These findings contradict the popular belief that vegetation always reduces erosion on sand dunes.

she pointed out study Newly planted vegetation on coastal sand dunes can speed up the erosion process from high tides, new research suggests. The authors of the study, published June 14 in the journal “Science Advances,” note that these results contradict the widely held view that plants always act to reduce sand dune erosion, the first line of defense in the landscape. Sand dunes, storms.

Experiments involved building beach dune models 70 meters long and 4.5 meters high and exposing them to storm surges in a 104-meter stream at Oregon State University.

An unusual experience

Scientists have previously studied sand dunes in the laboratory by creating plant mounds in mineral pools called tide pools. Those experiments showed that vegetation slows waves and prevents sand erosion. The benefit increases with larger and taller plants. But wave troughs are relatively small, usually a few meters long, and tests often last less than an hour, according to a press release posted on the York Alert website (EurAlert)

In the new study, the authors asked what would happen if dunes were exposed to large waves for long periods of time. Therefore, the team at Oregon State University created a 104-meter-long waterway, the largest experimental wave laboratory in the United States.

Next, they hauled 500 cubic meters of sand and scoured the beach for weeks, beautifying the dunes to look like a real beach. Then, they planted Panicum amarum, a plant common in dune environments, and let it grow. root inside. Paddy for 6 months.

Rusty Viakin, lead author and professor of geology and environmental studies at the University of Texas, explained that once the grass had settled, he ran the wave machine to simulate Hurricane Sandy, which hit the northeastern United States in 2012. It continued for 19 hours straight for a whole month.

“After exposing the dunes to storm surges every half hour, we stopped to study the shape of the dunes using a laser to assess the extent of erosion,” Viagen said in a statement to Al-Jazeera Net.

Hill erosion

The researcher added that the waves hit the body of the dune from top to bottom and on their way they gradually remove parts of the dune especially from the area where the plant is located.

Viagin explains, “Waves carved the body of the dune where the plants were planted, and then the dune in this area cracked, until it eroded completely, because the erosion energy was concentrated in a small area. The grass blocked part of each wave. After 14 hours, the waves carved and increased.” Erosion speed due to waves undermining a vertical section of sand 79 cm high.

At the end of the storm, vegetated dunes retained more sand than grass dunes, which lost 22% of their sand.

“We found in our research that newly transplanted coastal dunes lacked a more well-established root system and eroded faster than sand dunes with the same amount of sand and pressure,” Fiagan said.

The researcher emphasized that we still need to learn more about how different levels of vegetation affect the exposure of coastal dunes to wave-driven erosion, but the current study’s findings are an important step toward understanding the role vegetation plays in coastal processes. .

The study does not deny the role of vegetation in protecting sand dunes from storms, but Viagen points out that it is only effective in the case of moderate storms and not severe storms.