LAND, PUBLIC WORKS AND UTILITIES
224
Stormwater Drainage and Flood Control
The North and Northwest New Territories are particularly vulnerable to flooding.
Damage caused by flooding was widespread when typhoons Dot and Ira struck the territory in September and November, respectively. During the November typhoon, some 400 000 Tuen Mun residents were left without running water for four days due to the flooding of the Fu Tei fresh water pumping station.
The Drainage Services Department completed a study reviewing rainfall, stream flows and flooding predictions in 1993, with the aim of drawing up basin management plans for the main rivers in the North and Northwest New Territories and examining in more detail potential local flood mitigation measures. This was a follow-up to a territory-wide study in 1990.
In addition, pamphlets giving advice on what to do and what not to do in a flooding situation were distributed through the District Offices to people living in flood-prone areas.
The government commenced work during the year on the first stage of its largest scheme to alleviate the flooding problem in Northwest New Territories. Valued at $1.1 billion, this involves the construction of 14 kilometres of flood-ways and concrete-lined nullahs for the improvement of the Kam Tin River and Shan Pui River in Yuen Long. Design work for the remaining stages of this scheme and for the construction of main drainage channels in Ngau Tam Mei and San Tin, also in Northwest New Territories, is now in progress.
As an associated measure, about a dozen flood water pumping systems have also been constructed and are in operation to mitigate the impact of flooding in low-lying villages in the New Territories. Six more are planned.
The government is also working closely with the Shenzhen Municipality to resolve the flooding problem associated with the Shenzhen River, which divides Hong Kong and Shenzhen. The solution proposed involves the straightening, widening and deepening of some 17 kilometres of the river, to enhance its flow to reduce the flood risk in the catchments on both sides of the river. Preparatory work has been agreed upon by the two sides and is in progress.
The Land Drainage Bill, introduced in the Legislative Council in the middle of the year, is an essential component of the strategy to alleviate flooding in the New Territories. When passed into law, it will authorise government staff to access, inspect, clear and maintain important watercourses running through or bordering on private land, as a further attempt to reduce the risk of flooding.
Operation and Maintenance of the Drainage System
With the commissioning of each additional item of infrastructure, there is a consequential increased commitment in operations and maintenance. The volume of sewage treated territory-wide has increased from 385 million cubic metres in 1989 to 635 million cubic metres in 1993, of which 146 million cubic metres receive full biological treatment.
Since the establishment of the department, the approach to operation and maintenance of the public drainage system has progressively shifted from crisis management to preventive maintenance. The efficient maintenance of the drainage infrastructure is essential to ensure the proper and effective disposal of foul and storm water, and to prevent blockages and leaks which also cause foul odours, flooding or other nuisances to the public. The department now maintains 2900 kilometres of watercourses, drains and sewers. These are increasing at the rate of 130 kilometres per year. Some 45 000 clearance