Rising Seas Are Slowly Swallowing Coastal Communities

Coastal flooding may not make as many headlines as bushfires or storms, but experts say it is one of the biggest climate threats facing Australia today. Unlike river flooding, which rises quickly, coastal flooding creeps up slowly as sea levels get higher over time. This means millions of people living near the ocean, bays, and coastal lagoons could see their homes damaged — or even lost — in the years ahead. Scientists, politicians, and city planners are now racing to figure out what to do before the problem gets much worse.

There are two main types of coastal hazards people need to know about. The first is coastal erosion, when waves wear away land until cliffs or beaches collapse. The second is coastal inundation, when rising sea levels cause low-lying land to flood permanently or very often. Researcher Stokes explains that inundation will affect far more homes than erosion, even though erosion gets more attention because it looks dramatic.

Many affordable homes built after World War II were placed around coastal lagoons, where the land was flat and easy to build on. Areas like Woy Woy, Umina, Lake Illawarra, and Ballina have thousands of these properties. Even a small rise in sea level could put a huge number of families in danger. Many of those families do not have the money to simply pack up and move.

Independent MP Zali Steggall, whose electorate includes Sydney's northern beaches, says coastal flooding is being dangerously underestimated. She points to a 2022 event where heavy rain hit at the same time as a high tide, causing drains to overflow and flood large parts of the area. Cars floated down streets, schools closed, and the famous Manly Corso was completely underwater. Steggall says our stormwater systems were simply not built to handle this kind of combined event.

One growing idea in city design is called the 'sponge city.' This concept started in China and is now spreading around the world. Instead of hard concrete drains, sponge cities use porous roads that let rain sink into the ground, green rooftops covered in plants, and parks that turn into temporary wetlands during big storms. Australia actually helped develop some early ideas behind this approach.

However, experts warn that sponge cities work better for river flooding than for coastal flooding. Dr. Elisa Palazzo, a lecturer at the University of NSW, says that as sea levels rise, coastal flooding simply cannot be stopped with walls or clever drains. She suggests that cities may need buildings raised on stilts or even floating structures, like those already being tried in The Netherlands. 'Little by little cities will have to recede, and that is already happening,' she says.

One big question is: who should pay for all of this? Some homeowners have had to use their own money to make their houses stronger against floods. Neighbour Bernie Zietlow used his insurance payout to replace carpet with polished concrete, install waterproof kitchen cabinets, and move all his power points above flood level. He says that next time the floods come, he will simply hose the place out.

At a bigger level, some councils and groups like Greenpeace and Oxfam say fossil fuel companies should help pay for climate adaptation, since their products have helped cause climate change. CSIRO researcher Wise suggests governments offer land swaps instead of just buying people's homes — giving people a new, safer place to live rather than just handing over cash. The NSW Reconstruction Authority is working on a policy to deal with these questions, expected to be finished later this year.

Local governments are also struggling with the rising cost of maintaining roads and services in flood-prone areas. Wise calls sea level rise a 'significant chronic risk' — not a one-time disaster, but a slow, constant pressure that wears everything down over time. Planning ahead now, experts say, will save communities a great deal of pain and money in the future.