HK Submerged? Is This Map For Real?

By Debra Tan, Chien Tat Low, Dharisha Mirando 18 November, 2019

With so much press on the new sea level rise numbers - CWR's Tan, Low & Mirando fact check to see if we need to be worried

Climate Central's latest sea level rise (SLR) research showing 150mn being displaced by 2050 globally has created much noise in HK after Mingpao's coverage - yet the result is misleading
Not only did Mingpao factor in storm surges with SLR without making it clear, Climate Central's new CoastalDEM map also overestimates the impact on HK; the HK Observatory has also questioned it
Despite this, HK needs to be prepared for SLR PLUS storm surges but HK’s adaptation plans still fall short & no-sense climate strategies leave key infrastructure e.g. Exchange Square exposed

There has been much noise about sea level rise (SLR) recently thanks to a research paper from Climate Central that uses a new map called CoastalDEM to gauge the impact on coastal areas. The paper revealed catastrophic results – even with moderate levels of global warming, SLR will permanently flood areas that are home to around 150 million people by 2050; and by 2100, the number displaced will rise to 200 million.

In the case of Antarctic instability, annual coastal floods will reach further inland, affecting a total of 300 million people by 2050 and 480 million by 2100. The majority of people living on affected land are across eight Asian countries: China, Bangladesh, India, Vietnam, Indonesia, Thailand, the Philippines, and Japan – seven out of eight are developing countries.

While it is great that there is increased attention, the impact on HK is overstated– but that is not to say we are not at risk

These findings have certainly generated concern worldwide, with coverage by major media including The New York Times and BBC. In Hong Kong, a map of the affected areas in Hong Kong was published in Mingpao and we have received several queries as to whether this is real. While it is great that there is increased attention to the issue, the impact on Hong Kong is overstated– but that is not to say we are not at risk.  Here’s why …

Real or just alarmist? The problem with the Hong Kong map in Mingpao…

The above is the map in the Mingpao article. It looks bad. Mingpao created the map using data from CoastalDEM, assuming moderate global warming (RCP4.5).

The article implies that the above map is caused solely by SLR by 2050, but actually storm surge was included

The result, though shocking, is misleading. Two reasons – firstly, the article implies that the above is caused solely by SLR by 2050, but to reach the flood levels depicted in the above map, maximum high tide levels and maximum coastal flooding from typhoon storm surge were included.

There is a difference here – the impact of SLR due to global warming is permanent and likely irreversible, while the storm-surge-driven coastal flooding is event-driven. Below is the same map only with SLR by 2050; it looks slightly better but it’s still not great. If you want to play around with the CoastalDEM map with different scenarios, click here.

Secondly, but more importantly, there are issues with the new CoastalDEM map for Hong Kong…

The CoastalDEM map overestimates the impact on Hong Kong…

So how bad is the flooding?

Taking the high end of the local range of 0.41m, we added the local high tide of 2.5m bringing maximum SLR to 2.91m by 2050

We tested the calculations… There are 2 factors – (1) the height of SLR and (2) the underlying map. As we are heading to 3°C-4°C of global warming, to determine SLR we took the worst-case local scenario provided by the Hong Kong Observatory (HKO), which predicts SLR of 0.25m-0.41m under RCP 8.5 by 2050. Taking the high end of the local range of 0.41m, we added the local high tide of 2.5m bringing maximum SLR to 2.91m by 2050.

It is important to pick the right map when estimating the impact

And now for the maps… it is important to pick the right map when estimating the impact on Hong Kong as the results can be significantly different as seen from the graphic below – from hardly any impact on the left to moderate impact on the right.

  1. HK DTM map (5m grid) – hardly any impact (LH Side) – a 5m-grid Hong Kong Digital Terrain Model (DTM) released by the Lands Department of Hong Kong. It is clear that nearly the whole coastline of Hong Kong Island and Kowloon remain unaffected at 2.91m; and
  2. NASA SRTM map (30m grid) – moderate impact (RH Side) – produced by NASA’s Shuttle Radar Topography Mission (SRTM). This map shows parts of Kowloon, like Kai Tak and Tsing Yi, starting to show signs of coastal flooding at 2.91m.

