Since its establishment in September 1989, Drainage Services Department has been deploying concerted efforts to relieve the flooding problem in the territory. At that time, serious and frequent flooding was experienced in the low-lying flood plains of the North and Northwest New Territories. To combat the flooding problem, the Department has undertaken a number of consultancy studies and initiated a flood protection programme in the areas.

The programme includes a series of major river training projects that provide the primary drainage network to alleviate the flooding problem by improving the Shenzhen River, Ng Tung River, Shan Pui River and Kam Tin River. Besides, the programme also incorporates a number of flood protection schemes at the low-lying villages. Protective bund is built for enclosing the village area to prevent external flood water from entering into the village, whereas rainwater falling within the village area will be brought over the protective bund by pumping station to the nearby channel.

In recent years, the flooding problem has been further exacerbated. Rapid developments in the rural areas have expanded the built up and paved areas. Rainwater which formerly stored in fields or fish ponds or infiltrated as groundwater in undeveloped land will now become surface runoff and enter into the drainage system within a short period, thus increasing the flow in the system. This results in more frequent flooding because the existing drainage system is incapable of coping this additional flow.

In some old towns and aged urbanised areas such as Mongkok and Sheung Wan, the areas are completely built-up and composed of major residential, commercial and industrial sectors. However, the existing stormwater drainage system in the area has been built as a component of the progressive urban extension spanning over the past hundred years. It has a capacity designed only to meet the old drainage standards. Over the years, we have made various local modifications, improvements and extensions to the system. Nevertheless, the system is still inadequate to meet the current flood protection standards and flooding occurs during heavy rainstorms or typhoon. The Drainage Services Department therefore has commissioned a series of eight Stormwater Drainage Master Plan Studies to provide a comprehensive solution to the problem.

The Stormwater Drainage Master Plan Studies not only cater for the most severe flooding areas in North and Northwest New Territories such as Sheung Shui and Yuen Long, they also cover all the flood prone areas of the whole territory. In fact, different areas would experience various degree of flooding and the threat of flooding is closely related to the water depth, velocity, its return period, and also the flood damage that will be induced.

 
The Drainage Master Plan Study areas

The purpose of studies were fourfold :

Searching the data in the Drainage Asset Management System

During the course of the Stormwater Drainage Master Plan Studies, a number of drainage improvement options have been identified for the existing system. These can be categorised as follows:

The choice of improvement options depends upon the characteristics of individual catchment area. We need to take into account of the various constraints such as the configuration of the drainage system, land requirements, environmental consideration, traffic impact, interface with other projects, the location of major utilities and underground structures, etc.

Consequently, we formulated the most cost effective first aid and long term improvement measures to meet the current flood protection standards and future needs. First aid measures were carried out immediately after the study to provide immediate relief to the flooding problem. Long term improvement measure will upgrade and extend the existing drainage system such that after their implementation, the problem of flooding will have generally been resolved.

We will also reinforce our drainage maintenance and operation structure in the studies. With the setting up of the computerised stormwater drainage asset inventory and management system, a breakthrough on the management of drainage operation can be anticipated.

Download the Executive Summary of Drainage Master Plan Studies