NOAA Report – Marshes, Reefs, Mangroves: Natural and Cost Effective Ways to Manage Coastal Floods

A new study by the US National Oceanic and Atmospheric Administration (NOAA), reinforces the idea that natural infrastructure such as marshes, reefs, mangroves and beaches can help protect coastal areas from floods, storms and erosion.

Not only can natural infrastructure offer better protection, but it can also cost less, require less maintenance and, in some cases, even keep pace with sea level rise.

Furthermore, NOAA’s report says that natural systems can help improve water quality, provide habitat for many important species, and mitigate carbon going into our atmosphere.

Natural "green barriers" help protect this Florida coastline and infrastructure from severe storms and floods. (Credit: NOAA)
Natural “green barriers” help protect this Florida coastline and infrastructure from severe storms and floods. (Credit: NOAA)

Hybrid Systems

Although there may still be a need for built approaches in some locations, the study outlines many of the benefits of a “hybrid system” that combines the use of natural infrastructure with built infrastructure, such as openable flood gates or removable flood walls.

“There is a lot of potential innovation with hybrid approaches,” said Katya Wowk, Ph.D., NOAA senior social scientist, and the third co-author of the study. “Hybrid approaches, using both built and natural infrastructure, often provide more cost-effective flood risk reduction options and alternatives for communities when there is not enough space to use natural coastal protection alone.”

“There is no ‘one size fits all’ solution when it comes to what is best for a community in providing coastal protection from flooding,” said Ph.D., acting assistant secretary of commerce for conservation and management at NOAA, and co-author of the study.

“We all have to work to innovate, test, monitor, and develop a better suite of options that includes more natural and hybrid infrastructure alternatives for providing coastal protection to communities around the world.”

Coastal Threats – Floods, Storms and Erosion

Threats like coastal erosion, storms and flooding can reshape the shoreline and threaten coastal property. With approximately 350,000 houses, business, bridges and other structures located within 500 feet of the nation’s shoreline, erosion is a problem many U.S. coastal communities are addressing.

“Coastal resiliency and disaster risk reduction have become a national priority, and healthy coastal ecosystems play an important role in building resilient communities,” said Holly Bamford,

“We know that sea levels are rising and that coastal communities are becoming more vulnerable to extreme weather- and climate-related events,” she continued:

“Now is the time to invest in protection to secure our coasts, but we need to make those investments wisely and with a full understanding of the costs and benefits of different approaches”.

Examples of Natural and Hybrid Coastal Protection Schemes

Using a natural approach to coastal flood management is not new. Below are two recent examples of coastal flood management schemes using a hybrid approach – one in Asia, the other in Europe – combining built and natural infrastructure to help protect the coastline and the communities that live along it.

Mangroves in Indonesia

In March this year, the Indonesian and Dutch governments launched a plan to protect Java’s north coast with a hybrid approach, combining mangrove restoration with small-scale engineering projects.

Saltmarsh in Steart, England

In the UK, the Wildfowl & Wetlands Trust (WWT) and Environment Agency’s have worked together to develop a flood and coastal protection scheme at Steart Marshes. The scheme includes newly constructed flood banks, but also uses the shallow gradient and coarse vegetation of the saltmarsh to absorb wave energy naturally. This will help to protect local villages from storm surges, and protect the flood banks from erosion so that they last longer.

Steart Marshes Coastal Flood Management Scheme (Photo: Environment Agency)
Steart Marshes Coastal Flood Management Scheme (Photo: Environment Agency)

About the NOAA Study

The study, published in Environmental Science and Policy, assesses reports and peer-reviewed studies on the strengths and weaknesses of using built infrastructure, such as seawalls or dikes, natural infrastructure, or approaches which combine both.

The study focuses on how these approaches help coastal communities reduce their risk of flooding and erosion, as well as additional benefits, and the tradeoffs when decision makers choose one type over another. More about the study can be found here.

Examples of coastal defenses including natural infrastructure, managed realignment, and hybrid approaches. (Credit: NOAA).
Examples of coastal defenses including natural infrastructure, managed realignment, and hybrid approaches. (Credit: NOAA).