LCQ15: Landslide risk of slopes in Hong Kong

Following is a question by the Hon Cheung Hok-ming and a written reply by the Secretary for Development, Mrs Carrie Lam, in the Legislative Council today (May 11):


It has been reported that a landslide occurred earlier at a slope in Ho Man Tin although it did not rain that day, causing people to worry whether with the approach of the rainy season, the slope management and maintenance work carried out by the authorities is able to reduce the risk of landslides.  In this connection, will the Government inform this Council:

(a) of the number of existing man-made slopes and natural hillsides in Hong Kong, and whether the authorities have assessed the number of such slopes and hillsides with potential risk; of the plan and the time required for the authorities to deal with such dangerous slopes;

(b) of the number of landslides which occurred on natural hillsides, man-made slopes and retaining walls within the purview of the Government in the past three years, as well as the resultant casualties;

(c) of the number of landslides which occurred on privately-owned natural hillsides and man-made slopes in the past three years, as well as the resultant casualties;

(d) of the number of Dangerous Hillside Orders served last year and, among them, the number of orders which have been fully complied with, the number of persons convicted of non-compliance with such orders and the main reasons for their non-compliance;

(e) whether the authorities have plans to step up the inspection of both government and privately-owned slopes and enhance other relevant measures before the advent of the forthcoming rainy season so as to reduce the chance of landslides;

(f) regarding enhancement of public awareness about the risk of landslides arising from man-made slopes and natural hillsides, of the specific details of the public education activities organised by the authorities at present; and

(g) given that the Landslip Prevention and Mitigation Programme ("LPMitP") has been implemented by the authorities since 2010 to dovetail with the Extended Landslip Preventive Measures Programme which was completed at the end of 2010, with an aim to further reduce the risk of landslides, of the improvement made to LPMitP as compared with the previous programme; if no improvement has been made, of the reasons for that?



The Government has all along been attaching great importance to the work on slope safety and is committed to minimising the risk of landslides.  Apart from systematically implementing landslip prevention and mitigation programme targeting at slopes in public areas, the Government also requires owners of private slopes to undertake maintenance works. Furthermore, the public is reminded to adopt suitable preventive measures to minimise the risk of landslides before the onset of rainy season every year for protecting the safety of the public. In fact, our achievement in the works on slope safety in Hong Kong over the past three decades has won professional recognition.

My replies to the seven parts of the question are as follows:

(a) To manage slope safety work, the Geotechnical Engineering Office (GEO) of the Civil Engineering and Development Department has maintained records of man-made slopes in Hong Kong in its Catalogue of Slopes, which presently contains about 60,000 registered slopes.  It has also implemented the Landslip Preventive Measures Programme (LPMP) for over 30 years to deal with man-made slopes at relatively high risk in the Catalogue in a systematic manner.  All in all, we have upgraded about 4,600 Government slopes and conducted about 5,200 safety-screening studies on private slopes.  The overall landslide risk from slopes has thus been substantially reduced to a reasonably low level that is commensurate with the international best practice in risk management. As about 60% of the area in Hong Kong is natural slope, we have no statistics on the total number of natural slopes.  However, we have identified 2,700 or so natural slopes with known hazards.

After the completion of the LPMP in 2010, the remaining landslide risks mainly arise from man-made slopes with potential hazards that affect developed areas and natural slopes with known hazards which are close to existing buildings and important transport corridors. In this connection, the GEO launched the Landslip Prevention and Mitigation Programme (LPMitP) in 2010 to dovetail with the LPMP, which was due for completion at the end of the same year.

(b) and (c) The following table shows the number of landslip reports concerning registered government or private man-made slopes (including retaining walls) over the past three years:

Year  Number of landslip  Number of landslip  Total*
        reports concerning   reports concerning
        registered              registered private
        government slopes   slopes

2008       369                  65              434
2009        51                   14               65
2010       104                  12              116

* Most of the landslides were triggered by heavy rainstorms. In general, the number of occurrence of landslides is closely related to the rainfall distribution and intensity.

We have no statistics on injuries in the aforesaid reported landslide incidents but recorded one landslide incident in 2008 involving private and government land causing two fatalities.

(d) Last year, we issued 140 numbers of Dangerous Hillside Orders pursuant to the Buildings Ordinance to owners of private slopes.  87 dangerous slopes with upgrading works were completed by owners in compliance with the Orders. 21 Dangerous Hillside Orders are not yet due.

Some common reasons for owners failing to comply with the Order to complete slope upgrading works include:

(i) The owners are still acting on the Orders (e.g. hiring professionals, conducting investigation and submitting upgrading proposals for approval, etc.); and

(ii) The concerned owners have filed appeal against the Orders.

For the above reasons of not completing the slope upgrading works in accordance with the Dangerous Hillside Order, prosecution has not been instituted last year.

(e) and (f) To reduce landslide risk and protect public safety, the GEO always reminds owners' corporations and mutual aid committees of private buildings to complete routine inspections and necessary maintenance works for all their slopes before the onset of a rainy season by way of letters, announcement of public interests on television (TV APIs), radio broadcasts and press briefings on slope safety before the onset of rainy season.

Furthermore, the GEO plans to organise the following publicity and public education activities in 2011-12 to raise the public awareness of landslide risks arising from man-made and natural slopes:

(i) Production of new TV APIs on slope safety;
(ii) Tree planting activities (to raise public awareness on landslide hazard mitigation installations for natural slopes and caution them against the dangers of going near these installations during heavy rainstorms);
(iii) School seminars;
(iv) Site visits for secondary school teachers;
(v) Press briefings; and
(vi) Roving exhibitions at busy shopping malls.

(g) The new LPMitP introduces a new system to deal with natural slopes in addition to improving man-made slopes.  In accordance with a risk-based priority ranking system, the most deserving man-made slopes and natural slopes with known hazards are selected for follow-up action.

Under the LPMitP, we will conduct upgrading works for 150 government man-made slopes and safety-screening studies for 100 private man-made slopes each year.  As regards the natural slopes with known hazards and close to existing buildings and important transport corridors, we will conduct studies and necessary risk mitigation works for initially 30 natural slopes each year.  Overall, our target is to keep the landslide risks in Hong Kong to a reasonably low level in the long term.

Ends/Wednesday, May 11, 2011
Issued at HKT 14:19