How are engineers rising to the challenge of changing sea levels?

Sea level rise (SLR) isn’t a challenge for some hypothetical future.

It’s something that communities across the globe are already having to adapt to today.

The sea isn’t rising at the same rate everywhere at once.

Some places in the world are experience extreme instances of relative SLR (or rSLR), where SLR is intensified by the ground sinking (land subsidence)

Exploring how these places are adapting to such changes can help inform how coasts with a slower pace of SLR can adapt.

As a professor, I’m always keen that my students not only understand coastal engineering theory, but also look at practical examples of how communities are building resilience into local projects.

Japan and Indonesia

Tokyo and Jakarta provide examples of existing projects - partly or fully completed - that demonstrate how to adapt to more than 4m of ground subsidence.

Large parts of either city are currently under mean sea level, effectively similar to polders in the Netherlands (low-lying land that’s surrounded by dikes to keep the sea away).

In past decades, adaptation looked like building seawalls and then pumps to drain the water that could no longer flow out due to gravity. To regulate the flow, water gates also had to be constructed.

Finally, land has also been reclaimed from the sea, built to a level higher than the older ground behind.

Super levee

Tokyo is currently building what is often called the "super-levee" project.

Essentially, large areas of the city next to the levees (embankments) are being demolished.

The land is then being elevated several hundred metres next to the levees, so that it is at the same level as the top of the levee.

Houses and apartments are then rebuilt on top of the new levee.

Similar techniques - although not as extreme - can be seen in Ho Chi Minh City, Vietnam, Manila, Philippines or Miami, USA (which are building levees and elevating the level of roads, for example).

Small islands

Small islands are also adapting.

Fishing communities in the Danajon Bank in the Philippines have raised their houses to make up for the abrupt subsidence brought about by a large earthquake in 2013.

Tuvalu, a low-lying island country, is often cited as the most in danger regarding SLR.

A project by the United Nations Development Programme (UNDP) has come up with a long-term adaptation plan that has successfully leveraged international assistance to build some 20 hectares of raised, flood-resilient land.

We must engage with the public

It would be preferable not to have to deal with the significant challenge that sea level rise poses (by enhancing mitigation efforts).

Nevertheless, by formulating climate adaptation pathways, it is possible for engineers to engage in meaningful discussions with the public.

The engineering knowledge exists. Successful real life case studies are readily available to learn from.

But these adaptation efforts are very expensive and require a holistic understanding of all the issues involved.

Communicating with all stakeholders is essential.