How marsh grass could help from surges and devastating storms

How marsh grass could help protect us from climate change. Coastal marsh plants provide significant protection from surges and devastating storms. Research in MIT’s Parson’s lab can help coastal planners to take important details into account when planning projects. Countries must take advantage of this modeling in order to restore marshland with specific plants in certain areas. Marsh plants, ubiquitous along the world’s coasts, can play a major role in limiting damage to beaches due to sea level rise and storm surge.

How marsh grass could help

Now, a new study from the Massachusetts Institute of Technology provides more details of how these protective benefits work in real-world conditions shaped by waves and currents (how marsh grass could help). The study combined laboratory experiments using simulated plants in a large wave tank with mathematical modeling. Featured in Physical Review – Fluids, in a paper written by former MIT doctoral student Xiaoxia Zhang, now a postdoc and professor of civil and environmental engineering Heidi Knappf at Dalian University of Technology.

Coastal marsh plants

It is already clear that coastal swamps provide great protection against destructive buoyancy and storms. For example, it is estimated that $625 million in damages caused by Hurricane Sandy resulted from the wetting of wave energy provided by large areas of marshland along the affected coasts. But the new MIT analysis includes details about the plant’s morphology, such as the number of flexible leaves and vacuoles versus rigid stems, and the complex interactions of currents and waves coming from different directions.


This level of detail can enable coastal restoration planners to determine the swamp area needed to reduce the expected amount of storm surge or sea level rise, and to select the most appropriate vegetation types to provide maximum protection. “When you go into a swamp, you often see plants arranged in zones,” says Knapf, the Donald and Martha Harleman Professor of Civil and Environmental Engineering.”

Along the edge, you have plants that are more flexible, because they use their flexibility to reduce the forces of the waves you feel. In the next area, the plants are a little stiffer. They have a little more leaves.” As the regions age, plants become stiffer and more leafy and more effective at absorbing wave energy due to the larger leaf area.

Surges and devastating

The new modeling performed in this research, which involves working with simulation stations in a 24-meter wave reservoir at MIT’s Parsons Laboratory, helps coastal planners take these types of details into account when planning protection, mitigation, or restoration projects Empowerment.

“If you put the toughest plants to the side, they can’t survive, because they feel very high ripple strength. By describing why Mother Nature organizes plants in this way, we hope there is a more permanent restoration,” Knapf says.

Once established, bog plants provide a feedback cycle that not only aids in stabilization but also builds these fragile coastal lands, Zhang says. “After a few years, swamp grass begins to trap and retain sediment, and the elevation becomes higher and higher, which can keep pace with sea level rise,” she says.

Marsh and dyke work

Knapf says there is a growing awareness of the marsh’s protective effects. For example, the Netherlands is restoring lost marshes outside a dam that surrounds most of the country’s farmland, finding that marshes can protect the dam from erosion (how marsh grass could help); Marsh and dyke work together more effectively than dams alone in preventing floods.

Knapp says most of these efforts so far have been largely experimental, trial-and-error schemes. Now, they can take advantage of this modeling to see how much bog and what types of vegetation are required to provide the required level of protection. It also provides a more quantitative way to estimate the value that the marsh provides, she says.

“This might allow you to say more accurately, ’40 meters of swamp will reduce the waves a lot and therefore reduce overflow a lot.” One might use it to say, ‘I will save a lot of money in the next ten years if I reduce flooding by maintaining this swamp. This may help generate some political momentum for the restoration efforts. “It can help.”

Kotal simulations

The NAP itself is already trying to incorporate some of these findings into coastal planning processes. She works on a practice team led by Chris Esposito of the Gulf Water Institute, which serves the hurricane-hit Louisiana coast. “We want to get this work done in kotal simulations used for large-scale restoration and coastal planning,” she says.

“Understanding the wave damping process in actual vegetation wetlands is of great value, as it is essential in assessing the coastal defense value of these wetlands,” says Zhan Hu, associate professor of marine sciences at Sun Yat-sen University. Not associated with this work. “However, the challenge lies in the quantitative representation of the wave damping process, with many factors at play, such as plant elasticity, morphology, and currents coexisting together.”

China Scholarship Council

The new study “combines well the experimental results with analytical modeling to reveal the influence of each factor in the wave damping process. … Overall, this work is a trend toward a more accurate assessment of the wave damping potential,” Hu says. This is a concrete step in true coastal wetland management, which is essential to science-based design and nature-based coastal conservation management.” The work was supported in part by the National Science Foundation and the China Scholarship Council.

How marsh grass could help
How marsh grass could help from surges and devastating storms

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