So which is real?

Although CoastalDEM aims to improve on SRTM at global and national scales, results need to be interpreted with caution when it comes to individual cities like Hong Kong which has densely clustered tall buildings in coastal areas.

For Hong Kong we believe that CoastalDEM materially overestimates the impact of SLR by 2050, assuming they’re using the local projection for SLR. How do we know this? Because of Mangkhut. In September 2018 Super Typhoon Mangkhut brought storm tides that affected a few low-lying coastal areas. Storm tides measuring 3.88m at Victoria Harbour only affected Lei Yu Mun, Hang Fa Tsuen, and Tseung Kwan O but not the large areas highlighted in the CoastalDEM map. Since the projected SLR by 2050 in the worst case is only 2.91m, we know that the CoastalDEM map is an overestimation.

The Hong Kong Observatory (HKO) has also questioned the output

The Hong Kong Observatory (HKO) has also questioned the output, as it looks different from HKO’s own research and past observations. And it’s not just Hong Kong; even the Malaysian authorities think this new research is an “overestimation”.

Therefore, for Hong Kong use the HK DTM map which is freely available and is the most accurate.

CoastalDEM may be wrong for Hong Kong, but Hong Kong needs to be prepared for SLR PLUS storm surges

Hong Kong may appear to be safe from SLR by 2050 on the HK DTM map but it may not be so immune to extreme storm surges coupled with SLR.

According to CWR, HK is at risk of storm tides at 5.87m brought about by typhoons by as early as 2030…

…impacting areas like IFC & Exchange Square & has implications for almost 3/4 of HK’s GDP

According to CWR’s New Base Case Scenario in the recent co-authored CLSA report, Hong Kong is at risk of storm tides at 5.87m brought about by typhoons by as early as 2030. This would impact large swathes of Kowloon and Hong Kong Island. Central, Hong Kong’s financial district – including IFC, Exchange Square, and the headquarters of HSBC and Standard Chartered – would also be inundated as can be seen below. This has implications for almost three quarters of Hong Kong’s GDP due to the vulnerabilities to the real estate, trade and financial sectors. Read more here.

As we are on the track for warming of 2.9°C-3.4°C instead of 1.5°C-2°C, Hong Kong is heading for a “Hot, Thirsty, Sweaty & Wet” future. Scenarios must be adjusted to fit the new base case for future planning.

HK must seriously step up its adaptation plans alongside aggressively decarbonising its economy

To remain a global financial hub, Hong Kong must seriously step up its adaptation plans alongside aggressively decarbonising its economy. Unfortunately, Hong Kong’s adaptation plans still fall short and the current no-sense climate strategies leave key assets and infrastructure exposed. So get on top of Hong Kong’s water and climate risks now!


