Following is a question by the Hon Tang Ka-piu and a written reply by the Secretary for Development, Mr Paul Chan, in the Legislative Council today (November 18):
In the 2015 Policy Address, the Government proposed to apply the concept of revitalising water bodies to nullahs and river channels when carrying out large-scale drainage improvement works and drainage planning for new development areas, striving to achieve efficient drainage and, at the same time, promote greening, biodiversity, beautification and water-friendly activities (revitalisation works). The Government has indicated that it will engage a consultant to study the proposal for exploring practicable options for revitalising water bodies. In connection with revitalisation works, will the Government inform this Council:
(1) of the number of large-scale drainage improvement works commenced in the past five years, and set out in a table the names, expenditures, contents and anticipated completion dates of the various projects;
(2) whether it has set safety levels for the various nullahs across the territory according to their drainage capacities; if it has, of the details;
(3) of the average monthly displacement of the various nullahs across the territory, as well as the months with the highest and lowest displacement in each of the past five years;
(4) of the factors and conditions based on which the authorities decide whether or not to carry out revitalisation works;
(5) whether it will make reference to overseas experience in revitalising nullahs and river channels, including the construction methods and the arrangements for post-revitalisation management; of the examples of the overseas experience introduced by the authorities into the various completed and ongoing large-scale drainage improvement works, and set out the information by project name in a table;
(6) of the current numbers of completed and ongoing large-scale drainage improvement works which have incorporated, or have planned to incorporate, water-friendly activities, and set out the information by project name; the management models for various types of water-friendly activities;
(7) of the work progress of the aforesaid consultancy study;
(8) whether it has drawn up a priority list for various revitalisation works; if it has, of the details; of the number of revitalisation works to be commenced in the next five years, and set out in a table the names, contents and anticipated commencement dates of the various projects; and
(9) as Tai Wai Nullah is the upstream channelised section of Shing Mun River, and a number of residential areas are located on both sides of the river, whether the authorities will consider according priority to the revitalisation work of this nullah, so as to enable residents living nearby to experience the pleasure of water-friendly activities; if they will, of the details; if not, the reasons for that?
As regards the questions raised by the Hon Tang Ka-piu, the replies are as follows:
In the 2015 Policy Address, the Government proposed to conduct a consultancy study for exploring the practicable options for applying the concept of revitalising water bodies to nullahs and river channels when carrying out large-scale drainage improvement works and drainage planning for new development areas, so as to building sustainable drainage facilities and providing a better living environment. This is aimed at promoting greening, biodiversity, beautification and water friendliness, etc. in addition to achieving effective drainage.
My reply to the nine parts of the Hon Tang's question is as follows:
(1) Please refer to the annex for the large-scale drainage improvement works commenced by the Government in the past five years.
(2) The drainage systems in Hong Kong (including nullahs) shall be designed and constructed according to the flood protection standards prescribed in the "Stormwater Drainage Manual" published by the Drainage Services Department (DSD) to ensure that the drainage systems have sufficient drainage capacity to withstand designed peak flow. Each nullah has individual characteristics and the design of its hydraulic capacity is to be determined based on factors such as catchment characteristics and anticipated rainfall.
(3) The DSD does not install device to capture the flow data for each nullah. Nevertheless, the DSD will ensure clearance of drainage channels by way of inspections, desilting and maintenance works conducted before the onset of wet season and on a regular basis.
(4) The primary function of drainage systems is to convey and discharge the stormwater so as to alleviate the flood risk. The DSD regularly reviews the drainage capacity of nullahs and carries out drainage improvement works as required. During the planning and design of such drainage improvement works, the DSD will conduct a study to identify suitable revitalisation measures for incorporation and implementation with the drainage improvement works with due consideration of circumstances such as the geographical location, aesthetics, ecological value, degree of public enjoyment and technical feasibility.
(5) The DSD promulgated the Practice Note "Guidelines on Environmental and Ecological Considerations for River Channel Design" this year which describes that, in the design of drainage systems, the ecological value of drainage channels should be enhanced to its largest extent in addition to fulfilling the flood control requirements. The Practice Note introduces the measures and considerations in the design of green channels, appends with the case studies on the revitalisation projects of Korea's Cheonggyecheon River and Singapore's Kallang River. The Practice Note also lists out a number of representative local and overseas papers, design guidelines and reports, etc. for reference.
In a number of completed drainage improvement works, the DSD has introduced various water bodies revitalisation elements for improving biodiversity and enhancing ecological value, including construction of fish shelters and deflectors along river banks, construction of fish ladders in river channels, using natural substrate for river bed and planting suitable species within the river, etc. The experience is valuable and helps further promote the concept of revitalising water bodies. In particular, the drainage improvement works to Tai Po's Tai Po River (upper stream) and Lam Tsuen River (upper stream), Sai Kung's Ho Chung River, and Fanling's Kwan Tei River and Tan Shan River are successful examples completed in recent years.
(6) With steep terrain and high rainfall intensity of Hong Kong, water levels in nullahs and river channels would rise quickly during heavy rainstorms. For safety consideration, the existing nullahs and river channels that use the "flood mitigation" design concept may not be suitable for public access and conducting water-friendly activities.
In recent years, the Government has been promoting revitalisation of water bodies with a view to providing a better living environment for the public. Hence, the DSD will conduct a consultancy study to explore how to revitalise nullahs and river channels for promoting near-water activities in addition to achieving effective flood prevention. Reference will be made to relevant experience on the Mainland and overseas in formulating the management approach for these activities.
The large-scale drainage improvement works currently under construction with near-water activities is Reconstruction and Rehabilitation of Kai Tak Nullah. The design concept of the project is to revitalise the nullah through adopting landscaping measures and ecological features, with a view to constructing a green channel for the community and for public enjoyment.
(7) The DSD is currently conducting a tendering exercise for the feasibility study on revitalising water bodies, which is expected to commence in December 2015 for completion by end 2017.
(8) The abovementioned consultancy study will review the major river channels in Hong Kong and evaluate their circumstances such as the geographical location, aesthetics, ecological value, degree of public enjoyment and technical feasibility so as to explore practicable revitalisation proposals. The results of the study will serve as a reference for future large-scale drainage improvement works and planning drainage networks for new development areas. The Government currently has no detailed plan to revitalise the nullahs and river channels of adequate drainage capacity.
(9) According to the preliminary results of the on-going Drainage Master Plan Review Study for Shatin conducted by the DSD, there is no need to carry out any drainage improvement works to Tai Wai Nullah. Nevertheless, the abovementioned consultancy study will review the site-specific characteristics of Tai Wai Nullah to formulate some practicable revitalisation options for reference when drainage improvement works are considered necessary in future.
Ends/Wednesday, November 18, 2015
Issued at HKT 16:57