DSD Strengthens Responsive Management Measures for Rainy Season

A spokesman for the Drainage Services Department (DSD) said today (March 29) that the number of flooding blackspots in Hong Kong has reached the lowest in record. In order to further reduce the flood risks during rainstorms, the DSD will introduce the “just-in-time clearance” arrangement in this rainy season and proactively incorporate new technologies to enhance the effectiveness and efficiency of construction and maintenance works.

The spokesman said the DSD has removed a total of 126 flooding blackspots in the past 26 years, including the one at the junction of Morrison Hill Road and Lap Tak Lane in Wan Chai this year. There are only five remaining flooding blackspots in Hong Kong, including Shek Wu Wai in San Tin, Yuen Long; Lam Tsuen Valley Basin and Ting Kok Road in Tai Po; Chatham Road South in Tsim Sha Tsui and Pok Fu Lam Village in Southern District. Among them, the drainage improvement works at Ting Kok Road have been completed with its effectiveness being monitored for several years, and this flooding blackspot is expected to be removed after this rainy season.

“In order to further reduce the flood risks during rainstorms, we will introduce the ‘just-in-time clearance’ arrangement during weekday’s daytime in the upcoming rainy season.  Before the onset of a rainstorm, staff will be deployed to inspect about 200 locations which are susceptible to blockage by litters, fallen leaves or the like, and will immediately arrange for clearance works if necessary. Furthermore, our staff will inspect and clear all main drains and rivers immediately after a rainstorm or when a typhoon signal is about to lower to get ready for the challenges of further rainstorms,” the spokesman said.

Hong Kong faces an average rainfall of about 2400 millimetres a year, one of the highest among the cities in the Pacific Rim.  Flooding is inevitable under extreme rainstorms. Notwithstanding this, the DSD has analysed over 200 flooding cases between 2017 and 2019, finding that over 60 percent of them were due to blockage of drains by litters, fallen leaves or other washouts carried down by surface runoff. The “just-in-time clearance” arrangement is definitely an appropriate solution.

As high rainfall severely restricts the construction and maintenance of drainage facilities, thus affecting their capacities to cope with rainstorms, the DSD has been proactively incorporating new technologies. A new remote-controlled desilting robot has been procured for silt clearing works at submerged box culverts. The robot is able to go further inside submerged box culverts, and silt can also be transported to ground surface through a tube connecting to the robot which largely improves the efficiency of the desilting works. Workers can be spared from entering confined and submerged space of the culverts, and desilting works will no longer be limited mostly to dry seasons.

In order to increase construction efficiency of new works projects, the DSD also incorporated the Design for Manufacture and Assembly (DfMA) concept, together with the Building Information Modelling technique, to design structural modules which could more easily be built and assembled, amid the risks of inclement weather.

“The construction of dry weather flow interceptor at Cherry Street box culvert has adopted both DfMA and traditional cast in-situ method. While structural modules are constructed off-site, part of the structures are cast in-situ. The construction period is therefore expected to be shortened by about six months,” the spokesman added.

Apart from strengthening the responsive management measures before and after rainstorms, the DSD will continue to press ahead with its flood prevention strategy, which includes implementing underground stormwater storage schemes. Stormwater storage scheme aims to collect and temporarily store excessive rainwater during rainstorms, thus reducing the loading at downstream drains and the consequential flood risks. The four completed underground stormwater storage schemes in Tai Hang Tung, Sheung Wan, Happy Valley and On Sau Road have achieved remarkable results to prevent flooding in these areas. The DSD is collaborating with other departments to identify suitable public open space for construction of more underground stormwater storage schemes. By far, six locations are under planning, which include Shek Kip Mei Park, Tai Hang Tung Recreation Ground (extension), the Urban Council Centenary Garden in Tsim Sha Tsui, as well as Sau Nga Road Playground, Kwun Tong Ferry Pier Square and Hoi Bun Road Park in Kwun Tong District.

The relevant article was published on HKSAR Government Press Releases:

https://www.info.gov.hk/gia/general/202003/29/P2020032700643.htm?fontSize=1

The Drainage Services Department today (March 29) removed the flooding blackspot at the junction of Morrison Hill Road and Lap Tak Lane in Wan Chai. There are only five flooding blackspots remaining in Hong Kong, which include Shek Wu Wai in San Tin, Yuen Long; Lam Tsuen Valley Basin and Ting Kok Road in Tai Po; Chatham Road South in Tsim Sha Tsui and Pok Fu Lam Village in Southern District

The Drainage Services Department is planning to implement more underground stormwater storage schemes. So far, six stormwater storage schemes are under planning. They are located at Shek Kip Mei Park, Tai Hang Tung Recreation Ground (extension), the Urban Council Centenary Garden in Tsim Sha Tsui, as well as Sau Nga Road Playground, Kwun Tong Ferry Pier Square and Hoi Bun Road Park in Kwun Tong District

The Drainage Services Department (DSD) proactively incorporates new technologies to enhance the effectiveness and efficiencies of construction and maintenance works. Photo shows the new remote-controlled desilting robot recently procured by the DSD

The Drainage Services Department (DSD) proactively incorporates new technologies to enhance the effectiveness and efficiencies of construction and maintenance works. Photo shows the DSD desilting robot entering a submerged box culvert

The Drainage Services Department proactively incorporates new technologies to enhance the effectiveness and efficiencies of construction and maintenance works. Photo shows an operator remotely controlling a desilting robot