape are listed below : Dendritic Drainage Pattern Rectangular Drainage Pattern Radial Drainage Pattern 18. Dendritic Drainage Patternthe most common drainage patternin Hong Konge.g. Lam Tsuen River Rectangular Drainage PatternAppear at regions of the western New Territoriese.g. the upper course of Tuen Mun River Radial Drainage Patternfound on roughly conical mountainse.g. Sunset Peak 19. THE CASE OF SHENZHEN RIVER Longest river in Hong Kong Dendritic Drainage Pattern Between New territories and Shenzhen Early 90s, much rainfall lead to flooding Total four Regulation work of Shenzhen River Main source of flooding in Hong Kong 20. RAINFALL + CATCHMENT FACTOR +HUMAN INFLUENCE = HEAVY FLOODING 21. Humaninfluence 22. Construction Many constructions of rivers and channeloperating in North New Territories Some constructions need many years tofinish 23. Sha Po Tsai Village accident Serious accident causing death in 2010 The river constructions near found many industrial barriers and big stonesafter flooding maybe caused by theconstruction 24. Sha Po Tsai Village accident One of the branches in the village is blockedby the construction The rainstorm water cannot be drained out 25. Construction Kind of waste or barrier at riverbed Industrial waste Sand , stone and mud 26. 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 river flow 27. Deforestation or removal of vegetation Removal of trees near the river Solid is washed away easily River bank collapses water comes out 28. Urban planning and development Many natural rivers in New Territories Need to develop and construct channel Channel need to be changed or designedinto narrow or bend Avoid the buildings or facilities Lower the strength of draining out water 29. Urban planning and development Surface is made of concrete Increase surface run-off Water cannot be held or stored in the farm,pond, underground or others 30. Urban planning and development A map of Yuen Long and the shape of the channel 31. Ownership of land Rural village Channelization cannot be carried out in someprivate lands No right to clean up and repair Clog up the river flow 32. Ownership of landA private land in rural village 33. FLOODPREVENTION 34. THE IDEAS OF FLOOD PREVENTION Drainage Channels Pumping station Flooding Storage 35. THE MAJOR DRAINAGE CHANNELS IN NNT Shenzhen River Ng Tung River Sheung Yue River Ma Wat River 36. Before the improvement Flooding was always appearing in NNTwhen a rainstorm came Residents who living in low-lying area wereat risk 37. After the improvement The repaired Shenzhen River sectionrequired a drainage capacity that canresist a 50-year return flooding The flooding problems inSha Tin, Fanling, Sheung Shuiand Ta Kwu Ling area canbe alleviated. 38. THE FUNCTION OF THE FLOOD PUMPINGSTATION AND FLOODWATER STORAGEPOND Collect rainwater within the village Pump out the water collected in the pond Transfer the water to a floodwater fromstorage pond 39. THE EFFICIENCY OF THE FLOODPREVENTION 40. EVALUATION 41. IMPROVEMENT Flooding situation in the NNT has beenalleviated because of the 4 main channelswere rehabilitated and the flood pumping hasbeen completed Around 30,000 people who live in low-lyingareas are being protected 42. BEFORE THE CONSTRUCTION OFSHENZHEN RIVER Bend, meanderingtaking place Poor drainage ofwater 43. AFTER THE CONSTRUCTION OFSHENZHEN RIVER Depth of waterincrease from 3mto 7m Straightened Lower course flowhas upgraded Threat of floodingeliminated 44. EVALUATION Rivers are destroyed and cut down Drainage system cannot handle the rainfalleffectively Poor maintenance of channels 45. EVALUATION Amount of silt bring the problem of floodingagain Flooding constructions are carried out at tooslow a pace Not enough regulation on rural villages incomplete drainage projects 46. LACK OF PLANNING In 2008, drainage improvement works along Ma Wat River in NNTwas substantially completed. The level of protection against flooding atKau Lung Hang has been raised.adapted from DSD 07-08 annualreportThen, in2011 47. Recognising the aspirations of the public for greening toenhance quality of life and to help protect the environment, the DSDplaces great emphasis on the greening of drainage channel One of these examples is the Drainage Improvement for Ma WatRiver at Kau Lung Hang where large-scale greening work hasstarted. DSDNewsletter(09/04/2011) channel project carriedCriticism: comprehensive out without planning (e.g. lack of beautification work) extra cost incurred in redundant greening 48. SUGGESTION 49. SUGGESTION Set up more pumping stations Install additional drainage pipes Install additional grills that can reduce thepossibility of blockage 50. SUGGESTION Speed up the flooding preventionconstructions Manage the industrial waste carefully More co-operation with the rural villages soas to build a complete drainage system 51. SUGGESTION Government should consider all aspectsbefore implementation of the project(e.g.Greening on the case of Ma Wat River) Consultation on experts from different fields(e.g. engineers, environmentalists) Consultation on public (esp. local residents) 52. CONCLUSION Serious flooding in northern N.T. caused by1. Heavy rainfall2. Variation in drainage basin3. Problems of construction The government had achieved improvementsof flooding in northern N.T. Still need to reduce the occurrence offlooding 53. REFERENCE AND SOURCE www.dsd.gov.hk http://www.dsd.gov.hk/EN/Publicity_and_Publications/Press_Releases/news148.html http://www2.map.gov.hk/gih3/view/index.jsp http://www.greenpower.org.hk/river/eng/hkrivers.asp http://maps.google.com.hk/maps http://www.weather.com.hk/default.asp 54. END OF PRESENTATIONThank you !!!