Rivers collects rainwater and direct water flow to the sea. For thousands of years, rivers have been the cradle of life, communities and the economy. In today's Hong Kong, with a dense population and highrise buildings along the rivers, the usual practice is to straighten and broaden river channels and cover them with concrete to control flooding. The natural river landscapes have vanished, and so have the natural functions of rivers in purifying water, nurturing ecology and alleviating flooding. Natural rivers are replaced by lifeless concrete nullahs, such as Shan Pui River of Yuen Long, Lam Tsuen River of Tai Po, and Shing Mun River of Shatin. Tung Chung River is a rare natural river in Hong Kong. Since the 1990s, development in Tung Chung has threatened the river. Years of petitioning by local green groups have forced the government to reduce the reclamation size and designate the main flow of Tung Chung River as a Conservation Area. A River Park will also be built. This is a new attempt to retain a natural river in a new town in Hong Kong. How should the River Park be constructed, to avoid the fate of becoming a large nullah with artificial flower racks?
Tung Chung River is the only remaining large natural river in Hong Kong, with a rare estuary that is still free from serious damage by development projects. Tung Chung River originates from Lantau Peak and Sunset Peak and flows to Tung Chung Bay. The flow is abundant, with rich biodiversity. The river is home to quite a few rare and endangered species: Beijiang Thick-lipped Barb (Acrossocheilus beijiangensis), Romer's Tree Frog (Philautusromeri), Hong Kong Newt (Paramesotriton hongkongensis), Tri-spine Horseshoe Crab (Tachypleus tridentatus) and Pipefish. It has the richest freshwater fish species among local rivers and is designated as an "Ecologically Important Stream".
Development of Tung Chung New Town began in the 1990s. Today, over 300 hectares have been developed. In 2012, the Planning Department and the Civil Engineering and Development Department launched the Tung Chung New Town Extension Study. The initial proposal was to reclaim the sea at the estuary of Tung Chung River, which aroused much controversy as the estuary is of high ecological value. The government also planned, as common practice in developing new town, to channelise the natural river within the new town area for flood control and easy management. Tung Chung River passes through the new town development, and the lower course seemed likely to be completely covered by concrete. In the earlier stage, Wong Lung Hang in the south was channelised, and the river course was straightened and widened, then concrete was poured onto the deepened channel. The estuary here was reclaimed. Wong Lung Hang was as ecologically rich and had as good water quality as Tung Chung River. Upon channelisation, the natural landform and ecology were completely destroyed, and all that remains is an artificial drainage nullah.
Although the government has - in the Tung Chung New Town Extension Study - indicated that conservation elements would be added to improve drainage design, there are indeed no measures to ensure that the original flora and fauna could survive, as the habitat would be changed completely. Besides, Hong Kong has yet to develop proper works practice to safeguard river ecology. If the ecology of Tung Chung River is damaged in the beginning of the New Town Extension work, any improved drainage design would be futile. Green groups have therefore repeatedly emphasised the importance of Tung Chung River in past consultations on the New Town Extension Plan, and have submitted a joint petition to preserve the natural channel and estuary of Tung Chung River.
After years of petitioning, the government has now accepted the proposal to preserve the natural Tung Chung River. In the third stage public consultation, the related Environmental Impact Assessment (EIA) Report and the draft Tung Chung Valley Outline Zoning Plan, the authority has cancelled the reclamation plan at Tung Chung River estuary and Tung Chung Bay. The east and west main courses and a 30-metre wide band along the major tributary banks of Tung Chung River will be designated as Conservation Area. In addition, the lower course near the residential areas will not be channelised. Instead, polders will be built along the Conservation Area for flood control purposes, while minimising damage to the river habitat. Meanwhile, the government also proposed setting up a new River Park at the east river side, from Shek Mun Kap to Wong Ka Wai.
Say no to artificial park
The River Park is a new venture in Hong Kong that merits our support. Yet, can the designation of river channel and river bank as Conservation Area really protect the natural river ecology? Will it work by simply using polders to replace channelisation and carrying out an environmental impact assessment? The moves are in the right direction, but the most important part is the implementation. Otherwise, it is only empty talk. How will the public benefit through preserving Tung Chung River?
