Under the impacts of climate change, heavy rainfall caused by extreme weather is becoming more frequent. Earlier, the Hong Kong Observatory issued the first Red Rainstorm Warning Signal this year, but there was no extensive or serious flooding, reflecting the success of the efforts made by the Drainage Services Department (DSD) over the years. This time, I have invited three colleagues from the DSD to talk about how to strive for flood prevention work, beautifying the river environment, and promoting a water-friendly culture.

The DSD has eliminated 127 flooding blackspots since 1995. There are currently 4 flooding blackspots remaining in Hong Kong, with drainage improvement works for two of them are underway. The works at Pok Fu Lam Village are expected to be completed in the next year or two, while the works at Chatham Road South, Tsim Sha Tsui have been commenced in August last year. The other two blackspots are Lam Tsuen Valley Basin in Tai Po and Shek Wu Wai in San Tin, Yuen Long. For these two, the first stage of improvement works has been completed, and works for the next stage are under planning and design.

Three-pronged flood prevention strategy

Mr LAW Tsz-wai, Engineer (Electrical and Mechanical Projects Division) of the DSD, says that to reduce the flooding risks caused by rainstorms and to enhance the flood prevention capacity of urban drainage system, the DSD has developed a “three-pronged flood prevention strategy”, including “interception”, “flood storage” and “drainage improvement”, to combat flooding threats at various locations. “Interception” refers to intercepting and diverting stormwater for direct discharge to the sea or rivers. “Flood storage” refers to diverting stormwater to storage tanks during heavy rainstorms for temporary storage as buffer. As for “drainage improvement”, it refers to expanding or constructing underground drains.

Good Grab

Regarding “drainage improvement”, the DSD manages over 360 km of engineered channels. River training works to straighten, widen and deepen river channels, as well as regular desilting and cleaning works are carried out to strengthen the drainage capacity of river channels.

In recent years, the DSD has introduced various innovative technologies, including the “Good Grab” (the Grab) lately developed to help remove refuse from river channels. For example, in the downstream of the Kong Yiu River in Ta Kwu Ling, where rubbish tends to accumulate, the DSD has installed the Grab in place of manual rubbish clearance. The Grab can operate round-the rock. It takes about 15 minutes to complete an operation, picking up a maximum of 250 kg of rubbish each time, which is safer, faster and more thorough than manual clearance.

In addition, the Grab is equipped with an artificial intelligence system to monitor the river for blockages, also allowing it to automatically adjust its operation frequency in response to weather and water level data, so that clearance can be done as soon as possible ahead of inclement weather.

Drone team

To further increase the efficiency and safety of routine river inspections, the DSD set up a drone team last year and trained over 20 colleagues to operate the drones. Mr YEUNG Wai-shing, Wilson, Engineer (Hong Kong and Islands Division) of the DSD, says that the duty of the team includes regular inspections of river channels, watercourses and outfalls, as well as prompt inspections after rainstorms or whenever necessary, in order to arrange timely desilting and repairing works. Before heavy rains, they also use drones to help monitor the condition of construction sites and the surrounding drainage systems. As of April this year, the drone team had made over 230 operations, averaging 25 operations per month.

He adds that some river channels and watercourses are located in remote areas, which used to take a lot of time and resources to inspect. With their flexibility, the drones can be used to take aerial photographs of natural hillsides, woodlands and seashores in non-Restricted Flying Zones, saving half of the time for regular inspection, and making inspections safer and more efficient.

People-oriented design to promote a water-friendly culture

In recent years, apart from improving the flood prevention capability of river channels, the DSD has also incorporated more people-oriented designs along the riversides to promote a water-friendly culture. Mr TAI Wai-hin, Engineer (Mainland North Division) of the DSD, says that taking Nam Sang Wai in Yuen Long as an example, in view of the high popularity of its riversides , the DSD has beautified the confluence of Shan Pui River and Kam Tin River, as well as the maintenance access near the Yuen Long Bypass Floodway Engineered Wetland, converting them into public spaces with murals, a pavilion, benches, information boards, and so on, to enable the public to enjoy the scenery comfortably and get closer to the river. This has been well received by the public.

Jordan Valley Channel

Furthermore, the Jordan Valley Channel has been revitalised with the concept of “Rivers in the City”, featuring various design elements such as greening of channel, increasing public open space and promoting a water-friendly culture. For example, a “green coffee table” has been set up at the channel railings, and a selfie pod and solar power charger have been installed at the viewing platform to encourage public enjoyment.

In future, we will continue our efforts to enhance the flood prevention and discharge capacity of the areas concerned, to mitigate the flooding risk, and to address the severe challenges brought about by climate change. In the meantime, we will also consider the conservation of the ecological environment, and the compatibility of works with the community environment, so as to provide the public with better interactive experience with river channels.