Further Reading

  • Why Hong Kong Needs A Meat Tax – Want to help stop Amazon deforestation? How about better health? With Asia’s climate action looking bleak, Greenqueen’s Ho sees a meat tax as HK’s chance to become a regional leader
  • Nepal Clean Irrigation Initiative – Up in the mountains, communities still rely on fossil fuels but Solerico is out to change that in Nepal with solar-powered pumps. Their co-founder & CEO Spencer expand on the challenge, financials & impact
  • Race For Water – Fighting Plastic Pollution In Our Oceans – What does the world’s largest solar-powered catamaran have to do with ocean plastic pollution? The Race for Water Foundations’ Lee explores this sustainable solution for ocean conservation with us
  • Shrinking Plastics – Implications Of Tighter Regulations On The World Industry – Plastics are on the way out as governments put stricter laws in place. How should investors respond? WWF HK’s Rawle, Champagne & Hilton share from their latest report
  • Climate Action 100+ First Progress Report – Having brought 370+ global investors together, what has Climate Action 100+ achieved? From setting emissions reduction targets to disclosing climate scenario analyses, check out key results from their director Wright
  • Thirsty And Underwater: Rising Risks In Greater Bay Area – How will water & climate risks, including rising sea levels & droughts, threaten the already water-stressed Greater Bay Area (GBA)? CWR’s Tan & Mirando explain in their latest CLSA report and highlight companies’ failure in climate risk disclosures
  • No-Sense Climate Strategies: From DSD To HSBC – Hong Kong’s shortsighted & unrealistic climate plans will leave key assets & infrastructure exposed that mean the government, companies, investors and the public are even more exposed. China Water Risk’s Dharisha Mirando & Debra Tan expand
  • Hot, Thirsty, Sweaty & Wet: HK’s Future Down The Drain? – China Water Risk’s Woody Chan & Debra Tan look beyond current tensions and see very real threats to Hong Kong’s future from climate change. Get ready for a hot, thirsty, sweaty & wet future
  • Confronting Storms & Climate Risk In HK – Typhoons Hato and Mangkhut have wreaked havoc in the Greater Bay Area but Dr. Faith Chan from the University of Nottingham Ningbo believes these climate risks can be confronted, with Hong Kong leading the way
  • Building Flood Resilience For Hong Kong – HK is the rainiest city in the Pacific Rim and with the threat of climate change, it’s heading for a wetter future. The Drainage Services Department’s senior engineer Patrick Chan shares the city’s strategies to improve flood resilience
Debra Tan
Author: Debra Tan
Debra heads the CWR team and has steered the CWR brand from idea to a leader in the water risk conversation globally. Reports she has written for and with financial institutions analyzing the impact of water risks on the Power, Mining, Agricultural and Textiles industries have been considered groundbreaking and instrumental in understanding not just China’s but future global water challenges. One of these led the fashion industry to nominate CWR as a finalist for the Global Leadership Awards in Sustainable Apparel; another is helping to build consensus toward water risk valuation. Debra is a prolific speaker on water risk delivering keynotes, participating in panel discussions at water prize seminars, numerous investor & industry conferences as well as G2G and academic forums. Before venturing into “water”, she worked in finance, spending over a decade as a chartered accountant and investment banker specializing in M&A and strategic advisory. Debra left banking to pursue her interest in photography and also ran and organized philanthropic and luxury holidays for a small but global private members travel network She has lived and worked in Beijing, HK, KL, London, New York and Singapore and spends her spare time exploring glaciers in Asia.
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Chien Tat Low
Author: Chien Tat Low
Low has extensive inter-disciplinary research experience, which although wide-ranging, focuses on identifying hotspots to facilitate better planning. At CWR, Low uses spatial modelling and statistical analysis as well as remote sensing, cartography, and geo-statistics to map and assess water risks. In addition, he helps manage CWR’s extensive network of contributors and partners. CWR is Low’s first foray outside academia and he hopes to apply his 12 years of scientific know-how toward enhancing the understanding of water risk in Asia, including spatial temporal variabilities of anthropogenic and natural factors on water resources. Previously, Low was a postdoctoral fellow at the University of Hong Kong where he devised methodologies to measure and benchmark the quality of urban life in an Asian context. As a certified GIS Professional, he also taught GIS and spatial analysis modules there. Low’s research on urban, human and environmental health is published in 11 prominent international peer-reviewed journals; he has also written a chapter in a book on managing environmental hazards. His PhD thesis on place effect on human well-being was prize-winning. Low is currently the reviewer editor for the journal “Frontiers in Environmental Informatics” and also reviews other international journals such as “Applied Geography”.
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Dharisha Mirando
Author: Dharisha Mirando
Dharisha Mirando hails from the finance industry and joined CWR as she believes that climate and water factors are downplayed by the sector despite being significant investment risks. To tackle this, her ambition is to help build consensus, bridge the gap between finance and science, and engage with investors to incorporate these risks into their due diligence and portfolio management. This could in turn lead to innovative Green Finance instruments becoming more prevalent. She has already made strong headway as the lead author of a recently published report with Manulife Asset Management and the Asia Investor Group on Climate change, which highlights the imminent threats to Asian asset owners' portfolios from climate and water risks. Dharisha has also undertaken a number of speaking engagements on these pressing issues at investor and insurance conferences. Prior to joining CWR, Dharisha worked for a long-only public equities fund. She has also worked in the impact investment space in London and Singapore where she provided technical assistance to social enterprises, helped them raise equity investments, and managed a debt portfolio.
Read more from Dharisha Mirando →