In July, a torrential rainstorm linked to Typhoon Chanthu slammed into Hong Kong. More than 150 millimetres of hammering rain fell in an hour, causing flash floods that killed three people and damaged 3,000 houses. Such events are likely to become more common. Climate change is making many of the world’s coastal cities increasingly vulnerable to flooding from the effects of sea-level rise, intensified typhoons, storm surges and rapid urbanisation. Hong Kong, located on the South China Sea, is one of these. The flooding this summer served as a reminder that the government’s heavy engineering-led approach to managing the risks needs revamping.
Since the 1960s, the city has seen 136 severe storms, with six to seven typhoon cyclones affecting the region every year, often causing flooding. Over the last three decades, more than 380 people have died in floods, and there have been major financial losses. A single storm in May 1992 caused more than 100 million HKD (US$12.9 million) worth of damage to properties, fish ponds, farmlands and telecommunication utilities.
After this event, the Hong Kong government established the Drainage Services Department (DSD), with the primary purpose of overseeing flood management. So far, the DSD has invested over 20 billion HKD (US$2.6 billion) in improving flood infrastructure, and engineering technological solutions. But, as Typhoon Chanthu has shown, this engineering-led approach is inadequate. Sustainable flood risk management, using concepts such as “living with floods” or “making space for water”, being applied in countries including the United Kingdom, offers more options for achieving a win-win strategy on flood mitigation, socio-economic development and the environment. These strategies may provide Hong Kong and the wider Pearl River Delta with useful insights.
Hong Kong, often dubbed Asia’s world city, is one of the most important global financial centres. In 2009, its per capita GDP was US$42,800 – the fifteenth largest in the world. It was also ranked as the fifth most expensive big city on the planet in 2008. But this high-value property faces increasing risks. About 424,000 people and 100 billion HKD (US$12.9 billion) are currently vulnerable to storms in Hong Kong – the seventh highest economic exposure level to such weather events in the world, according to the World Health Organization Collaborating Centre for Research on the Epidemiology of Disasters (CRED).
Much of Hong Kong’s landscape is hilly, which limits urban development in many places and has led planners to create more space through land reclamation in flood-prone districts. A population of over 7 million is settled along the lower-lying costal area. There is a tension here: while the Hong Kong Government has realised the region’s vulnerability to flooding, it is keen to develop the area most in danger – and attempts to ameliorate the flood risk have so far been poor.
The tragic loss of life this July was a wake-up call – and a reminder that more challenging future is on its way. Storms, along with sea level rise and heavy rain will be more frequent in light of climate change. The Hong Kong observatory (HKO) reports that total annual rainfall in Hong Kong has risen in the last 50 years from 226.5 centimetres in the 1950s to 251.8 centimetres between in the 1990s. Moreover, the return period for torrential rainstorms shortened between 1900 and 2008. In this context, and despite the red-hot property market, planners must stop building in Hong Kong’s flood-prone area. We should accept the fact that flooding is hard to control and be prepared to “live with floods” and provide more space for flood storage.
The United Kingdom offers useful lessons here. The country has had some serious flood events in the past century and its flood-management policies are worthy of note. Importantly, the country’s strategies recognise that future climatic change is unpredictable; that flooding is a part of nature; and that we are no longer only using hard engineering to control floods, but also need to apply adaptation to enable communities to cope with risks.
The United Kingdom’s overarching policy statement on this issue (Planning Policy Statement 25, or PPS25) offers more options on flood mitigation. It includes the concept of “making space for water”, aiming to give more space for flood restoration and restricting development plans in high-risk areas. The best approach is to plan before building, hence the PPS25 ensures that the assessment process and sustainability appraisal consider social, economic and environmental aspects in all development projects. It then further appraises the cost-benefits, with broad engagement from all stakeholders through public participation.
Public participation is key to progress. The Coastal Flood Management Plan (CFMP) in England’s Humber Estuary is a good example. The CFMP has welcomed members of the local community and NGOs onto the committee that assesses the project’s progress. There is no doubt that this level of public participation in the decision-making process can increase the time it takes to take a project forward. On the other hand, it provides dynamic, open and interactive approaches that ensure a scheme really engages with local concerns surrounding flood management and helps to minimise any bias on the perception of flood-management processes. The authorities can also learn from the process, for example using residents’ knowledge of local flood history to supplement their computational models.
Back in Hong Kong, most of the work carried out under the DSD’s core strategy – the 1996 Drainage Master Plan (DMP) – has been engineering-led. Its projects have included widening and straightening the main river streams, such as the Shenzhen River and Kam Tin River, in the New Territories, one of Hong Kong’s three main regions; building underground sewerage; restoring ponds for collecting flood water; and monitoring the hydraulic conditions of main urban drainage.
As a result of this narrow focus on technological solutions, today it is almost impossible to find any "natural streams" in Hong Kong as nearly all the rivers have been converted into artificial channels. The sustainability implications of these engineering projects are often not fully considered and research has already shown that river regulation works have caused negative ecological impacts. For example, following 1997 flood-engineering works in the Deep Bay area – a wetland area of high ecological value and an important habitat for birds – 346,000 square metres of fishponds were found to be at risk of disappearing. In addition, as a result of 1990s river regulation, 11 out of a total of 32 local freshwater fish species are now threatened with extinction.
The DSD has, to an extent, realised its mistakes and has started to experiment with ecological restoration in concrete channels located in the Yuen Long floodway. The main idea is to compensate environmental loss and rebuild the wetland habitat by, for example, installing reed-beds and building water ponds for birds, freshwater fish, frogs and dragonflies. This might point towards a more sustainable approach to flood management, but progress is relatively slow – and there are no other restoration projects on concrete channels currently being undertaken.
The DSD’s approach to information sharing also raises concerns. The organisation has conducted flood-risk modelling and mapping of intensive rainfall in highly populated areas since the early 2000s, and has released information on flooding black spots to the public. But, collectively, the spots only cover a small area and vital information is not made available. The DSD needs to provide more transparent flood-risk data to enable the public to prepare for floods. This happens elsewhere in the world, for instance in Australia, where flood mapping provides detailed risk data by location.
Furthermore, the DSD’s focus is largely limited to urban and rural issues, even though Hong Kong is also exposed to coastal inundations, as flooding in the fishing town of Tao O has shown. Monitoring sea and tide level falls to the HKO, while the Civil Engineering and Development Department (CEDD) deals with seawall maintenance and beach improvement. Governance of coastal-flood management in Hong Kong remains blurred and adequate strategies and policies are still lacking, even as the dangers increase. Here, and at every level of Hong Kong’s flood-risk management, a more coherent approach is needed. Now, more than ever, it is necessary to formulate a long term and sustainable flood-management strategy for Hong Kong and the wider Pearl River Delta.
Faith Chan is a research cluster associate, Gordon Mitchell senior lecturer and Adrian MacDonald professor, all at the School of Geography, University of Leeds.
Homepage image from Marc Oh!