Information Paper for Legislative Council
Panel on Planning, Lands and Works
Meeting on 23 July 1998

Flood Control and Prevention


The Administration presented an information paper on flood control to Members at the meeting on 4 April 1995. Subsequent updates have been presented to Members on 24 April 1996 and 15 January 1998. This paper provides the latest update on progress with flood control projects and measures.

Strategies for Flood Control

2. Following a series of territorial-wide studies completed in 1993, a three level flood prevention strategy has been adopted. It involves:

  • long-term structural measures to upgrade the drainage capacity of all main drainage systems and secondary drainage systems to defined standards based on consequences and needs of the area to be protected,

  • short-term improvement and management measures to ensure a high service level both before and after the long-term measures are in place, and

  • land use management and legislation to control developments at the planning stage, especially in the flood plains in the New Territories, to avoid adverse impacts on drainage and increased risk of flooding, and to introduce legislation to overcome access problems in execution of systematic maintenance works.

Recent Flood Incidents

3. The first half of 1998 has been an exceptionally rainy period. We have already had two major flooding events on 24 May and 9 June respectively. The heavy rainfall caused considerable flooding in the territory, especially in the Northern New Territories and West Kowloon. In the Northern New Territories, the flooding on 24 May was exacerbated by the flood water release from the Shenzhen Reservoir combined with high tide. Most of the flooded areas were low-lying agricultural land but a number of villages and isolated houses were also affected. In West Kowloon, part of the Nathan Road (near Prince Edward Road) was flooded and traffic was disrupted. The flood subsided soon after the rain weakened. These two areas are the most flood prone areas in the territory and indeed we are focusing our effort on the improvement works in these two areas, as explained in the following paragraphs.


Long-Term Structural Measures

4. Long-term structural measures involve construction of extensive large-scale civil engineering works to provide drainage services to the strategic flood protection standards. These include river training projects and village flood protection schemes. We have also launched Drainage Master Plans Studies to draw up plans to upgrade the drainage network, including the secondary drains, to meet long-term development needs. These projects will take many years to complete because of their scale, the need for land resumption where private lands are encountered, as well as environmental and ecological considerations.

River Training Projects

5. River training projects for the main rivers in the New Territories are underway. An update of the programme is given at .Tables 1, 2 and 3.

6. The most critical flood mitigation project in the NNT is the Shenzhen River Regulation Project, since it is the only outlet for many major rivers, such as River Indus and River Beas, in the area. Stage I of the Project was completed in April 1997. Stage II Works are now in full swing and scheduled for commissioning by 2000. Planning for Stage III Works is already in hand, with construction scheduled for completion in 2004. Works at River Indus and River Beas will start shortly so that the programme will dovetail with Stage II of the Shenzhen River Regulation Project.

7. In the North-western New Territories, the entire flood prevention scheme comprises training of the main river channels in Tin Shui Wai, Yuen Long, Kam Tin and Ngau Tam Mei, and lastly, the Yuen Long Bypass Floodway which will divert flow from the uplands away from the urban areas in Yuen Long. Works in the Tin Shui Wai basin have been completed, and have proven to be effective in flood prevention in the area. Construction of the Yuen Long Main Drainage Channel together with the downstream sections of the Kam Tin Main Drainage Channel are in progress and will be completed by the end of this year. These works will bring significant relief to the flooding problem of Yuen Long Town and the low lying areas along the Kam Tin River. Indeed, the works completed so far are already substantially functional in relieving flood problems. However, to achieve the full strategic flood protection standards, all long-term structural measures, including the Yuen Long By-pass Floodway, will have to be completed. Planning and design for another 25 km of new river channels are underway including the upper reaches of Kam Tin River, Ngau Tam Mei drainage channel and some smaller channels.

8. The Rural Drainage Rehabilitation Scheme will rehabilitate and improve six stream-courses in the NT. Works include improving the secondary drainage systems in the upper part of the drainage basins that are urgently needed to supplement the main drainage channels. The first package of works is scheduled to commence by end of 1998. An update of the projects is given at Tables 1 and 2.

Village Flood Protection Schemes

9. These schemes will protect low-lying villages that are at levels below the nearby drainage channels by constructing an earth bund around the village and collecting water in a flood storage pond for pumping into the drainage channels. To date, 15 schemes have been completed. Currently five flood protection schemes are under construction in the New Territories to protect 12 low lying villages. They are scheduled to complete before 1999. Another eight schemes in the North-western NT are at various stages of planning and detailed design. An update of the time frame of these are given at Tables 1 and 2.

West Kowloon Stormwater Drainage Improvement Project

10. West Kowloon has been identified as one of the most urgent areas for drainage improvement. A comprehensive upgrading of the drainage system for the area, known as the West Kowloon Stormwater Drainage Improvement Project is underway. Stage I commenced in early 1998 to upgrade the critical sections of the drainage system. Although the entire Stage I will be completed in 2002, we have advanced the installation of two major relief drains in order to provide an initial relief to the flooding situation in the Mong Kok area before the 1999 wet season. Stage II will commence in 1999 for completion in 2004. After completion of Stage I and Stage II, there will be a substantial improvement to the stormwater drainage system. The system will be further upgraded under Stage III works to the full flood protection standard which is targeted for completion by 2007. An update of the project is given at Table 4.

