Hong Kong’s drainage system prevented a greater impact: Guy Carpenter

The 2008 rainstorm alone generated HK$237m incurred claims.

Hong Kong’s recent historical rainfall has been salvaged by its effective drainage system, keeping it afloat from a larger impact on the insurance sector, according to a Guy Carpenter report.

Notably, two significant weather events, Super Typhoon Mangkhut (2018) and Typhoon Hato (2017), led to substantial insurance claims of HK$3.06b and HK$858m, respectively.

The 2008 rainstorm alone generated HK$237m incurred claims, according to the Hong Kong Federation of Insurers (HKFI).

The market, with an annual rainfall of 2,400mm, faces flooding risks in low-lying rural, flood-prone areas, and older urban zones. Hong Kong frequently experiences tropical cyclones and monsoon troughs, resulting in heavy precipitation. 

The rainfall from 7 to 8 September alone amounted to one-quarter of the annual average. 

To combat this, the Drainage Services Department, established in 1989, focuses on flood prevention and sewage management. They've enacted long-term measures, designing drainage systems for 10- to 50-year rainstorms in rural areas and 50- to 200-year rainstorms in urban zones.’

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In rural regions, rivers were modified for greater capacity, and low-lying villages received protective embankments. Stormwater was directed to drainage channels.

Urban areas implemented a "three-pronged flood prevention strategy" involving upstream interception, flood storage, and downstream drainage enhancement.

Drainage tunnels, spanning 21km, redirect stormwater to rivers or the sea. Stormwater storage tanks at various locations temporarily hold water to ease downstream drainage systems. Plans are underway for five more tanks.

Local drainage improvements increased river capacity and added new underground drains. Over 100 km of river sections and 90 km of drains have been upgraded so far.

These infrastructure investments have effectively reduced damage caused by heavy rainfall, enabling Hong Kong to quickly resume normal economic activities following flooding events. 

An illustrative example is the city's MTR subway system, which resumed full operation on all lines by September 9.