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Global sea-level rise coupled with a city subsiding on its own foundations is a dangerous combination. Nowhere do you see the effects of “sinking cities” more than in densely populated urban centers around the world’s coasts. Sinking cities are now a widespread phenomenon; unless serious steps are taken to combat this growing problem, the results will be devastating.

Cause and Effect

Coastal cities such as Jakarta, Dhaka, Bangkok, and Miami are at constant risk of exposure to coastal flooding, high tides, and storm surges. Global warming causes water to expand, and increasingly melts glacial ice caps, the combination of which causes rising sea levels. Most sources predict that oceans will rise between 0.3 to 2.5 meters (1- 8 feet) by 2100. In New York City, this means that 725 square kilometers (280 square miles) of urban land will be lost. Coastal cities are being inundated by rising seas, but they’re also subsiding, or sinking, from reasons including groundwater extraction, depletion of oil wells, geological factors, or just the sheer weight of the skyscrapers. As cities sink and seas rise, in less than 100 years, some of the world’s major cities might literally find themselves underwater.

 

The Search for Sustainable Solutions

Although the future of urban coasts may look bleak, most cities and their respective governments are taking action to protect their coastlines from this imminent threat. In cities such as Bangkok and Tokyo, there are new regulations regarding groundwater extraction that are both reducing the rate of subsidence and restoring groundwater levels (an important source of fresh water for many regions). Solutions also include updating infrastructure, creating new zoning regulations, and coastal defense systems to protect from rising sea levels and superstorms. Hurricane Sandy hit the Atlantic seaboard in 2012, and $70 billion in damages, loss of property, and loss of life later, the coastal cities hit by this superstorm are still recovering.

Rebuild By Design

In the United States, the search is on for sustainable solutions that will protect cities against the next storm surge and constantly rising tides. Five years ago, Superstorm Sandy struck New York, bringing record-breaking wind gusts and deadly flooding. In New York City, 53 people died – nearly half of them were from Staten Island. After Superstorm Sandy’s devastation, the federal government has launched Rebuild By Design (RBD), a competition for expert groups offering strategies and solutions to prepare for the next big storm. RBD resulted in 7 projects chosen to protect the coastlines of NYC and NJ, and a model to help create research-based, collaborative processes that prepare communities and regions for future challenges. One of these plans is the Resilient by Design Bay Area Challenge, launched in early 2017.

The premise of RBD was both simple and audacious: as flood risks increase due to intensified storms and sea-level rise, organizers asked the question – can the Bay Area come together to shift its course and build a more resilient region before a big disaster hits, and can we address other regional challenges along the way? Since then, 10 design concepts were selected to inspire, catalyze action, and push the Bay towards a more resilient future.

Courtesy of SCAPE Landscape Architecture DPC. 

Livin’ on the Edge

Nearly half of the world’s population resides along coastal areas from San Francisco to small Indonesian Islands. The effects of climate change – including sea-level rise, increased storminess, ocean warming, and acidification – negatively impact the physical spaces coastal communities call home, and the livelihoods coastal residents have built. Coastal communities already face regular flooding due to higher tides, and some suffer more frequent natural disasters or watch tourist-attracting coral reefs and marine life fade.
Catastrophic Hurricane Katrina in 2005 devastated hundreds of thousands of people, especially those from already vulnerable communities with the fewest resources and most flood-prone homes, forcing many to leave metro areas and increasing socio-economic disparities. $14.5 billion in levee investments has left residents that returned to rebuild their homes and communities only slightly better off than they were pre-Katrina.
Recent mega-hurricanes Harvey, Irma, and Maria have all raised the same question: What should we do to help reduce massive cleanup and rebuilding efforts for dozens of towns and cities that have already developed infrastructure and neighborhoods on vulnerable flood-prone land? Altogether, the past decade’s storms could cost up to nearly $400 billion in damages, without even taking into account the compounding effects of uprooting and disrupting families, businesses, and local economies. Some communities and local leaders are starting to realize that the “wait for the next one and rebuild after” model isn’t cutting it. In Ocean Breeze, a Staten Island community, instead of rebuilding on vulnerable flood plains, some residents have chosen to leave old neighborhoods behind and let nature take its course. However in most places, because of livelihood or lifestyle, people still prefer to live near the coasts and accept unmitigated flooding risk.

Harnessing Nature for Resilient Coastlines

Part of the solution for coastal flooding lies in restoring native coastal habitats like oyster reefs, tidal wetlands, and mangrove forests that serve as natural coastal protection.
The Staten Island Living Breakwaters project, a “necklace” of 9 breakwaters, is aimed at protecting the southern tip of Staten Island by reducing the height of waves hitting the shore and as a result extending the width of the sandy beach, providing additional protection. The breakwaters are “Living” infrastructure designed not only for risk reduction but also for the ecological enhancement of the local marine environment. The ecologically designed breakwaters alongside the use of bio-enhancing materials will help reestablish habitat complexity and mimic the functionality of natural oyster reefs that historically dominated the area. Oyster reefs are known keystone species that bolster the local aquatic community, and as ecosystem engineers which create and maintain a complex underwater system. Restoring these aquatic communities boosts coastal fisheries, provides valuable habitat for marine food chains to grow, all of which work to buffer our cities from storms and protect communities from costly damages and renovations.

Sinking cities, rising sea levels, and storm surges worsened by global warming are our new reality, and doing nothing is the biggest risk of all. It is up to us to find creative solutions that allow us to adapt and survive sustainably while protecting our environment.

Weeks after Hurricane Florence ravaged the Carolinas, and on the sixth anniversary of Superstorm Sandy in New York, the four-part series examines how cities are preparing for the real-time effects of climate change.

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