Title: Sustainable Stormwater Drainage 1. Edwin, Distinguished - PDF document

1 DSD Research & Development Forum 2016 Theme: “Striving Innovation in Sustainable Stormwater Drainage” Date: 8 November 2016 Venue: Lecture Hall, 1/F., Hong Kong Science Museum, TST Keynote Address by Ir HON Chi-keung, Permanent Secretary for Development (Works) Title: Sustainable Stormwater Drainage 1. Edwin, Distinguished Speakers, Ladies and Gentlemen, Good Morning. It is my first time to join your R&D Forum, and I am most happy to speak to you on this occasion. You have chosen the theme for the morning session as “Striving Innovation in Sustainable Stormwater Drainage” and I think this is indeed very timely after we had experienced some rather unusual weather condition just a few weeks ago. 2. Let’s have a look first of this a video clip which was widely shared in the social media after the heavy rainfall event on 19 October. Such horrific scene happening in our built up areas is quite unexpected especially at this time of the year. 3. Indeed, this is the first time of having a Black Rainstorm Warning in October since we have the rainstorm warning system from 1998. In fact, October had the highest mean temperature in record and the maximum hourly rainfall record in October was also broken. This particular rainstorm event together with the subsequent Super Typhoon Haima came at the end of October is really unprecedented. 4. This is the severe flooding in Yangtze River basin in China this summer. Wuhan city was inundated. It was the most severe rainstorm since 1998, which recorded 44% of annual rainfall within just one week. The city has issued a red alert due to this rainstorm, the highest in China’s four-color warning system. The City’s metro was affected, roads were closed and many areas of the city were flooded. 5. So all these are writings on the wall. And the climate change impacts may be beyond our anticipation. To this, we should ask whether we are prepared to face this challenge. In particular, is our drainage infrastructure ready or is it sustainable?

2 6. Talking about Climate Change, we are concerned with extremities like increased occurrences of prolonged hot weather ������� extreme rainfall events, both in terms ��� ��������� ���� �������� ����� severe typhoons (such like the Haiyan hitting ��������������������������������������������������� sea level in Hong Kong and hence the risk of flooding will increase especially under the threat of storm surges brought about by tropical cyclones. 7. All these climate change phenomena bring significant threats to the built-up area, particularly so for Hong Kong which is well known for being a very densely populated city. 8. For us, we are probably living in the most densely populated environment in the world, perhaps just second to Bangladesh. This is obviously creating a big challenge to us in terms of managing crisis arising from climate change. Moreover, we are working very hard to expand our built up environment in response to housing demand and also public aspiration for improving our living standards. So space is coming more and more an issue to everyone including our drainage network. Whether we are geared up to protect ourselves against flooding risks in terms of land use planning or priority setting will have to be resolved. 9. So I think the question for us is how best we could provide Hong Kong with a sustainable drainage system within all these constraints. 10. In the past, we had been making use of the hard engineering approach to managing flooding risks. We built engineering channels, conduits or flood ponds to serve the purpose. These were particularly the case for the New Territories where space at that time was not much of a concern. 11. But these measures are obviously not sustainable at this time especially with the threat of climate change and space concerns. Obviously we need to put our brains together to new measures. 12. In fact whether we have sufficient conditions to adopt the traditional hard engineering approach is not something entirely new to us. This has happened in the built up areas for years. So we have built interception tunnels upstream or storage tanks, all of them making use of the available space underground. 13. The Lai Chi Kok Drainage Tunnel and Happy Valley Storage Scheme are just two examples. There are others as well.

3 14. But the question for us: - are these sufficient? And just imagine if 44% of our annual rainfall, like the case of Wuhan I just mentioned, and that is about 1,000mm, came within just one week in Hong Kong. Imagine if a super typhoon approach us from the westerly direction bring up storm surge of over 5 metres above principal datum. All the areas marked red in this map would become flooded. So are we prepared? 15. To cope with the upcoming climate change, I think you know that the Government is taking actions in earnest. The 2015 Paris Climate Conference (COP21) has reached an agreement to set a goal of limiting global warming to less than 2 degrees Celsius (° C) compared to pre-industrial levels. We have established a Steering Committee on Climate Change, and this is chaired by CS for Adm, with a view to holistically overseeing the necessary actions. 16. And I think we are all familiar with the 3 strategies to handle climate change: Mitigation, Adaption, and Resilience. 17. For mitigation, this is about reduction of further carbon footprint and this is very important and applies to all sectors. Clearly we have a role to play here by adopting green procurement ������������������������������������������������������ devices in our operation like our pumps. Another area we could assist is that our facilities do occupy quiet sizeable land and there is good opportunity for us to have some renewable energy devices such as PV cells in our facilities. Understand that you are already working on this for the Shui Ho Wan STW. 18. But in terms of flood control, I think our main focus will be on the adaption and resilience aspects. 19. For adaption, we are talking about our ability of anticipating adverse effects of climate change as well as minimizing the damage. So are how are we going to adapt to significant rise in sea level then? Hong Kong is not alone. 20. This MOSE Project - Modulo Sperimentale Elettromeccanico (MOSE) is about protecting the city of Venice and the Venetian Lagoon from flooding. The project is an integrated system consisting of rows of mobile gates installed at the outer islands such as mouth of Lido etc. Two short videos here show the operation of mobile gates. 21. Simply speaking, there are buoyant flap gate, which are hollow and full with water, embedded in the seabed under normal situation. When the gate has to close, air is injected into the flap gates which will then lift due to buoyancy.

4 22. The Thames Barrier is another example and it spans 520 metres across the River Thames near Woolwich, protecting 125 square kilometres of central London from flooding caused by tidal surges. It was constructed in as early as 1982 and the gate crest level is as high as +7.05mCD. 23. How about the cities nearby? The Marina Barrage is a dam in Singapore built at the confluence of five rivers, across the Marina Channel. It provides water storage, flood control and recreation. 24. So, how about us? Could these examples be applicable to Hong Kong? Is a mobile flood gate scheme feasible for protecting our Harbour Area? There will be questions - when a major storm surge event happened inundating the metro area – on why we have not thought about similar protection schemes. So could we have similar barriers at the east and west entrances to our Victoria Harbour? 25. I understand the department is looking into this and of course, a number of issues including practicality, resources implications, impact to the marine traffic and environment etc. And this may prove eventually to be not cost-effective. In that case, we may have to do more on the resilience part. 26. Resilience, in simple term, is how we could live with water and how much we could tolerate flooding. Let’s have a look of what others are doing. 27. This is the Water Square in Benthemplein, Rotterdam. The idea is simple as it adopts the concept of land co-use. The water square combines water storage with the improvement of the quality of urban public space. No one would like to have basketball during heavy rainfall. So can we design our drainage facilities such that they could be used by the general public? 28. Another good example is, I think a lot of people know already - the Malaysian Stormwater Management and Road Tunnel (SMART). The 11.5km long 13.2m diameter tunnel is the world-first dual-purpose tunnel diverts flood waters away from the confluence of the two rivers. 29. In fact for us, I know that we are already using similar concept of multi-purpose land use. Here shows the flood lake in Anderson Road Quarry Development. In addition to the purpose of floodwater storage, the flood lake also designed for public leisure purposes, and the water body will also mitigate the heat island effect. 30. The Tung Chung River Park is another often cited example which we should be proud of. It is under the Tung Chung New Town Extension project.