Drainage Master Plans

11. Drainage Master Plans (DMP) cover all flood prone areas of the territory. A total of seven DMP studies are in progress to review the condition and performance of the existing stormwater drainage systems in a comprehensive manner, including all reported flooding incidents. These studies will draw up both long-term and short-term measures to upgrade the system to cope with future development needs. In addition, a computerised asset management system will be developed to support future maintenance of the stormwater drainage system. The areas covered by these studies and their time frame are shown at Figure 1 attached.

12. All DMP studies are in progress. The first study, namely the Yuen Long, Kam Tin, Ngau Tam Mei & Tin Shui Wai DMP Study, has been substantially completed. Major recommendations put forward under the first study have been endorsed, and will be implemented in two stages, based on development needs. The works, which are scheduled to start in August 2001, will upgrade both the primary and secondary drains to strategic flood protection levels. This will provide safeguards against most local floods, such as those encountered in Yuen Long on 9.6.98. The second DMP study covers northern Hong Kong Island. It is showing that the existing drainage systems, particularly those in the urban area, are of inadequate capacity. The study has put forward an option of diverting stormwater from the upland catchments via a tunnel directly into the sea. This would substantially reduce the amount of works necessary to enlarge major culverts in the built-up areas. The feasibility and costs of the option are being evaluated in detail.

Short-term Improvement and Management Measures

13. These are on-going measures, which include preventive maintenance to identify and remove blockages, local drainage improvement works in rural areas, surveillance of construction sites and flood warning systems.

Preventive Maintenance Works

14. To ensure that the problematic drains are inspected on a systematic basis, especially before and during the rainy season, DSD undertakes a preventive maintenance programme to inspect, desilt and repair the stormwater drain system both in the urban and rural areas. Under this preventive maintenance programme, at least 800km (40% of total) of river channels, main water courses, culverts and stormwater drains are inspected every year, and about $120 million is spent on the necessary maintenance works annually. With the assistance of the Urban Services Department and the Regional Services Department, more effort is being made to keep road gullies and catchpits clear of rubbish so that it will not block the road side gullies.

Flooding Blackspots

15. DSD has been keeping track of 108 blackspots across the territory where flooding has occurred frequently in the past. The causes of flooding in these blackspots are carefully investigated and, wherever possible, short term remedial measures are implemented. The ultimate solution to the flooding at all these blackspots rests with the implementation of the long-term structural measures, however, we have been able to improve the situation at 24 of the locations. In the West Kowloon area, we have expedited interim measures including: installing additional gullies to in-take surface runoff, conducting Close Circuit Television surveys and urgent cleansing of drains underneath Nathan Road and its environs, and diver inspection and desilting of major multi-cell box culverts to ensure proper running of the drainage system.

Rural Planning and Improvement Strategy

16. The Rural Planning and Improvement Strategy programme will provide local drainage improvement to villages in the New Territories. Under this programme, there are at present 56 minor stormwater drainage projects estimated at a total cost of $340 million. 30 projects have been completed, 6 are under construction, and the remaining 20 are under planning and design. To expedite project delivery, we are implementing some projects under a design and construction consultancy commencing mid 1998.

Flood Warning System

17. Before long-term improvement works are provided, to help minimize flood losses, systems have been set up to warn villagers when flood water reaches a predetermined alert level. There are 8 local Flood Warning Systems installed, located in flood-prone areas such as Tin Ping Shan, Fung Wong Wu, Shek Wu San Tsuen, and Tai Tau Ling. Warning notices are disseminated through flood sirens or through automatic telephone calls to the village representatives.

Planning and Legislative Measures

18. These are non-structural means to prevent further aggravation of flooding problems due to uncontrolled developments and urbanization in the flood-plains, mostly in the New Territories, through planning and legislative measures. These measures include:

    Land Use Planning and Drainage Impact Assessment
    Land Drainage Ordinance

Land Use Planning and Drainage Impact Assessment

19. Since urbanisation and infrastructure development have significant impact on the drainage system, the DSD is providing drainage advice in the drawing up of land use plans to ensure that the overall land use proposal is compatible with land drainage requirement. In addition, proponents of major infrastructures are required to carry out Drainage Impact Assessments to identify and mitigate any adverse impact to drainage in the area as part of the project. This requirement applies to both public and private developments and has been promulgated to relevant personnel by Advice Notes setting out the procedures. This arrangement has been effective in controlling the drainage impact caused by new developments.

