Several Asian coastal cities face the twin threats of rising sea levels and land subsidence due to over-exploitation of groundwater. Plans are afoot to relocate fast-sinking cities like Jakarta. Asia Insurance Review spoke to urbanist and architect Ms Supriya Krishnan, to understand if some creative solutions can halt the sinking of the vulnerable cities of Asia.
Several coastal cities across the globe, including in Asia, are slowly but surely going underwater. Jakarta, Ho Chi Minh City, Bangkok, Manila, Dhaka, Shanghai and a few more in Asia are sinking faster than the climate change-induced rise in sea levels.
Most of these cities have huge infrastructure to support their large populations. They are also ever-expanding and require huge amounts of water for industrial and domestic uses and this leads to over-exploitation of groundwater resources, which are not replenished and becomes the main cause of land subsidence. The growing subsidence exposes them further to coastal flooding, high tides and storm surges.
Christian Aid, a UK-based Christian organisation in its eight-city case study ‘Sinking Cities, Rising Seas: A perfect storm of climate change and bad development choices’ published in 2018 said, “The subsidence not only increases the absolute risk of flood, but also the areas affected. High tides can penetrate further inland and floods may recede more slowly. This means that there is increased risk of salination of soils that were previously fertile.”
Threat to coastal cities is more from within and less from the sea
The Global Facility for Disaster Reduction and Recovery report, The Making of a Riskier Future: How our Decisions are Shaping Future Disaster Risk documents that the threat to the coastal megacities comes not as much from the sea but from within.
According to the World Economic Forum’s ‘The Global Risks’ Report 2019’ the sprawling coastal cities are sinking at the same time as seawaters seep in. This is due to the sheer weight of growing cities, combined with the groundwater extracted by their residents. Unregulated groundwater extraction by our growing population is the main cause of land subsidence — or the sinking of land.
The report said, “About 90% of all coastal areas would be affected to varying degrees by rising sea levels and their subsiding land mass. Some cities will experience sea-level rises as high as 30% above the global mean.”
Asia leads in global urban transformation
Urbanist and architect Supriya Krishnan said, “Asian countries, especially India and China, lie at the centre of gravity of our planet’s urban transformation. By 2050, India alone is expected to add to itself an equivalent of the population of the United States of America.
“As far as development is concerned, cities in the emerging world have always had a skewed demand supply ratio. Demand has always superseded supply. Also, only a limited number of cities started out with an ‘urban plan’ that could respond to this demand. Hence, unlike the civilisations of yore, modern cities have the dual responsibility of planning for burgeoning demands in economic terms (jobs, health) while balancing the outfalls from this pattern of growth.
“The outfalls include dealing with varying levels of environmental degradation, air and water pollution, stressed lifestyles, impacts from climate events and pressure on existing infrastructure services among others,” she said.
The negative consequences from this unbridled growth are outpacing the development trajectory required to accommodate such unaccounted-for changes. Overburdened sewer systems, unmindful land use, overuse of groundwater and contaminated water supply are widespread.
Jakarta, the fastest sinking city could be relocated
In April this year, Indonesian President Joko Widodo announced his decision to relocate Jakarta the present capital of Indonesia.
Jakarta is home to over 10m people and is sinking at one of the fastest rates in the world. Almost half the city now sits below sea level. The subsiding impact is immediately apparent in north Jakarta, which has sunk around 2.5 metres in the last decade and is continuing to sink an average of 1-15 cm a year.
Bandung Institute of Technology Professor Heri Andreas, who has studied Jakarta’s land subsidence for the past 20 years, said, “If we look at our models, by 2050 about 95% of north Jakarta will be submerged.”
Speaking about the proposal to shift Jakarta to a new location, Ms Krishnan said, “While newer cities have the luxury of adopting state-of-the-art planning strategies, the pervasive problem lies in existing cities that are seeing unprecedented expansion. The sheer numbers in these cities would make ‘moving’ them to other locations unfeasible, from an economic and social stand point.”
“Serious issues of sinking cities cannot be tackled by a single project or a band aid solution. The three main networks that make a city: Blue (water), green (open spaces) and grey (roads, built infrastructure) will need to be evaluated together for joint solutions as all of them have a role in mitigating impacts from climate and subsidence,” she said.
Research by Deltares, an independent institute for applied research in the field of water and subsurface based in Netherlands, has brought out the fact that in many coastal and delta cities, land subsidence exceeds absolute sea level rise.
For climate, the past is no longer a good guide for the future
Ms Krishnan said, “It is worthwhile keeping in mind that as far as climate is concerned, the past is no longer a good guide for the future. As the frequencies and intensities of climate related events rise and get more unpredictable, planning decisions cannot be based on historical assumptions.
“In a domain that will require fast-paced research, global knowledge-sharing initiatives will be critical to learn from experience. Initiatives such as the 100 Resilient Cities and the upcoming Coalition for Disaster Resilient Infrastructure are steps in this direction,” said Ms Krishnan.
According to the United Nations Sustainable Development Goal 11, “Sustainable development cannot be achieved without significantly transforming the way we build and manage our urban spaces.” Hence, the answer to land subsidence lies in understanding this complexity of the city and taking a ‘systems’ perspective to urban planning.
“By various estimates, 75% of the infrastructure that is needed to fulfil the demands of the population projected for 2050 does not exist today. One may notice that in constantly evolving cities, the imbalance in real estate value, means that the process of planning is restricted to redevelopments, refurbishment, insertions and improvements,” said Ms Krishnan.
“According to the Global Infrastructure Hub, emerging economies account for 54% to 60% of the total global investment needs in infrastructure. As long-lasting investment assets, they have huge potential to steer better growth models to achieve ecological and environmental balance. However, integrated decision making that can consider a view of all these systems is difficult.”
“Overarching risks from flooding and sinking need to be mainstreamed into all development decisions through better and sustained engagement between stakeholders. Innovative techniques such as nature-based solutions, multifunctional urban spaces, adaptive urban plans could be brought into development parlance to improve its application,” she said. A
| Innovative techniques adopted in Asia
Nature-based solutions
Putrajaya Wetland, Malaysia is a constructed wetland and perhaps the largest constructed freshwater wetland in Southeast Asia. Its main environmental function is to treat catchment water before it enters Putrajaya Lake, thus ensuring that water in the lake remains clean and unpolluted.
Multifunctional urban spaces
The Cheonggyecheon river redevelopment in Seoul in South Korea. An elevated highway in the centre of the city was demolished to restore a rive underneath to create a natural public space and improve environmental quality.
Adaptive urban plans
Sponge City Initiative in China invests in projects that aim to soak up floodwater to make up for disappearing natural water bodies due to intense urbanisation.
|