OREGON STATE UNIVERSITY

OSU scientists simulate wave conditions to determine value of wetland vegetation

08/02/2010

CORVALLIS, Ore. – Coastal wetland vegetation may reduce shoreline erosion and sediment deposition by dampening the energy and power of incoming waves and storm surge, according to new research under way at Oregon State University.

The work is unprecedented and information created from it will allow for an increased understanding of ecological services associated with wetland habitat.

In the United States today 60 percent of the population lives within 50 miles of coastline and growth in these areas is expected to continue. That will put pressure on maintaining wetlands at the water-land interface – a landscape, which if healthy, has the capability of mitigating impacts of both natural and man-made disaster on the greater environment and human communities.

“Being able to quantify additional ecological services for wetlands whose value for fish and wildlife habitat is already well-documented provides further incentive to maintain and manage coastal wetlands,” said Dennis Albert, an Oregon State University professor in the College of Agricultural Sciences. “Land use planning and coastal resource management benefit directly from a better understanding of the role wetlands and plant communities play in protecting our homes, communities and aquatic habitat.”

Together with Dan Cox, an OSU professor in the College of Engineering, Albert is leading a National Science Foundation-funded project to conduct ecological modeling of emergent vegetation for sustaining wetlands in high wave energy coastal environments. The project focuses on improving scientific understanding of wave attenuation and sediment deposition in the near-shore, wetland environment.

The OSU researchers are also studying plant survival under different wave patterns and strengths, and the ability of the plants to recover after storm damage.  

Taking place in the large wave flume at the O.H. Hinsdale Wave Research Laboratory at OSU, the study is the first of its kind to document the response of wetland plant beds taken from coastal environments to simulated waves.

The flume is 104 meters long, 3.6 meters wide and 4.6 meters deep. In use since 1972, it is the largest facility in North America used for coastal research. Beginning in the spring of 2009, Albert collected and cultivated Schoenoplectus pungens, commonly called threesquare bulrush, in 12 eight-foot-long planters. The planters were combined into three 32-foot long parallel beds of vegetation that were placed in the flume in early July 2010.

Students and researchers from OSU, Louisiana State University, Harvey Mudd College, Kyoto University (Japan), and Seoul National University are measuring the effects of the plants on waves of varying height and velocity. Early results show that the height of the wave, which is also a measurement of the energy contained within the wave, is reduced by more than two-thirds as it passes through the vegetation.

Future experiments will measure the amount of incoming sediment trapped by the vegetation and the ability of the plants to survive waves of differing characteristics.

“The lack of control in the field making it exceedingly difficult to quantify what’s occurring,” said Cox, a professor in the OSU’s School of Civil and Construction Engineering. “By using the large wave flume, we can introduce live plants into a controlled environment at prototype-scale where we can document their response, and then test their reactions to different variables and conditions.”

Coastal environments are increasingly prone to modification, both by humans and by nature, the researchers note.  An example of the ability of wetlands to buffer storm damage was observed during hurricanes Katrina and Rita when earthen levees that were fronted by wetlands experienced less damage during the storms and therefore required less post-storm repair.

The development of strategies to protect wetlands and other ecologically important systems has been recognized for more than a decade. However, the difficulty of conducting research in the coastal wetland environment had created numerous challenges for scientists and policy makers. As a result, the services provided by coastal wetlands, including wave-energy reduction and erosion control, sediment and nutrient accumulation, and habitat functions that support commercial and sport fish, shellfish, and water fowl, as well as overall biological diversity, have not been regularly incorporated into economic and development models.

“We’ve understood many of the values of coastal wetlands for some time, but this is one of our first opportunities to accurately measure the amount of wave energy reduction and sediment accumulation that occurs because of the plants,” said Albert, whose research has focused on coastal wetlands of the Great Lakes for more than 20 years.

“Energy reduction and sediment collection benefit both the organisms within the wetlands, and the human community who live at the margins of the wetlands and depend partially on fish and other organisms of the marsh for their livelihood.”