Coastal cities such as New York and Miami are at  risk of flooding, high tides, and storm surges. Climate change causes water to expand and melts glacial ice caps, accelerating the rise of sea levels. As seas rise, some of the world’s major coastal cities, which are home to half of the human population, might find themselves underwater in less than a century. By 2100, the most recent IPCC report predicts oceans will rise 0.44-0.76 m (1.4-2.5 ft) under the intermediate greenhouse gas (GHG) emissions scenario, and 0.63-1.01 m (2.1-3.3 ft) under the very high GHG emissions scenario. Due to variable conditions and elevations, the water level in any particular place may rise by much more. In New York City, as much as 6 feet of sea level rise is expected by 2100. 

 

The search for sustainable solutions

Most cities and their governments are taking action to protect their coastlines from this imminent threat. In Bangkok and Tokyo, there are new regulations regarding groundwater extraction that reduce the rate of subsidence and restore 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. In New York City, annual storm seasons make urban flooding a critical infrastructure problem. 

 

Learning from the past

Altogether, the past decade’s storms totaled $800 billion in damages, an average of ($80.2 billion per year).In 2005, Hurricane Katrina affected hundreds of thousands of people, especially those from already vulnerable communities with few resources and flood-prone homes, forcing many to leave metro areas and increasing socio-economic disparities. Despite the $14.5 billion invested in levee improvements after the historic storm, Hurricane Ida, a comparatively strong storm, still left New Orleans and the populations outside the levees flooded in water.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 land vulnerable to floods?Many communities have come to the conclusion that a passive approach to natural disasters does not work. In Ocean Breeze, a Staten Island community, instead of rebuilding on vulnerable flood plains, some residents have chosen to leave old neighborhoods behind to allow nature to return, an approach known as “managed retreat”. However, in most places, people still prefer to live near the coasts and accept unmitigated flooding risk.

 

Preparing for the future

In 2012, Superstorm Sandy struck New York, bringing record-breaking wind gusts and deadly flooding. In New York City, over 69,000 residential units were destroyed, thousands were displaced, and  44 citizens

perished. After Superstorm Sandy, the federal government launched Rebuild By Design (RBD), a competition for expert groups offering strategies and solutions to prepare for the next big storm. This competition selected 7 projects to protect the coastlines of NYC and New Jersey, as well as a model to help prepare communities for future challenges. Rebuild by Design’s goal was simple yet audacious: as the risk of flooding increases due to intensified storms and sea-level rise, can communities join together to shift its course and build a more resilient society before a big disaster hits, while also addressing other challenges along the way? One of the competition’s winners was a project designed to protect Staten Island from future storms, called the Living Breakwaters Project.  

Harnessing nature’s engineering tricks

Living Breakwaters is a “necklace” of 9 breakwaters, aimed to promote coastal resilience for Staten Island by reducing the height of waves hitting the shore and extending the width of the beach. These breakwaters are “living” infrastructures as they help revive local marine ecosystems. The combination of ecologically designed breakwaters and bio-enhancing materials reestablishes habitat complexity and mimics the wave-weakening functionality of the natural oyster reefs that had previously dominated the area.As keystone species, oyster reefs bolster the local aquatic community by providing food, refuge, and protect shorelines by reducing erosion; they are ecosystem engineers that turn into wave buffers over time while providing a home for a variety of marine organisms. Not only do the living buffers restore aquatic communities, they also protect communities from storms while local fisheries benefit from cleaner waters. The project’s integration of ECOncrete’s concrete armor into the breakwaters stabilizes the infrastructure while creating habitat for local species. The green breakwater armor differs from traditional concrete armor due to its ability to support important local species, such as ecosystem engineering oysters. Not only does the ECOncrete infrastructure encourage marine life to thrive, the added weight, surface complexity, and natural ability to change with ocean conditions increases stability and durability of the structure.

Nature-based infrastructure solutions

There are many ways to armor our cities against intensifying storms and warming seas. A consensus is forming among coastal policymakers, planners, and developers: resilience-building projects are responsible not only for the protection of our waterfronts, but also for ecosystem preservation. Solutions such as living shorelines (“soft edges” such as marsh plantings, dunes, and mangrove restorations) are gaining popularity. Where “hardened coasts” or concrete infrastructures are needed, hybrid solutions are becoming integral tools for projects aiming to set a new standard for coastal construction.