An Office of the Ombudsman probe revealed that more than 40 percent of landslides that occurred over the past decade involved government-built slopes, with some of them seeing repeated incidents within three years after the first slip.

The finding came after the watchdog launched a direct investigation operation in November into the government's work on landslide prevention, mitigation and management of slope safety risks, which also took in relatively more serious landslides involving government-built slopes since 2015.

It said Hong Kong recorded an annual average of around 214 landslides from 2015 to 2024, nearly one third below the annual average of around 300 landslides between 1989 and 2014.

The office found private man-made slopes, which number 15,800 accounted for around 5 percent of them, which it said was "understandable" given that government slopes, which number 38,600, form the bulk of the city's 61,000 man-made, with the rest, 6,300, involving mixed maintenance responsibility.

The failure rate of government slopes was still higher than that of private slopes by one to three times between 2020 and 2024, after the office discounted the actual difference between the number of incidents involving the two kinds of slopes.

A particular slope also saw four landslides happen "at different parts" within five years, the office found.

"Although the consequence-to-life category of all these government slopes with repeated landslides was not the highest category 1 the highest potential severity of casualties in the event of slope failure – and not every incident was large in scale, the recurrence of incidents inevitably raises concerns about the potential risks and structural safety of these slopes," the office said.

As such, the office has made a total of 32 recommendations to departments involved in landslide prevention, mitigation and management, namely the Civil Engineering and Development, Lands, Highways, Water Supplies and Architectural Services.

The government watchdog suggested the Civil Engineering and Development Department continue with its regular review of whether there was any room to optimise the current selection criteria of government-built slopes for inclusion in its landslip prevention and mitigation programme and consider expanding the scope of slope maintenance audits to include post-incident investigations and response actions.

It also urged the other four departments to make use of the centralised slope maintenance database to monitor the latest situations on slope maintenance, share common maintenance issues, as well as assess impact of heavy rainfall on slopes.