Enhancing slope appearance has become a priority for the Civil Engineering Department. Committed to landscaping every government slope, it plans to spend $60 million this year in slope beautification.

Refreshing appearance: There are a number of ways to beautify slopes and retaining walls, such as planting flowers and keeping existing trees. An artist's impression of the slope on Lyttelton Road, Mid-levels, after upgrading and greening work. (Sketch provided by Urbis Limited)

According to Deputy Director of Civil Engineering Raymond Chan, methods presently adopted to beautify slopes include soft landscaping and hard landscaping, or a combination of both.

Planting trees, shrubs and creeping plants are some examples of soft landscaping techniques.

Hard landscaping methods include using planter walls, introducing tree rings to preserve existing trees and shrubs, and drilling holes for creepers.

The landscaping and bio-engineering techniques to be adopted greatly depend on the geology and gradient of the slopes, Mr Chan said.

"The steeper the slopes, the more difficult to grow plants on them. For gentle slopes, say less than 30 degrees in gradient, we can plant all sort of trees, shrubs and grasses.

"However, if we want to grow plants on steeper slopes, say over 45 degrees in gradient, we have to introduce erosion-control mats to prevent soil erosion and ensure that the plants are able to take root.

"For slopes which are over 75 degrees in gradient, we have to use stone-pitching, planter walls or creepers to enhance their appearance."

Under the Landslip Preventive Measures Programme, the department has to upgrade some 250 slopes each year. The department's aim is to turn more than 70% of the slopes into vegetation slopes.

"The remaining 30% are either too steep or they are rock slopes which cannot support the growth of any plants. We have to adopt hard landscaping methods to enhance their appearance," Mr Chan elaborated.

Recently, the department has been successful in providing a green cover to a slope on Sai Yeung Choi Street North.

Another major greening project which is now proceeding is the slope-upgrading works along South Lantau Road. In this project, 24 slopes have been selected for upgrading.

"Since all these slopes are located in a country park area, we are going to provide vegetation cover to them to blend them with the surrounding environment," Mr Chan added.

The project will be completed by the end of next year.

Mr Chan said it is inexpensive to beautify slopes in Hong Kong, adding that the expenditure of slope beautification projects is not more than 10% of the total expenditure of slope upgrading works.

Private slope owners are also encouraged to use landscape treatment to blend their slopes with the surroundings, Mr Chan noted, adding that the department issued a layman's guide last year to offer advice to private slope owners.

Satisfactory greening effect of a slope can only be achieved through appropriate maintenance and management, Mr Chan said.

"Landscape maintenance is not difficult and all we need to do is to replenish soil and firm up plants when necessary, control pest and disease without delay, prune and weed appropriately, and replace dead, missing plants and eroded grass cover when necessary. "

There are many advantages of slope beautification. It not only improves the appearance of slopes, but also raises the land value and creates a green environment, Mr Chan concluded.