Plan for Future Storms and Coastal Floods in Hong Kong and the Greater PRD Bay Area

Hong Kong has spent hugely expensively (over 200 million HKD) on inland and coastal flood engineering measures and effectively reducing the floods. However, recent coastal floods implied something we must do more other than investing in engineering and technological infrastructures to improve climate resilience.

However, during the last two summer, two fierce storm surge events from Typhoon Hato (August 2017) and Typhoon Mangkhut (September 2018) caused severe floods and other damages to Hong Kong, Macau and cities across the Greater Bay area of the Pearl River Delta. Intensive rainstorms, storm surges and high tidal waves caused severe floods mainly in low-lying coastal areas or habourfront, which recalled us some memories from Heng Fa Estate in Heng Kong East. Typhoon Mangkhut (2018) and Hato (2017) caused severe surges. The sea-level that recorded by the HKO at Quarry Bay (Victoria Harbour) reached at 3.88 metres by typhoon Mangkhut, and at 3.57 metres by Hato. Other low-lying areas e.g. Tai Po Kau, recorded the maximum water level reached up to 4.71 metres (by Mangkhut) and 3.77 metres (by Hato).

Many coastal low-lying areas in Hong Kong, e.g. Tai O town (see Figure 1), Shek Pik, Mui Wo, Cheung Chau, Siu Sai Wan, South horizons, Lei Yue Mun, Tseung Kwan O, Sha Tin, Tai Po, Sai Kung, Lau Fau Shan, Peng Chau, etc. have been inundated by sea water. Other cities in the PRD, such as Macau, Shenzhen and the south of Guangzhou (at Nansha districts) were also flooded during the visit from Mangkhut and Hato. Afterwards, many coastal infrastructures (e.g. sewage treatment works, breakwaters of piers, beaches and harbour-front promenades) were also damaged in both events.

The Intergovernmental Panel on Climate Change (IPCC) project the global mean sea-level will be increased from 0.6 to 1.4 metres (depends on the ice-melting of the polar ice sheets and various developmental climatic scenarios) by the recent AR4 and AR5 reports. Each year will normally have 3-5 typhoons to visit us. Sometimes if storm surge combines with an astronomical high tide may occurs, which means the sea-level will be further risen for 1 to 2 metres. Under these threats (with surges, high tide and sea-level rise), we should be well prepared for future storms. Mixed options should be adopted by improving the coastal engineering measures (e.g. sea-walls, breakwaters and embankments), alongside with soft measures (e.g. establish a flood warning system to Hong Kong and the PRD, initiate flood insurance system, further improve the emergency plans after floods, etc.).

Recently, the governments of Hong Kong and the Guangdong-Hong Kong-Macao Greater Bay Area voiced out to collaborate further on the Pearl River Bay Area Development Plan. We should take this as an opportunity to establish a long-term regional flood risk management plan for Hong Kong and other cities in the PRD, as storms are affecting the whole region. We should work together with the PRD governments tightly on flood risk management and climate change adaptation plans, which will be vitally important to the region.

Dr Faith Chan – Assistant Professor in Geographical Sciences, Faculty of Science and Engineering, University of Nottingham Ningbo China; Senior Visiting Research Fellow; Water@Leeds Research Center, University of Leeds, United Kingdom

Photo Source: Tai O coastal flood when typhoon Mangkhut hit Hong Kong on 15-16 September 2018. (Eddie Tse approved to use)