What goes up but doesn’t come down? Rising Seas

Dr Ben McGarry Dr Ben McGarry
Principal, Decarbonisation – Australia
10 November 2020
6 min read

The Philippine archipelago officially comprises 7641 islands, not including the thousands of shoals and sandbars that emerge during low tide. While technically not on the map, some of these vanishing sandbars and islands (as locals still call them) have become popular destination spots among tourists around the world because of their ephemeral nature and beautiful stretches of white sand beaches.

Other islands and areas in the country and in many parts of the world, however, have a different, saddening story. Rapidly rising sea levels have led to some being swallowed up, with others tragically on the verge of following suit.

While we've always had to defend against natural elements, now the very resource responsible for keeping us alive – water – is increasingly becoming a danger to our habitats. Climate change creates rising seas, coastal erosion and more floods in large coastal cities, with four out of five people in Southeast and East Asia living in cities affected by sea-level rise.

Previously, we have retreated in the way that populations in India continually move to higher ground following landslides and flooding, or we create defences – usually walls, canals and levies – as Amsterdam does.

Yet, as sea levels continue to rise more than ever before, simply fighting or fleeing may no longer be feasible. The alternatives will be clever guerilla actions that use smart engineering, new technologies and adaptable ways of living. But the biggest change will be our mindsets: Are we ready start to living with the effects of climate change rather than reacting against it?

What's happening?

Around 40 per cent of the world's population lives within 100 km of the ocean, and the oceans make up 72 per cent of the Earth's surface area. At the same time, sea levels have been rising for the past century as the planet warms. Communities respond in whatever ways they can. Thai fishing villages move and rebuild when inundation becomes too severe.

In many developing world settlements, 'retreat' is the only option as there is no other solution. This doesn't always result in a social benefit because populations, with few economic resources to start with, can end up in worse living conditions than they experienced in their coastal settlements.

What of the large cities? Jakarta, the capital of Indonesia, which has been sinking and prone to inundation for many years, is now choosing to retreat. The Indonesian President in 2019 announced the capital will be shifted to a new site in Borneo at a cost of AUD 47 billion.

In the first waves of migration, 1.5 million people will relocate to the new city. Other Asian cities with substantial asset bases are making plans to defend their cities rather than relocate. For example, Singapore is currently negotiating integrated coastal protection solutions for the island state estimated to cost around USD 72 billion.

In Europe, Venice has its own response to rising sea levels, eroding soils and severe high tides with a 78-gate seawall called MOSE that has cost €6.3 billion so far.

But these expensive fight-or-flight options will not be a solution that all cities can use. There simply isn't the money.

Changing our mindset – how do we work with water?

With modern engineering and technologies, threatened coastal cities can also fight a guerilla action against the changing climate and its attendant inundation.

Cities are looking to divert or ride over flood waters. For instance, Tokyo, suffers from coastal subsidence and has historically built seawalls in addition to the Metropolitan Area Outer Underground Discharge Channel, a massive tunnel system 50 metres under Tokyo designed to allow flood waters to surge underneath the city rather than across it.

In some of China's major Pearl River delta cities, the problem is too much concrete covering what used to be open nature areas that would otherwise absorb and channel groundwater. In response, the Chinese government is building 'Sponge Cities' where permeable road and footpath surfaces absorb flood waters.

Flood-prone Mumbai is also looking into sponging flood waters with new road surfaces, and Bangkok is experimenting with giant underground cisterns that collect flood waters.

Sea-threatened cities such as Amsterdam and Rotterdam respond the other way around: their city councils constantly build-up their sinking footpaths and roads to keep the city's elevation where it needs to be.

As climate change brings rising sea levels and coastal erosion, governments and their engineers will have to deploy a range of strategies to ensure that city populations can remain living on coasts, within their budgetary constraints, and in a way that does not create further socio-economic issues. This will require a shift in mindset, a commitment to live with the changing climate, rather than fighting it.

Letting nature take over

However, let's get philosophical. Should humans dominate nature, or should we let nature take its course? Are we here to overcome nature or do we run and relocate when nature overwhelms us? What's the middle ground? Is there a way to stay in our cities and not fight the water?

The Dutch have a long history of coexisting with sea levels and their thinking is moving from a defensive-engineering approach, to a 'living with nature' policy. One of their ideas builds on the Amsterdam tradition of securing structures on wooden stilts; instead, they're building floating communities and suburbs.

These pontoon-based communities are already operating and inhabited in Amsterdam and are well-accepted. They are less expensive to build than seawalls and they allow for a social-housing component to be built into the floating communities, ensuring equity. The United Nations has a project devoted to this idea, which its engineering partner MIT believes can be expanded to floating cities.

One of the advantages of learning to live with climate change is that governments can reimagine national resources, unlocking potential through 'offshoring' – placing infrastructure on the sea itself. Along the Atlantic coast of the United States, and in shallow areas of Asia and North Sea, offshore wind farms and marine current turbines are being built, while a number of floating wind farms are in development or have early pilots. Learning to live with our new water dynamics can also be practical.

Some of these ideas may once have been assigned to the 'futuristic' or even 'crackpot' basket. Nevertheless, learning to live with our changing climate might be the only solution for certain cities and will become a necessity for national budgets.

Look at the Brisbane River ferry terminals, in which the wharf is able to passively pivot with the flooding river on giant 'hinges'. The wharf goes with the flow, instead of becoming increasingly resistant, saving the infrastructure.

The way forward

The economics of keeping us safe will become increasingly fraught. In affluent coastal communities around the world, tensions abound between residents' rights to private coastline access and public access to the beach. Governments are already rejecting calls to use public money to shore-up residential shorelines. The cost-benefit of defending shorelines against constantly rising seas is not in favour of building seawalls.

The way ahead will be to expand our options from simply fight or flight – defend or retreat – into a guerilla action against the problem of water and our cities. This is going to entail new technologies, new engineering techniques and powerful monitoring and sensing platforms.

It will involve a great deal of science, engineering and strong political leadership. Collaboration will be critical and it will be impossible to operate with an individualistic mentality when it's every country for themselves.

Most of all, it will require positive thinking – a change of mindset: we'll no longer fight nature or run from it; we will embrace it, and live with it.

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Stephanie Groen
Written by
Stephanie Groen

Dr Ben McGarry
Written by
Dr Ben McGarry

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