Super Typhoon Mangkhut is a flood threat, but climate change will bring much worse

Super Typhoon Mangkhut is forecast to hit Hong Kong tomorrow. Have we learned from the past to minimise the threats?

On August 29, several districts in the New Territories experienced torrential rain and flash floods, even on an amber rainstorm warning. This led to severe flood damage to cars, and electrical equipment and appliances. Firefighters and volunteers had to evacuate animal shelters to save the creatures from drowning.

As a coastal city with a subtropical climate, Hong Kong receives around 2,400mm of rainfall yearly - 80 per cent during the typhoon season. A large part of the city is also located in low-lying, flood-prone areas.

Thanks to its severe-weather warning system and storm protections, Hong Kong stays reasonably prepared for floods, but recent events such as last year's Typhoon Hato, which triggered the most severe No 10 signal and caused widespread flooding, showed that these measures may be inadequate.

Climate change will also make flooding more frequent and severe. By 2100, floods that would have occurred once every 50 years will return every three years or less - as a result of rising sea levels and changing rainfall patterns. Many cities around the world have now adopted flood-protection standards against once-in-a-century floods; parts of the Netherlands can even withstand floods seen once in 10,000 years. Without adequate safety measures, more than 687,000 people and HK$9.3 trillion worth of assets in Hong Kong are predicted to be at risk.How Hong Kong is preparing for strongest storm in decadesFlood-risk management needs to be anticipatory, rather than reactive. Flood-risk profiles should be publicised, so insurance companies can gauge risk, and so building developers can install appropriate flood-proofing measures.

Aside from improving traditional flood-management measures, we need to learn to live with inevitable flooding.

Weather warnings must reflect actual safety conditions. Local warnings such as the special announcement on flooding must possess legal validity; it's counterproductive if they do not ensure a state of readiness and let people respond properly.

The cost of playing catch-up on flood protection and remedial works is high, but trivial compared to the potential damages. It is no longer a question of if, but when the next flood will strike.

Photo copyright: SCMP

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