LCQ16: Flooding problem in New Territories North

​Following is a question by the Hon Holden Chow and a written reply by the Secretary for Development, Mr Michael Wong, in the Legislative Council today (September 29):
It has been reported that in the early hours on August 6 this year when a Red Rainstorm Warning Signal and a Special Announcement on Flooding in the northern New Territories were in force, serious flooding occurred on Lin Ma Hang Road near the roundabout of Heung Yuen Wai Highway in the New Territories North (NTN). As a result, two motor vehicles broke down and, among them, a seven-seater vehicle was almost submerged. Some residents in the New Territories have pointed out that serious flooding often occurs in the NTN (particularly in rural areas) during periods of heavy rain, threatening the safety of the residents' properties and lives. In this connection, will the Government inform this Council:
(1) whether it has plans to conduct a comprehensive review on the planning of the stormwater drainage facilities in the NTN; if not, of the reasons for that;
(2) of the number and other details of flood barriers installed by the Drainage Services Department (DSD) in the past five years for the residential areas in flood-prone districts;
(3) of the quantity of sandbags currently kept in stock by the DSD for residents and shop operators in need to borrow before the onset of flooding, and how the DSD ensures the timely delivery of sandbags to them; and
(4) given that flooding occurred on the major roads (including Man Kam To Road and the aforesaid roundabout) in the NTN during the heavy rainstorms in early August this year, and caused serious traffic congestion, of the Government's plans to improve the stormwater drainage facilities of such roads so as to prevent the recurrence of traffic congestion caused by flooding?

Hong Kong, in particular the North District of the New Territories, was affected by a series of heavy rainstorms in recent months. The Hong Kong Observatory has issued nine Special Announcements on Flooding in the northern New Territories this year, more than the annual average of the past 10 years of five announcements. These rainstorms caused flooding in a number of areas in the North District.
Having consulted the Drainage Services Department (DSD), the Civil Engineering and Development Department (CEDD) and the Highways Department (HyD), the reply to the four parts of the Hon Chow's question is as follows:
(1) To systematically examine the adequacy and effectiveness of the stormwater drainage facilities in the northern New Territories, the DSD completed the first Drainage Master Plan Study in the northern New Territories as early as in 1999. The stormwater drainage improvement measures proposed in the study were already progressively completed and put in operation, such as the major river training projects of Shenzhen River, Ng Tung River, Sheung Yue River, as well as the village flood protection schemes implemented for low-lying villages. With the completion of the above works, the extensive flooding situations in the North District of the New Territories have been remarkably improved.
To cater for the circumstances such as the development of the district, updated land use planning or climate change, which came after the completion of the Drainage Master Plan Study, the DSD completed a Drainage Master Plan Review Study for North District in 2011. The scope of the study covered villages with flooding records and assessment of the performance of their stormwater drainage systems. Based on the results of the study, the DSD formulated new stormwater drainage improvement measures. Besides, according to conditions such as the nature, locations and severity of the flooding as well as land use, the DSD appropriately consolidated a series of proposed stormwater drainage improvement measures.
At present, the DSD is carrying out the works project 4118CD "Drainage Improvement in Northern New Territories - Package B (Remaining Works)" in the northern New Territories covering the Tsung Yuen (Kwu Tung North) area, which is anticipated to be completed in 2022. In addition, the DSD is also planning and designing the works project 4165CD "Drainage Improvement Works at North District" and the works project 4173CD "Drainage Improvement Works in Ta Kwu Ling" to further enhance the drainage capacity of the relevant district.
(2) In response to the actual needs and requests of the residents affected by flooding, the DSD has in the past five years installed flood barriers at locations susceptible to flooding. Details are as follows:
Location with flood barriers installed Number of installations
(1) Tai O 12
(2) Lei Yue Mun 43
(3) Heng Fa Chuen 8
Total 63
(3) Whenever there is a heavy rainstorm, the DSD will deploy manpower to specifically handle flooding incidents and clear blocked channels. When Hong Kong is affected by a typhoon, the DSD will deploy emergency response teams to station at the locations prone to flooding and will assist the local residents to handle flooding problems, including placing sand bags and installing water pumps at specific locations to reduce the flood risk.
In addition, the DSD will review the stock of sand bags at different locations prior to the rainy season and typhoon season every year, for timely provision of sand bags to the residents at the locations that are susceptible to flooding when necessary. The current inventory of sand bags of the DSD is as follows:
Location with sand bags provision Number of sand bags
(1) Ta Kwu Ling 300
(2) Shek Wu Wai, San Tin 400
(3) Hang Tau Village, Sheung Shui 300
(4) Low-lying coastal area in the northwest of Yuen Long  3 000
(5) Luen On San Tsuen, Tuen Mun 600
(6) Kar Wo Lei, Tuen Mun 800
(7) Sham Tseng San Tsuen 350
(8) Sam Mun Tsai New Village 300
(9) Tai O 800
(10) Nam Wai, Sai Kung and Tseung Kwan O South 250
(11) Lei Yue Mun 400
(12) Heng Fa Chuen 150
(13) South Horizons 150
Total 7 800
(4) Heavy rainstorms are likely to increase the loading of the drainage system at localised low-lying areas, such as Man Kam To Road and Lin Ma Hang Road. In addition, the road gullies and rainwater inlets that collect surface runoff are easily blocked by rubbish, soil, leaves or other obstructions during the heavy rainstorms, which causes various degrees of flooding at the relevant locations. The DSD, the CEDD and the HyD are all very concerned about the flooding incidents and have taken immediate follow-up actions. To prevent recurrence of similar serious flooding at the above road sections, relevant follow-up measures have been put in place as follows:
  The CEDD has swiftly completed the desilting works of the road drainage facilities within its project boundary at Man Kam To Road, and has also collaborated with the DSD to clear the box culvert underneath this road section so as to allow the stormwater to be drained away quickly. To cope with unexpected flooding incidents, emergency services have also been incorporated into the works contract of the Man Kam To Road site. Ahead of impending heavy rain, the relevant works contractor will also step up inspections and will clear debris and obstacles in the drainage channels within the project area to ensure clearance of the channels.
  During heavy rainstorms, large amount of rubbish, soil, leaves and other obstructions may be washed into the river/channel, leading to the rise of river/channel water level and causing flooding to nearby roads. The DSD immediately installed screens and water level monitoring system at Kong Yiu Channel (KYC) to facilitate timely arrangement of clearance work at the river/channel in order to prevent serious flooding conditions as far as possible.
To prevent vegetation or soil from being washed away during heavy rainstorms and hence blocking KYC adjoining Lin Ma Hang Road, and affecting its drainage capacity, the CEDD is now paving up the landscaping areas within the location affected by flooding with concrete or paving blocks. The CEDD will also construct flood walls along the Lin Ma Hang Road affected by flooding (adjoining KYC) to improve the flood defence of that area. At the same time, a vehicular maintenance ramp at the side of KYC will be constructed to facilitate emergency channel clearance work. In addition, to further enhance the drainage capacity, the HyD is arranging to provide additional gullies at the road sections concerned. The above improvement works are in planning and design stage. The Government will commence the relevant works the soonest possible to reduce the flood risk at the road sections concerned.
Ends/Wednesday, September 29, 2021
Issued at HKT 14:00