The name "River Park" raises some concern as to whether it will become a park of leisure facilities instead of functioning to preserve the natural state of Tung Chung River – that is, retaining the hydrology from the upper course to the estuary, to Tung Chung Bay. Therefore, there should be no artificial landscaping such as a built waterfall in the park that will change the hydrology while prohibiting river fauna from migrating between the upper and lower courses. Besides, the channel should not be covered with concrete for easy maintenance, as the impermeable concrete layer would be a barrier to water movement between the river and the subsurface water in the soil that nurtures the riverbank vegetation. During the dry season the underground water would also fail to supplement the river to maintain the flow.
All landscaping works should be avoided as far as possible. The natural river and coastal plants, soil, rocks and water pools form by erosion and sedimentation during a long period of time, and are impossible to recreate artificially. Even if these micro-habitats are re-created to a certain extent, they can hardly withstand flushing by flood water in future. Therefore, it is best to avoid civil engineering works in the river channel and along the banks.
Usually, surface flow and water collected in the storm water drains will not be treated and are directly discharged into nearby river. In the future extended Tung Chung New Town, these waters will also be discharged into Tung Chung River. The waters may be polluted and hence threaten the river ecology. The government plans to build a Sustainable Urban Drainage System (SUDS) in Tung Chung West, which will include a regional rainwater detention and infiltration pool. The system is intended to collect rainwater in the drains and filter it through a wetland ecology system before discharging into the river. If the water is seriously polluted, it will be treated in the sewage treatment plant. However, the system is new and yet to be proven effective. It is nonetheless a good beginning for the government to aim to tackle the pollution problem of surface and storm water flows.
Public-friendly water bodies
If the River Park can truly retain the ecology, water quality, landscape and the natural estuary of Tung Chung River, it will become a precious treasure for the public. There are already programmes of integrating rivers in the city in some parts of the world. For example, the Active, Beautiful, Clean (ABC) Waters Programme of Singapore has turned the rivers and lakes into parts of the city, and upgraded water quality and the environment so the public can fully enjoy the waters for leisure and recreation. The internationally renowned Cheonggyecheon in South Korea was a buried channel in the city that was re-engineered into an open area for the public to get close to natural water. In Taiwan, there are also river parks such as Dong-shan River Park, which adopt special landscaping designs.
Public safety in the River Park will be a major challenge too. Tung Chung River has a large gradient, and precipitation in Hong Kong may be heavy, and arrive suddenly. When a rainstorm arrives, water flow in Tung Chung River will rise rapidly. It is worrying that the River Park is within the flooding area.
The EIA report stated that there will be viewing decks and boardwalks for the public to enjoy the river. If the facilities are far from the channel, then safety is ensured while the public access function is reduced. If the facilities are close to the channel, then the viewing decks and boardwalks may be submerged in flood water during rainstorms. The facilities must be designed to avoid floodwater and damage by pebbles and rocks, and should be easily cleaned after rainstorms. In addition, visitors must be prohibited from using the facilities before a serious flood comes. With today's technology, the risk of flooding can be estimated. When there is a thunderstorm warning or poor weather, the facilities should be closed, as is the case with outdoor swimming pools.
Conservation before development
As Tung Chung River is a rare large local river that nurtures rich biodiversity, the River Park should put more emphasis on ecological education. There are many hiking trails and trekking sites near the river. A visitor centre can be set up at the River Park to provide information and guided tours for hiking and trekking activities, and even offer facilities, supplies, training and hostel services. At present, most visitor centres in country parks and the Wetland Park provide only visit and guided tour services. There is a lack of support for thorough ecotours.
River Park, polders and SUDS are all new to Hong Kong, indicating that the government has given up the outdated concept of transforming river channel into concrete nullahs when developing new towns. If it can be successfully implemented, the co-existence of city and natural river will become a classic example that allows the public to appreciate the significance of rivers. Green groups welcome the fact the government is finally responding to the public's call for protection of Tung Chung River.
Work on the extension plan for Tung Chung New Town will start soon. The rural area in the lower course of Tung Chung River will be transformed into residential areas. Green groups hope the government will put conservation before development: that is, to realise the Conservation Area and River Park before the development plan begins. The government must also closely monitor the extension work, to prevent the Conservation Area along the natural river from being occupied and damaged, and to ensure that the works do not damage or obstruct the river channel so as to minimise flooding risks during rainstorms.
Text | Henry Lui & Dr. Cheng Luk-ki