Since its establishment in 1989, DSD has been charged with the task of wastewater treatment and stormwater drainage, protecting Hong Kong citizens against flooding and providing them with proper sewage services.
Overview of Flood Prevention in 2014-15
To safeguard the general public against flooding, we make reference to international standards in designing and constructing stormwater drainage systems, and carry out regular inspections and timely maintenance works. In 2014, Hong Kong’s annual rainfall was over 2,600 millimetres, slightly higher than the average of 2,400 millimetres between 1981-2010. During the year, the Hong Kong Observatory issued two Black, six Red and 17 Amber Rainstorm Warnings.
In 2014-15, DSD continued to implement various flood prevention projects to upgrade the flood protection levels and mitigate flooding risks in the relevant areas. In addition to ensuring proper operation of our facilities, DSD carried out reviews on the Drainage Master Plan (DMP) of various districts in stages with a view to formulating the corresponding strategies for Hong Kong’s future development.
Bringing the Number of Flooding Blackspots down to Ten
In an annual review conducted in early 2015, we evaluated the effectiveness of the completed drainage improvement works and further eliminated one flooding blackspot at Tuen Mun San Tsuen, reducing the total number of flooding blackspots from 11 to 10.
Total number of flooding blackspots
Among the remaining 10 flooding blackspots, drainage improvement works for some of them have been commissioned. The effectiveness of which are being monitored and the relevant flooding blackspots will be eliminated in due course. Improvement works for the remaining ones are under planning, design and construction. We will closely monitor their respective drainage conditions during the rainy season and endeavour to eliminate all flooding blackspots as soon as possible.
Operation and Maintenance of Existing Drainage Facilities
In 2014-15, we continued to carry out routine inspections and preventative maintenance works for the stormwater drainage facilities. DSD manages a total of 2,400 kilometres and 360 kilometers of underground stormwater drains and engineered channels respectively, as well as 35 stormwater pumping stations. To ensure smooth operation of the drainage systems, we carry out regular functional and structural checks, clear blockages prior to the rainy season and after heavy rainstorms in a timely manner, and make repairs where needed. Last year, we inspected over 2,000 kilometres of drains and rivers.
Emergency and Response
- The “Emergency and Storm Damage Organisation” (ESDO) is well prepared to handle emergencies and flooding incidents all year-round
- The Emergency Control Centre will be activated in the event of an emergency in order to coordinate emergency clearance tasks for blocked stormwater drains and rivers in Hong Kong; respond to flooding reports; share flooding information within the government; and issue flooding-related messages and warnings to the general public when needed
Stormwater Storage Schemes
- Diverting stormwater to underground storage tanks for temporary storage during heavy rainstorms to relieve the burden of downstream drainage systems
- Stormwater storage schemes at Tai Hang Tung, Sheung Wan and Happy Valley (Phase 1) are now in operation
- Intercepting stormwater on higher ground at upstream, diverting and directly discharging to the sea or into rivers, thereby substantially mitigating flooding risks in downstream areas
- Obviating the need for large-scale drainage improvement works in downstream urban areas and thereby avoiding impacts to traffic and the public
- Four drainage tunnels, including Kai Tak Transfer Scheme, and Hong Kong West, Lai Chi Kok and Tsuen Wan Drainage Tunnels, totaling about 21 kilometres in length, are now in operation
Village Flood Protection Schemes
- Building flood protection embankments to separate low-lying villages from the surrounding land and prevent external runoff from entering the villages
- Building flood storage ponds and stormwater pumping stations in villages for temporary storage of stormwater during heavy rainstorms and subsequent discharge by pumping
- 27 Village Flood Pumping Schemes are currently in operation, providing flood protection for 35 low-lying villages
Planning, Design and Construction of New Drainage Facilities
Review of Drainage Master Plans
Since its establishment, DSD completed eight Drainage Master Plans (DMPs) and three drainage studies, covering flood-prone areas of the territory.
To cope with the latest development in Hong Kong, as well as potential impacts arising from climate change, we review and update DMPs timely to assess the effectiveness of existing and recently completed drainage improvement works in a comprehensive manner, and recommend further enhancement measures as necessary.
The review of DMPs for Yuen Long district and North New Territories, as well as the drainage study for Happy Valley, were completed in 2011. The review of DMPs for West Kowloon, East Kowloon, Tai Po, Sha Tin and Sai Kung districts are underway and are expected to be completed in coming one to two years. Review studies for Northern Hong Kong Island commenced in 2014 while the remaining review studies are being planned.
In 2014-15, we continued with the following major flood prevention projects:
Shenzhen River Regulation Project Stage IV
Shenzhen River Regulation Project Stage IV aims to enhance flood protection levels for the river section between the estuary of Ping Yuen River and Liantang/Heung Yuen Wai Boundary Control Point. The works will improve the 4.5 kilometres section of Shenzhen River between Ping Yuen River and Pak Fu Shan and construct a flood retention lake of 80,000 cubic metres. Wetland flora and riverbank greening elements will be planted to enrich the ecology of Shenzhen River.
Advance works for the Shenzhen River Regulation Project Stage IV, involving re-alignment of a boundary patrol road adjacent to the river section, was completed in February 2015. The entire project is slated for completion in 2017 with a budget of around $1 billion.
Happy Valley Underground Stormwater Storage Scheme
To alleviate the flood risk in the Happy Valley and Wan Chai districts, we initiated the Happy Valley Underground Stormwater Storage Scheme (HVUSSS) in 2012. The project involves construction of an underground storage tank with a capacity of 60,000 cubic metres, a box culvert of about 650 metres long and a stormwater pumping room rated at a peak flow of 1.5 cubic metres per second. It is the first flood prevention project with a movable crest weir system applied in conjunction with a Supervisory Control and Data Acquisition (SCADA) system in Hong Kong.
Phase 1 of HVUSSS was completed in March 2015 and an underground storage tank of 30,000 cubic metres was put into operation. Riding on its success, the project team aims to complete Phase 2 before the 2018 rainy season. The project estimate is about $1 billion.
Kai Tak River Improvement Works
The project aims to upgrade flood protection level of East Kowloon through reconstruction and rehabilitation of a 600-metre upstream section (between Po Kong Village Road and Tung Kwong Road) and a 500-metre midstream section (from Tung Kwong Road to Prince Edward Road East) of Kai Tak River. A new box culvert of about 400 metres long will also be built adjacent to Kai Tak River upstream.
Kai Tak River Upstream and Midstream Improvement Works commenced in November 2011, and is planned for completion in 2017. The project estimate is about $2.8 billion.
Managing Underground Drainage and Sewerage Networks
DSD currently manages a total of over 4,500 kilometres of underground drains and sewers. Many of them show signs of wear and tear and we schedule regular inspection plans to monitor the conditions of these underground pipes and conduct rehabilitation works as and when necessary. In 2014-15, we rehabilitated about 23 kilometres of drains and sewers at a cost of about $85 million.
In anticipation of growing needs for rehabilitation, we are now formulating a long-term and territory-wide replacement and rehabilitation (R&R) strategy in order to better manage our underground pipes. At the same time, we also research and apply various cutting-edge R&R techniques to efficiently maintain our underground facilities so as to improve the cost-effectiveness of our works.