Overview of Storm Surge
During the passage of tropical cyclones, the associated strong winds push the sea water towards the coast causing a rise of the sea level. In addition, the low atmospheric pressure of the tropical cyclone also sucks up the sea water near the cyclone centre. Such phenomenon is called storm surge. If storm surge occurs during astronomical high tide, the sea can rise to a high level and cause flooding in low-lying coastal areas.
Measures for Storm Surge Spots
Most of the storm surge spots are located at low-lying coastal areas. Seawater infusion or inundation may occur when the sea level rises. Measures, such as additional drainage system or drainage improvement works, may not effectively solve the problem of seawater infusion or inundation. To handle this problem, provision of flood walls, installation of demountable flood barriers and installation of flap valves at the drainage outlet can prevent seawater from flowing in, thus lowering the flooding risk.
In response to storm surge, government departments and citizens need to cooperate to reduce the impact. Apart from the above measures, the government will consider non-structural measures, such as Early Alert System at storm surge spots. Upon the issuance of storm surge alerts by the Hong Kong Observatory on the storm surge spots DSD will, at the relevant locations, deploy pumping facilities, install water-stop boards, and/or provide sandbags for the residents' use. DSD will also deploy emergency gangs to station at the sites prone to serious inundation for implementing flood alleviation measures, such as removal of blockage at drains, to minimise the flooding risk arising from storm surge. The government will arrange emergency and evacuation plans, if necessary.