A landslip warning will be issued by the Hong Kong Observatory in conjunction with Geotechnical Engineering Office when there is a high risk of many landslips as a result of persistent heavy rainfall. The Landslip Warning is aimed at drawing attention of the public to the risk from landslips due to heavy rain. It is intended to prompt the public to take precautionary measures to reduce their exposure to risk posed by landslips. On the issuance of such a warning, a Landslip Special Announcement will be sent to the local radio and television stations for broadcast to the public and the announcement will be updated at regular intervals until the likelihood of landslips has diminished.

The Landslip Warning is aimed at predicting the occurrence of numerous landslips, and isolated landslips which cannot be predicted will occur from time to time in response to less severe rainfall when the Warning is not in force.

Like all forecasts, a Landslip Warning represents an assessment of the weather based on the latest information available at the time. There will unavoidably be false alarms as well as occasions when heavy rain which may cause landslips develops suddenly and affects parts of Hong Kong before a warning can be issued.

A network of over 120 automatic raingauges installed in the territories provides real-time rainfall data to the Landslip Warning System.

Real-time rainfall data are transmitted to the GEO control centre using mobile phone network.

By combining the real-time rainfall, the rainfall forecast in the coming few hours and the spatial distribution of slope features, together with a correlation model between rainfall and landslides, the need for issuing the Landslip Warning can be assessed.

Rainfall distribution
Distribution of slope features
HKO's weather radar image
Rainfall and landslide correlation models

HKO issues the Landslip Warning when the decision is made.

Television and radio stations broadcast the Landslip Warning at regular interval, together with advice on the precautionary measures to be taken by the general public at regular intervals.

Relevant government departments mobilize their Emergency Control Centres at the same time.