Waves are extending the long reach of climate change, and the effects are closer to home than you think.
I recently discovered a website that really drives home the difference a single foot of water can make. Built by the National Oceanic and Atmospheric Administration, the Sea Level Rise Viewer mapping tool lets you see what your country and neighbourhood could look like in the event of coastal flooding or sea level rise. A foot of water may just seem like a drop in the vast ocean, but with a mere click of a slider, I made entire continents shrink. Country borders were redrawn, coastlines disappeared and oceans became emptier as islands and archipelagos vanished.
Slowly I watched the simulated waves submerge apartments, condominiums, houses and trailer parks. Gone are what used to be my local supermarkets and cinemas, slipping under pixelated water. It was fascinating to play around with until I was struck by the sobering reminder that these are actual predictions of what may be engulfed. I realised that my family home in Florida, USA, would no longer be in the middle of the Sunshine State but a beachfront property with waves at our doorstep.
Unless you’re a surfer, where waves come from and what they do before they reach the shore may not have crossed your mind. The reality is that ocean waves are not just those lapping rhythmically on our shores. Under the right conditions, waves can soar to towering heights and intrude inland into coastal communities, damaging seawalls, corroding nearby infrastructure, zapping electrical boxes of their power, and overflowing drains.
Waves are generated by energy passing through water, and they hold onto that energy as they move, carrying it across the ocean. Most waves are created by the friction between wind and the water’s surface; the disturbance creates a wave crest that propagates through the water. And when wind strength increases, such as during tropical storms or cyclones, the waves grow. These conditions can allow for rogue waves — that is, when waves move in different directions during a storm, they can sometimes form giant swells that can reach tens of metres high.
In 2017, New Zealand locals experienced some of the biggest waves to hammer Auckland’s western beaches in more than 20 years, with walls of white water reaching three metres high. Persistent westerly winds were the cause of these massive waves, with MetOcean Solutions confirming one of its buoys had recorded a 19.4 metre wave; for comparison, a 25 metre wave is about the height of an eight-storey building. MetOcean Solutions senior oceanographer Dr Tom Durrant commented: “This is one of the largest waves recorded in the Southern Hemisphere.”
With large waves often comes destruction. These problems are interwoven between beachfront populations, so if one area is affected, others may suffer the consequences as well. Many coastlines around the world are being battered by the increase in wave intensity and already face existing pressures such as increasing urbanisation and recreational use, which are likely to be exacerbated by climate change. Climate change impacts pose particular challenges to coastal communities because they often occur simultaneously (eg a storm surge, intense rainfall and catchment runoff all at once) and may manifest differently in different places, which doesn’t allow for a blanket solution. The impacts are likely to be a significant and enduring feature of any country’s future, but through understanding the drivers behind them, coastal communities will be more able to effectively respond and build resilience.
How climate change factors in
Coasts are shaped by the sea and its waves. If you live near the ocean, chances are you will be affected by it sooner rather than later. As we continue to be dismissive of the threats posed by climate, we invite the ocean ever closer to our doorstep. The latest climate change projections from Australia’s national research body, the Commonwealth Scientific and Industrial Research Organisation, are anything but reassuring. A warming climate means a super-charged atmosphere, leading to more intense storms. Powerful storms often mean faster winds that can lead to waves imbued with more force, and when they reach the coast, they bring more destructive potential.
Waves are not the only factors that cause water levels to rise along the coast during a storm event such as a hurricane. Rising sea levels, tides, rain, and storm surges all play a part in causing extensive damage, as we are already seeing worldwide. In Australia, ex-tropical cyclone Debbie inundated homes and businesses after torrential rain caused rivers to swell. In the US, the storm surge of Hurricane Sandy did some of the worst damage, reaching almost 2.4 metres in parts of the Jersey Shore and 2 metres around New York City. At the time of this publication, we will be into the cyclone season (November to April), with 8-10 tropical cyclones expected in the southwest Pacific. As the 2017 Atlantic hurricane season showed, it only takes one bad storm to change a community — think about those still suffering from Hurricane Harvey, which flooded Houston, Texas in the US; Hurricane Irma, which decimated Caribbean island nations; and Hurricane Maria, which plunged Puerto Rico into darkness and isolation.
The Intergovernmental Panel on Climate Change projected in 2013 that sea levels would rise by 18–59 centimetres by the end of this century — and a recent report increases projections as the Arctic “unravels”. Miami, Florida has become a poster child for rising seas in the US, but it is not the only coastal city facing dramatic challenges due to rising sea levels caused by climate change. Places like the Solomon Islands, Kiribati, and China are also grappling with the issue. In China, rising sea levels could result in the displacement of 45 million people from coastal cities. Kiribati President Anote Tong has purchased 5,000 acres (20 square kilometres) on Vanua Levu, one of the Fiji islands, as a potential refuge due to its high elevation.
Protecting low-lying coastal communities from climate change
Water is often the lifeblood of a town or city. It can also be the very thing that destroys it. The relationship a coastal community has with its neighbouring ocean will change as sea levels rise and storms strengthen, so we need to start thinking now about how to combat this issue.
In New Zealand, the Deep South National Science Challenge is tasked with finding adaptation solutions for climate change and building a model that can predict the effects far into the future. David Carlson, director of the World Climate Research Programme, told New Zealand Geographic: “A rover on Mars is easy compared to a climate model. For people to be able to simulate how the planet works on a set of computers is unbelievable.” It’s no wonder why it’s difficult to come up with solutions to such a complex and ever-evolving problem. The Deep South National Science Challenge is hoping to refine their model, and in light of widespread flooding in 2017, they also wrote a report with New Zealand insurance company Motu about the destructive realities faced by coastal homes, with possible global ramifications.
On a global scale, proposed solutions include the installation of tidal valve flap gates to allow storm water through but not seawater in coastal communities, a major pumping system for seawater intake in case of flooding, raising roads and the height limits on sea walls, and possibly implementing building codes that require new properties be elevated and made with water-resistant materials. In Miami, The Nature Conservancy is working with city officials and global engineering firm CH2M to develop ways that nature can help combat… well, itself. Coastal regions already have natural defences that can help absorb rainwater, mitigate coastal flooding, and provide a wave barrier — think of the mangrove forests, coral reefs, seagrass beds, salt marshes and oyster beds that often hug coastlines.
For instance, healthy coral reefs around the world can absorb 97% of the energy from waves headed towards the coast. Wave height can also be reduced by 13–66% over a 100-metre-wide mangrove belt or by 50–100% over a 500-metre-wide mangrove forest. “Green infrastructure” projects draw inspiration from nature to achieve desired results, while “grey infrastructure” includes the pipes, pumps, and ditches engineered to manage stormwater. By combining the already existing grey infrastructure in these beachfront cities with green infrastructure, the hope is that this hybrid solution can help reduce the effects of rising seas and storm surges on coastal communities.
Seaside real-estate is still popular despite the potential danger of rising waves. As more condominiums, hotels and other human-made structures are built closer to the ocean, coastal cities and towns should think about including financing and facilitating systems to recycle water and possibly implementing watershed management. Scientists and political officials need to work together to study responses of nearby wetlands to storm surge events to learn from and adapt new tools, use hydrologic models to project run-off and future water supply, develop emergency response plans regarding extreme weather, and conduct climate change impact and adaptation training for all government officials. The above steps can help mediate the problems caused by increased wave destruction.
If watching the horror unfold in the Atlantic Ocean brought on by powerful hurricanes taught us one thing, it’s that we need to better prepare our coastal communities for climate change. Waves of change are forming, and these affected communities shouldn’t be short of solutions against the rising seas.
Edited by Ivy Shih