Land Drainage Ordinance

20. Some of the previous flooding incidents were attributed to lack of maintenance in the river channels. Difficulties in obtaining consent to enter private lands to execute river maintenance works have been overcome by the Land Drainage Ordinance, which was enacted in 1994 to empower the Drainage Services Department to gain access in private lands to execute necessary maintenance works. Five Drainage Authority Areas covering the major flood prone basins in the NT have been designated, in which the Drainage Services Department may enter private lands to undertake maintenance works for flood prevention. These measures will enable us to carry out preventive maintenance programme more effectively. This ensures that the flooding situation does not further deteriorate.


21. The Administration is implementing the flood prevention strategy to upgrade drainage works in the territory to a current standard via a three-tier plan, which includes long-term structural measures, short-term improvement and management measures and planning and legislative measures. Many of the long-term measures are well underway although the full benefits will not be apparent for some time. Before the long-term measures can deliver their benefits, every effort is being made to alleviate flooding problems by implementing short-term measures and close monitoring of vulnerable areas.

July 1998
Works Bureau

Table 1 - Summary of Major Flood Control Projects
in the Northwestern New Territories

(Situation as at 30.6.98)

PWP No.TitleEstimated
Construction Cost
60CD/ANWNT Development - Main Drainage
Channels for Yuen Long and Kam Tin
Stage I
Contract A (DC/90/03)
Contract B (DC/93/03)
Completion Works to Contract A



43CD/ANWNT Development - Main Drainage
Channels for Yuen Long and Kam Tin
Stage I Contract C
(DC/94/06 & DE/95/17)



81CD/BNWNT Development - Main Drainage
Channels for Yuen Long and Kam Tin -remainder
Phase 1
Phase 2
Phase 3 (TDD)



22CD/BNWNT Development - Main Drainage
Channels for Yuen Long and Kam Tin -remainder
Phase 4 (TDD)



29CD/BNWNT Development - Main Drainage
Channels for Ngau Tam Mei
Phase 1
Phase 2 (TDD)



30CD/BVillage Flood Protection for Yuen Long,
Kam Tin and Ngau Tam Mei - Stage I
Pok Wai
Chuk Yuen Tsuen/Ha San Wai
Wang Chau



35CD/AMain Drainage Channels for San Tin, NWNT
Phase 1 Village Flood Protection Works for San Tin
Phase 2 Village Flood Protection Works for Chau Tau



73CD/BMain Drainage Channels for San Tin, NWNT
Phase 3, Part 1 - Eastern Main Drainage
Channel for San Tin



70CD/BYuen Long Bypass Floodway (TDD) 445 3/01 12/03
64CD/BRural Drainage Rehabilitation Scheme - NWNT Portion 85 3/00 2/03
473CL/AVillage Flood Protection for Ha Mei San Tsuen 37 4/97 7/98
74CD/BVillage Flood Protection for Yuen Long,
Kam Tin and Ngau Tam Mei - Stage II
Mai Po Lo Wai/Mai Po San Tsuen
Remainder Villages



71CD/AVillage Flood Protection for Yuen Long,
Kam Tin and Ngau Tam Mei - Stage 1
Sha Po Tsuen (DC/95/01 & DE/95/04)




**60CD-Contract A (DC/90/03) was forfeited in 4/97. The remaining works are carried out under Completion Works to Contract A (DC/97/04).

***Main works postponed after consultation with village representatives to observe the effectiveness of a Cat. D item and other drainage improvement works.

Table 2 - Summary of Major Flood Control Projects
in the Northern New Territories

(Situation as at 30.6.98)

PWP No.TitleEstimated Construction Cost ($M)Start DateCompletionDate
Shek Wu Hui Development Package 4 River Training in Area 30B 260 9/98 3/01
72CD/A (TDD)Village Flood Protection for Tsung Pak Long and Tai Tau Leng 80 2/96 8/98
53CD/B (TDD)Main Drainage Channels for Fanling, Sheung Shui & hinterland
Stage 1 - Lower Indus & River Beas Training
Stage 2 - Indus River Training



91CD/ARural Drainage Rehabilitation Scheme
- River Indus



64CD/BRural Drainage Rehabilitation Scheme
- River Beas




Table 3 - Shenzhen River Regulation Project
(Situation as at 30.6.98)

PWPNo.TitleEstimated Construction Cost
($M) (Note)
Start DateCompletion Date
24CDStage I 150 [300] 5/95 4/97
44CD Stage II Phase I (Advance Work) 145 [145] 11/96 11/98
31CDStage II Phase II
Contract A (Upstream)
Contract B (Downstream)

245 [490]


90CDStage III 394 [708] 4/01 9/04
1038 [1850]

Note: Costs quoted are those shared by Hong Kong side; total construction cost in []

Table 4 - Major Urban Drainage Projects
(Situation as at 30.6.98)

PWP No.TitleEstimated Construction
Cost ($M)
Start Date
89CD/AWest Kowloon Drainage
Improvement - Stage I
380 4/98 10/02
59CD/BWest Kowloon Drainage
Stage II
Stage III